ORIGINAL ARTICLE
Short Implant to Support Maxillary Restorations:
Bone Stress Analysis Using Regular and
Switching Platform
Nivaldo Antônio de Carvalho, DDS, Erika Oliveira de Almeida, DDS, MS,
Eduardo Passos Rocha, DDS, MS, PhD,* Amı́lcar Chagas Freitas Jr, DDS, MS,
Rodolfo Bruniera Anchieta, DDS, MS, and Sidney Kina, DDS, MSÞ
Purpose: The aim of this study was to evaluate stress distribution on peri-implant bone simulating the influence of implants with
different lengths on regular and switching platforms in the anterior
maxilla by means of three-dimensional finite element analysis.
Materials and Methods: Four mathematical models of a central incisor supported by an external hexagon implant (diameter,
5.0 mm) were created, varying the length (15.0 mm for long implants [L] and 7.0 mm for short implants [S]) and the diameter of
the abutment platform (5.0 mm for regular models [R] and 4.1 mm
for switching models [S]). The models were created using the
Mimics 11.11 (Materialise) and SolidWorks 2010 (Inovart) software. Numerical analysis was performed using ANSYS Workbench 10.0 (Swanson Analysis System). Oblique forces (100 N)
were applied to the palatine surface of the central incisor. The bone/
implant interface was considered perfectly integrated. Maximum
(Rmax) and minimum (Rmin) principal stress values were obtained.
Results: For the cortical bone, the highest stress values (Rmax)
were observed in the SR (73.7 MPa) followed by LR (65.1 MPa), SS
(63.6 MPa), and LS (54.2 MPa). For the trabecular bone, the highest
stress values (Rmax) were observed in the SS (8.87 MPa) followed by
the SR (8.32 MPa), LR (7.49 MPa), and LS (7.08 MPa).
Conclusions: The influence of switching platform was more evident for the cortical bone in comparison with the trabecular bone
for the short and long implants. The long implants showed lower
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From the *Department of Dental Materials and Prosthodontics, Araçatuba
Dental School, UNESP - Univ. Estadual Paulista; and †Post Graduate
Center, São Leopoldo Mandic School Campinas, São Paulo, Brazil.
Received December 15, 2010.
Accepted for publication March 21, 2011.
Address correspondence and reprint requests to Erika Oliveira de Almeida,
DDS, MS, UNESP - Departamento de Materiais Odontológicos e
Prótese, R. José Bonifácio, 1193, Araçatuba - SP, CEP 16015-050,
Brazil; E-mail: [email protected]
This study was supported by the Sao Paulo Research Foundation
(FAPESP - Brazil, no. 2008/00209-9).
The authors report no conflicts of interest.
Copyright * 2012 by Mutaz B. Habal, MD
ISSN: 1049-2275
DOI: 10.1097/SCS.0b013e31824dbab7
The Journal of Craniofacial Surgery
stress values in comparison to the short implants, mainly when the
switching platform was used.
Key Words: Bone biology, implantology, osseointegration,
prosthodontics
(J Craniofac Surg 2012;23: 00Y00)
A
lthough high long-term success rates with osseointegrated implants for the treatment of completely or partially edentulous
patients have been reported,1Y3 implant failure, marginal bone loss,
and patient discomfort still occur.4Y9
Bone loss usually begins at the crestal area of the cortical
bone and can progress toward the apical region, jeopardizing the
longevity of the implant and prosthesis.8 It is suggested that optimization of an implant may favor the mechanical environment for
bone maintenance.3
One interesting proposal suggests that a so-called platform
switching protocol could ensure better bone levels, at least in the
short term.10 According to this principle, the abutment/implant joint
is moved to the center of the implant and keeps far from the periimplant bone, which is maintained away from the inflammatory
cells.11,12 Consequently, if this concept is proven to be predictable,
it would certainly impact the aesthetic outcome of implants placed
in the aesthetic zone and should be tested.11Y13
The maxilla may present insufficient bone quantity for insertion of long implants, which is a prosthetic-surgical challenge
owing to reduced bone quality and quantity usually represented by
bone types III and IV.14 In these conditions, the placement of short
implants has been introduced as an alternative treatment strategy
to deviate from advanced surgical techniques.15Y17 Clinical studies
have demonstrated that a short implant may be a viable long-term
solution for regions with limited bone height,18Y20 although the risk
seems to increase if the crown-to-implant ratio exceeds the guidelines established for natural teeth (1:1).21
Numerous publications have addressed the issue of implant
length as a predictor of implant survival.22Y28 These studies have
produced conflicting results. Some studies report high failure rates
with short implants,22Y24 whereas other studies report high survival
rates.20,25Y28
Considering the need for additional studies to evaluate stress
distribution with short implants and its association with switching
platform, the aim of this study was to evaluate the influence of
switching platform in short implants in the anterior region of maxilla
by means of the three-dimensional finite element analysis.
