Effects of splinted prosthesis supporteda wide implant or two implants:a three-dimensional finiteelement analysis

Heng-Li HuangJehn-Shyun HuangChing-Chang KoJui-Ting HsuChih-Han ChangMichael Y. C. Chen

Authors’ affiliations:Heng-Li Huang, Jui-Ting Hsu, Chih-Han Chang,Institute of Biomedical Engineering, NationalCheng Kung University, Tainan, TaiwanChing-Chang Ko, Department of Oral Science,University of Minnesota School of Dentistry,Minneapolis, MN, USAJehn-Shyun Huang, Institute of Oral Medicine,National Cheng Kung University, Tainan, TaiwanMichael Y. C. Chen, Department of Oral &Maxillofacial Surgery, China Medical UniversityHospital, Taichuang, Taiwan

Correspondence to:Chih-Han ChangInstitute of Biomedical EngineeringNational Cheng Kung UniversityNo. 1 Ta-Hsueh RoadTainan 701TaiwanTel.: þ88-66-2757575-63427Fax: þ88-66-2343270e-mail: cchang@mail.bme.ncku.edu.tw

Key words: finite element analysis, oral implants, splinted crowns

Abstract

Objectives: Three-dimensional finite element (FE) models of splinted prosthetic crowns

were studied and stress analyses were evaluated with different types of implant support,

including standard, wide or two implant(s) for partial, posterior edentulous restorations.

Material and methods: The FE models were constructed based on a cadaver mandible

containing the 2nd premolar and the 1st molar. The crowns of these two teeth were

modeled as connected and disconnected to mimic the splinted and non-splinted designs,

respectively. One standard implant was placed at the premolar region, while three types of

implant support, one at a time (the standard implant, wide implant and two implants),

were used to support the molar crown. A 100 N oblique load was applied to the buccal cusp

on each crown. The FE simulation was validated experimentally via strain gauge

measurement.

Results: The experimental data were well correlated with the FE predictions (r2¼0.97).

When compared with the standard implant used in the molar area, the wide implant and

two implants reduced the peak stress in crestal bone by 29–37% for both splinted and non-

splinted cases. Inserting the standard implant into both the premolar and molar area, the

bone stresses were identical for splinted and non-splinted designs. However, splinting the

adjacent crowns has shown to decrease the bone stresses at the premolar region by 25%,

while the wide implant or two implants were placed at the molar region.

Conclusion: The biomechanical advantages of using the wide implant or two implants are

almost identical. The benefit of load sharing by the splinted crowns is notable only when

the implants on the premolar and molar regions have different supporting ability.

Implant-based restorations for molar teeth

present a challenging area in biomechanical

research. This is primarily due to the com-

plicated implant-prosthetic structures and

the complexity of stress-related bone adap-

tation. In the molar region, large chewing

forces occur that can be detrimental to the

prostheses and alveolar bone (Rangert et al.

1995; Ishigaki et al. 2003). This may in-

duce marginal bone loss and decrease im-

plant stability, thus imperiling the implant

and its supra-structures (Brunski 1999;

Miyata et al. 2000).

Three designs – widening the diameter of

implant, using two implants or splinting the

crowns – have been suggested to improve the

biomechanical performance of implant-sup-

ported molar restorations. Studies reported

that using wider implants could decrease the

percentage of failures (van Steenberghe et al.

1990; Davarpanah et al. 2001) and increase

the removal torque (Ivanoff et al. 1997).

Likewise, using two implants to support a

single crown could reduce the rotational

moment (Bahat & Handelsman 1996) and

decrease implant mobility (Balshi et al.Copyright r Blackwell Munksgaard 2005

Date:Accepted 7 July 2004

To cite this article:Huang H-L, Huang J-S, Ko C-C, Hsu J-T, Chang C-H,Chen MYC. Effects of splinted prosthesis supported awide implant or two implants: a three-dimensionalfinite element analysis.Clin. Oral Impl. Res. 16, 2005; 466–472doi: 10.1111/j.1600-0501.2005.01124.x

466

1996). Splinting the adjacent prosthetic

crowns was also used to decrease peak stres-

ses by load sharing (Guichet et al. 2002).

Each of these three designs has its own

advantages. However, the biomechanical

criteria for choosing one design over the

others have not been defined. It has been

stipulated that using a large diameter of

implants and two implants can increase

stiffness of the implant(s) and bone-to-im-

plant contact surfaces (Langer et al. 1993;

Balshi & Wolfinger 1997). Nevertheless,

the use of wide-diameter implants could

lead to bone loss when narrow posterior

ridges exist (Davarpanah et al. 2001).

