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Biomechanical analysis and comparison of 12 dental implant systems using 3D finite element study ab
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Rui Liang , Weihua Guo , Xiangchen Qiao , Hailin Wen , Mei Yu , Wei Tang , Lei Liu , b
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Yongtao Wei & Weidong Tian a
State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, P.R. China
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Department of Mechanical and Engineering, College of Architecture and Environment, Sichuan University, Chengdu, P.R. China c
Department of Oral and Maxillofacial Surgery, West China College of Stomatology, Sichuan University, Chengdu, P.R. China Published online: 08 Apr 2014.
To cite this article: Rui Liang, Weihua Guo, Xiangchen Qiao, Hailin Wen, Mei Yu, Wei Tang, Lei Liu, Yongtao Wei & Weidong Tian (2014): Biomechanical analysis and comparison of 12 dental implant systems using 3D finite element study, Computer Methods in Biomechanics and Biomedical Engineering, DOI: 10.1080/10255842.2014.903930 To link to this article: http://dx.doi.org/10.1080/10255842.2014.903930
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Computer Methods in Biomechanics and Biomedical Engineering, 2014 http://dx.doi.org/10.1080/10255842.2014.903930
Biomechanical analysis and comparison of 12 dental implant systems using 3D finite element study Rui Lianga,b1, Weihua Guoa1, Xiangchen Qiaoa, Hailin Wena,c, Mei Yua,c, Wei Tanga,c, Lei Liua,c, Yongtao Weib* and Weidong Tiana,c* a
State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, P.R. China; bDepartment of Mechanical and Engineering, College of Architecture and Environment, Sichuan University, Chengdu, P.R. China; cDepartment of Oral and Maxillofacial Surgery, West China College of Stomatology, Sichuan University, Chengdu, P.R. China
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(Received 9 July 2012; accepted 10 March 2014) Finite element analysis plays an important role in dental implant design. The objective of this study was to show the effect of the overall geometry of dental implants on their biomechanics after implantation. In this study, 12 dental implants, with the same length, diameter and screw design, were simulated from different implant systems. Numerical model of right mandibular incisor bone segment was generated from CT data. The von-Mises stress distributions and the total deformation distributions under vertical/lateral load were compared for each implant by scores ranking method. The implants with cylindrical shapes had highest scores. Results indicated that cylindrical shape represented better geometry over taper implant. This study is helpful in choosing the optimal dental implant for clinical application and also contributes to individual implant design. Our study could also provide reference for choice and modification of dental implant in any other insertion sites and bone qualities. Keywords: dental implant; implant shape; finite element
1. Introduction Since it was introduced by Bra˚nemark and his colleagues in the 1970s (Adell et al. 1970), the dental implant has been widely used to replace a missing tooth. Dental implants received a great deal of attention in clinic by virtue of the improved comfort and stability, excellent biting force (Pera et al. 1998; Fontijn-Tekamp et al. 2000) and high success rate without compromising the adjacent teeth (Buser et al. 1997; Brocard et al. 2000; Testori et al. 2001). However, a number of factors may lead to the failure of dental implants (Natali and Pavan 2002; Susarla et al. 2008; Cooper 2010). Among these, poor biomechanics of implant is the major cause of failed implantation (Salvi and Bra¨gger 2009; Huang et al. 2010; Olate et al. 2010). Load transferring of an implant may be influenced by variation of implant design, bone qualities and so on. It was suggested that the shape design of a dental implant plays an important role on the implant biomechanics (Lee et al. 2005). Studies have shown that different shape designs will result in a significant difference in the distribution of stress around implants. However, there is no general agreement on the optimal shape of dental implants. It was suggested that screw-type cylindrical implant was superior to the tapered implant in biomechanics (Clelland et al. 1991). On the contrary, after a systemic comparison of a number of dental implant systems, Rieger et al. (1990) showed that tapered implants had better biomechanical properties compared
with cylindrical implants (Rieger et al. 1990). Holmgren et al. (1998) considered that stepped cylindrical implants were better than cylindrical or tapered shape in terms of their biomechanics (Holmgren et al. 1998). The conflicted conclusions may be due to the variations of bone quality, threads, implants dimensions and so on. On the other hand, the variety of commercial dental implant systems with different shapes, diameters, lengths and screws also reflected the conflicts in dental implant design. The debate about ideal design will lead to confusion in clinic (Lee et al. 2005). Hence, this study was designed to evaluate the stress and its distribution on a number of commercial available dental implants and surrounding bones. To determine the influence of implant shape on the subsequent biomechanics, only implants with similar dimensions and thread were considered. Three-dimensional finite element analysis (FEA) was carried out to analyse the selected individual implants biomechanically.
