Literature review

Effectofsplintingandinterproximalcontacttightnessonloadtransferbyimplantrestorations Analysisofloadtransferandstressdistributionbysplintedandunsplintedimplant-supportedfixedcementedrestorationsLOADTRANSFERANDSTRESSBYSPLINTINGANDUNSPLINTING A5yearprospectiverandomizedclinicaltrialontheinfluenceofsplintedandunsplintedoralimplantsretainingamandibularoverdenture-prostheticaspectsandpatientsatisfaction TheEffectofSplintingImplant-SupportedRestorationsonStressDistributionofDifferentCrown-ImplantRatiosandCrownHeightSpaces

4 articles are attached below to review -Summarize each article in one page. -Cover all aspects in the paper. -Clear comparison between splinted & unsplinted, and mention if there is an advantage over the other.

528 THE JOURNAL OF PROSTHETIC DENTISTRY VOLUME 87 NUMBER 5

system have been relatively successful, screw loosening
continues to be a frequent complication.2-4 Sutter et
al5 suggested that an internally connected abutment
design transfers occlusal loads to the implant body,
with less impact on the abutment screw threads.
Several studies have reported success with the use of
these systems for single-tooth restorations.6-8

The use of individual implant-supported restora-
tions can facilitate and simplify laboratory procedures.
In contrast, the fabrication of passive splinted frame-
works with conventional methods has been only
moderately successful.9 Several techniques for mini-
mizing framework misfit for multiple units are
available, such as sectioning and soldering, specialized
impression techniques, selective internal adjustments,
electrical discharge machining (spark erosion), and

Effect of splinting and interproximal contact tightness on load transfer by
implant restorations

David L. Guichet, DDS,a Diane Yoshinobu, DDS,b and Angelo A. Caputo, PhDc
School of Dentistry, University of California, Los Angeles, Calif.

Statement of problem. To circumvent the difficulty of achieving a passive framework fit, some authors
have suggested that multiple adjacent implants be restored individually. This protocol requires that each
unit be able to withstand mastication forces. Non-splinted restorations have numerous interproximal con-
tacts that require adjustments prior to placement, with an unknown outcome relative to load transfer.
Purpose. This in vitro simulation study examined the effect of splinting and interproximal contact tight-
ness on passivity of fit and the load transfer characteristics of implant restorations.
Material and methods. A photoelastic model of a human partially edentulous left mandible with 3
screw-type implants (3.75 × 10 mm) was fabricated. For non-splinted restorations, individual crowns were
fabricated on 3 custom-milled titanium abutments. After the units were cemented, 5 levels of interproxi-
mal contact tightness were evaluated: open, ideal (8 µm shim stock drags without tearing), light (ideal
+10 µm), medium (ideal + 50 µm), and heavy (ideal + 90 µm). For splinted restorations, five 3-unit fixed
partial dentures were fabricated, internally adjusted with silicone disclosing material, and cemented to the
model. Changes in stress distribution under simulated non-loaded and loaded conditions (6.8 kg) were
analyzed with a polariscope.
Results. In the simulated alveolar structures, non-splinted restorations with heavier interproximal con-
tacts were associated with increased tensile stresses between implants; occlusal loads tended to concentrate
around the specific loaded implant. Splinted restorations shared the occlusal loads and distributed the
stresses more evenly between the implants when force was applied. The load-sharing effect was most evi-
dent on the center implant but also was seen on the terminal abutments of the splinted restorations.
Conclusion. The results of this in vitro study suggest that excessive contact tightness between individual
crowns can lead to a non-passive situation. In this experiment, splinted restorations exhibited better load
sharing than non-splinted restorations. (J Prosthet Dent 2002;87:528-35.)

Several prosthetic options are available for the
restoration of multiple adjacent implants. Because it is
difficult to fabricate a passively fitting prosthesis on
multiple implants, some authors have suggested that
adjacent implants be restored individually.1 It is
believed that separating adjacent units allows the
resulting restorations to seat passively. Although sin-
gle-tooth restorations supported by an external hex

CLINICAL IMPLICATIONS

Within the limitations of this study, the results suggest that meticulous verification of
interproximal contact tightness should be performed to ensure the passive fit of non-
splinted restorations. If compromises exist in the position, the load-carrying capacity
and/or biomechanical stability of the proposed implant restorations may be affected.
Splinting may foster the reduction or sharing of loads and is therefore recommended
in these circumstances.

Presented at the annual meeting of the Pacific Coast Society of
Prosthodontics, Seattle, Wash., June 29-July 1, 2000.

aLecturer, Division of Advanced Prosthodontics, Biomaterials, and
Hospital Dentistry.

bStaff Prosthodontist, VA Medical Center, West Los Angeles, Calif.
cProfessor of Biomaterials Science, Division of Advanced

Prosthodontics, Biomaterials, and Hospital Dentistry.

laser welding. All of these procedures are technique-
sensitive, and results are limited by the accuracy of the
indexing method. It has been suggested that adhesive-
based correction procedures, in which machined
cylinders or discs are bonded underneath implant
frameworks, can improve the fit of the suprastructure
to the implants.10 Cement-retained fixed partial den-
tures (FPDs) have been shown to achieve better
passivity than screw-retained FPDs.11 Non-splinted
restorations facilitate oral hygiene and may engender
less stress development in the restoration and alveolar
structure during mandibular flexure.12-15

Splinting generally has been used to stabilize mobile
teeth and restore edentulous spaces.16 With the excep-
tion of Ante’s law,17 which has been questioned in
several studies,18,19 specific clinical guidelines for
splinting are lacking. Implant-supported restorations
are splinted primarily to aid in the distribution of
occlusal forces.20 Bending overload has been shown to
lead to coronal bone loss, as well as screw and implant
fracture.21-24 Based on clinical findings, finite element
models, and photoelastic studies, it has been recom-
mended that multiple implants be rigidly
connected.25-28 Limited experimental models have
demonstrated that splinting abutments can reduce the
occlusal forces transferred to the periodontium and
concentrate tensile and shear stresses in the connector
regions.29-33

The restoration of multiple units with single-tooth
implants is an attempt to circumvent the problem of
achieving passive fit with splinted restorations.
However, the restoration of individual adjacent
implants requires careful adjustment of interproximal
contacts. Campagni34 suggested that, for natural den-
tition, interproximal contacts should be adjusted to
allow an 8-µm metallic shim to drag without tearing.
Other authors have been less specific about the
method and measurement needed to establish ideal
contact.35,36 Without the aid of the periodontal liga-
ment around implants, contact adjustment may be
more critical.

What constitutes an acceptable level of fit varies
among clinicians,37 and the biological and mechanical
effects of misfit have been debated. Retrospective clin-
ical and animal studies failed to demonstrate any
differences in bone response with varying degrees of
prosthetic misfit.38,39 Rubin and Lanyon40 hypothe-
sized that because no evidence of new bone formation
was found under static loads, the bone essentially
ignored constant loads as osteoregulatory stimuli.
Adaptive bone remodeling did occur in animal ulnas
under dynamic loading. The authors concluded that
bone is “genetically programmed” to accept a particu-
lar level and distribution of functional strain within the
bone. Deviations may result in an adaptive increase or
decrease in the bone mass.

GUICHET, YOSHINOBU, AND CAPUTO THE JOURNAL OF PROSTHETIC DENTISTRY

MAY 2002 529

Static strains from misfitting prostheses may not
directly cause adverse bone reactions, but non-passive
restorations may magnify dynamically applied occlusal
loads (additive force). Studies have shown that load
magnification leads to bone loss.22-24 In animal stud-
ies, excess occlusal heights of 180 µm or more
(occlusal overload) led to an increase in bone loss
around implants with controlled oral hygiene.41,42
Skalak20 reported that misfit may fatigue implant com-
ponents and reduce failure loads.

The purpose of this in vitro simulation study was to
examine the effect of splinting and interproximal con-
tact tightness on passivity of fit and the load transfer
characteristics of implant restorations.

MATERIAL AND METHODS

A quasi-3-dimensional photoelastic stress analysis
of the mandibular left posterior quadrant was
designed for this study.43 An anatomically correct
skeletal form was used to create a master cast, mold,
and photoelastic resin “patient cast.” Three 3.75- ×
10-mm screw-type implants (Nobel Biocare,
Goteborg, Sweden) were embedded in the first and
second premolar and first molar positions to simulate
complete integration. The anterior implant was placed
anatomically with a 6% mesial inclination to parallel
the canine tooth angulation. A medium-modulus
photoelastic resin designed to simulate healthy bone
was used (PL-2; Measurements Group Inc, Raleigh,
N.C.).

Accepted clinical and laboratory procedures were
used to fabricate and deliver the restorations. An
anatomically correct wax gingival form overlaid the
photoelastic resin to simulate the thickness of gingival
tissues during impression-making procedures.
Implant-level pick-up impression posts (EP Square
Impression Copings; Implant Innovations Inc, Palm
Beach Gardens, Fla.) were oriented on the implants.
A custom tray was fabricated to adapt loosely to the
impression posts, and a light-bodied vinyl polysilox-
ane impression was made (Extrude; Kerr, Romulus,
Mich.). Implant analogs were secured in the impres-
sion, and silicone that represented soft tissue (GI
Mask; GC America Inc, Alsip, Ill.) was added to the
internal aspect of the impression surrounding the
implant analog necks. The impression was poured in
vacuum-mixed die stone (Die Keen; Heraeus Kulzer,
South Bend, Ind.), and a working cast was created.
Teeth were fashioned in inlay wax in an anatomically
correct manner with a 1-mm buccal cutback for
porcelain application. A condensation silicone mold
(Coltene/Whaledent, Mahwah, N.J.) was placed over
the FPD wax pattern to allow for multiple replica-
tions.

The single-unit and FPD designs studied were
cement-retained restorations based on 2-piece abut-

ment posts (EP; Implant Innovations Inc). The abut-
ments were delivered to the working cast and modified
according to the manufacturer’s recommendations to
allow for occlusal and axial clearance, cervical emer-
gence, taper, and path of draw. A uniform total taper
of 6 degrees was achieved with a precision-milling
machine (F-1; Ney/Degussa, Bloomfield, Conn.).
The abutments were polished to a medium-high finish
with rubber wheels. Resin copings (Pattern Resin; GC
Corp, Tokyo, Japan) were made for each abutment
without the use of a die spacer. The copings were posi-
tioned on the abutments and then assembled in the
silicone mold. Wax was subsequently injected into the
mold to form the wax patterns. Five replications were
completed for the FPDs and one set for the single-unit
restorations.

An implant cast verification index was fabricated to
verify the implant orientation and abutment relation-
ships and to orient the individual restorative units
prior to investing and casting. The index was fabricat-
ed as follows: Three square implant-level impression
posts were secured to the stone cast, joined with den-
tal floss and acrylic resin (Relate; Parkell,
Farmingdale, N.Y.), and placed in boiling water for
10 minutes prior to sectioning. After the solid index
was separated, lead film foil was placed between the
sections, and acrylic resin was applied on each side of
the foil. The separator was removed, and the 3 sec-
tions were boiled for an additional 10 minutes to
ensure complete polymerization. The 3 resin indices
were placed without contact on the photoelastic
model, and the thin separation was luted with cyano-
acrylate gel and accelerator (Rocket-heavy; Dental
Ventures of America Inc, Corona, Calif.). Implant
replicas were added to the impression posts, and the
verification assembly was seated in low-expansion
mounting stone (Whip Mix Corp, Louisville, Ky.) The
stone was allowed to harden. The index was verified
visually with the 1-screw test (Scheffield fitting test),9

THE JOURNAL OF PROSTHETIC DENTISTRY GUICHET, YOSHINOBU, AND CAPUTO

530 VOLUME 87 NUMBER 5

and stress analysis testing on the photoealstic model
was used to determine that the index accurately pro-
duced the implant relationships.

FPD wax patterns were sectioned interproximally
and rejoined on the implant verification index with
cyanoacrylate gel (Zap-it; Dental Ventures of North
America) prior to spruing and investing. For the non-
splinted, single-unit restorations, contacts between the
implants were separated and waxed to form a “heavy”
contact that would allow polishing procedures.
Margins (margin wax; Metalor, North Attleborough,
Mass.) were finished under ×10 microscopy.

The investment, burnout, and casting techniques
were standardized. Patterns were sprued and invested
individually in a phosphate-bonded investment (Cera-
Fina; Whip Mix Corp) with the casting technique
described by White.9 After bench polymerization and
burnout, the investment rings were cast in a gold-
palladium alloy (Silhouette 550SL; Argen Alloys Inc,
San Diego, Calif.). Devesting was completed in the
usual manner with minimum use of aluminum oxide
air abrasives on critical interfaces. Burs were used
under laboratory microscopes to eliminate internal
casting inaccuracies.

Further internal adjustments were made by painting
a thin layer of die lubricant (Belle de St. Clair,
Chatsworth, Calif.) on the abutments and removing
any wet, shiny areas on the lightly air-abraded internal
surfaces of the castings.44 Adjustments were made
until the best seating of the castings was achieved and
confirmed under microscopy. The cement-retained
FPDs were adjusted as described above with a silicone
disclosing medium (Fit-Checker; GC Corp) (Fig. 1).