Higher failure rates for wide implant have

been found in clinical reports (Ivanoff et al.

1999; Attard & Zarb 2003). Furthermore,

the stress states in the narrow space of bone

between the two implants are unclear.

Studies on the crown splinting showed

controversial results, which require further

investigation. (Herbst et al. 2000; Guichet

et al. 2002; Naert et al. 2002).

The aim of this study was to compare the

biomechanics between standard implants,

wide implants and two implants supports

with and without splinting the prosthetic

crowns for posterior, fixed, partial dentures

using three-dimensional (3D) finite element

(FE) analyses. The experimental strain

gauge analysis (ESGA) was also performed

to validate the FE simulation.

Material and methods

A posterior portion of a human cadaver

mandible containing the second premolar

and the first molar was used to construct

the FE model of alveolar bone. This man-

dible segment was approximately 32 mm

mesiodistally, 12 mm buccolingually at the

premolar site and 15 mm buccolingually at

the molar site. The bone height was 36 mm.

Cylindrical implants were used IMZ (FRIA-

DENT AG, Manheim, Germany). This is

3.75 mm in diameter for the standard im-

plant and 5 mm in diameter for the wide

implant. The length of the implant was fixed

at 12 mm. The detailed geometry and com-

ponents of the implant were omitted and the

cylindrical root was modeled.

3D FE analyses

Computer tomography (CT) images of

frontal plane (1 mm interval between

images) of the above-mentioned human

mandible were obtained. An in-house im-

age processing program was used to detect

the boundaries of various materials, i.e.,

the crown, cortex, as well as cancellous

bone, from each CT image. This program

uses various thresholds in CT number and

gradient values to separate different materi-

als. A depth-first search algorithm (Huang

et al. 2002) is used to detect the contours of

each material. The mandible model was

rendered using ANSYS (Swanson Analysis

Inc., Huston, PA, USA) in which cylinder

holes were removed for the incorporation

of implants as described below. Clinically,

because of the limited buccolingual man-

dibular width in the premolar region, the

standard size implant was selected for this

area.

To investigate the effects of crown

splinting and various molar implant sup-

ports, three implant support conditions

(standard implant, wide implant and two

implants) combined with two crown states

(splinted and non-splinted crown) were

modeled. In total, six FE models con-

structed with 10-node tetrahedral p-ele-

ment (ANSYS solid 148) were generated.

To label these models, two sets of symbols

were used. The first set of the symbol

indicates the splint factor: ‘Spl’ for splinted

and ‘nSpl’ for non-splinted. The second set

of the symbol represents the implant’s

configurations, i.e., S for standard implant,

W for wide implant and T for two im-

plants. Table 1 summarizes the notations

of these six models. The FE models of Spl-

S, Spl-T and nSpl-W are shown in Fig. 1.

Table 1. Design parameters of dental implant and prostheses on posterior partial edentu-lous (2nd premolar and 1st molar) restoration

Model Layouts of implants Types of prostheses

Spl-S 2nd premolar 1st molar Splinting prosthetic crowns

nSpl-S

3.75 mm

Non-splinting prosthetic crowns

Spl-T6.25 mm

Splinting prosthetic crowns

nSpl-T Non-splinting prosthetic crowns

Spl-W5.0 mm

Splinting prosthetic crowns

nSpl-W Non-splinting prosthetic crowns

Spl, splinted crown; nSpl, non-splinted crown; S, standard implant; T, two implants; W, wide implant.

Fig. 1. Illustrations of (a) Model Spl-S, the splinted crown were supported by one standard implant at the 1st

molar site and one standard implant at the 2nd premolar site. The oblique loads (100 N each) were applied on

the buccal functional cusps. (b) Model Spl-T, the splinted crown were supported by two standard implants at

the 1st molar site and one standard implant at the 2nd premolar site. (c) Model nSpl-W, the non-splinted crowns

were supported by one wide implant at the 1st molar site and one standard implant 2nd at the premolar site. Spl,

splinted crown; nSpl, non-splinted crown; S, standard implant; T, two implants; W, wide implant.

Huang et al . Stress analysis of implant & prostheses designs

467 | Clin. Oral Impl. Res. 16, 2005 / 466–472

To examine the convergence level, the

p-value of the p-element was set to be

bounded between 2 (initial value) and 8

until the convergence was accomplished.

The p-level tolerance for convergence cri-

teria was set as the global strain energy

change less than 5%.