2.
2.1 Implant selection Twelve dental implant models of identical length, diameter and thread but different shapes were used (Figure 1). For each implant, the length and the diameter were 10 and 3.3 mm, respectively. Moreover, each
*Corresponding authors. Email: [email protected]; [email protected] q 2014 Taylor & Francis
Materials and methods
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Figure 1.
R. Liang et al.
3D models (A– L) and 2D blueprints (a– l) of 12 dental implants with different shapes.
implant has the same size of thread (ACME) at the 8 mm upper part, and no thread structure for the remaining part. The shape design was carried-out according to the published data of each commercial implant system, including OSSTEM (OSSTEM, Seoul, Korea), ERA (Sterngold Dental LLC, Carlsbad, CA, USA), Spectra (Implant Direct LLC, Calabasas Hills, CA, USA), Noble Biocare (Nobel Biocare AB, Goteborg, Sweden), ITI (Institute Straumann AG, Basel, Switzerland), MDI (3M ESPE AG, St Paul, MN, USA) and FRIADENT (Friadent GmbH, Mannheim, Germany). These dental implants were divided into 12 groups. Details of selected implant systems were listed in Table 1.
2.2
Mandibular bone model
CT data (Figure 2(a)) were obtained from a 24-year-old male volunteer. The external mandible model was generated using Mimics 10.01 (Materialisen NV, Leuven, Belgium) (Figure 2 (b)). Data of central incisors and surrounding bone were extracted from the mandible and input to Geomagic11 (Geomagic Inc., Morrisville, NC, USA). Boolean operation was carried-out in Pro/e (4.0, PTC, Needham, MA, USA), and data of mandible bone were computed using the CAD model. Likewise, 3D CAD model of each dental implant was obtained before they were assembled onto the mandibular bone model (Figure 2(c)). Assembly models of drawing or detached drawing are shown in Figure 2(c),(d).
Computer Methods in Biomechanics and Biomedical Engineering
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Table 1.
Details of selected 12 implant systems, including manufacturers, product models, number of nodes and elements.
Groups
Manufacturers
Product models
A B C D E F G H I J K L
Nobel Biocare ERA Mini OSSTEM ADIN ITI OSSTEM MDI Nobel Biocare MDI Nobel Biocare OSSTEM FRIADENT
MK III TiUnite Micro ERA GSIII ISP-X Standard Plus implants US II PLUS Collared O-Ball Noble Speedy Classic O-Ball Novle Active US III PLUS Plus Stepped Screw
Each model is composed of nine parts (Figure 2(c) (d)): namely, crown, gutta-percha, air, connecting screw, abutment, implant, cortical bone, cancellous bone and mandibular canal. The abutment and implant were connected together by connecting a screw. Screw holes were filled with gutta-percha in this study as it is the commonly used filling material for most endodontic applications (Camps and Pertot 1996). Conversion of solid model to finite elements model was carried-out using ANSYS Workbench 13.0 (Swanson Analysis, Inc., Huston, PA, USA). 2.3
3
Materials properties
Implant-borne prosthesis consisted of five parts, namely, implant, abutment, connection screw, gutta-percha and
Elements of group
918,475 902,346 922,909 915,276 919,314 917,929 895,394 895,160 897,398 916,440 915,583 915,893
631,627 623,037 634,825 630,397 632,208 631,131 616,176 616,249 618,012 630,917 630,666 630,980
crown. Each of them was made from isotropic materials. Three types of materials were involved; details of them are listed in Table 2. In contrast, as an anisotropic material, bone mechanics varies along axis, and it was distinctive between bone types (cortical or cancellous bone) (Wu et al. 2010). Details of bone mechanical properties are presented in Table 3. For all groups, linear-static analysis was carried-out.