The single-unit and FPD restorations were deliv-
ered to the patient model with a standard protocol.
The specimens were seated with zinc oxide–eugenol
temporary cement (Temp-Bond; Kerr) under a 4.5-kg
load for 1 minute followed by a 0.9-kg load for 2 min-
utes and then bench set. Excess cement was removed
prior to testing. Each specimen was evaluated under
the same conditions.

Prior to any evaluation, the photoelastic resin cast
was determined to be free of residual stress. The model
was immersed in mineral oil to minimize surface
refraction and then placed in the field of a circular
polariscope (Measurements Group Inc), as described
previously.28 The non-splinted, single-unit restora-
tions were tested for stress generation within the
supporting structures with varying contact tightness.
After cementation of the non-splinted units, inter-
proximal contacts were adjusted by placing metallic
shims (Shim stock; Almore International Inc,
Beaverton, Ore.) of varying thickness into the inter-
proximal spaces to simulate different degrees of
contact tightness. The following thicknesses were

Fig. 1. Silicone disclosing medium used to identify interfer-
ences for internal adjustment of fixed partial denture.

GUICHET, YOSHINOBU, AND CAPUTO THE JOURNAL OF PROSTHETIC DENTISTRY

MAY 2002 531

used: open, ideal (8-µm tin foil shim could drag
between contacts without tearing) (Fig. 2), light (ideal
+ 10 µm), medium (ideal + 50 µm), and heavy (ideal
+ 90 µm). Stresses generated by the various degrees of
contact were observed and photographed within the
polariscope.

Vertical loads of 6.8 kg were applied in a straining
frame by means of a calibrated load cell mounted on
the movable head of a loading frame. Loads were
monitored with a digital read-out (Models 2130 and
2120A; Measurements Group Inc). For each of the
FPDs and contact conditions, the loading point loca-
tions were over the anterior, middle, and posterior
implants. The model was immersed in a tank of min-
eral oil to minimize surface refraction and thereby
facilitate photoelastic observation. The resulting
stresses in all areas of the supporting structure were
monitored and recorded photographically in the field
of the circular polariscope. Each loading and observa-
tion sequence was repeated at least 2 times to ensure
reproducibility of the results. The model was allowed
to rest between each test series to ensure that the
observed stresses were not residual but the result of
applied conditions.

RESULTS

The results for non-loaded test conditions are pre-
sented in Figure 3. No stresses were observed in
non-splinted restorations with open contacts. A low
level of coronal stress (<1⁄2 fringe order) developed between the implants when the interproximal contacts were adjusted to an ideal contact. With the addition of a 10-µm shim in both interproximal spaces (light con- tact), coronal stresses became more evident among the 3 implants (1⁄2 fringe order). With a 50-µm shim (medi- um contact), an increase in stress among the implants was identified (1 fringe order), as were stresses along the implant threads and apices (1⁄2 fringe order). Placement of a 90-µm shim (heavy contact) resulted in

high levels of stress in the coronal region (11⁄2 fringe
orders) and increased stress along the implant threads
and apices (1 fringe order).

Splinted FPDs generally exhibited low stress levels
in the alveolar structure. The FPDs were ranked in
order of increasing stress (Fig. 3). After cementation,
FPDs 1 and 2 were essentially free from stress, with the
exception of low interproximal stress between the dis-
tal implants (<1⁄2 fringe order). FPDs 3 and 4 exhibited

Fig. 2. Eight-µm tin foil shim dragged between interproximal
contacts without tearing to establish ideal contact tightness.

Fig. 3. Non-loaded data. Non-splinted restorations trans-
ferred increased stress as contact tightness increased.
Open = least stress, heavy = most stress. Splinted restora-
tions transferred stresses generated upon placement. FPDs 1
and 2 exhibited least stress; FPD 5 exhibited most stress.

THE JOURNAL OF PROSTHETIC DENTISTRY GUICHET, YOSHINOBU, AND CAPUTO

532 VOLUME 87 NUMBER 5

low levels of stress along the distal threads of the ante-
rior implant and interproximally between the posterior
implants (1⁄2 fringe order). Only FPD 5 exhibited a sig-
nificant amount of stress (1 fringe order) in the same
areas mentioned for FPDs 3 and 4. Most of the FPDs
consistently demonstrated low stress distribution.

The results for loaded test conditions are presented
in Figures 4 through 6. For each of the FPDs and con-
tact conditions, peak stresses were manifested under
the loaded implant; remote stress concentrations were

of equal or lesser intensity. For this reason, the loaded
implant was isolated for analysis.

Anterior implant data are presented in Figure 4. For
both splinted and non-splinted restorations, stress
concentrated on the mesial aspect of the implant (Fig.
4). In the non-splinted group, stress increased as con-
tact tightness increased (open to heavy = 2-3 fringe
orders). Splinted restorations exhibited the same load-
ing characteristics but with slightly less mesial stress
(FPDs 1 and 3-5 = 11⁄2 fringe orders, FPD 2 = 2 fringe
orders). Splinted restorations also distributed loads to

Fig. 4. Anterior load, 6-degree mesial implant inclination. Non-splinted restoration concen-
trated stress on mesial aspect of loaded implant. Stress increased as contact tightness
increased. Splinted restorations exhibited same loading characteristics but with slightly less
mesial stress.

Fig. 5. Middle load, non-splinted restoration. Stress concentrated around loaded implant and
exhibited higher peak stress than in splinted group. Splinted restorations exhibited load shar-
ing and transferred significantly less stress to loaded middle implant.

GUICHET, YOSHINOBU, AND CAPUTO THE JOURNAL OF PROSTHETIC DENTISTRY

MAY 2002 533

the distal aspect of the implant in the coronal half, but
to a lesser degree than on the mesial aspect (FPD 2 =
1⁄2 fringe order, FPDs 1 and 3-5 = 1 fringe order).
Stresses were distributed slightly more evenly in the
splinted group than in the non-splinted group.

Middle implant data are presented in Figure 5. In
the non-splinted group, a high level of stress (11⁄2
fringe orders) was identified along the threads and
alveolar structure of the restoration with open con-
tacts. Lower-intensity stresses were seen on the
anterior and posterior implants (not depicted). With
increasing interproximal contact tightness (open to
heavy), peak stress levels continued to concentrate
along the mesial aspect of the loaded implant (2 fringe
orders). Stresses around the anterior and posterior
implants also increased in complexity, but at a com-
paratively reduced intensity. Conversely, in the splinted
group, less force was transferred to the supporting
structure. Stresses were distributed more evenly
among the 3 implants, and all 5 FPDs exhibited low
stress levels (1 fringe order).

Posterior implant data are presented in Figure 6. In
the non-splinted group, high levels of stress concen-
trated along the loaded implant. Less intense stress was
identified in the anterior and middle implants. As
interproximal contact tightness increased, an associat-
ed shift in peak stress from the mesial aspect to the
distal aspect of the loaded implant was observed (open
to medium = 11⁄2 fringe orders). Only in the heavy-con-
tact group were the peak stresses significantly higher
on the distal aspect of the coronal portion of the

implant (21⁄2 fringe orders, the highest peak stress
observed in this study). In the splinted group, occlusal
loads applied to the posterior implant were not shared
as evenly as loads applied to the middle implant.
Stresses tended to concentrate on the coronal aspect of
the posterior implant (11⁄2-2 fringe orders) but were
not as intense as those associated with the non-splint-
ed, heavy-contact posterior implant.

DISCUSSION

A passively fitting prosthesis has been considered a
prerequisite for the success and maintenance of
osseointegration. Passivity is a particular concern with
multiple implants because of documented inaccuracies
in the casting and soldering process. One way to avoid
this problem is to restore the implants individually.
High success rates with single-tooth implants and
altered abutment/implant connections have fostered
confidence in the individual-restoration protocol,
which eliminates the need for procedures designed to
minimize framework misfit.

The individual restoration of multiple adjacent
implants also minimizes component loosening and/or
fractures as the mandible undergoes flexure and tor-
sion during function.12 With a finite element model of
the human mandible, Korioth and Hannam13 record-
ed a range of deformation (0.46 to 1.06 mm) during
simulated tooth clenching. Hobkirk and Schwab14
observed a medial deflection of the mandible of up to
420 µm during active opening and protrusive jaw
movements. Reports of significant amounts of

Fig. 6. Posterior load, non-splinted restoration. As contact tightness increased, higher stresses
were noted. This was most evident in distal aspect of implants in heavy tightness group.
Splinted restorations shared stresses to lesser degree than seen in middle load group (Fig. 4).
Character of stress distribution in FPDs was similar, and magnitude was of equal or slightly
greater value than seen in medium contact tightness condition.

mandibular flexure have engendered concerns about
potentially harmful forces along the implant/bone
interface with rigidly connected superstructures.
Fischman15 suggested that a complete-arch restoration
be avoided in favor of freestanding, short-span,
implant-supported prostheses. Individually restored
implants enable better oral hygiene access and
improved axial and interproximal contours.

Multiple single-unit restorations do have disadvan-
tages. This restorative design may not be possible if
each implant is not placed in the correct location and
angulation. A lack of hard tissue and anatomic land-
marks may prevent appropriate spacing and the use of
an adequate number of implants. Moreover, although
individual restoration may simplify laboratory proce-
dures, the adjustment of interproximal contacts with
multiple adjacent implants is difficult. Fixed prostho-
dontic textbooks suggest that floss or articulating
paper be used to adjust and evaluate proximal con-
tacts.35,36 These techniques are variable and do not
allow a quantitative evaluation of contact tightness.
Without the presence of periodontal ligaments around
implants, the adjustment of interproximal contacts
becomes more critical.

Campagni34 suggested that interproximal contacts
be modified until an 8-µm metallic shim can be dragged
through the contact without tearing. In the present
study, little to no stress developed within the supporting
structure when the contacts were adjusted accordingly
(Fig. 3). When a 10-µm shim was placed between the
restorations (light contact), stresses developed in the
coronal area between the implants. Higher levels of
stress developed in the coronal areas and along the
implant threads when medium and heavy contacts were
tested. These data suggest that the individual restora-
tion of multiple adjacent implants does not necessarily
result in a passively restored prosthesis. Interproximal
contacts must be carefully adjusted without creating an
open contact, which increases in difficulty with a larger
number of units and a screw-retained design.

Non-splinted restorations also must withstand mas-
ticatory loads individually. In the present study, high
levels of stress were concentrated on the loaded
implant, with little transfer of load to the neighboring
implants. Increased contact tightness was associated
with increased stress intensity along the loaded implant
(Figs. 4 and 5). Implant-supported FPDs are splinted
to foster the distribution of occlusal forces and to pre-
vent the transfer of detrimental force levels to the
supporting implants, which may lead to bone resorp-
tion and component failures.21-24 When multiple units
are splinted, occlusal forces are “absorbed” within the
framework: tensile and shear stresses are concentrated
in the connector regions, which reduces the force
transferred to the periodontium.32,33 A comparison of
the non-splinted and splinted data in Figure 4 illus-

trates this phenomenon. It should be noted that forces
were not as evenly distributed when anterior or poste-
rior abutments were loaded as when middle implants
were loaded (Fig. 5).

Occlusal stresses tended to concentrate on the
loaded implant; these stresses were similar in magni-
tude (11⁄2 fringe orders) to those observed for
non-splinted restorations with either ideal or light
interproximal contacts. These data suggest that the
effect of splinting is limited, which is consistent with
previous findings. An insubstantial cross-arch distribu-
tion of load limited to 2 to 3 teeth or the implants
closest to the applied load has been reported for splint-
ed prostheses.29-31

Splinting may have a beneficial effect when off-axis
implants are restored. The anterior implant evaluated
in the present study had a 6% mesial inclination. When
non-splinted implants were loaded, stress concentrated
on the mesial threads. As contact tightness increased,
the stress intensified. In the splinted group, loading
was associated with stress concentrations in the same
locations, but at a lower magnitude.

The design of the present study minimized the con-
founding variables associated with animal and human
studies. The applicability of the results is limited, how-
ever, by the fact that photoelastic data were interpreted
visually. It should be noted that all modeling systems
(including finite element analysis, mathematical mod-
els, and strain-gauge analysis) are limited when the
biologic system is studied. Long-term clinical studies
are needed to determine whether varied masticatory
loads on non-splinted and splinted restorative designs
affect implant survival. The decision to splint implants
may be more important when no anterior guidance
exists or when the patient has parafunctional habits.
Implants placed in poor-quality bone or grafted areas
also may benefit from splinting.

CONCLUSIONS

Within the limitations of this photoelastic stress
analysis study, the following conclusions were drawn:

1. Splinting effectively reduced peak stresses in the
loaded middle implant of a 3-unit FPD. When restora-
tions were not splinted, stresses concentrated around
the loaded implant.

2. Load sharing by splinted restorations was least
significant when loads were applied to the terminal
posterior implant of the FPDs. Axial loads in splinted
and non-splinted restorations were similar.

3. Load sharing by splinted restorations was
observed when loads were applied to the anterior ter-
minal abutment, which was positioned slightly off-axis.
This result suggests that splinting may be effective
with off-axis implants.