MATERIALS AND METHODS
After approval by the human ethics committee (process no.
2008/01845) and signing of the informed consent, a tomographic
& Volume 23, Number 3, May 2012
Copyright © 2012 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
1
The Journal of Craniofacial Surgery
de Carvalho et al
& Volume 23, Number 3, May 2012
TABLE 1. Materials Properties Used in the Model
Material
FIGURE 1. Models with short implants and long implants.
examination of the maxilla of a patient was conducted to obtain
tomographic images in DICOM format. Four mathematical models
representing the anterior segment of the maxilla were fabricated
using Mimics 11,11 (Materialise, Leuven, Belgium) and Solid
Works 2010 (Inovart, São Paulo, Brazil) software.
All models were restored with a crown cemented on the
abutment, varying the implant length (7.0 and 15.0 mm) and the
platform diameter (4.1 and 5.0 mm), simulating 2 regular situations
(short regular model [SR] and long regular model [LR]) and 2
switching situations (short switching model [SS] and long switching
model [LS]; Fig. 1).
The external hexagon implants SIN (Sistema de Implante,
SP, Brazil) Revolution (5.0 15.0 and 5.0 7.0 mm) were restored with a crown IPS e-max Press (Ivoclar Vivadent, Schaan,
Liechtenstein) cemented on the abutment (4.1 and 5.0 mm in diameter) with the cement Variolink II (Ivoclar Vivadent), 0.05 mm
in thickness. Then, the assembly was inserted in the anterior segment of the maxilla with cortical and trabecular bone corresponding to the region of the right central incisor (Figs. 2A, B). The crown
presented 13.07 mm in height, 8.8 mm in mesiodistal width, and
7.1 mm buccal-lingual width.
After fabrication, the models were transferred to the finite
element software Ansys Workbench 10.0 (Swanson Analysis, Inc,
Houston, PA) to determine the regions and generate the finite element mesh.
The mechanical properties of the structures were based on
the specific literature (Table 1).29,30 All materials were considered
isotropic, homogeneous, and linearly elastic. The bone/implant interface was considered as perfectly integrated.31,32 One oblique
loading (45 degrees) was applied on the palatine surface of the
crown of the right central incisor (100 N; Fig. 3A).33 The fixed
support was determined in the 3 Cartesian axes (x = y = z = 0) to
characterize the boundary condition (Fig. 3B).
Parabolic tetrahedral elements of 0.8 mm in dimension were
used for the mesh (Fig. 2C). The refinement of the mesh was established through convergence analysis (6%).29 The models presented
the number of elements ranging from 144,882 to 154,622 and the
number of nodes ranging from 230,600 to 242,353.
For analysis of the results, the maximum (Rmax) and minimum (Rmin) principal stress values for the cortical and trabecular
bone were obtained. According to Dejak and Mlotkowsk,34 these
Cortical bone
Trabecular bone (type III)
Implant
Abutment and screw
Variolink II
IPS e-max Press
Elastic
Poisson
Modulus (MPa) Ratio
13.800
1.600
110.000
100.000
8.300
95.000
0.26
0.3
0.35
0.35
0.3
0.3
References
Huang et al. (2008)
Tada et al. (2003)
Huang et al. (2008)
Huang et al. (2008)
Manufacturer’s specifications
Manufacturer’s specifications
analyses criteria are appropriate for predicting failures in nonductile
materials.