2.4
Elements and nodes
Ten-node tetrahedral elements were previously used in quadratic displacement and modelling irregular meshes (Wu et al. 2010), therefore same method was applied in this study. Accordingly, all models were meshed with tetrahedron elements, giving the average element size of 0.35 mm for all FEA models. The mesh generation resulted in a total of about 900,000 nodes and 620,000 elements (Table 1). Considering the scale of each element, material properties can be considered constant within the element (Yang and Xiang 2007). Moreover, given implants were tightly implanted and there was no shift of implants after implantation; therefore, linear contact mode was applied in order to reduce the amount of computation, and the connection of all parts of the models was assumed to be of ‘bonded’ type.
2.5
Figure 2. Assembly of mandibular bone model and dental implant model. (a) One section from CT data. (b) The external mandible model was generated by Mimics. (c) Implant A was assembled with the mandibular bone model and crown. (d) The models consisted of nine parts: namely, crown, gutta-percha, air, connecting screw, abutment, implant, cortical bone, cancellous bone and mandibular canal.
Nodes of group
Boundary conditions and loads
For all groups, same boundary conditions and loads were used (Figure 3). The degrees of freedom were constrained at the nodes of buccal and lingual areas (Figure 3(B)). Vertical intrusion (along the axis of implant) was 200 N (Figure 3(a)) and the shear force (opposed to the buccal – lingual axis) was determined to be 100 N (Figure 3(b)).
2.6
Ranking by scores
As von-Mises stress and total deformation are two of the most important factors in dental implant systems, selected
4 Table 2.
R. Liang et al. Mechanical properties of titanium, porcelain and gutta-percha.
Titanium Porcelain Gutta-percha
Table 3.
E (MPa)
V
Reference
Implant, abutment, connection screw Crown Gutta-percha
1.10E þ 05 6.89E þ 04 0.69
0.35 0.28 0.32
Kong et al. (2008) Kong et al. (2008) Ausiello et al. (2001)
Mechanical properties of cortical and cancellous bones.
Cortical Cancellous
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Parts
Ex (MPa)
Ey (MPa)
Ez (MPa)
Vxy
Vyz
Vxz
Gxy (MPa)
Gyz (MPa)
Gxz (MPa)
12,700 210
17,900 1148
22,800 1148
0.18 0.055
0.28 0.322
0.31 0.055
5000 68
7400 434
5500 68
dental implants were ranked according to their mechanical properties under external loads as elsewhere described (Reiger et al. 1990). Briefly, von-Mises stress and total deformation of cortical/cancellous bone around implants were determined in the presence of vertical or shear force of each implant system. A total of eight measurements for each implant were determined. For each measurement, the 12 implants were re-arranged according to their biomechanical behaviours from excellent to poor, scores of 12– 1 were given to each implants under each measurement accordingly. Average scores of eight measurements for each implant were determined, where the implant shape with the highest average score is decided to be the optimal design.
3.
Results
Contour plots of stress and deformation are shown in Figures 4– 6. The stress and deformation of neighbouring bone were measured under vertical load and shear (Table 4). The stress and deformation of cortical and cancellous bones were subsequently scored and are listed in Table 5 and Figure 7(i), and the ranking of them is shown in Figure 7(a) – (h).