4. As interproximal contact tightness increased, pas-
sivity decreased. Heavier interproximal contact

THE JOURNAL OF PROSTHETIC DENTISTRY GUICHET, YOSHINOBU, AND CAPUTO

534 VOLUME 87 NUMBER 5

implant fracture: a retrospective clinical analysis. Int J Oral Maxillofac
Implants 1995;10:326-34.

25. Wright KW, Yettram AL. Reactive force distributions for teeth when
loaded singly and when used as fixed partial denture abutments. J
Prosthet Dent 1979;42:411-6.

26. Stegaroiu R, Sato T, Kusakari H, Miyakawa O. Influence of restoration
type on stress distribution in bone around implants: a three-dimensional
finite element analysis. Int J Oral Maxillofac Implants 1998;13:82-90.

27. Landry KE, Johnson PF, Parks VJ, Pelleu GB Jr. A photoelastic study to
determine the location of the nonrigid connector in a five-unit interme-
diate abutment prosthesis. J Prosthet Dent 1987;57:454-7.

28. Davidoff SR. Restorative-based treatment planning: determining ade-
quate support for implant-retained fixed restorations. Implant Dent
1996;5:179-84.

29. White SN, Caputo AA, Anderkvist T. Effect of cantilever length on stress
transfer by implant-supported prostheses. J Prosthet Dent 1994;71:493-
9.

30. Wylie RS, Caputo AA. Fixed cantilever splints on teeth with normal and
reduced periodontal support. J Prosthet Dent 1991;66:737-42.

31. Itoh H, Caputo AA, Wylie R, Berg T. Effects of periodontal support and
fixed splinting on load transfer by removable partial dentures. J Prosthet
Dent 1998;79:465-71.

32. Yang HS, Lang LA, Felton DA. Finite element stress analysis on the effect
of splinting in fixed partial dentures. J Prosthet Dent 1999;81:721-8.

33. el-Ebrashi MK, Craig RG, Peyton FA. Experimental stress analysis of den-
tal restorations. VII. Structural design and stress analysis of fixed partial
dentures. J Prosthet Dent 1970;23:177-86.

34. Campagni WV. The final touch in the delivery of a fixed prosthesis. CDA
J 1984;12:21-9.

35. Shillingburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE.
Fundamentals of fixed prosthodontics. 3rd ed. Chicago: Quintessence;
1997. p. 391-2.

36. Rosenstiel SF, Land MF, Fujimoto J. Contemporary fixed prosthodontics.
3rd ed. St. Louis: Mosby; 1998. p. 747-9.

37. Kan JY, Rungcharassaeng K, Bohsali K, Goodacre CJ, Lang BR. Clinical
methods for evaluating implant framework fit. J Prosthet Dent 1999;81:7-
13.

38. Jemt T, Book K. Prosthesis misfit and marginal bone loss in edentulous
implant patients. Int J Oral Maxillofac Implants 1996;11:620-5.

39. Carr AB, Gerard DA, Larsen PE. The response of bone in primates around
unloaded dental implants supporting prostheses with different levels of
fit. J Prosthet Dent 1996;76:500-9.

40. Rubin CT, Lanyon LE. Kappa Delta Award paper. Osteoregulatory nature
of mechanical stimuli: function as a determinant for adaptive remodel-
ing in bone. J Orthop Res 1987;5:300-10.

41. Miyata T, Kobayashi Y, Araki H, Motomura Y, Shin K. The influence of
controlled occlusal overload on peri-implant tissue: a histologic study in
monkeys. Int J Oral Maxillofac Implants 1998;13:677-83.

42. Miyata T, Kobayashi Y, Araki H, Ohto T, Shin K. The influence of con-
trolled occlusal overload on peri-implant tissue. Part 3: A histologic study
in monkeys. Int J Oral Maxillofac Implants 2000;15:425-31.

43. Mahler DB, Peyton FA. Photoelasticity as a research technique for ana-
lyzing stresses in dental structures. J Dent Res 1955;34:831-8.

44. White SN, Sorenson JA, Kang SK. Improved marginal seating of cast
restorations using a silicone disclosing medium. Int J Prosthodont
1991;4:323-6.

Reprint requests to:
DR DAVID L. GUICHET
PROVIDENCE PROSTHODONTICS
1310 WEST STEWART DR, SUITE 202
ORANGE, CA 92868
FAX: (714)771-7557
E-MAIL: dguichet@ngaseminars.com

Copyright © 2002 by The Editorial Council of The Journal of Prosthetic
Dentistry.

0022-3913/2002/$35.00 + 0. 10/1/124589

doi:10.1067/mpr.2002.124589

GUICHET, YOSHINOBU, AND CAPUTO THE JOURNAL OF PROSTHETIC DENTISTRY

MAY 2002 535

tightness in non-splinted restorations resulted in a
non-passive situation.

REFERENCES

1. Solnit GS, Schneider RL. An alternative to splinting multiple implants:
use of the ITI system. J Prosthodont 1998;7:114-9.

2. Laney WR, Jemt T, Harris D, Henry PJ, Krogh PH, Polizzi G, et al.
Osseointegrated implants for single-tooth replacement: progress report
from a multicenter prospective study after 3 years. Int J Oral Maxillofac
Implants 1994;9:49-54.

3. Henry PJ, Laney WR, Jemt T, Harris D, Krogh PH, Polizzi G, et al.
Osseointegrated implants for single-tooth replacement: a prospective 5-
year multicenter study. Int J Oral Maxillofac Implants 1996;11:450-5.

4. Scheller H, Urgell JP, Kultje C, Klineberg I, Goldberg PV, Stevenson-
Moore P, et al. A 5-year multicenter study on implant-supported single
crown restorations. Int J Oral Maxillofac Implants 1998;13:212-8.

5. Sutter F, Schroeder A, Buser DA. The new concept of ITI hollow-cylinder
and hollow-screw implants: Part I. Engineering and design. Int J Oral
Maxillofac Implants 1988;3:161-72.

6. Moberg LE, Kondell PA, Kullman L, Heimdahl A, Gynther GW.
Evaluation of single-tooth restorations on ITI dental implants. A prospec-
tive study of 29 patients. Clin Oral Implants Res 1999;10:45-53.

7. Levine RA, Clem DS III, Wilson TG Jr, Higginbottom F, Solnit G.
Multicenter retrospective analysis of the ITI implant system used for sin-
gle-tooth replacements: results of loading for 2 or more years. Int J Oral
Maxillofac Implants 1999;14:516-20.

8. Gomez-Roman G, Schulte W, d’Hoedt B, Axman-Krcmar D. The Frialit-2
implant system: five-year clinical experience in single-tooth and imme-
diately postextraction applications. Int J Oral Maxillofac Implants
1997;12:299-309.

9. White GE. Osseointegrated dental technology. Carol Stream (IL):
Quintessence; 1993. p. 61, 103-29.

10. Stumpel LJ III. The adhesive-corrected implant framework. J Calif Dent
Assoc 1994;22:47-50, 52-3.

11. Guichet DL, Caputo AA, Choi H, Sorenson JA. Passivity of fit and mar-
ginal opening in screw- or cement-retained implant fixed partial denture
designs. Int J Oral Maxillofac Implants 2000;15:239-46.

12. English CE. Biomechanical concerns with fixed partial dentures involv-
ing implants. Implant Dent 1993;2:221-42.

13. Korioth TW, Hannam AG. Deformation of the human mandible during
simulated tooth clenching. J Dent Res 1994;73:56-66.

14. Hobkirk JA, Schwab J. Mandibular deformation in subjects with osseoin-
tegrated implants. Int J Oral Maxillofac Implants 1991;6:319-28.

15. Fischman B. The rotational aspect of mandibular flexure. J Prosthet Dent
1990;64:483-5.

16. Serio FG. Clinical rationale for tooth stabilization and splinting. Dent
Clin North Am 1999;43:1-6, v.

17. Ante IH. The fundamental principles of abutments. Mich State Soc Bull
1926;8:14-23.

18. Nyman S, Ericsson I. The capacity of reduced periodontal tissues to sup-
port fixed bridgework. J Clin Periodontol 1982;9:409-14.

19. Nyman S, Lindhe J. Prosthetic rehabilitation of patients with advanced
periodontal disease. J Clin Periodontol 1976;3:135-47.

20. Skalak R. Biomechanical considerations in osseointegrated prostheses. J
Prosthet Dent 1983;49:843-8.

21. Quirynen M, Naert I, van Steenberghe D. Fixture design and overload
influence marginal bone loss and fixture success in the Branemark sys-
tem. Clin Oral Implants Res 1992;3:104-11.

22. Hoshaw SJ, Brunski JB, Cochran GV. Mechanical loading of Branemark
implants affects interfacial bone modeling and remodeling. Int J Oral
Maxillofac Implants 1994;9:345-60.

23. Rangert B, Jemt T, Jorneus L. Forces and moments on Branemark
implants. Int J Oral Maxillofac Implants 1989;4:241-7.

24. Rangert B, Krogh PH, Langer B, Van Roekel N. Bending overload and

Analysis of load transfer and stress distribution by splinted

and unsplinted implant-supported fixed cemented

restorations

J . N I S S A N
*
, O . G H E L F A N

*
, M . G R O S S

*
& G . C H A U S H U

†
Departments of

*
Oral Rehabilitation and

†
Oral and Maxillofacial Surgery, The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel

SUMMARY Controversy remains over the rehabilita-

tion of implant-supported restorations regarding the

need to splint adjacent implant-supported crowns.

This study compared the effects of simulated occlusal

loading of three implants restored with cemented

crowns, splinted versus unsplinted. Three adjacent

screw-shaped implants were passively inserted into

three holes drilled in a photo-elastic model. Two

combinations of cemented restorations were fabri-

cated; three adjacent unsplinted and three adjacent

splinted crowns. Strain gauges were connected to the

implant necks and to the margins of the overlaying

crowns. Fifteen axial static loads of 20-kg loadings

were carried out right after each other via a custom-

built loading apparatus. Strain gauges located on

the implant neck supporting splinted restoration

demonstrated significantly (P < 0Æ001) more strain

(sum of strains = 3348Æ54 microstrain) compared

with the single crowns (sum of strains = 988Æ57

microstrain). In contrast, significantly (P < 0Æ001)

more strain was recorded on the strain gauges located

on the restoration margins of the single crowns (sum

of strains = 756Æ32 microstrain) when compared with

splinted restorations (sum of strains = 186Æ12 micro-

strain). The concept of splinting adjacent implants to

decrease loading of the supporting structures may

require re-evaluation. The clinical relevance of these

findings needs further investigation.

KEYWORDS: load, stress distribution, splinted,

unsplinted

Accepted for publication 19 March 2010

Introduction

Occlusal load and its distribution is considered to be one

of the principal components that influences the success

and failure of implant-supported restorations over time

(1–4). The traditional rationale for splinting teeth was

to increase retention and resistance resulting in

decreased stresses, improving prosthesis stability (5).

The rationale of splinting in implant dentistry to

minimize stress by increasing the resistance area over,

which the load is distributed, is controversial (6). The

biomechanical advantages following splinting restora-

tions are still unclear (7). Evidence-based data to

support splinting are largely missing for teeth and even

more for implants (7, 8).

Some authors have maintained that occlusal loads

transferred to implants supporting splinted restoration

are larger than those applied to implants supporting

unsplinted restorations because of the development of

moments (6, 9). Clinical studies on the successful

restoration of unsplinted adjacent implant-supported

restorations in partially edentulous individuals have

been reported (10–14). Implant splinting did not

significantly improve implant success rates for

implant-supported fixed partial dentures (97Æ1%)
compared to single-implant restorations (94Æ3%) (14).
Furthermore, splinting did not have an effect on crestal

bone loss (15).

This study examined load transfer and stress distri-

bution of simulated axial occlusal loading on adjacent

ª 2010 Blackwell Publishing Ltd

doi: 10.1111/j.1365-2842.2010.02096.x

Journal of Oral Rehabilitation 2010 37; 658–662

J o u r n a l o f Oral Rehabilitation

implant-supported fixed restorations. The effects on

splinted and unsplinted implant-supported restorations

are compared using strain gauge analysis.

Materials and methods

A photo-elastic block model (PLM-4B*) with modulus

of elasticity 450 ksi [range of human bone (16)]

was constructed. The model dimensions were 15Æ8
· 35Æ2 · 32 mm. Three holes were drilled vertically in a
straight line in the mid-axis of the photo-elastic model

at predetermined locations to lengths of 12 mm. Dril-

ling was carried out according to surgical protocols with

successive drill diameters in sequence to minimize

residual stresses in the model. Stresses introduced into

the photo-elastic model by the drilling process were

relieved by placement of the model in an oven on a

teflon surface for 120 min at 70 �C. The model was
cooled in the closed oven. Stress relief was verified with

the aid of a circular polariscope, and the model was

found to be stress free. Implants were located 7Æ8 mm
from the edge of the model and each implant separated

by 4 mm. Three external hex, screw type titanium

implants of diameter 3Æ8 mm, of length 12 mm† were
inserted into the model. The 2-mm implants’ neck

protruded forms the superior surface.

Two strain gauges (Strain-gauge EA-06-015EH-120*)

were cemented (M-Bond 200*) horizontally onto the

neck of each implant on the buccal and lingual aspects

at a 180�-inclination to each other prior to abutment
and crown placement. These strain gauges measured

the bending components (tension ⁄ compression) cre-
ated from both vertical and horizontal vectors arising

from applied forces. Strain gauges were connected to a

strain indicator (Strain Indicator System 5000*) that

provided a simultaneous direct reading of strain in

microstrain units of all model components for each

loading session. The described design has been used in

previous studies (17).