Material properties of the cortical and the

cancellous bone of the six models were

applied as transversely isotropic and lin-

early elastic (O’Mahony et al. 2001) while

the materials of implant and prosthetic

crown were assumed to be isotropic, and

linearly elastic (Sertgoz & Guvener 1996;

Ciftci & Canay 2000). All materials’ prop-

erties are listed in Table 2. The bite forces

were applied to buccal cusps of two pros-

thetic crowns with 451 bucccal inclination

(Fig 1). The load magnitudes were 100 N

for each site. The boundary condition

was constrained at the bottom surface of

the mandibular bone in all directions. The

bone–implant interface was identified as

bonded in all models to simulate osseoin-

tegration.

The mesh model Spl-S was further used

for the experimental validation. In this

model, the material properties, loading

and boundary conditions were re-assigned

based on the experimental setup described

in the next paragraph. The principal strains

of this validation model were compared

with those measured from the experi-

ments. The surface nodes on the lingual

mandible near the implant, corresponding

to the measured areas of experimental

strain gauges, were selected to calcu-

late the mean principal strains for the

comparison.

ESGA

Using the acrylic resin (Tempron, GC,

Kasugai, Japan), a posterior mandibular

sample was duplicated from the same man-

dibular cadaver used in the FE modeling.

The splinted second premolar and first

molar crown (crown type of Model Spl-S)

was also replicated with another acrylic

resin (Luxatemp, DMG, Hamburg, Ger-

many). The material properties of these

two resins were measured by the uni-axial

compressive test on cube specimens that

were plastered with bi-axial strain gauges.

The Young’s modulus was calculated from

the slope of the stress-strain curve within

the elastic region. The Poisson’s ratios

were obtained from the quotient of the

transverse (et) and axial (ea) strains, that

is, n¼ et/ea. These material properties are

listed in Table 3 and were used in the

validation FE model mentioned above.

Two stainless steel cylinders (diameter

3.75 mm, length 12 mm), mimicking the

implants, were embedded in the mandibu-

lar model with the splinted crown. Two

single-axis strain gauges (KFG-1-120-C1-

11L1M2R, KYOWA, Tokyo, Japan) were

cemented on the lingual side of mandibular

model near the implant with cyano-acry-

late cement (CC-33A, KYOWA), oriented

toward the directions of the minimal prin-

cipal strain obtained from the validation FE

model (Fig. 2).

In order to evaluate various loading ef-

fects, a clamping jig was designed with an

adjustable screw-system so that the verti-

cal load could be transferred into an oblique

load on the implant/mandible construct.

On the premolar crown and the molar

crown, a force was applied either at the

center fossa with vertical direction or at the

buccal cusp with 451 buccal inclination;

hence, in total, there were four loading

conditions (Table 4). For each of these

four loading cases, two force magnitudes,

100 and 200 N, were applied. The strain

values were recorded through the data ac-

quisition system (instruNet Hardware,

GW instruments, Inc., Somerville, MA,

USA). Each measurement was repeated

three times.

Results

Table 4 shows the minimum (compressive)

principal strains in the experimental model

and the validation FE model under the four

loading conditions. In general, the experi-

Table 2. Material properties of the finite element models

Material Young’s modulusE (MPa)

Poisson’sratio n

Shear modulusG (MPa)

Cortical bone Ex¼ 12,600 nxy¼ 0.3 Gxy¼ 4850nyz¼ 0.253

Ey¼ 12,600 nxz¼ 0.253 Gyz¼ 5700nyx¼ 0.3

Ez¼ 19,400 nzy¼ 0.39 Gxz¼ 5700nzx¼ 0.39

Cancellous bone Ex¼ 1148 nxy¼ 0.055 Gxy¼ 68nyz¼ 0.01

Ey¼ 210 nxz¼ 0.322 Gyz¼ 68nyx¼ 0.01

Ez¼ 1148 nzy¼ 0.055 Gxz¼ 434nzx¼ 0.322

Titanium 110,000 0.35Porcelain 70,000 0.19

The vectors of x, y and z indicate the buccolingual, infero-superior and mesiodistal direction,

respectively.

Table 3. Young’s Modulus and Poisson’s ratio of each material of the experimental modelwas assigned to the validation finite element model

Material Young’s modulus E (MPa) Poisson’s ratio n

Resin (temporon) 2979 0.4Resin (Luxa temp) 6880 0.4Steel (ASTM-A242) 200,000 0.3

Fig. 2. The strain gauges were attached on the lin-

gual side of the experimental mandibular mold. The

resistors of each strain gauge were set along the

direction of minimum principal strains obtained

from the finite element model. Arrows indicate

the four loading points (dimples) located on the

central fossa and functional cusps.

Huang et al . Stress analysis of implant & prostheses designs

468 | Clin. Oral Impl. Res. 16, 2005 / 466–472

mental strains were higher than the simu-

lated strains and the differences were 10%

to 50%. However, comparing within all

loadings, the experimental and simulated

results did show a consistent relationship.