RESULTS
For the cortical bone, the maximum (Rmax) principal stress
was highest in SR (73.7 MPa) followed by LR (65.1 MPa), SS (63.6
MPa), and LS (54.2 MPa; Fig. 6). The influence of switching platform was evident for the short and long implants. In the short
switching model (SS), the Rmax decreased 13.7% in comparison to
the short regular model (SR), whereas in the long switching model
(LS), the Rmax decreased 16.74% in comparison to the long regular
model (LR). The increase in implant length showed a decrease of
11.6% in the Rmax for the short regular model (SR) in comparison
to the long regular model (LR) and of 14.7% for the short switching
model (SS) in comparison to the long switching model (LS). The
minimum (Rmin) principal stress was highest in SR (1.66 MPa) and
the other models exhibited similar values of Rmin (0.48 MPa for
LS, j0.32 MPa for LR, and 0.20 for SS; Fig. 4).
For the trabecular bone, the maximum (Rmax) principal stress
was highest in SS (8.87 MPa) followed by SR (8.32 MPa), LR
(7.49 MPa), and LS (7.08 MPa; Fig. 5). The influence of switching platform was more evident for cortical bone in comparison to
the trabecular bone. In the short regular model (SR), the Rmax decreased 6.2% in comparison to the short switching model (SS),
whereas in the long switching model (LS), the Rmax decreased 5.4%
in comparison to the long regular model (LR). The influence of
the implant length was more evident for trabecular bone of the
switching models in comparison to the cortical models. The increase in implant length showed a decrease of 9.9% in the Rmax for
the short regular model (SR) in comparison to the long regular
model (LR) and of 20.1% for the short switching model (SS) in
comparison to the long switching model (LS). The minimum (Rmin)
principal stress was highest in SR (1.66 MPa) and the others models
presented similar values of Rmin (0.48 MPa for LS, j0.32 MPa for LR,
and 0.20 for SS; Fig. 5).
For all models (SR, LR, SS, and LS), the maximum principal
stress (Rmax) was concentrated on the lingual region of the cortical
bone near the platform (Fig. 6).
DISCUSSION
The results of the current study demonstrated that the use
of switching platform reduced the stress in the peri-implant bone,
FIGURE 2. A, Representative complete model with cortical and trabecular
bone. B, Invisible model to show the components. C, Finite element
mesh of the model.
2
FIGURE 3. A, Loading. B, Fixed support conditions.
* 2012 Mutaz B. Habal, MD
Copyright © 2012 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery
& Volume 23, Number 3, May 2012
Stress Distribution on Peri-Implant Bone
FIGURE 6. Rmax for the cortical bone in SR, LR, SS, and LS.
FIGURE 4. Rmax and Rmin (MPa) for cortical bone in SR, LR, SS, and LS.
mainly in the cortical bone that exhibited a decrease in maximum
principal stress values (Rmax) of 13.7% for the short implants and
16.74% for the long implants. These results are in agreement with
Hsu et al35 who reported that models with switching platform exhibited a decrease in stress values nearly 10% in comparison to the
models with regular platform.
These findings might be explained by the biologic width
formed near the implant/abutment interface, which may be caused
by the microgap located at the edge of the interface. For the platform
switching protocol, the biologic width extends horizontally from the
abutment to the edge of the collar of the implant and the remainder
extends apically to this region, which should facilitate bone preservation.36 This observation provides direct evidence that the biologic process resulting in the formation of the biologic dimension
and position of hard and soft tissues around a dental implant has a
great capacity to influence and direct the bone remodeling process
than does the ability of a bone loading implant surface to resist the
resorptive process of crestal bone remodeling that results from the
biologic attempt to create adequate spaces for soft tissue attachment to the implants.10
Similar results were confirmed by the retrospective study of
Prosper et al37 when observed that the switching platform reduced
the bone loss for both immediate loading and conventional surgical
protocol with 2 steps. Calvo-Guirado et al38 radiographically observed reduced bone loss for cases with switching platform and
stated that bone maintenance may result from alteration in the biologic process. Romanos and Nentwig39 suggested that the reduced
bone loss generated by switching platform depends on the primary
stability of the implant after surgery, interarch occlusal stability, and
controlled diet during osseointegration.