Impressions were taken by the open tray technique

with acrylic splinted transfer copings
‡

using custom

acrylic trays. Polyether impression material was used
§
.

A master working model was fabricated on which all

the restorations were fabricated on attached fixed

abutments with 2 mm gingival height.

Two groups of restorations were cast in Remanium

CoCrMo Model Casting Alloy-GM 380:

1 Three unsplinted crowns (Fig. 1).

2 Three splinted crowns (Fig. 2).

The restorations were fabricated with the occlusal

anatomy of upper first molars with the same mesio-

distal and bucco-lingual dimensions using a silicone

index.

Screw-retained abutments were placed at a con-

trolled torque of 35 Ncm. During each loading session,

the restorations were cemented onto the implant

abutments using temporary cement
¶
. No residual stress

was apparent in the photo-elastic model as verified by

visual inspection. Contact points of the individual

restorations were fabricated so that dental floss passed

with slight difficulty according to standard clinical

procedure.

An additional third strain gauge was cemented

horizontally onto each cast restoration at the cervical

margin parallel to the margin in the mid-buccal

dimension (EA-06-032DE-350*). These were designed

to measure the peripheral strain in the margins of each

casting.

Fifteen static loadings were carried out right after

each other with 20 kg weights via a custom-built

loading apparatus. Load was applied simultaneously

through three individual pins to the inner inclines of

the buccal cusps of each set of restorations at 0� to the
vertical axis (Fig. 3).

Fig. 1. Unsplinted crowns.

*Vishay Measurement Group Inc., Raleigh, NC, USA.
†
Nobel Biocare, Zurich, Switzerland.

‡
Duralay Reliance Dental Mfg Co., Worth, IL, USA.

§
Impregum F; ESPE, Seefeld, Germany.

¶
Temp Bond, NE Kerr, CA, USA.

L O A D T R A N S F E R A N D S T R E S S B Y S P L I N T I N G A N D U N S P L I N T I N G 659

ª 2010 Blackwell Publishing Ltd

For each loading, strain gauge recordings were made.

Strain gauges measure electrical resistance. During

extension or contraction, the strain gauge records

changes in electrical resistance. The degree of distortion

of the strain gauge is recorded in calculated microstrains

values, where strain = € = DL (change in length of the
strain gauge) ⁄ L (lm ⁄ m) = DR (change in electrical
resistance in the strain gauge) ⁄ R.

Statistical analysis

Descriptive analysis consisted of mean and standard

deviation of microstrain values for each group. Groups

were compared by the use of the one-way parametric

analysis of variance (ANOVA). P values of <0Æ05 were considered statistically significant.

Results

Strain gauges located on the implant neck supporting

splinted restoration demonstrated significantly (P <

0Æ001) more strain (sum of strains = 3348Æ54 micro-
strain) compared with the single crowns (sum of

strains = 988Æ57 microstrain) (Table 1). In contrast,
significantly (P < 0Æ001) more strain was recorded on the strain gauges located on the restoration margins of

the single crowns (sum of strains = 756Æ32 microstrain)
when compared with splinted restorations (sum of

strains = 186Æ12 microstrain) (Table 2).

Fig. 3. A custom-built loading apparatus.

Fig. 2. Splinted crowns.

Table 1. Microstrain values on implant necks

Implant

Strain Gauge

location

Restoration

modality

Microstrain values

M �SD

1 B* Single 162Æ64 69Æ41
Splint 1884Æ40 59Æ62

P
NS

Single 10Æ27 1Æ62
Splint 48Æ40 4Æ86

2 B
NS

Single 48Æ53 2Æ66
Splint 31Æ13 1Æ25

P* Single 529Æ20 4Æ21
Splint 965Æ01 19Æ28

3 B* Single 117Æ13 3Æ96
Splint 233Æ60 4Æ01

P* Single 121Æ00 7Æ20
Splint 186Æ00 11Æ77

NS, Not Significant; B, Buccal; P, Palatinal.

*P < 0.001.

Table 2. Microstrain values on crown margins

Crown

Restoration

modalities

Microstrain values

Mean �SD

1* Single 134Æ26 1Æ16
Splint 87Æ00 6Æ33

2* Single 407Æ46 3Æ50
Splint 21Æ26 1Æ03

3* Single 214Æ60 11Æ23
Splint 77Æ86 0Æ91

*P < 0.001.

J . N I S S A N et al.660

ª 2010 Blackwell Publishing Ltd

Discussion

Occlusal loads on osseointegrated implants are cited as a

significant factor in the long-term success of implant-

supported restorations (1, 6). It is common clinical

practice to join adjacent implant-supported restorations

in the restoration of the partially edentulous. Resistance

and retention forms may be a major indication for

splinting. An additional rationale of splinting implant

crowns together is to favourably distribute the non-

axial loads, minimize their transfer to restoration and

the supporting bone and to increase the total load area

(18). This practice is taken from concepts of splinting

teeth, where the assumption is that joined linear and

non-collinear units improve the collective resistance to

forces and alters the centre of rotation of the joined

units (19).

Several in vitro studies reported conflicting results.

Guichet et al. (20) in a 3D photo-elastic study support

this concept reporting that cemented splinted restora-

tions exhibited better load sharing than non-splinted

restorations. Brunsky et al. (6) maintained that loading

of splinted implant-supported crowns generates mo-

ments resulting in greater forces on the implants when

compared to the applied force. Kim et al. (21) compared

provisional and permanent cement retained, and

screw-retained 2-unit splinted restorations using a

photo-elastic and strain gauge bench model. A single

provisionally cemented restoration showed the least

stress compared to splinted and cantilevered modalities.

On the contrary, clinical studies do not seem to

support splinting. Glantz et al. (9) reported on unex-

pectedly high functional bending moments on the

implants in vivo, on maximum biting and chewing in a

conventional cross arch splinted restoration. Bender

(10) in a 4-year clinical study reported higher success

rates for adjacent unsplinted cemented restorations

when compared to adjacent splinted cemented restora-

tions. He maintains that non-splinted restorations allow

the optimal transfer of stress to the supporting struc-

tures. In another clinical study consisting of 199

implants and 74 partially edentulous patients, splinted

implants showed greater crestal bone loss (0Æ2 mm
more) than non-splinted ones. These differences were

statistically significant. They concluded that splinted

implants appeared to favour greater crestal bone loss

(22).

This study compared cemented single versus splinted

configurations. The results showed that in single

unsplinted restorations, significantly (P < 0Æ001) less stress was generated in the implant neck when compared

to splinted restorations (988Æ57 versus 3348Æ54 micro-
strain). For each single restoration, there is inherent

inaccuracies because of component misfit (crown ⁄ abut-
ment and abutment ⁄ implant) resulting in preload
stresses. When several adjacent implant restored crowns

are joined, there is a summation of these misfit inaccu-

racies, and significantly increased moments because of

splinting, resulting in transfer of increased loads to the

implants and supporting structures (6). This can also

explain the disparity of microstrain values on implant

necks exhibited between the implants.

In contrast, significantly (P < 0Æ001) more strain was recorded on the strain gauges located on the restoration

margins of the single crowns when compared with

splinted restorations (756Æ32 versus 186Æ12 micro-
strain). Therefore, cemented splinted restorations

exhibited better load sharing than non-splinted stora-

tions, however, they transferred more forces towards

the implant neck because of bending moments.

In addition, in this study, implants were loaded in a

vertical inclination, while in the clinical setup, non-

axial loads are also generated. Moreover, occlusal

contacts are most often lateral (lateral function and

parafunction, and asymmetric contraction of the jaw

closing muscles combine). As a result, non-axial

loading is generally the rule. These factors will all

combine to greatly increase the bending moments

observed in this study. Consequently, additional

moments yield significantly higher strain values in

the implant neck and restorations than seen in the

study.

The present discusses axial loading of splinted and

unsplinted implant-supported restorations. Future

studies should asses whether same results will be still

obtained following non-axial loading.

Within the limitations of this experimental model,

the following conclusions may be drawn:

1 Single unsplinted restorations transfer significantly

less load to the implants and supporting structure

than splinted restorations.

2 Splinted restorations transfer significantly less load to

the crown margins than unsplinted restorations.

3 The concept of splinting adjacent implants to decrease

loading of the supporting structures may require

re-evaluation.

4 The clinical relevance needs to be investigated with

controlled long-term clinical studies.

L O A D T R A N S F E R A N D S T R E S S B Y S P L I N T I N G A N D U N S P L I N T I N G 661

ª 2010 Blackwell Publishing Ltd

References

1. Skalak R. Biomechanical consideration un osseointegrated

prothesis. J Prosthet Dent. 1983;49:843–848.

2. Isidor F. Loss of osseointegration caused by occlusal load of

oral implants. A clinical and radiographical study in monkeys.

Clin Oral Implants Res. 1996;7:143–152.

3. Leung KC, Chow TW, Wat PY, Comfort MB. Peri-implant

bone loss: management of a patient. Int J Oral Maxillofac

Implants. 2001;16:273–277.

4. Isidor F. Influence of forces on peri-implant bone. Clin Oral

Implants Res. 2006;17:8–18.

5. Serio FG. Clinical rationale for tooth stabilization and splint-

ing. Dent Clin North Am. 1999;43:1–6.

6. Brunski JB, Puleo DA, Nanci A. Biomaterials and biomechan-

ics of oral and maxillofacial implants : current status and

future developments. Int J Oral Maxillofac implants.

2000;15:15–46.

7. Grossmann Y, Finger IM, Block MS. Indications for splinting

implant restorations. J Oral Maxillofac Surg. 2005;63:

1642–1652.

8. Gross M, Laufer BZ. Splinting osseointegrated implants and

natural teeth in rehabilitation of partially edentulous patients.

Part I: laboratory and clinical studies. J Oral Rehabil.

1997;24:863–870.

9. Glantz PO, Rangert B, Svensson A, Stafford GD, Arnvidarson

B, Randow K et al. On clinical loading of osseointegrated

implants. A methodological and clinical study. Clin Oral

Implants Res. 1993;4:99–105.

10. Bender MF. Unsplinted crowns on implants in subantral

augmented region: an evolution. J Oral Implantol. 1995;

2:121–131.

11. Lindh T, Gunne J, Tillberg A, Molin M. A meta-analysis of

implants in partial edentulism. Clin Oral Implants Res.

1998;9:80–90.

12. Naert I, Koutsikakis G, Duyck J, Quirynen M, Jacobs R, van

Steenberghe D. Biologic outcome of implant-supported resto-

rations in the treatment of partial edentulism. part I: a

longitudinal clinical evaluation. Clin Oral Implants Res.

2002;13:381–389.

13. Simon RL. Single implant-supported molar and premolar

crowns: a ten-year retrospective clinical report. J Prosthet

Dent. 2003;90:517–521.

14. Weber HP, Sukotjo C. Does the type of implant prosthesis

affect outcomes in the partially edentulous patient? Int J Oral

Maxillofac Implants. 2007;22(Suppl):140–172.

15. Blanes RJ, Bernard JP, Blanes ZM, Belser UC. A 10-year

prospective study of ITI dental implants placed in the posterior

region. II: influence of the crown-to-implant ratio and

different prosthetic treatment modalities on crestal bone loss.

Clin Oral Implants Res. 2007;18:707–714.

16. Van Staden RC, Guan H, Loo YC. Application of the finite

element method in dental implant research. Comput Methods

Biomech Biomed Engin. 2006;9:257–270.

17. Nissan J, Gross M, Shifman A, Assif D. Stress levels for well-

fitting implant superstructures as a function of tightening

force levels, tightening sequence, and different operators.

J Prosthet Dent. 2001;86:20–23.

18. Kim Y, Oh TJ, Misch CE, Wang HL. Occlusal considerations in

implant therapy: clinical guidelines with biomechanical ratio-

nale. Clin Oral Implants Res. 2005;16:26–35.

19. Faucher RR, Bryant RA. Bilateral fixed splints. Int J Perio Rest

Dent. 1983;3:8–37.

20. Guichet DL, Yoshinobu D, Caputo AL. Effect of splinting and

interproximal contact tightness on load transfer by implant

restorations. J Prosthet Dent. 2002;87:528–535.

21. Kim WD, Jacobson Z, Nathanson D. In vitro stress analyses of

dental implants supporting screw-retained and cement-

retained prostheses. Implant Dent. 1999;8:141–150.

22. Rokni S, Todescan R, Watson P, Pharoah M, Adegbembo AO,

Deporter D. An assessment of crown-to-root ratios with short

sintered porous-surfaced implants supporting prostheses in

partially edentulous patients. Int J Oral Maxillofac Implants.

2005;20:69–76.

Correspondence: Dr Joseph Nissan, Department of Oral Rehabilitation,

School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel.

E-mail: nissandr@post.tau.ac.il

J . N I S S A N et al.662

ª 2010 Blackwell Publishing Ltd

This document is a scanned copy of a printed document. No warranty is given about the accuracy of the copy.

Users should refer to the original published version of the material.