This indicated a high correlation between

the experimental and the FE approaches

(r2¼0.97). Moreover, the experimental-

ly measured compressive strains were

doubled when the loading increased from

100 to 200 N, which indicated the linear

status of this model.

Figure 3 shows the von Mises stress

distributions on the cortical bone of the six

FE models. High stresses were located at the

alveolar crest around the implants, which

matched the clinical observations of crestal

bone loss (Rangert et al. 1995). In addition,

no stress was concentrated at the space

between the two implants of two-implant

models (Models Spl-T and nSpl-T).

The peak von Mises stresses on the

cortical bone around each implant of the

six models are shown in Fig. 4. With

the splinted prosthesis, the peak stresses

of bone at the first molar region decreased

by 29% in Model Spl-Tand 31% in Model

Spl-W, respectively, as compared with

Model Spl-S. Likewise, with non-splinted

prosthetic crowns, the peak stresses of

bone at the first molar region were reduced

by 37% in Model nSpl-T and 35% in

Model nSpl-W, respectively, as compared

with Model nSpl-S. However, the peak

stress difference between the wide implant

and two implants, for both splinted and

non-splinted groups, was not significant.

As for the splinting effect, with a standard

implant under molar crown, the differences

of peak bone stresses between Model Spl-S

and Model nSpl-S were not significant at

both premolar and molar regions. However,

in two-implant models, the peak stress at

premolar region for splinted crown (Model

Spl-T) decreased by 25% as compared with

non-splinted crown (Model nSpl-T). In the

wide implant models, the peak stress at

premolar region decreased by 36% on com-

paring Model Spl-W with Model nSpl-W.

This demonstrated that the splinted factor is

vital only if the support of the implant at the

first molar region is stronger than that at

the premolar region.

Discussion

The predicted principal strains by the vali-

dation FE model had a trend similar to

those measured from ESGA among all

loadings. The deviations in strain values

between the ESGA and the FE simulation

may be attributed to the measuring error

in material properties, loading locations

and directions between two approaches.

The orientation of the strain gauge, which

does not align perfectly with the direction of

principal strains, may also contribute to the

deviations in strain. However, these devia-

tions proportionally change in response to

the alternation of biomechanical parameters

in the models. For the purpose of comparing

different implant designs, the FE simulation

in this study was, therefore, verified.

The anatomic accuracy of the present FE

models was assured by the computed to-

mography images. In general, the simu-

Table 4. The mean microstrains (MS) and standard error (SE) measured form the experi-mental in vitro test, which were compared with strains of the validation finite elementmodel (FEM)

Load (N) Loaded position Implant no. Experiment (me) FEM (me) strains

MS SE

100 Pre-BC 1 759 49 610100 Pre-BC 2 387 4 415100 M-BC 1 219 10 240100 M-BC 2 729 11 606100 Pre-CF 1 164 7 128100 Pre-CF 2 25 7 46100 M-CF 1 27 3 33100 M-CF 2 211 7 120200 Pre-BC 1 1527 32 1219200 Pre-BC 2 792 4 829200 M-BC 1 488 3 479200 M-BC 2 1393 12 1325200 Pre-CF 1 335 7 255200 Pre-CF 2 53 14 91200 M-CF 1 43 6 66200 M-CF 2 377 7 240

Pre-BC, buccal cusp of the 2nd premolar; M-BC, buccal cusp of the 1st molar; Pre-CF, central fossa of

the 2nd premolar; M-CF, central fossa of the 1st molar.

Fig. 3. The von Mises stress distributions on the

crest bone for the models with (a) splinted crowns

and (b) non-splinted crowns. Spl, splinted crown; n-

Spl, non-splinted crown; S, standard implant; T, two

implants; W, wide implant.

120100

80604020

0Spl-S Spl-T Spl-W

120100

80604020

0nSpl-S nSpl-T nSpl-W

Implant 1 Implant 2 Implant 3

Implant 1 Implant 2 Implant 3

Max

imum

EQ

V (

Mpa

)M

axim

um E

QV

(M

pa)

a

b

Fig. 4. The peak von Mises stress of cortical bone

around each implant for (a) the splinted crown and

(b) the non-splinted crown. Implant 1 is placed in

the 2nd premolar region while Implant 2 and Im-

plant 3 are placed in the 1st molar region. Spl,

splinted crown; n-Spl, non-splinted crown; S, stan-

dard implant; T, two implants; W, wide implant.