However, other studies36,40,41 found similar bone loss for both
switching and regular platforms. This may result from the insertion
of implants immediately after exodontia in all these studies with
immediate loading, which may have caused similar bone loss for all
groups. Chaushu et al42 and Maló et al43 reported lower success rates
for implant inserted immediately after exodontia (75%) in comparison to the implants inserted not immediately (100%).
In the present study, the stress was concentrated on the lingual
region of the cortical bone. The same region was found by Hsu et al35
in experimental and FE models, especially under lateral loading.
The current study found that a long implant and a switching
platform provided biomechanical benefits for the delay-loaded implants. However, the decrease in the stress value for the trabecular
bone was higher when the implant length was evaluated for the
models with switching platform, with a 20.1% decrease in maximum
principal stress (Rmax) from model SS to model LS. The decrease in
crestal bone stress induced by the increase in the implant length in
the maxilla was confirmed by Otate et al,44 who found that short
implants presented statistically significant differences, with early
loss of implant in comparison to the long implant. Moreover, other
authors45 believe that, for long-term evaluation, the implant length
could be more important than the diameter is because, before oral
cavity exposure and loading, vertical osseous loss is present, and it
can be close to 0.2 mm/y; in the future, the implant may lose important contact between the bone and the implant surface.
Although a linear behavior was established between the
structures in the present study, it can be suggested that the switching platform or long implants improve stress distribution in the periimplant maxillary bone. Additional studies are required to conduct
an anisotropic evaluation of the properties of cortical and medullary bone using friction coefficients to simulate an immediate
loading considering the influence of the switching platform in short
implants in the maxilla. In addition, longitudinal clinical studies and
animal studies should be conducted to complement the findings of
the present study.
CONCLUSIONS
According to the methodology used, it was concluded that:
1. the influence of the switching platform was more evident in the
cortical bone in comparison to the medullary bone,
2. the switching platform reduced the maximum principal stress
(Rmax) of the short and long implants, and
3. the long implant presented a lower value of maximum principal stress (Rmax) than the short implant did, mainly when the
switching platform was associated.
REFERENCES
FIGURE 5. Rmax and Rmin (MPa) for trabecullar bone in SR, LR, SS, and LS.
1. Kirsch A, Mentag P. The TMZ endosseous two phase implant systems:
a complete oral rehabilitation treatment concept. J Oral Implantol
1986;12:576Y589
2. Eckert SE, Parein A, Myshin HL, et al. Validation of dental implant
systems through a review of literature supplied by systems
manufacturers. J Prosthet Dent 1997;77:271Y279
3. Qian L, Todo M, Matsushita Y, et al. Effects of implant diameter,
insertion depth, and loading angle on stress/strain fields in
implant/jawbone systems: finite element analysis.
Int J Oral Maxillofac Implants 2009;24:877Y866
* 2012 Mutaz B. Habal, MD
Copyright © 2012 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
3
de Carvalho et al
The Journal of Craniofacial Surgery
4. Ibbott CG. In vivo fracture of a basket-type osseointegrating dental
implant: a case report. Int J Oral Maxillofac Implants 1989;4:255Y256
5. Friberg B, Jemt T, Lekholm U. Early failure in 4641 consecutively
placed Brånemark dental implants: a study from stage I surgery to the
connection of completed prosthesis. Int J Oral Maxillofac Implants
1991;6:142Y146
6. Adell R, Eriksson B, Lekholm M, et al. A long term follow-up study
of osseointegrated implants in the treatment of totally edentulous
jaws. Int J Oral Maxillofac Implants 1990;5:347Y359
7. Frost HM. Skeletal Structural Adaptations to Mechanical Usage
(SATMU): refining Wolff’s law: the bone remodeling problem.