Journal of Oral Rehabilitation 1999 26; 195 – 202

A 5-year prospective randomized clinical trial on the
influence of splinted and unsplinted oral implants
retaining a mandibular overdenture: prosthetic aspects and
patient satisfaction
I . N A E R T *, S . G I Z A N I *, M . V U Y L S T E K E† & D . V A N S T E E N B E R G H E‡ *Department of Prosthetic
Dentistry, School of Dentistry, Oral Pathology and Maxillofacial Surgery, Faculty of Medicine, Catholic University Leuven; †Department of

Statistics, Computing Centre, Catholic University Leuven; and ‡Department of Periodontology, School of Dentistry, Oral Pathology and

Maxillofacial Surgery, Faculty of Medicine, Catholic University Leuven, Leuven, Belgium

SUMMARY Prosthetic outcome and patient satisfac- After 5 years of observation, the Bar group pre-

sented the highest retention capacity and the leasttion were evaluated in order to investigate

prosthetic complications but revealed more mu-whether there is a need or advantage to splint two

cositis and gingival hyperplasia. Patient satisfac-implants in the mandible retaining a hinging over-

denture. This study included 36 fully edentulous tion rated similar for all groups although the

Magnet group showed lower retention force

s.

Allpatients randomly divided into three groups ac-

cording to the attachment system they received: patients would repeat the same treatment even

though the majority of the Magnet group wouldmagnets, ball attachments or straight bars (refer-

ence group). None of the implants failed during prefer a more retentive solution because of limited

denture stability.the whole observation period in any of the groups

.

Introduction

Full edentulism can substantially affect oral and gen-

eral health as well as overall quality of life (Gift &

Redford, 1992; Marcus et al., 1996).

Patient satisfaction with dentures is influenced by

various factors including denture quality, the available

denture bearing area, the quality of dentist – patient

interaction, previous experience with dentures, pa-

tient’s personality and psychologic well-being (Boer-

rigter et al., 1995).

Replacing the lost tissues by means of complete den-

tures is challenging both for the dentist and the patient

(Zarb, 1982; Davis, 1990). Nevertheless, some people

do not succeed in acquiring new skills with their den-

tures and thus suffer psychologically because of im-

paired function, comfort, self-image and social

interaction.

Because of the good prognoses of some endosseous

implant systems, these patients can be successfully

treated with implant-retained overdentures. Several

studies reported the clear benefits of overdenture treat-

ment, versus the conventional denture for a number of

aspects such as: aesthetics, speech, chewing, fit and

retention, function and quality of life (Burns et al.,

1994; Cune, Putter & Hoogstraten, 1994; de Grand-

mont et al., 1994). The impact on these aspects of

different attachment systems retaining the overden-

tures is lacking so far.

Therefore, a 5-year randomized clinical trial was set

up to investigate the prosthetic outcome and patient

satisfaction with mandibular hinging overdentures on

different attachment systems. The peri-implant out-

come is discussed in a separate paper (Naert et al.,

1998).

© 1999 Blackwell Science Ltd 195

196 I . N A E R T et al.

Fig. 1. The three different attachment systems used for each group: a, Bar group; b, Magnet group; c, Ball group.

Materials and methods

This study included 36 completely edentulous patients

(19 women and 17 men) with a mean age 63·7 years

(range 36 – 85). All of them were edentulous for at least

more than 1 year and all complained about their exist-

ing lower dentures. The exclusion criteria were the

following: insufficient bone volume to harbour at least

two 10 mm implants, Angle class II jaw relationship,

psychological problems for accepting a removable den-

ture, gagging reflexes, less than 1 year of edentulism in

the mandible, absence of a maxillary complete denture

and administrative or physical considerations that

would seriously affect the surgical procedure or consti-

tute a hindrance for a 5-year follow-up.

At the beginning of the treatment the medical status

as well as the dental history of each patient were

recorded. The initial examination also included the

evaluation of the existing dentures, the estimation of

dysfunctional problems and a questionnaire concern-

ing the patient satisfaction of the original denture.

Each patient was provided with two screw shaped

c.p. titanium implants (Brånemark system®*) in the

symphyseal area of the mandible, approximately in the

canine region with a connecting line paralleling the

terminal mandibular hinge axis (Naert et al., 1988).

After 3 – 5 months transmucosal standard Brånemark®

abutments were installed.

A randomization scheme divided the 36 patients into

three groups of equal size according to the retention

system (Fig. 1). In the first group (Bar group), which is

the reference group, the attachment system was an

egg-shaped Dolder bar with continuous clip† splinting

* Nobel Biocare AB, Gothenburg, Sweden.
† Cendres et Metaux SA, Biel, Switzerland.

© 1999 Blackwell Science Ltd, Journal of Oral Rehabilitation 26; 195 – 202

I N F L U E N C E O F S P L I N T E D A N D U N S P L I N T E D O R A L I M P L A N T S 197

Table 1. Summary of the questionnaire split up in three parts:
in the first part patients gave their answers on a ordered scale

ranging from 1 (very bad) to 9 (excellent), the second part

includes questions that had to be answered with just yes/no
response and in the third part a more descriptive answer was

requested

First part
A. How do you find your new prosthesis in general?
B. How well does your new prosthesis remain in place?
C. How well can you eat with your new prosthesis?
D. How well can you talk with your new prosthesis?
E. How do you find the appearance of your prosthesis?

Second part
F. Do you avoid contact with other people because of fear

loosing your prosthesis?
G. Does your new prosthesis bother your mind?
H. Does food impaction regularly occur under your prosthesis?
I. Does your expectations became real with your new

prosthesis?
J. Would you repeat the same treatment?

Third part
K. How many times do you take out your prosthesis because

of discomfort?
L. If you should repeat the treatment, would you choose: (1

)

the same solution or (2) fixed prosthesis?

Table 2. Variables that might interfere with an equal balance
for the three treatment groups*

Ball groupMagnet groupBar group

Age (years) 6465 6

1

5/75/77/5Gender (men/

women)
Period of edentulism 15 11·514·8

(years)
Bone height in ca- 24·9 25·923·8

nine region (mm)
Bone quality†

8 pat.Class 2 4 pat.5 pat.
Class 3 7 pat. 8 pat. 4 pat.

Bone quantity†

Class A 1 pat. 0 pat. 0 pat.
Class B 2 pat. 3 pat. 3 pat.

7 pat.Class C 7 pat. 6 pat.
3 pat. 2 pat.2 pat.Class D

pat., patients.

* There was not any statistical difference for the variables tested

between the three groups (P\0·05).
† According to Lekholm & Zarb (1985).

just a ‘yes/no’ response and a third part of the question-
naire demanded a more descriptive answer. Table 1

summarizes the three parts of the questionnaire. Finally,

the temporomandibular joints and masticatory muscles

function was assessed according to an anamnestic and

clinical dysfunction index (Helkimo, 1979).

Statistical analysis

Differences in patient satisfaction per group at the fifth

year, as well as the variation in patient satisfaction over

time were analysed by a non-parametric Kruskal – Wallis

ANOVA test.

Both the objective and the subjective retention of

the overdenture for the whole group was analysed by a

non-parametric Spearman correlation analysis.

both implants. In the second group (Magnet group) two

open-field magnets‡ and in the third group (Ball group),

two ball attachments (SDCB 115-17*) were used. The

occlusion, laterotrusion and protrusion were assessed on

the articulator and intraorally to secure a balanced

occlusion in centric relation without anterior tooth

contact.

Patients were scheduled for follow-up visits at 1 week

post-prosthesis insertion and 4, 6, 12, 24, 36, 48 and

60 months post-abutment installation.

The retention of the overdenture was measured by

means of a dynamometer§ with a maximum capacity of

20 N and the mean of three repeated measurements was

calculated (Naert et al., 1990). The mechanical complica-

tions of the attachment components were recorded as

well as the soft-tissue complications of the denture

bearing area (mucositis, soreness, ulcer decubitus and

hyperplasia) for the whole observation period.

Patient satisfaction was investigated through a ques-

tionnaire. A part of this questionnaire included ques-

tions in which patients gave their answers on a ordered

scale ranging from 1 (very bad) to 9 (excellent). A second

part included questions that had to be answered with

Table 3. Mean retention force (gram, mean of three repeated
measurements) of the overdentures measured by means of a

dynamometer at the baseline (prosthesis installation), the first

and the fifth year and the total decrease over time between

baseline and fifth year per group

Ball groupMagnet groupBar group

370 655Baseline 1677
Force 1st year 1855 362 73

0

5671101240Force 5th year

Total decrease −437 −260 −88
‡ Dyna Engineering BV, Bergen op Zoom, The Netherlands.
§ Correx, Bern, Switzerland.

© 1999 Blackwell Science Ltd, Journal of Oral Rehabilitation 26; 195 – 202

198 I . N A E R T et al.

Table 4. Frequency distribution of the number of prosthetic
complications for the 5-year observation period per group

Bar group Magnet group Ball group

Retention element
21 123Wear
21 0Corrosion –
1 11Fracture 0

25100Loosening of abut-
ment screw

3 2 –Loosening of gold
screw

– –Activation of clip 12
2 –Change of clip –

– – 13Exchange of rubber
ring

Exchange of O-box – – 16
53 –Exchange of magnet –

1 3Rebasing 4
0 1 0Remounting

00New denture made 1

one changed address and could not be traced at the

end of the third year follow-up, while from the Ball

group one patient was not able to be present at the

last two control-visits because of severe medical rea-

sons. Finally, from the Magnet group one patient did

not show up at the last control because she was un-

satisfied with the treatment.

When analysing the withdrawn patients regarding

baseline data, such as: age, gender, period of eden-

tulism, bone quality and quantity these did not re-

veal any detectable differences from those followed.

Implant failures

Only one implant failed at the time of abutment

surgery. It was replaced at the same position by an-

other implant without further complications. No im-

plant failed in any of the groups after loading during

the 5-year observation period.

Prosthetic outcome

At year 5, the highest retention of overdentures was

measured in the Bar group (1240 g, range 0 – 2000 g)

and the lowest for the Magnet group (110 g, range

0 – 456 g) (Table 3). Comparing the retention forces

between the baseline (prosthesis installation) and

year 5, a decrease of retention took place over time

for all groups. The steepest decrease of the retention

force over time was observed in the Bar group

(437 g), the least in the Ball group (88 g).

The Magnet and Ball group presented the highest

incidence of prosthetic complications when compared

to the reference group. For example in the Magnet

group frequent renewal of magnets because of wear

and corrosion and in the Ball group frequent tighten-

ing of the abutment screws, besides renewal of the

The level of significance was set at 0·05 unless oth-

erwise stated.

Results

Due to the randomization scheme factors that could

influence the balancing criteria were found not to be

statistically different between the three groups (Table

2).

Patients drop -out

All except five patients were followed during the

whole observation period. From the Bar group two

patients died after 2 years of follow-up and another

Table 5. Frequency distribution of the number of
times that denture supporting mucosa
complications occurred and the number of patients
to whom it occurred during the follow-up visits
per group

Bar group Magnet group Ball group

Times Patients Times Patients Times Patients

3Mucositis 322512
000 023Soreness

Ulcer decubitus 6 3 12 4 8 6
33347Hyperplasia 9

© 1999 Blackwell Science Ltd, Journal of Oral Rehabilitation 26; 195 – 202

I N F L U E N C E O F S P L I N T E D A N D U N S P L I N T E D O R A L I M P L A N T S 199

Magnet group Ball groupBar group

Mean (s.d.) Sum of the ranks Mean (s.d.)Mean (s.d.) Sum of the ranksSum of the ranks

A. How do you find your new prosthesis in general?
105·5000 7·4 (1·8)8·7 (0·4) 133·5000 6·6 (2·2) 139·0000

B. How well does your new prosthesis remain in place?
8·9 (0·3)6·3 (2·4) 185·500092·5000*8·0 (1·5) 100·0000

C. How well can you eat with your new prosthesis?
8·5 (0·8) 167·00008·7 (0·4) 122·0000 6·4 (2·2) 89·0000*

D. How well can you talk with your new prosthesis?
7·3 (1·4) 179·50008·6 (0·9)105·00007·8 (1·4) 93·5000

E. How do you find the appearance of your new prosthesis?
137·00007·7 (0·6)136·00007·7 (1·7)8·2 (0·7) 105·0000

* Statistically different at the 5% level from the other groups.

Table 6. Mean (s.d.) and
sum of the ranks from
questions answered on an
ordered scale ranging from
1 (very bad) to 9
(excellent) per group at
year 5

O-rings and the O-ring-boxes were mostly needed.

The most common complication for the Bar group

was the reactivation of the overdenture clips (Table

4).

One denture was remade (Bar group) at the pa-

tient’s request to have a brighter colour of teeth.

Eight dentures had to be relined: one, three and four

in the Bar, Magnet and Ball group, respectively

(Table 4).

Mucositis and hyperplasia more often occurred in

the Bar group, while ulcer decubitus was observed

more often in the Magnet and Ball groups (Table 5).