Huang et al . Stress analysis of implant & prostheses designs

469 | Clin. Oral Impl. Res. 16, 2005 / 466–472

lated results of FE modeling depend con-

siderably on the geometric structures of the

models. In previous FE studies, the man-

dibular model was either simplified as a

rectangular configuration (Stegaroiu et al.

1998; Wang et al. 2002) or constructed by

a digital laser scanner (Ciftci & Canay

2000; Akca & Iplikciogiu 2001). The latter

approach provides accurate surface topogra-

phy but lacks the cortical shell informa-

tion, which may over/underpredict stress/

strain distribution of bone around the im-

plant. Further, by introducing the trans-

versely isotropic model (O’Mahony et al.

2001), the characteristic of bone material

was better reflected.

The use of the wide implant or two

implants in the molar region can provide

the advantage of reducing stress in the

surrounding bone as shown in this study.

This is because of the increased structural

capacity and the enlarged bone–implant

contact area offered by these implants.

Balshi et al. (1996) indicated that a molar

crown supported by a standard size implant

can easily introduce large bending mo-

ments to bone because the dimension of

the crown is usually greater than the dia-

meter of the implant. Therefore, the wide

implant or two implants are suggested for

placement at the molar region to reduce

the possibility of overload, which may lead

to implant failure associated with the mar-

ginal bone loss (Rangert et al. 1995).

However, whether the wide-diameter im-

plant (D¼5 mm) or two implants (D¼3.75 mm) is preferred for the edentulous

molar restoration is still an issue. Based on

the outcomes of this study, differences

between these two treatments are not sig-

nificant. Therefore, with sufficient poste-

rior mandibular bone width (buccal–lingual

direction), the wide implant is suggested to

reduce the surrounding bone stress due

to the simplicity of its surgical procedures.

However, according to the report of Davar-

panah et al. (2001), placing the wide im-

plants in narrow posterior ridges can lead to

marginal bone loss that may raise the risk

of implant failure. Therefore, in the cases

of insufficient posterior mandibular bone

width, two implants are preferred because

the stress reduction by two implants is

about the same as that induced by the

wide implant. Further, the narrow distance

(2.5 mm in this study) between the two

implants of the two-implant treatment

would not increase the bone stress. Never-

theless, it is necessary to note that recent

clinic reports (Ivanoff et al. 1999; Attard &

Zarb 2003) showed that using wide im-

plants could result in higher failure rates

than that of the standard implant. How-

ever, the authors pointed out that the fail-

ure might be associated with the surface

treatment and shape of the implant and

patients’ bone quality rather than the usage

of wide implants.

Some scientific data suggested that pros-

thetic crown splinting had biomechanical

advantage and could raise the success rate

because occlusal force could be shared

through splinted crowns, thus decreasing

the peak-stresses (Guichet et al. 2002;

Wang et al. 2002). However, there is in-

sufficient quantitative evidence to support

this hypothesis. Wang et al. (2002) had

developed simplified FE models to evaluate

this splinting effect and demonstrated that

splinting the prosthetic crowns could re-

duce stresses in bone. Similar observations

were presented in the study of Guichet

et al. (2002) using photoelastic models.

However, in their simulations the implant

structures were loaded on the premolar

only. When loading is applied to a single

crown and, by splinting the crowns, the

loading would redistribute itself through

the implant under the unloaded crown,

and then the peak stress of bone is de-

creased certainly. In the present research,

the bite forces were exerted at both func-

tional cusps of two crowns to mimic full

contacts of normal occlusion. The results

of the present study showed that there is no

significant difference between Model Spl-S

and Model nSpl-S; that is, with standard

implants for both premolar and molar, the

splinting effect is minimal. Our result

appears to support clinical observations of

Herbst et al. (2000), who showed a similar

survival rate for the splinted prosthetic

crown and non-splinted prosthetic crowns.

However, we cannot explain why some

clinicians observed higher implant failure

in the splinted cases than in non-splinted

cases (Naert et al. 2002). Further invest-

igations such as crown misfit as propo-

sed by Jemt & Book (1996) may pro-

vide some clues and help answer this

question.

However, the combination of one wide

implant or two implants at the molar

region and one standard implant at pre-

molar region provided a notable stress-

sharing effect when prosthetic crowns

were splinted. By sharing, stresses in pre-

molar regions decreased more than 25%,

which may protect overload damage if

patients have an inadequate bone quality

in their premolar ridge. Therefore, the

splinted prostheses should only be consid-

ered when two crowns are held by different

implant supports.