3.1
Von-Mises equivalent (EQV) stress of bones
Table 4 shows the stress difference between cancellous bone and cortical bone by orders of magnitude. Figures 4 and 5 show the von-Mises stress (MPa) distribution of
Figure 3. Fixed support from buccal and lingual bone surface (B) the red arrows (A) indicates the direction of force under vertical load 200 N (a) and shear load 100 N (b).
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Computer Methods in Biomechanics and Biomedical Engineering
Figure 4.
The von-Mises stress distribution (MPa) on cortical bone around implant under vertical load (A– L) and shear load (a –l).
cortical and cancellous bones, respectively. The figures show that the stress concentration area for cortical bone was located at the cortical bone around the neck of implant. This was identical for all dental implant systems. Moreover, it was shown that under vertical load, the stress transferring of cancellous bone along the cylindrical shape and hemispheroidal dental implants was shorter than the tapered implants. For the former two types of implants, the stress was close to zero at the bottom, while it was noticeable at the bottom of tapered implants. Under shear load, load transferring along buccal side went deeper than lingual side regardless of shapes. In Figures 4 – 6, (A)– (L) are under vertical load and (a)– (l) are under shear. Ranking of the maximal stress with either vertical load or shear load is given in Figure 7(a),(c),(e),(d).
3.2
5
Total bone deformation
The total deformation of cortical bone and cancellous bone is given in Figure 6. There was no order of magnitude difference of deformation for the two types of bones under vertical or shear load (Table 4).
However, with vertical load, the deformed area was clustered at the neighbouring bones near the neck of implants for all models, while the deformation of models A, C and E was less and more evenly distributed than others at the middle and lower parts as shown in Figure 6. When the shear load was applied, the deformation was clustered at similar area to the deformation under vertical load, and only the maximal deformed area was observed at the middle part of the model B. The ranking of deformation of all models is listed in Figure 7(b),(d),(f),(h).
3.3 Ranking of dental implants As previously mentioned, all groups had similar vonMises stress distribution and total deformation. Therefore, the optimum implant was determined by the maximum stress/deformation. Table 5 lists the maximum stress and deformation of each dental implant, where they were individually marked with a digit from 1 to 12 according to their mechanical properties under external loads as elsewhere described (Reiger et al. 1990). Subsequently, implants were compared with others by their scores, before
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Figure 5.
R. Liang et al.
The von-Mises stress distribution (MPa) on cancellous bone around implant under both vertical load (A– L) and shear load (a– l).
they were then arranged in Figure 7(a) –(h), sequentially. Considering the stress and deformation magnitude and distribution, implants A, G and E were thought to be optimal in this condition. 4. Discussions In this study, 12 commercially available dental implants with different shapes and with the same length, diameter and thread were analysed by means of three-dimensional linear elastic FEA. Both cortical and cancellous bones were considered, and the influence of vertical load and shear load on the mandibular central incisor segment was determined. Most of the previous work studied the influence of thread, dimensions of implant or bone quality (Bumgardner et al. 2000; Steigenga et al. 2003; Bozkaya et al. 2004) on the biomechanics of dental implants; however, as an important aspect of dental implant design, shapes of implants have significant effect on their biomechanics (Lee et al. 2005). The shapes of commercial available dental implants varied from cylindrical, coniform, tapered or stepped. Few studies have systemically
investigated the influence of shapes on the biomechanics implants. This work indicated that the adjacent alveolar bones of models A, G and E have smaller and more even stress distribution than others. As the upper parts of these three implants were cylindrical, it may suggest that cylindrical shape is the optimal geometry for the bone model. Both cortical and cancellous bones adjacent to the dental implant models A and E received the least deformation under either vertical load or shear load compared with the remaining models. It implied that the cylindrical shape of dental implant represents the optimal shape for dental implant, which was consistent to the design of the most commercial dental implants. However, our conclusion is different from elsewhere stated by Holmgren et al. (1998) who suggested that stepped cylindrical implant type was better than straight cylindrical implant using a twodimensional comparative study. It may be attributed to the variation of methods. Moreover, we observed that the stresses on the alveolar bone in models K and L were less than models B and D, which is again different from previous work by Quaresma et al. (2008), where stepped cylindrical implant was suggested to produce greater
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Computer Methods in Biomechanics and Biomedical Engineering
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Figure 6. The deformation distribution (mm) of cortical bone and cancellous bone around implant under both vertical load (A– L) and shear load (a– l).