Patient satisfaction

Patient satisfaction at year 5 derived from questions

concerning general satisfaction, phonetics and aes-

thetics was similar in all groups. On the other hand,

questions related to prosthesis stability and chewing

comfort scored significantly lower in the Magnet

group (P = 0·05) (Table 6).
Patient satisfaction for chewing comfort, phonetics

and aesthetics in all groups hardly varied between

baseline and year 5. However, a significant decrease

of the general satisfaction and the denture stability

was noted in the Magnet group (P = 0·03) (Table 7).
Food impaction was revealed to occur regularly in

all groups. Patients in all groups would repeat the

same treatment if they had to start again (Table 8).

All patients were satisfied with their overdenture.

The majority seldom removed the overdenture be-

cause of discomfort. Most of the patients preferred

this treatment to a fixed prosthetic solution, except

for half of the Magnet group (Table 9).

Although instructed, only half of the patients took

out their overdentures during the night.

Only a very weak correlation (r = 0·35, P = 0·07)
was found between the subjective and objective mea-

sured retention forces of the overdenture at year 5

when the whole group was considered.

Finally, at the end of the observation period only

one patient in the Magnet group reported signs and

symptoms of TMJ-dysfunction, while at the begin-

ning of the study nine patients presented anamnestic

or clinical dysfunction.

Discussion

Five patients could not assist the whole follow-up

scheme, which is not surprising, considering the

rather aged study population.

Although this study was set up to investigate the

prosthetic outcome of splinted and unsplinted oral

implants retaining mandibular hinging overdentures,

the implant outcome was included for completeness.

As shown for the bar-retained hinging overdentures

(Naert et al., 1997b) which is a reliable treatment,

unsplinted implants retaining an overdenture seem to

do as well (Naert et al., 1998).

© 1999 Blackwell Science Ltd, Journal of Oral Rehabilitation 26; 195 – 202

200 I . N A E R T et al.

The Bar group provides the highest retention force

while magnets the lowest. This is in agreement with

our results at 3-years (Naert et al., 1997a) with previ-

ous reports (Burns et al., 1994; Naert et al., 1994;

Hooghe & Naert, 1997; Petropoulos, Smith & Kousve-

lati, 1997). All three groups presented a decrease of

retention force over time which was more pronounced

in the Bar group. Deactivation of the clip-bar compo-

nents over time can explain this, because reactivation

of the clip only took place on the patient’s request. In

the two other groups the retention elements were

renewed each time the patients complained or when

the components were fractured or showed advanced

wear.

When correlating the subjective with the objective

measured retention force of the overdenture at year 5

for the whole group, only a very weak correlation was

found which is in contrast with the 3-year results,

where a strong correlation was found (Naert et al.,

1997a). This difference may be explained by the fact

that the patients got used to their new overdentures

with time and they did not complain even if the den-

ture retention was not satisfactory.

The Bar group presented the least prosthetic compli-

cations which is in accordance with other studies

(Naert et al., 1994; Hooghe & Naert, 1997). Indeed,

only two clips in the Bar group needed replacement

while in the Magnet and the Ball group 53 magnets

and 29 rubber ring or boxes needed renewal. When

comparing the 3-year (Naert et al., 1997a) with the

5-year results, it becomes apparent that the number of

prosthetic complications in the groups with the un-

splinted implants increased considerably during the last

2 years. This contrasts with the results of Davis, Rogers

& Packer (1996) where the majority of the complica-

tions concentrate during the first year. Our results can

be explained by the keeper’s ageing over time. Indeed,

each time the magnet, the rubber ring and the O-box

had to be renewed, the original keeper was kept in

place. Thus, only the magnet, O-ring or O-ring-box

were changed.

The Bar group patients had more hyperplasia and

mucositis while in the two other groups ulcer decu-

bitus was more frequently observed. A remarkable fact

is that mucositis and ulcer decubitus continued to be

present in the same patients throughout the 5 years,

while hyperplasia was observed in more and more pa-

© 1999 Blackwell Science Ltd, Journal of Oral Rehabilitation 26; 195 – 202

T
a

b
le

7
.

M

e
a
n

(s
.d

.

)
a
n

d
su

m
o

f
th

e
ra

n
k

s
fo

r
th

e
ti

m
e

b
e
tw

e
e
n

b

a
se

li
n

e
(p

ro
st

h

e
si

s
in

st

a
ll

a
ti

o
n

)
a
n

d
y

e
a
r

5
,

fr
o

m
q

u
e
st

io
n

s
a
n

sw

e
re

d
o

n
a
n

o
rd

e
re

d
sc

a
le

ra
n

g
in

g
fr

o
m

1

(v
e
ry

b
a
d

)
to

9
(e

x
ce

ll
e
n

t)
p

e
r

g
ro

u
p

B
a
ll

g
ro
u
p

M
a
g
n

e
t

g
ro
u
p

B
a
r

g
ro
u
p

S
u

m
o
f
th
e
ra
n
k

s
B

a
se
li
n

e
m

e
a
n

5
-y

e
a
r

m
e
a
n

B
a
se

li
n
e
m
e
a
n
B
a
se
li
n
e
m
e
a
n
5
-y
e
a
r
m
e
a
n
S
u
m
o
f
th
e
ra
n
k

s
d

if
fe

r-
S

u
m

o
f

th
e

ra
n

k
s

5
-y
e
a
r
m
e
a
n
(s
.d

.)

e
n

c

e
s

d
if

fe
re

n
ce

s
(s

.d
.)

(s
.d

.)
(s

.d
.)
d
if
fe
re
n
ce
s
(s
.d
.)
(s
.d
.)

A
.

H
o

w
d

o

y
o

u
fi

n
d

y
o

u
r

n
e
w

p
ro

st
h

e
si
s
in

g
e
n

e
ra

l?
1

2
3

·

0
0

0
0

*
7

·9
(1

·8
)

7
·4

(1
·8

)
7

7
·0

0
0

0
8

·3
(0

·5
)

8
·7

(0
·4

)
5

3
·0

0
0

0
7

·3
(1

·1
)

6
·6

(2
·2

)

B
.

H
o

w
w

e
ll

d
o
e
s
y
o
u
r
n
e
w
p
ro
st
h
e
si

s
re

m
a
in

in
p

la
ce

?
8

·0
(0

·3
)

6
·3

(2
·4

)
1

2
3

·0
0

0
0

*
8

·2
(1

·4
)

8
·9

(0
·3

)
7
7
·0
0
0
0
8

·6
(0

·5
)

8
·0

(

1
·5

)
5
3
·0
0
0
0

C
.

H
o
w
w
e
ll

ca
n

y
o

u
e
a
t

w
it

h
y
o

u
r
n
e
w
p
ro
st
h
e
si

s?
1

0
8
·0
0
0
0

8
·4

(0
·9

)
8

·5
(0

·8
)

8
·6

(0
·5

)
1

0
2

·0
0
0
0
8
·7
(0
·4

)
4

2
·0

0
0
0
7

·8
(1

·2
)

6
·4

(2
·2
)

D
.

H
o
w
w
e
ll
ca
n
y
o

u
ta

lk
w

it
h

y
o
u
r
n
e
w
p
ro
st
h
e
si

s?
8

·6
(0
·5
)

7
·8

(1
·4

)
5
1
·5
0
0
0
8
·5
(0
·5
)

7
·3

(1
·4
)
1

1
2

·0
0
0
0

8
·5

(0
·5
)
8
·6
(0

·9
)

1
7

9
·5

0
0
0

E
.

H
o
w
d

o
y
o

u
fi
n
d
th
e

a
p

p
e
a
ra

n
ce
o
f
y
o
u
r
n
e
w
p
ro
st
h
e
si

s?
’’

8
·5
(0
·5
)
8

·2
(0

·7
)

4
1

·0
0
0
0
8
·5

(0
·7

)
7

·7
(1

·7
)

1
0

5
·0

0
0

0
6

·7
(3

·3
)

7
·7

(0
·6

)
8
5
·0
0
0
0

*
S

ta
ti

st
ic

a
ll

y
d

if
fe

re
n

t
a
t

th
e

5
%

le
v
e
l

fr
o

m
th

e
o

th
e
r

g
ro
u
p
s.

I N F L U E N C E O F S P L I N T E D A N D U N S P L I N T E D O R A L I M P L A N T S 201

Table 8. Positive answers to the second part of the question-
naire per group at the first and at the last year of the follow-up

period with the new overdentures

Ball groupMagnet groupBar group

1st year 5th year 1st year1st year 5th year5th year

F. Do you avoid contact with other people because of fear loosing
your prosthesis?

0/12 2/11 0/121/12 0/110/9

G. Does your new prosthesis bother your mind?
0/12 1/11 0/124/12 0/111/9

H. Does food impaction regularly occur under your prosthesis?
9/12 10/11 8/12 6/117/12 5/9

I. Did your expectations became real with your new prosthesis?
5/11 12/1211/12 9/9 9/1110/12

J. Would you repeat the same treatment?
11/11 10/1112/1211/1212/12 8/9

All patients would prefer the same treatment, if they

had to choose again even though the Magnet group’s

expectations did not became real. This can be ex-

plained by the dramatic improvement when compared

to the previous unretained full dentures (see Naert et

al., 1997a). The impaired denture retention in the

Magnet group, lead those patients to prefer a more

fixed solution, even if they did not consider overden-

ture therapy as a second-class treatment.

Conclusions

(1) The Bar group presented the highest retention

capacity of the overdenture over time. The retention

capacity of the Ball group remained more stable over

time.

(2) The Bar group presented the least prosthetic com-

plications.

(3) The groups with the unsplinted implants presented

more prosthetic complications in the last 2 years of the

study probably because of the ageing of the male reten-

tion elements.

(4) The Bar group revealed more mucositis and gingi-

val hyperplasia while in the unsplinted groups more

decubitus ulcers were observed. The incidence of hy-

perplasia increased for all groups over time indepen-
dently of the retention device.

(5) General patient satisfaction rated similar for all

groups but the Magnet group scored lower for the

specific question related to retention and chewing

comfort.

(6) Most of the patients would seek the same kind of

treatment, although in the Magnet group more pa-

tients would prefer a more fixed solution.

tients over time. This applies to all three treatment

groups. However, the plaque index as well as the

bleeding index at year 5 did not significantly differ with

the outcome at year 1 (Naert et al., 1998).

Although half of the patients did not remove their

dentures, the distribution was equal for the three

groups. This underlines the psycho-social impact of

edentulism.

When considering general patient satisfaction no sig-

nificant differences appeared between splinted and un-

splinted implants. However, when specific questions
were addressed such as for retention and chewing
comfort, magnets scored lower at year 5.

Bar group Magnet group Ball group

5th year 1st year 5th year5th year 1st year1st year

K. How many times do you take out your prosthesis because of discomfort?
9/12�never 5/9�never 10/12�never 9/11�never 12/12�never 10/11�never
2/12�1/day 2/9�1/day

1/11�B5/day2/11�B5/day2/12�B5/day2/9�B5/day1/12�B5/day

L. If you should repeat the treatment, would you choose: (1) the same solution or (2)
fixed prosthesis?
11/12�same 7/9�same 9/12�same 6/11�same 10/12�same 11/11�same
1/12�fixed 2/9�fixed 5/11�fixed3/12�fixed 2/12�fixed

Table 9. Answers to the third part of
the questionnaire per group at the first
and at the last year of the follow-up
period with the new overdentures

© 1999 Blackwell Science Ltd, Journal of Oral Rehabilitation 26; 195 – 202

202 I . N A E R T et al.

References

BOERRIGTER, E., GEERTMAN, M., VAN OORT, R., BOUMA, J., RAGHOE-

BAR, G., VAN WAAS, M., VAN’T HOF, M., BOERING, G. & KALK, W.

(1995) Patient satisfaction with implant-retained mandibular

overdentures. A comparison with new complete dentures not

retained by implants: a multicentre randomised clinical trial.

British Journal of Oral and Maxillofacial Surgery, 33, 282 – 288.
BURNS, D., UNGER, J., ELSWICK, R. & GIGLIO, J. (1994) Prospective

clinical evaluation of mandibular implant overdentures: Part

II — patient satisfaction and preference. Journal of Prosthetic

Dentistry, 73, 364 – 369.
CUNE, M., PUTTER, C. & HOOGSTRATEN, J. (1994) Treatment out-

come with implant-retained overdentures: I — Clinical finding

and predictability of clinical treatment outcome. Journal of

Prosthetic Dentistry, 72,

144 – 151.

DAVIS, D. (1990) The role of implants in the treatment of edentu-

lous patients. International Journal of Prosthodontics, 3, 42 – 50.
DAVIS, D., ROGERS, J. & PACKER, M. (1996) The extent of mainte-

nance required by implant-retained mandibular overdentures.

The International Journal of Oral and Maxillofacial Implants, 11,
767 – 774.

DE GRANDMONT, P., FEINE, J.S., TACHÉ, R., BOUDRIAS, P., DONOHUE,

W.B., TANGUAY, R. & LUND, J.P. (1994) Within-subject compari-

sons of implant-supported mandibular prostheses: Psychometric

evaluation. Journal of Dental Research, 73 (5), 1096 – 1104.
GIFT, H. & REDFORD, M. (1992) Oral health and the quality of life.

Clinical Geriatric Medicine, 27, 120 – 132.
HELKIMO, M. (1979) Epidemiological surveys of dysfunction of the

masticatory system. In: Temporomandibular Joint. Function and

Dysfunction (eds G.A. Zarb & G.E. Carlsson), 175. Munksgaard,

Copenhagen.