There are limitations associated with the

current simulations. First, only one oblique

force was applied to the models. In reality,

the occlusal force can be multi-directional,

which may complicate the stress situa-

tions. However, it has been demonstrated

in this study that using a vertical force, the

trend in stress comparison between differ-

ent designs remains the same. With a

linear, elastic model used in this study, it

is unlikely that other loading conditions

will yield a different result with regard to

implant designs. Second, the material prop-

erties of the mandible were assumed to

be regionally homogenous, which may pri-

marily affect the stress values rather than

the general trends.

Conclusions

FE studies cannot reliably be transferred to

the clinic without clinical trials or further

evidence. However, the FE analysis re-

flects the underlying mechanical aspect of

a bio-structure. Therefore, the conclusions

of this study should be regarded as a general

principle and useful information to clini-

cians.

(1) Employing wide implant or two im-

plants for posterior partial prostheses

could provide a benefit to reduce stres-

ses in bone. The percentage of stress

reduction is almost identical for both

designs. The narrow space of bone

between the two implants of the

two-implant treatment does not pro-

voke stress concentration. The selec-

tion between these two treatments

can be based on the anatomic condi-

tions rather than their biomechanical

effects.

(2) The advantage of load sharing by the

splinted prosthetic crowns is not abso-

lute. It is notable only when the sup-

porting implants of the two crowns

have a significant difference in biome-

Huang et al . Stress analysis of implant & prostheses designs

470 | Clin. Oral Impl. Res. 16, 2005 / 466–472

chanics, such as using the standard

implant on premolar region and the

wide or two implants on the molar

region.

Acknowledgement: This research was

supported by Grant NSC 92-2320-B-006-

058 from National Science Council,

Taiwan, Republic of China.

Resume

Des modeles d’elements finis (FE) tridimensionnels

de couronnes prothetiques attaches ont ete etudies et

les analyses de stress ont ete evalues avec differents

types de support d’implants comprenant le standard,

le large ou deux implants pour des restaurations

posterieures partielles. Les modeles FE ont ete con-

struits sur base de mandibule de cadavre contenant

deux premolaires et une molaire. Les couronnes de

ces deux dents ont ete modelees comme connectees

et non-connectees pour mimer respectivement les

modeles avec attache ou sans. Un implant standard a

ete place dans la region premolaire tandis que trois

types d’implants supportaient en un temps (l’im-

plant standard, l’implant large et deux implants) ont

ete utilises pour porter la couronne molaire. Une

charge oblique de 100 N a ete appliquee sur la

cuspide vestibulaire de chaque couronne. La simula-

tion FE a ete validee experimentalement via une

mesure par jauge de force. Les donnees experimen-

tales etaient en bonne correlation avec les previsions

FE (r2¼ 0,97). Compares a l’implant standard utilise

dans la zone molaire, l’implant large et la combinai-

son de deux implants reduisait le pic de stress dans

l’os crestal de 29 a 37% tant dans les cas attaches

que non-attaches. En inserant l’implant standard

dans la zone premolaire et molaire, le stress osseux

etait identique pour les modeles attaches et non-

attaches. Cependant, l’attache reliant les couronnes

adjacentes s’accompagnait d’une dimininution des

stress osseux dans la region premolaire de 25%,

tandis que l’implant large ou les deux implants

etaient places dans la region molaire. Les avantages

biomecaniques de l’utilisation d’un implant large ou

de deux implants sont quasi identiques. Le benefice

d’une charge partagee par les couronnes solidarisees

n’est visible que lorsque les implants des regions

premolaires et molaires ont des capacites de support

differentes.

Zusammenfassung

Ziel: Bei der Rekonstruktion von Lucken im hinte-

ren Seitenzahnbereich untersuchte man in einem

dreidimensionalen Finiteelement-Modell (FE) ze-

mentierte Kronen und wertete in Belastungs-Analy-

sen verschiedene Implantatabstutzungen aus, nam-

lich auf Standardimplantaten, Wide neck-Implantaten

oder auf zwei Implantaten.

Material und Methoden: Das FE-Modell basierte

auf den Werten eines Leichenunterkiefers in der

Region des zweiten Pramolaren und ersten Molaren.

Die Kronen auf diesen beiden Zahne wurden jeweils

zusammenhangend und einzeln modelliert, so dass

man die verblockte und unverblockte Situation

nachempfinden konnte. In der Pramolarenregion

implantierte man ein Standartimplantat. In der

Molarenregion wahlte man jeweils eine von drei

verschiedenen Varianten der Abstutzung fur die

Kronen: ein Standardimplantat, ein Wide neck-Im-

plantat oder zwei Implantate. Auf den buccalen

Hocker jeder Krone liess man schrag eine Kraft

von 100 N auftreffen. Die FE-Simulation eichte

man experimentell mit Hilfe von Dehnmessstreifen.