Anat Rec 1990;226:403Y419
8. Isidor F. Loss of osseointegration caused by occlusal load of oral
implants: a clinical and radiographic study in monkeys.
Clin Oral Implants Res 1996;7:143Y152
9. Oh TJ, Yoon J, Misch CE, et al. The causes of early implant bone
loss: myth or science? J Periodontol 2002;73:322Y333
10. Lazzara RJ, Porter SS. Platform switching: a new concept in implant
dentistry for controlling postrestorative crestal bone levels.
Int J Periodontics Restorative Dent 2006;26:9Y17
11. Cappiello M, Luongo R, Di lorio D, et al. Evaluation of
peri-implant bone loss around platform-switching implants.
Int J Periodontics Restorative Dent 2008;28:347Y355
12. Canullo L, Fedele GR, Iannello G, et al. Platform switching and
marginal bone-level alterations: the results of a randomized-controlled
trial. Clin Oral Implants Res 2010;21:115Y121
13. Maeda Y, Miura J, Taki I, et al. Biomechanical analysis on platform
switching: in there any biomechanical rationale? Clin Oral Implants Res
2007;18:581Y584
14. Capelli M, Zuffetti F, Del Fabbro M, et al. Immediate rehabilitation
of the completely edentulous jaw with fixed prosthesis supported
by either upright or tilted implants: a multicenter clinical study.
Int J Oral Maxillofac Implant 2007;22:639Y644
15. Hagi D, Deporter DA, Pilliar RM, et al. A targeted review of study
outcomes with short (G or = 7 mm) endosseous dental implants
placed in partially edentulous patients. J Periodontol
2004;75:798Y804
16. das Neves FD, Fones D, Bernardes SR, et al. Short implantsVan
analysis of longitudinal studies. Int J Oral Maxillofac Implants
2006;21:86Y93
17. Renouard F, Nisand D. Impact of implant length and diameter on
survival rates. Clin Oral Implants Res 2006;17:35Y51
18. Deporter DA, Todescan R, Watson PA, et al. Use of the Endopore
dental implants to restore single teeth in the maxilla: protocol and early
results. Int J Oral Maxillofac Implants 1998;13:263Y272
19. Gunne J, Astrand P, Lindh T, et al. Tooth implant supported fixed
partial dentures: a ten year report. Int J Prosthodont 1999;12:216Y221
20. Tawil G, Younan R. Clinical evaluation of short, machined-surface
implants followed for 12 to 92 months. Int J Oral Maxillofac Implants
2003;18:894Y901
21. Schulte J, Flores AM, Weed M. Crown-to-implant ratios of single tooth
implant-supported restorations. J Prosthet Dent 2007;98:1Y5
22. Bahat O. Treatment planning and placement of dental implants in
the posterior maxillae: report on 732 consecutive Nobelpharma
implants. Int J Oral Maxillofac Implants 1993;8:151Y161
23. Snauwaert K, Duyck J, van Steenberghe D, et al. Time dependent
failure rate and marginal bone loss of implant supported prosthesis:
a 15 year follow-up study. Clin Oral Investig 2000;4:13Y20
24. Pierrisnard L, Renouard F, Renault P, et al. Influence of implant
length and cortical anchorage on implant stress distribution.
Clin Implant Dent Relat Res 2003;5:254Y262
25. Feldman S, Boitel N, Weng D, et al. Five-year survival distributions
of short-length (10 mm or less) machined-surface and Osseostite
implants. Clin Implant Dent Relat Res 2004;6:16Y23
26. Renouard F, Nisand D. Short implants in the severely resorbed maxilla:
a 2-year retrospective clinical study. Clin Implant Dent Relat Res
2005;7:S104YS110
27. Rokni S, Todescan R, Watson P, et al. An assessment of crown-to-root
4
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
& Volume 23, Number 3, May 2012
ratios with short sintered porous-surface implants supporting prosthesis
in partially edentulous patient. Int J Oral Maxillofac Implants
2005;20:69Y76
Gentile MA, Chuang SK, Dodson TB. Survival estimates
and risk factors for failure with 6 5.7 mm implants.