HOOGHE, M. & NAERT, I. (1997) Implant supported overdentures —

the Leuven experience. Journal of Dentistry, 25, 25 – 35.
LEKHOLM, U. & ZARB, G.A. (1985) Patient selection and prepara-

tion. In: Osseointegration in Clinical Dentistry (eds P.-I. Brånemark,

G.A. Zarb & T. Albreksson), pp. 199 – 209. Quintessence Publis-

ing Co. Inc., Chicago.

MARCUS, P., JOSHI, A., JONES, J. & MORGANO, S. (1996) Complete

edentulism and denture use for elders in New England. Journal

of Prosthetic Dentistry, 76, 260 – 266.

NAERT, I., DE CLERCQ, M., THEUNIERS, G. & SCHEPERS, E. (1988)

Overdentures supported by osseointegrated fixtures for the

edentulous mandible: A 2,5 year report. The International Journal

of Oral and Maxillofacial Implants, 3, 191 – 196.

NAERT, I., GIZANI, S., VUYLSTEKE, M. & VAN STEENBERGHE, D.

(1997a) A randomised clinical trial on the influence of splinted

and unsplinted oral implants in the mandibular overdenture

therapy. Clinical Oral Investigations, 1, 81 – 88.

NAERT, I., GIZANI, S., VUYLSTEKE, M. & VAN STEENBERGHE, D. (1998)

A 5-year randomised clinical trial on the influence of splinted

and unsplinted oral implants in the mandibular overdenture

therapy. Part I: peri-implant outcome. Clinical Oral Implant

Research, 9, 170 – 177.

NAERT, I., HOOGHE, M., QUIRYNEN, M. & VAN STEENBERGHE, D.

(1997b) The reliability of implant retained hinging overdentures

for the fully edentulous mandible. An up to 9-year longitudinal

study. Clinical Oral Investigations, 1, 119 – 124.

NAERT, I., QUIRYNEN, M., HOOGHE, M. & VAN STEENBERGHE, D.

(1994) A comparative prospective study of splinted and un-

splinted Brånemark implants in mandibular overdenture ther-

apy: A preliminary report. Journal of Prosthetic Dentistry, 72,

144 – 151.

NAERT, I., QUIRYNEN, M., VAN STEENBERGHE, D. & DARIUS, P. (1990)

A comparative study between Brånemark and IMZ implants

supporting overdentures: prosthetic considerations. In: Tissue

Integration in Oral Orthopaedic and Maxillofacial Reconstruction (eds

W.R. Laney & D.E. Tolman), pp. 179 – 193. Quintessence Pub-

lishing Co. Inc., Chicago.

PETROPOULOS, V., SMITH, W. & KOUSVELATI, E. (1997) Comparison

of retention and release periods for implants overdenture at-

tachments. The International Journal of Oral and Maxillofacial

Implants, 12, 176 – 185.

ZARB, G. (1982) Oral motor patterns and their relation to oral

prostheses. Journal of Prosthetic Dentistry, 47, 472 – 478.

Correspondence: Professor I. E. Naert, Department of Prosthetic

Dentistry, School of Dentistry, Oral Pathology and Maxillofacial

Surgery, Kapucijnenvoer 7, B-3000 Leuven, Belgium. E-mail:

ignace.naert@med.kuleuven.ac.be

.
© 1999 Blackwell Science Ltd, Journal of Oral Rehabilitation 26; 195 – 202

This document is a scanned copy of a printed document. No warranty is given about the
accuracy of the copy. Users should refer to the original published version of the material.

T
a
s
r
r

a
m
a

p

c

J Oral Maxillofac Surg
69:2990-2994, 201

1

The Effect of Splinting Implant-Supporte

d

Restorations on Stress Distribution of
Different Crown-Implant Ratios and

Crown Height Spaces
Joseph Nissan, DMD,* Ora Gross, DMD,† Oded Ghelfan, DMD,‡

Ilan Priel, DMD,§ Martin Gross, BDS, LDS, MSc,� and
Gavriel Chaushu, DMD, MSc¶

Purpose: To assess whether splinting can counterbalance the detrimental effects of varying the
crown-to-implant (C/I) ratio and crown height space (CHS) by decreasing nonaxial overload stresses.

Materials and Methods: Three implants were inserted into a photoelastic block model. Two strain
gauges were cemented onto the neck of each implant on the buccal and lingual aspects and provided a
simultaneous direct reading of strain. Four groups of splinted cement-retained restorations with C/I ratios
of 1:1, 1:1.5, 1:1.75, and 1:2 were used. CHSs were 10, 15, 17.5, and 20 mm, respectively. Fifteen stati

c

loadings were carried out simultaneously with 20-kg weights via a custom-built loading apparatus at 30°
to the vertical axis.

Results: Occlusal force application at 30° showed a statistically significant increase in both buccal
(1,911.65 � 110 vs 3,252.06 � 150) and palatal (35.58 � 7 vs 286.85 � 15) microstrain values as the C/I
ratio increased from 1:1 to 1:1.5 (P � .001). Force application at 30° in cases with C/I ratios of 1:1.75
and 1:2 resulted in fracture of the abutment screw followed by dislodgement of the crowns. Failures
were noted at a CHS of 15 mm or greater.

Conclusions: In this biomechanical mode, splinting does not prevent prosthetic failure when the CHS
is 15 mm or greater. Vertical bone augmentation is highly recommended in cases with a CHS of 15 mm
or greater.
© 2011 American Association of Oral and Maxillofacial Surgeons

J Oral Maxillofac Surg 69:2990-2994, 2011

a
d
a
c

0

d

he clinical parameters that lead to biomechanically
dvantageous conditions after splinting implants in
pecific clinical situations are unclear.1 The traditional
ationale for splinting teeth was to decrease stresses,
esulting in increased prosthesis stability.2 One clas-

sical clinical indication was increased crown-to-root
ratio.3 However, evidence-based data to support such
n indication are largely missing for teeth and even
ore so for implants.1,4 Increasing the crown length

nd degree of nonaxial load over an implant-sup-
orted prosthesis increases the risk of excessive oc-
lusal overload because of an increased moment

Received from The Maurice and Gabriela Goldschleger School of

Dental Medicine, Tel Aviv University, Tel Aviv, Israel.

*Senior Lecturer, Department of Oral Rehabilitation.

†Instructor, Department of Oral Rehabilitation.

‡Instructor, Department of Oral Rehabilitation.

§Instructor, Department of Oral Rehabilitation.

�Associate Professor, Department of Oral Rehabilitation.

¶Associate Professor, Department of Oral and Maxillofacial Surgery.

2990
Downloaded for Anonymous User (n/a) at Imam Abdulrahman Bin Faisal Univ

For personal use only. No other uses without permission. Copy

rm.5 A related term is crown height space (CHS),
efined as the distance measured from the crest of the
lveolar bone to the plane of occlusion. The biome-
hanics of CHS is related to lever arm mechanics.6

Nonaxial loading creates a significant lateral moment,
which increases proportionally to the increase in
CHS, resulting in stress concentration at the implant
neck.7

Implants are nonmobile; therefore, when nonaxial
forces are applied to an implant, they are concen-
trated at the implant abutment junction and the crest
of the supporting bone.8,9 Overload leads to stress

Address correspondence and reprint requests to Dr Nissan:

Department of Oral Rehabilitation, The Maurice and Gabriela Gold-

schleger School of Dental Medicine, Tel Aviv University, 4, Klackin

St, Tel Aviv, Israel; e-mail: nissandr@post.tau.ac.il

© 2011 American Association of Oral and Maxillofacial Surgeons

278-2391/11/6912-0015$36.00/0

oi:10.1016/j.joms.2011.06.210

ersity from ClinicalKey.com by Elsevier on February 16, 2020.
right ©2020. Elsevier Inc. All rights reserved.

mailto:nissandr@post.tau.ac.il

i
m
l
i
s
m
b
p

s
s
c
a
a
m
p
v
c
M
r
c

w
a
a

(

w
t
w

c

1
s
c
c

s
m
s
1
m
g
r

t
s
p
C
r
s
s

2

L
p
s
s
u

S
t
i
s
w
g

NISSAN ET AL 2991

that may cause mechanical failure of the prosthetic
components and bone microfractures that could lead
to implant loss.10-12 The rationale of splinting in im-
plant dentistry is to minimize stress by increasing the
resistance area over which the load is distributed.13

However, clinical studies are contradictory. Implant
splinting did not significantly improve implant suc-
cess rates for implant-supported fixed partial dentures
(97.1%) compared with single-implant restorations
(94.3%).14 Furthermore, splinting did not have an
effect on crestal bone loss at different crown-to-
implant (C/I) ratios.15

The purpose of this study was to assess whether
splinting can counterbalance the detrimental effects
of varying the C/I ratio and CHS by decreasing non-
axial overload stresses.

Materials and Methods

A photoelastic block model (PLM-4B; Vishay Measure-
ment Group, Raleigh, NC) with a modulus of elasticity
of 450 kilopounds per square inch (range of human
bone) was constructed. The model dimensions were
15.8 � 35.2 � 32 mm.

Three holes were drilled vertically in a straight line
n the mid axis of the photoelastic model at predeter-

ined locations to lengths of 12 mm. Implants were
ocated 7.8 mm from the edge of the model and each
mplant separated by 4 mm. Three external hex,
crew-type titanium implants with a diameter of 3.8
m and length of 12 mm (Nobel Biocare, Gothen-

urg, Sweden) were inserted into the model. Implants
rotruded 2 mm from the superior surface.
Two strain gauges (EA-06-015EH-120; Vishay Mea-

urement Group) were cemented (M-Bond 200; Vi-
hay Measurement Group) horizontally onto the ma-
hined neck of each implant on the buccal and lingual
spects at a 180° inclination to each other before
butment and crown placement. These strain gauges
easured the bending components (tension/com-
ression) created from both vertical and horizontal
ectors arising from applied forces. Strain gauges were
onnected to a strain indicator (System 5000; Vishay
easurement Group) that provided a simultaneous di-

ect reading of strain in microstrain units of all model
omponents for each loading session (Fig 1).
Impressions were taken by the open-tray technique
ith acrylic splinted transfer copings (Duralay; Reli-

nce Dental Mfg Co, Worth, IL) by use of custom
crylic trays. Polyether impression material was used
Impregum F; ESPE, Seefeld, Germany). A master
orking model was fabricated, and all the restora-

ions were fabricated on attached fixed abutments
ith 2 mm of gingival height.
Four groups of restorations were cast in Remanium

obalt-chromium-molybdenum Model Casting Al-

Downloaded for Anonymous User (n/a) at Imam Abdulrahman Bin Faisal Univ
For personal use only. No other uses without permission. Copy

loy-GM 380 (Dentaurum, Ispringen, Germany) (Fig 2):
) 3 splinted crowns with a C/I ratio of 1:1, 2) 3
plinted crowns with a C/I ratio of 1:1.5, 3) 3 splinted
rowns with a C/I ratio of 1:1.75, and 4) 3 splinted
rowns with a C/I ratio of 1:2.
All the restorations were fabricated with the occlu-

al anatomy of the upper first molars with the same
esiodistal and buccolingual dimensions by use of a

ilicone index. Occlusocervical dimensions were 6,
1, 13.5, and 16 mm in length to compensate for 2
m of the implant neck and 2 mm of the abutment

ingival height. CHSs were 10, 15, 17.5, and 20 mm,
espectively.

Cement-retained abutments were placed at a con-
rolled torque of 35 N-cm. During each loading ses-
ion, the restorations were cemented onto the im-
lant abutments with TempBond NE (Kerr, Orange,
A). Cementation with provisional cement to allow

etrievability is indicated because of abutments of
ufficient height and acceptable retention. Fifteen
tatic loadings were carried out simultaneously with
0-kg weights via a custom-built loading apparatus.
oad was applied simultaneously through 3 individual
ins to the inner inclines of the buccal cusps of each
et of restorations at 30° to the vertical axis (Fig 3) to
imulate the mean off-axis interval in the clinical sit-
ation.
For each loading, strain gauge recordings were made.

train gauges measure electrical resistance. During ex-
ension or contraction, the strain gauge records changes
n electrical resistance. The degree of distortion of the
train gauge is recorded in calculated microstrain values,
here strain � € � �L (change in length of strain

auge)/L (in micrometers per meter) � �R (change in

FIGURE 1. Master model with strain gauges connected to cervical
part of implant. (Reprinted from Nissan J, Ghelfan O, Gross O, et
al: The effect of crown/implant ratio and crown height space on
stress distribution in unsplinted implant supporting restorations.
J Oral Maxillofac Surg 69:1934, 2011.)

Nissan et al. Splinting and Stress Distribution. J Oral Maxillofac

Surg 2011.

electrical resistance in strain gauge)/R.

ersity from ClinicalKey.com by Elsevier on February 16, 2020.
right ©2020. Elsevier Inc. All rights reserved.

(

Surg 2

2992 SPLINTING AND STRESS DISTRIBUTION

STATISTICAL ANALYSIS

Descriptive analysis consisted of mean and standard
deviation of microstrain values for each group. Groups
were compared by use of 1-way parametric analysis of
variance. P � .05 was considered statistically significant.