Resultate: Die experimentellen Daten korrelierten

sehr gut mit den FE-Voraussagen (r2¼0.97). Ver-

glich man die in der Molarenregion verwendeten

Standartimplantate mit den Wide neck-Implantaten

und zwei Implantaten, so reduzierte sich die Spit-

zenbelastung im crestalen Knochen um 29–37%,

bei den verblockten wie auch bei den unverblockten

Versionen. Setzte man sowohl im Pramolaren wie

auch im Molarengebiet Standardimplantate, so war

die Knochenbelastung fur die verblockte wie auch

fur die unverblockte Version gleich gross. Wenn aber

das Wide neck-Implantat oder zwei Implantate in

der Molarenregion gesetzt worden waren, so ver-

mochte die Verblockung der Implantat-Kronen die

Knochenbelastung in der Pramolarenregion um

25% zu senken.

Zusammenfassung: Ob man das Wide neck-Im-

plantat oder zwei Implantate verwendet, die biome-

chanischen Vorteile sind beinahe identisch. Man

erreicht durch das Verblocken von Kronen erst

dann einen spurbaren Vorteil bezuglich Lastenver-

teilung, wenn die Implantate in der Pramolaren-

und Molarenregion verschiedene Tragfahigkeiten

aufweisen.

Resumen

Objetivos: Se estudiaron modelos tridimensionales

de elementos finitos (FE) de coronas protesicas y se

evaluo el analisis de estres con diferentes tipos de

soporte implantario, incluyendo implantes estandar,

anchos o dos implantes, para restauraciones par-

ciales en posteriores edentulos.

Material y metodos: Se construyeron dos modelos

FE basados en mandıbula de cadaver conteniendo el

21 premolar y el 1er molar. Las coronas de estos dos

dientes se modelaron como conectadas y desconec-

tadas para imitar los disenos conectados y desconec-

tados, respectivamente. Se coloco un implante

estandar en la region premolar, mientras que para

soportar la corona molar se colocaron tres tipos de

implantes, uno a la vez, (un implante estandar, un

implante ancho y dos implantes). Se aplico una carga

oblicua de 100N en la cuspide bucal de cada corona.

La simulacion de elementos finitos se valido experi-

mentalmente por medio de medicion de tension.

Resultados: Los datos experimentales se correlacio-

naron bien con las predicciones FE (r2¼ 0.97). Al

comparase a los implantes estandar usados en el area

molar, el implante ancho y dos implantes redujeron

el pico de estres en el hueso crestal en un 29–37%

tanto para los caso ferulizados como para los no

ferulizados. Al insertar el implante estandar tanto en

la region premolar como en la molar, los estres oseos

fueron identicos para los disenos ferulizados como

para los no ferulizados. De todos modos, la feruliza-

cion de las coronas adyacentes mostro un descenso

del estres oseo en un 25%, mientras el implante

ancho o los dos implantes se colocaron en la region

molar.

Conclusion: Las ventajas biomecanicas de usar el

implante ancho o dos implantes fueron casi identi-

cas. El beneficio de compartir la carga al ferulizar las

coronas es notable solo cuando los implantes en las

regiones premolar y molar tienen diferente capacidad

de soporte.

References

Akca, K. & Iplikciogiu, H. (2001) Finite element stress

analysis of the influence of staggered vs. straight

placement of dental implants. International Journal

of Oral & Maxillofacial Implants 16: 722–730.

Attard, N.J. & Zarb, G.A. (2003) Implant pros-

thodontic management of partially edentulous

Huang et al . Stress analysis of implant & prostheses designs

471 | Clin. Oral Impl. Res. 16, 2005 / 466–472

patients missing posterior teeth: the Toronto experi-

ence. Journal of Prosthetic Dentistry 89: 352–359.

Bahat, O. & Handelsman, M. (1996) Use of wide

implants and two implants in the posterior jaw: a

clinical report. International Journal of Oral &

Maxillofacial Implants 11: 379–386.

Balshi, T.J., Hernandez, R.E., Pryszlak, M.C &

Rangert, B. (1996) A comparative study of one

implant vs. two replacing a single molar. Interna-

tional Journal of Oral & Maxillofacial Implants

11: 372–378.

Balshi, T.J. & Wolfinger, G.J. (1997) Two-implant-

supported single molar replacement: interdental

space requirements and comparison to alternative

options. International Journal of Periodontics &

Restorative Dentistry 17: 427–435.

Brunski, J.B. (1999) In vivo bone response to bio-

mechanical loading at the bone/dental–implant

interface. Advances in Dental Research 13:

99–119.