stresses on the alveolar bone than the conical implant. Baggi et al. (2008) studied five dental implants with variations of shapes, lengths, diameters, abutments and Table 4.
connection methods from ITI, Ankylos and Branemark implant systems. Although it was suggested that the stress on the neighbouring bone of implant systems had a large
The maximum value of stress and deformation of the cancellous and cortical bones. Cortical Vertical
A B C D E F G H I J K L
Cancellous Shear
Vertical
Shear
EQV (MPa)
Deformation (mm)
EQV (MPa)
Deformation (mm)
EQV (MPa)
Deformation (mm)
EQV (MPa)
Deformation (mm)
35.14 39.57 36.99 55.3 30.6 35.29 37.68 35.67 33.38 41.21 38.4 46.42
1.87 2.57 2 2.23 1.92 1.88 1.73 1.99 2.02 1.94 2.2 2.21
151.78 147.97 154.39 152.85 113.48 151.89 112.59 119.55 131.39 155.26 136.99 138.65
4.48 5.75 4.68 5.07 4.51 4.49 4.45 4.85 4.86 4.77 5.15 4.72
4.68 2.96 2.59 2.49 5.47 4.8 5.39 2.83 3.02 2.43 2.25 4.91
1.63 2.37 1.78 2.01 1.66 1.64 1.58 1.79 1.82 1.79 2 1.95
4.28 6.05 3.44 4.65 4.8 4.36 5.17 3.78 3.68 3.6 3.87 9.47
1.87 3.35 2.05 2.38 1.82 1.87 1.87 2 2.04 2.23 2.36 2.42
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R. Liang et al.
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Table 5.
A B C D E F G H I J K L
Scores of dental implant systems.
a
b
c
d
e
f
g
h
Average scores
11 1 6 2 9 10 12 7 5 8 4 3
10 4 7 1 12 9 6 8 11 3 5 2
11 1 8 3 9 10 12 5 4 6 2 7
5 6 2 3 11 4 12 10 9 1 8 7
11 1 8 2 9 10 12 7 5 6 3 4
5 7 9 10 1 4 2 8 6 11 12 3
10 1 6 3 12 9 11 8 7 5 4 2
7 2 12 5 4 6 3 9 10 11 8 1
8.75 2.875 7.25 3.625 8.375 7.75 8.75 7.75 7.125 6.375 5.75 3.625
arrangement in his work, given the amount of variations, the most effective factor may be missed in his work. Moreover, the deformation of bone was dependent on the external stress and its own mechanical properties. When the bone quality was assumed to be the same, the deformation was proportional to the stress. Therefore, the least obvious deformation of bone was observed when the smallest stress was applied to models A, G and E, indicating that the models A, G and E were suggested to be the optimal shapes of dental implants. In conclusion, this FEM study indicated that the shapes of Nobel Biocare MK III, MDI Collared O-Ball and ITI Standard Plus implants are the optimal designs for mandibular incisor segment. This work provided an
Figure 7. Twelve implants were ranked according to their von-Mises stress (a, c, e and g) and deformation (b, d, f and h) on cortical (a– d) or cancellous bones (e– h), where the vertical load (a, b, e, f) and shear load (b, d, g, h) were applied, respectively. Their average score were calculated and ranked (i).