FIGURE 2. The 4 groups of restorations with different C/I ratios
(Reprinted from Nissan J, Ghelfan O, Gross O, et al: The effect
unsplinted implant supporting restorations. J Oral Maxillofac Surg

Nissan et al. Splinting and Stress Distribution. J Oral Maxillofac

FIGURE 3. Loading apparatus with 3 individual pins oriented to
inner inclines of buccal cusps. (Reprinted from Nissan J, Ghelfan O,
Gross O, et al: The effect of crown/implant ratio and crown height
space on stress distribution in unsplinted implant supporting resto-
rations. J Oral Maxillofac Surg 69:1934, 2011.)

Nissan et al. Splinting and Stress Distribution. J Oral Maxillofac
Surg 2

011.

Downloaded for Anonymous User (n/a) at Imam Abdulrahman Bin Faisal Univ
For personal use only. No other uses without permission. Copy

Results

Occlusal force application at 30°, in implant-sup-
ported splinted restorations with different C/I ratios,
showed a statistically significant increase in both buc-
cal (1,911.65 � 110 vs 3,252.06 � 150) and palatal
35.58 � 7 vs 286.85 � 15) microstrain values as the

C/I ratio increased from 1:1 to 1:1.5 (P � .001). Force
application at 30° in cases with C/I ratios of 1:1.75
and 1:2 resulted in fracture of the abutment screw
followed by dislodgement of the crowns. The CHS
ranged from 10 to 20 mm. Failures were noted at a
CHS of 15 mm or greater when force application was
at 30° (Table 1).

:1.5, 1:1.75, and 1:2) and CHSs (10, 15, 17.5, and 20 mm).
n/implant ratio and crown height space on stress distribution in
34, 2011.)

011.

Table 1. MICROSTRAIN VALUES FOR EACH GROUP

Crown/
Implant

Ratio

Crown
Height
Space
(mm)

Microstrain Value With Force
Application at 30° (Mean � SD)

Buccal Palatal

1:1 10 1,911.65 � 110 35.58 � 7
1:1.5 15 3,252.06 � 150 286.85 � 15
1:1.75 17.5 — —
1:2 20 — —

Nissan et al. Splinting and Stress Distribution. J Oral Maxillofac

(1:1, 1
of crow
69:19

Surg 2011.

ersity from ClinicalKey.com by Elsevier on February 16, 2020.
right ©2020. Elsevier Inc. All rights reserved.

s
d
p

l
r
r
(
(

r
i
p
t
1

l
g
t
(
m
v
b

w
f
1
n
l
m

d
s
c
p

p

NISSAN ET AL 2993

Discussion

Most of the fixed implant-supported prostheses
nowadays are cemented because of superior occlu-
sion, esthetics, passivity, and loading characteris-
tics.16 Therefore resistance and retention forms
may be a major indication for splinting, although
some current clinical protocol trends would show a
return to the use of screw-retained restorations for
reasons of retrievability. An additional rationale for
splinting implant crowns together is to favorably
distribute the nonaxial loads, minimize their trans-
fer to the restoration and supporting bone, and
increase the total load area.17 Splinting the crowns
reduced the peri-implant bone stress under hori-
zontal load in a finite element analysis model espe-
cially recommended for implants surrounded by
poor-quality bone.18 A photoelastic study of a par-
tially edentulous mandible examined the effect of
splinting and interproximal contact tightness on the
load transfer to implant restorations.19 It showed that
plinted restorations shared the occlusal loads and
istributed the stresses more evenly between the im-
lants when force was applied.
The literature addressing the concept of C/I ratio is

imited. A retrospective cohort study questioned the
ole of the C/I ratio in the potential failure of implant
estorations. The C/I ratio of implants in function
1:1.3) was similar to that in those implants that failed
1:1.4).20 Another study concluded that a C/I ratio of

1:1.5 (range, 1:0.8 to 1:3.0) did not affect crestal bone
levels.21 An additional study with C/I ratios in the
ange of 1:1 to 1:2 showed no correlation of peri-
mplant bone loss with C/I ratio.22 Similarly, a 10-year
rospective study concluded that implant restora-
ions may be successful even with C/I ratios between
:2 and 1:3.15

A potentially more significant factor related to
C/I ratio is CHS.6 The biomechanics of CHS is re-
ated to lever mechanics. Nonaxial loading of 30°
enerated a proportional increase in stress distribu-
ion when prosthetic height increased from 6 mm
17.72 MPa) to 12 mm (30.09 MPa).23 CHS of 15
m or greater is regarded as biomechanically unfa-

orable, resulting in increased stress at the crestal
one/implant area.24

Blanes et al15 concluded that implant restorations
ith C/I ratios between 1:2 and 1:3 may be success-

ul. The mean reported CHS in this study was less than
5 mm. In another study a mean C/I ratio of 1:1.5 did
ot increase crestal bone loss. When 4 implant

engths were used, the CHS was always less than 15
m.21 Thus these findings can again explain the fact

that the C/I ratio is not the most detrimental for

alveolar bone loss.
Downloaded for Anonymous User (n/a) at Imam Abdulrahman Bin Faisal Univ
For personal use only. No other uses without permission. Copy

This study used the strain gauge technique to in-
vestigate the effects of splinting implant-supported
restorations with different C/I ratios and CHSs on
nonaxial stresses at the implant cervical area. Axial
loading of an implant-supported prosthesis produces
minimal stress to the supporting bone compared with
nonaxial loading. Changes in the angle of force appli-
cation resulted in greater stress to supporting bone.
Implant design, prosthesis height, and the use of an
offset implant may reduce stress, but the reduction
cannot compensate for the increase found with non-
axial loading.23,25 Furthermore, different prosthesis

esigns, implant designs, or implant configurations
hared the same finding in which most stresses were
oncentrated in the cervical area when force was ap-
lied to implant-supported prostheses.25-27 The results

of our study showed that force application at 30° signif-
icantly increased both buccal (1,911.65 � 110 vs
3,252.06 � 150) and palatal (35.58 � 7 vs 286.85 �
15) microstrain values as the C/I ratio increased from
1:1 to 1:1.5 (P � .001). Furthermore, C/I ratios of
1:1.75 and 1:2 resulted in fracture of the abutment
screw followed by dislodgement of the crowns, and
failures were noted at a CHS of 15 mm or greater.
Splinting could not reduce stresses at the cervical area
nor compensate for the detrimental effect of C/I ratio
and CHS of 15 mm or greater, which resulted in
failure of the restoration.

Although the results seem contradictory to previ-
ously mentioned in vitro studies,18,19 they are com-

atible with the available clinical studies.14,15,20-22

Those studies show no detrimental effect of 1:1.75
and 1:2 C/I ratios because whenever the CHS was
mentioned, it was less than 15 mm.15,21 Splinting did
not have an effect on crestal bone loss.15 Moreover,
splinting can result in greater crestal bone loss.21

Within the limitations of this experimental model,
the following conclusions may be drawn regarding
splinted implant-supported restorations:

1. Nonaxial loading of 30° generated a propor-
tional increase in stress distribution when the
C/I ratio and CHS increased.

2. Prosthetic failure occurred at a C/I ratio of
1:1.75 or greater and CHS of 15 mm or greater.

3. Splinting increased cervical stresses and could
not prevent prosthetic failure.

4. The CHS may be more significant than the C/I
ratio in assessing biomechanically related detri-
mental effects.

On the basis of the findings, our hypothesis is that
vertical ridge augmentation resulting in a CHS of less
than 15 may decrease the risk of prosthetic failure.
The clinical relevance needs to be investigated with

controlled long-term clinical studies testing the ef-
ersity from ClinicalKey.com by Elsevier on February 16, 2020.
right ©2020. Elsevier Inc. All rights reserved.

1
1
2
2
2
2
2
2
2
2

2994 SPLINTING AND STRESS DISTRIBUTION

fects of additional modifiers, such as “offset implant”
positioning and an internal hex-head connection im-
plant system. Similarly, different grafting procedures
should be considered. Because the grafting recom-
mendation is based on a theoretic study, it would
need a clinical counterpart to have ultimate validity.

References
1. Grossmann Y, Finger IM, Block MS: Indications for splinting

implant restorations. J Oral Maxillofac Surg 63:1642, 2005
2. Serio FG: Clinical rationale for tooth stabilization and splinting.

Dent Clin North Am 43:1, 1999
3. Grossmann Y, Sadan A: The prosthodontic concept of crown-

to-root ratio: A review of the literature. J Prosthet Dent 93:559,
2005

4. Gross M, Laufer BZ: Splinting osseointegrated implants and
natural teeth in rehabilitation of partially edentulous patients.
Part I: Laboratory and clinical studies. J Oral Rehabil 24:863,
1997

5. Richter EJ: In vivo horizontal bending moments on implants.
J Oral Maxillofac Implants 13:232, 1998

6. Misch CE, Goodacre CJ, Finley JM, et al: Consensus conference
panel report: Crown-height space guidelines for implant den-
tistry—Part 1. Implant Dent 14:312, 2005

7. Barbier L, Schepers E: Adaptive bone remodeling around oral
implants under axial and nonaxial loading conditions in the
dog mandible. Int J Oral Maxillofac Implants 12:215, 1997

8. Brunski JB: Biomechanical factors affecting the bone-dental
implant interface. Clin Mater 10:153, 1992

9. Weinberg LA: Reduction of implant loading using a modified
centric occlusal anatomy. Int J Prosthod 11:550, 1998

10. Isidor F: Loss of osseointegration caused by occlusal load of
oral implants. A clinical and radiographic study in monkeys.
Clin Oral Implants Res 7:143, 1996

11. Leung KCM, Chow TW, Wat YP, et al: Peri-implant bone loss:
Management of a patient. Int J Oral Maxillofac Implants 16:273,
2001

12. Isidor F: Influence of forces on peri-implant bone. Clin Oral
Implants Res 17:8, 2006

13. Brunski JB, Puleo DA, Nanci A: Biomaterials and biomechanics
of oral and maxillofacial implants: Current status and future
developments. Int J Oral Maxillofac Implants 15:15, 2000

14. Weber HP, Sukotjo C: Does the type of implant prosthesis

affect outcomes in the partially edentulous patient? Int J Oral
Maxillofac Implants 22:140, 2007 (suppl)
Downloaded for Anonymous User (n/a) at Imam Abdulrahman Bin Faisal Univ
For personal use only. No other uses without permission. Copy

15. Blanes RJ, Bernard JP, Blanes ZM, et al: A 10-year prospective
study of ITI dental implants placed in the posterior region. II:
Influence of the crown-to-implant ratio and different prosthetic
treatment modalities on crestal bone loss. Clin Oral Implants
Res 18:707, 2007

16. Hebel KS, Gajjar RC: Cement-retained versus screw-retained
implant restorations: Achieving optimal occlusion and esthet-
ics in implant dentistry. J Prosthet Dent 77:28, 1997

17. Misch CE: Occlusal considerations for implant-supported pros-
theses, in Dental Implant Prosthetics. St Louis, MO, Mosby,
2005, pp 472-510

8. Wang TM, Leu LJ, Wang J, et al: Effects of prosthesis materials
and prosthesis splinting on peri-implant bone stress around
implants in poor-quality bone: A numeric analysis. Int J Oral
Maxillofac Implants 17:231, 2002

9. Guichet DL, Yoshinobu D, Caputo AA: Effect of splinting and
interproximal contact tightness on load transfer by implant
restorations. J Prosthet Dent 87:528, 2002

0. Schulte J, Flores AM, Weed M: Crown-to-implant ratios of single
tooth implant-supported restorations. J Prosthet Dent 98:1,
2007

1. Rokni S, Todescan R, Watson P, et al: An assessment of crown-
to-root ratios with short sintered porous-surfaced implants sup-
porting prostheses in partially edentulous patients. Int J Oral
Maxillofac Implants 20:69, 2005

2. Tawil G, Aboujaoude N, Younan R: Influence of prosthetic
parameters on the survival and complication rates of short
implants. Int J Oral Maxillofac Implants 21:275, 2006

3. Sütpideler M, Eckert SE, Zobitz M, et al: Finite element analysis
of effect of prosthesis height, angle of force application, and
implant offset on supporting bone. Int J Oral Maxillofac Im-
plants 19:819, 2004

4. Misch CE, Steignga J, Barboza E, et al: Short dental implants in
posterior partial edentulism: A multicenter retrospective 6-year
case series study. J Periodontol 77:1340, 2006

5. Pierrisnard L, Hure G, Barquins M, et al: Two dental implants
designed for immediate loading: A finite element analysis. Int
J Oral Maxillofac Implants 17:353, 2002

6. İplikçioğlu H, Akça K: Comparative evaluation of the effect of
diameter, length and number of implants supporting three-unit
fixed partial prostheses on stress distribution in the bone. J
Dent 30:41, 2002

7. Satoh T, Maeda Y, Komiyama Y: Biomechanical rationale for
intentionally inclined implants in the posterior mandible using
3D finite element analysis. Int J Oral Maxillofac Implants 20:

533, 2005
ersity from ClinicalKey.com by Elsevier on February 16, 2020.
right ©2020. Elsevier Inc. All rights reserved.

• The Effect of Splinting Implant-Supported Restorations on Stress Distribution of Different Crown …

Materials and Methods
Statistical Analysis
Results
Discussion
References