Ciftci, Y. & Canay, S. (2000) The effect of veneering

materials on stress distribution in implant-sup-

ported fixed prosthetic restorations. International

Journal of Oral & Maxillofacial Implants 15:

571–582.

Davarpanah, M., Martines, H., Kebir, M., Etienne, D.

& Tecucianu, J.F. (2001) Wide-diameter implants:

new concepts. International Journal of Perio-

dontics & Restorative Dentistry 21: 149–159.

Guichet, D.L., Yoshinobu, D. & Caputo, A.A.

(2002) Effect of splinting and interproximal con-

tact tightness on load transfer by implant restora-

tions. Journal of Prosthetic Dentistry 87:

528–535.

Herbst, D., Nel, J.C., Driessen, C.H. & Becker, P.J.

(2000) Evaluation of impression accuracy for os-

seointegrated implant supported superstructure.

Journal of Prosthetic Dentistry 83: 555–561.

Huang, H.L., Chang, C.H., Ko, C.C., Lin, C.L &

Huang, J.S. (2002) Stress analyses of dental pros-

theses with various implant supported designs.

Journal of Medical & Biological Engineering 22:

s17–s24.

Ivanoff, C.-J., Grondahl, K., Sennerby, L., Berg-

strom, C. & Lekholm, U. (1999) Influence

of variations in implant diameters: a 3- to

5-year retrospective clinical report. International

Journal of Oral & Maxillofacial Implants 14:

173–180.

Ivanoff, C.-J., Sennerby, L., Johansson, C., Rangert,

B. & Lekholm, U. (1997) Influence of implant

diameters on the integration of screw implants.

An experimental study in rabbits. International

Journal of Oral and Maxillofacial Surgery 26:

141–148.

Ishigaki, S., Nakano, T., Yamada, S., Nakamura, T.

& Takashima, F. (2003) Biomechanical stress in

bone surrounding an implant under simulated

chewing. Clinical Oral Implants Research 14:

97–102.

Jemt, T. & Book, K. (1996) Prosthesis misfit and

marginal bone loss in edentulous implant pa-

tients. International Journal of Oral & Maxillo-

facial Implants 11: 620–625.

Langer, B., Langer, L., Herrmann, I. & Jorneus, L.

(1993) The wide fixture: a solution for special

bone and a rescue for the compromised implant.

part 1. International Journal of Oral & Maxillo-

facial Implants 8: 400–408.

Miyata, T., Kobayashi, Y. & Araki, H. (2000) The

influence of controlled occlusal overload on peri-

implant tissue. Part 3: a histologic study in

monkeys. International Journal of Oral & Max-

illofacial Implants 15: 425–431.

Naert, I., Koutsikakis, G., Duyck, J., Quirynen, M.,

Jacobs, R. & van Steenberghe, D. (2002) Biologic

outcome of implant-supported restoration in the

treatment of partial edentulism. Part 1. A long-

itudinal clinical evaluation. Clinical Oral Im-

plants Research 13: 381–389.

O’Mahony, A.M., Williams, J.L. & Spencer, P.

(2001) Anisotropic elasticity of cortical and con-

cellous bone in the posterior mandible increa-

ses peri-implant stress and strain under oblique

loading. Clinical Oral Implants Research 12:

648–657.

Rangert, B., Krogh, P.H.J. & Langer, B. (1995)

Bending Overload and implant fracture: a

retrospective clinical analysis. International Jour-

nal of Oral & Maxillofacial Implants 10:

326–334.

Sertgoz, A. & Guvener, S. (1996) Finite element

analysis of the effect of cantilever and implant

length on stress distribution in an implant-sup-

ported fixed prosthesis. Journal of Prosthetic Den-

tistry 76: 165–169.

Stegaroiu, R., Sato, T. & Kusakari, H. (1998)

Influence of restoration type on stress distribution

in bone around implants: a three-dimensional

finite element analysis. International Journal of

Oral & Maxillofacial Implants 13: 82–90.

van Steenberghe, D., Lekholm, U., Bolender, C.,

Folmer, T., Henry, P. & Herrmann, I. (1990)

Applicability of osseointegrated oral implants in

the rehabilitation of partial edentulism: a prospec-

tive multicenter study on 558 fixtures. Interna-

tional Journal of Oral & Maxillofacial Implants

5: 272–282.

Wang, T.M., Leu, L.J., Wang, J.S. & Lin, L.D. (2002)

Effects of prosthesis materials and prosthesis

splinting on peri-implant bone stress around im-

plants in poor-quality bone: a numeric analysis.

International Journal of Oral & Maxillofacial

Implants 17: 231–237.

Huang et al . Stress analysis of implant & prostheses designs

472 | Clin. Oral Impl. Res. 16, 2005 / 466–472