Computer Methods in Biomechanics and Biomedical Engineering experimental support for choosing an optimal dental implant system in clinic, and design or modification of dental implants. Last but not the least, it also provided a method to adjust the design of dental implant systems in the remaining insertion sites with variation in bone quality.
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Funding This work was supported by grants from the National High Technology Research and Development Program of China [No. 2011AA030107], National Basic Research Program of China (973 Program) [No. 2010CB944800], the Doctoral Foundation of Ministry of Education of China [Nos 20110181120067 and 20110181110089], the Key Technology R&D Program of Sichuan Province [Nos 2012SZ0013 and 2012SZ0035], Basic Research Program of Sichuan Province [No. 2011JY0125] and Youth Foundation of Sichuan University [No. 0040305505064]. Conflict of interest statement: The authors declare no competing financial interests.
Note 1.
These authors contributed equally to this work.
References Adell R, Hansson BO, Bra˚nemark PI, Breine U. 1970. Intraosseous anchorage of dental prostheses. Scand J Plas Reconstr Surg Hand Surg. 4(1):19 – 34. Anitua E, Orive G, Aguirre JJ, Ardanza B, Andı´a I. 2008. 5-Year clinical experience with BTI dental implants: risk factors for implant failure. J Clin Periodontol. 35(8):724 –732. Ausiello P, Apicella A, Davidson CL, Rengo S. 2001. 3D-finite element analyses of cusp movements in a human upper premolar, restored with adhesive resin-based composites. J Biomech. 34(10):1269– 1277. Baggi L, Cappelloni I, Maceri F, Vairo G. 2008. Stress-based performance evaluation of osseointegrated dental implants by finite-element simulation. Simul Model Pract Theory. 16 (8):971 – 987. Bozkaya D, Muftu S, Muftu A. 2004. Evaluation of load transfer characteristics of five different implants in compact bone at different load levels by finite elements analysis. J Prosthet Dent. 92(6):523– 530. Brocard D, Barthet P, Baysse E, Duffort JF, Eller P, Justumus P, Marin P, Oscaby F, Simonet T, Benque´ E, Brunel GA, et al. 2000. Multicenter report on 1,022 consecutively placed ITI implants: a 7-year longitudinal study. Int J Oral Maxillofac Implants. 15(5):691– 700. Bumgardner JD, Boring JG, Cooper RC, Gao C, Givaruangsawat S, Gilbert JA, Misch CM, Stefik DE. 2000. Preliminary evaluation of a new dental implant design in canine models. Implant Dent. 9(3):252– 260. Buser D, Mericske-Stern R, Bernard JP, Behneke A, Behneke N, Hirt HP, Belser UC, Lang NP. 1997. Long-term evaluation of non-submerged ITI implants. Part 1: 8-year life table analysis of a prospective multi-center study with 2359 implants. Clin Oral Implants Res. 8(3):161– 172. Camps JJ, Pertot WJ. 1996. Young’s modulus of warm and cold gutta-percha. Endod Dent Traumatol. 12(2):50– 53.