Int J Oral Maxillofac Implants 2005;20:930Y937
Huang H-L, Hsu J-T, Fuh L-J, et al. Bone stress and interfacial
sliding analysis of implant design on an immediately loaded maxillary
implant: a non linear finite element study. J Dent 2008;36:409Y417
Tada S, Stegaroiu R, Kitamura E, et al. Influence of implant design
and bone quality on stress/strain distribution in bone around implants: a
3-dimensional finite element analysis. Int J Oral Maxillofac Implants
2003;18:357Y368
Asmussen E, Peutzfeldt A, Sahafi A. Finite element analysis of stresses
in endodontically treated, dowel-restored teeth. J Prosthet Dent
2005;94:321Y329
Sorrentino R, Aversa R, Ferro V, et al. Three-dimensional finite
element analysis of strain and stress distributions in endodontically
treated maxillary central incisors restored with different post, core
and crown materials. Dental Mater 2007;23:983Y993
Baggi L, Cappelloni I, Girolamo M, et al. The influence of implant
diameter and length on stress distribution of osseointegrated implants
related to crestal bone geometry: a three-dimensional finite element
analysis. J Prosthet Dent 2008;100:422Y431
Dejak B, Mlotkowski A. Three-dimensional finite element analysis
of strength and adhesion of composite resin versus ceramic inlays
in molars. J Prosthet Dent 2008;99:131Y140
Hsu J-T, Fuh L-J, Lin D-J, et al. Bone strain and interfacial sliding
analysis of platform switching and implant diameter on an immediately
loaded implant: experimental and three-dimensional finite element
analysis. J Peridontol 2009;80:1125Y1132
Canullo L, Rasperini G. Preservation of peri-implant soft and hard
tissues using platform switching of implants placed in immediate
extraction sockets: a proof-of-concept study with 12-to-36-month
follow-up. Int J Maxillofac Implants 2007;22:995Y1000
Prosper L, Redaelli S, Pasi M, et al. A randomized prospective
multicenter trial evaluating the platform-switching technique
for the prevention of postrestorative crestal bone loss.
Int J Oral Maxillofac Implants 2009;24:299Y308
Calvo-Guirado JL, Ortiz-Ruiz AJ, López Marı́ L, et al. Immediate
maxillary restoration of single-tooth implants using platform switching
for crestal bone preservation: a 12-month study. Int J Oral Maxillofac
Implants 2009;24:275Y281
Romanos GE, Nentwig G-H. Immediate functional loading in
the maxilla using implants with platform switching: five-year results.
Int J Maxillofac Implants 2009;24:1106Y1112
Crespi R, Capparè P, Gherlone E. Radiographic evaluation of bone levels
around platform-switched and nonYplatform-switched implants used
in an immediate loading protocol. Int J Oral Maxillofac Implants
2009;24:920Y926
Degidi M, Iezzi G, Scarano A, et al. Immediately loaded titanium
implant with a tissue-stabilizing/maintaining design (‘beyond
platform switch’) retrieved from man after 4 weeks: a histological
and histomorphometrical evaluation. A case report.
Clin Oral Implants Res 2009;19:276Y282
Chaushu G, Chaushu S, Tzohar A, et al. Immediate loading of
single-tooth implants: immediate versus non-immediate implantation. A
clinical report. Int J Oral Maxillofac Implants 2001;16:267Y272
Maló P, Rangert B, Dvarsater L. Immediate function of Brånemark
implants in the esthetic zone: a retrospective clinical study with
6 months to 4 years of follow-up. Clin Imp Dent Relat Res
2000;2:138Y146
Otate S, Lyrio MCN, Moraes M, et al. Influence of diameter and length
of implant on early dental implant failure. J Oral Maxillofac Surg
2010;68:414Y419
Spiekermann H, Jansen VK, Richter EJ. A 10-year follow-up study
of IMZ and TPS implants in the edentulous mandible using bar-retained
overdentures. Int J Oral Maxillofac Implants 1995;10:231Y243
* 2012 Mutaz B. Habal, MD
Copyright © 2012 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.