9
Clelland NL, lsmail YH, Zaki HS. 1991. Three-dimensional finite element stress analysis in and around the Screw-Vent implant. Int J Oral Maxillofac Implants. 6(4):391 – 398. Cooper LF. 2010. Factors influencing primary dental implant stability remain unclear. J Evid Based Dent Pract. 10(1):44–45. Fontijn-Tekamp FA, Slagter AP, Van Der Bilt A, Van ’T Hof MA, Witter DJ, Kalk W, Jansen JA. 2000. Biting and chewing in overdentures, full dentures, and natural dentitions. J Dent Res. 79(7):1519– 1524. Holmgren EP, Kilgren LM, Mante F. 1998. Evaluating parameters of osseointegrated dental implants using finite element analysis – a two-dimensional comparative study examining the effects of implant diameter, implant shape, and load direction. J Oral Implantol. 24(2):80 – 88. Huang HL, Hsu JT, Fuh LJ, Lin DJ, Chen MY. 2010. Biomechanical simulation of various surface roughnesses and geometric designs on an immediately loaded dental implant. Comput Biol Med. 40(5):525– 532. Kong L, Sun YY, Hu KJ, Liu YP, Li DH, Qiu ZH, Liu BL. 2008. Selections of the cylinder implant neck taper and implant end fillet for optimal biomechanical properties: a three-dimensional finite element analysis. J Biomech. 41(5):1124– 1130. Lee JH, Frias V, Lee KW, Wright RF. 2005. Effect of implant size and shape on implant success rates: a literature review. J Prosthet Dent. 94(4):377– 381. Natali AN, Pavan PG. 2002. A comparative analysis based on different strength criteria for evaluation of risk factor for dental implants. Comput Methods Biomech Biomed Eng. 5(2):127 – 133. Olate S, Lyrio MC, Moraes M, Mazzonetto R, Moreira RW. 2010. Influence of diameter and length of implant on early dental implant failure. J Oral Maxillofac Surg. 68(1):414–419. Pera P, Bassi F, Schierano G, Appendino P, Preti G. 1998. Implant anchored complete mandibular denture: evaluation of masticatory efficiency. Oral function and degree of satisfaction. J Oral Rehabil. 25(6):462– 467. Quaresma SE, Cury PR, Sendyk WR, Sendyk CA. 2008. A finite element analysis of two different dental implants: stress distribution in the prosthesis, abutment, implant, and supporting bone. J Oral Implantol. 34(1):1 –6. Reiger MR, Adams WK, Kinzel GL. 1990. A finite element survey of eleven endosseous implants. J Prosthet Dent. 63 (4):457 – 465. Salvi GE, Bra¨gger U. 2009. Mechanical and technical risks in implant therapy. Int J Oral Maxillofac Implants. 24(9): 69 – 85. Steigenga JT, Shammari KF, Nociti FH, Misch CE, Wang HL. 2003. Dental implant design and its relationship to long-term implant success. Implant Dent. 12(4):306– 317. Susarla SM, Chuang SK, Dodson TB. 2008. Delayed versus immediate loading of implants: survival analysis and risk factors for dental implant failure. J Oral Maxillofac Surg. 66 (2):251 – 255. Testori T, Wiseman L, Woolfe S, Porter SS. 2001. Prospective multicenter clinical study of the osseotite implant: four-year interim report. Int J Oral Maxillofac Implants. 16(2):193–200. Wu T, Liao WH, Dai N, Tang C. 2010. Design of accustom angle dabutment for dental implants using computer-aided design and nonlinear finite element analysis. J Biomech. 43(10): 1941– 1946. Yang J, Xiang HJ. 2007. A three-dimensional finite element study on the biomechanical behavior of an FGBM dental implant in surrounding bone. J Biomech. 40(11):2377– 2385.
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Biomechanical analysis and comparison of 12 dental implant systems using 3D finite element study ab
a
a
ac
ac
ac
ac
Rui Liang , Weihua Guo , Xiangchen Qiao , Hailin Wen , Mei Yu , Wei Tang , Lei Liu , b
ac
Yongtao Wei & Weidong Tian a
State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, P.R. China
b
Department of Mechanical and Engineering, College of Architecture and Environment, Sichuan University, Chengdu, P.R. China c
Department of Oral and Maxillofacial Surgery, West China College of Stomatology, Sichuan University, Chengdu, P.R. China Published online: 08 Apr 2014.
To cite this article: Rui Liang, Weihua Guo, Xiangchen Qiao, Hailin Wen, Mei Yu, Wei Tang, Lei Liu, Yongtao Wei & Weidong Tian (2014): Biomechanical analysis and comparison of 12 dental implant systems using 3D finite element study, Computer Methods in Biomechanics and Biomedical Engineering, DOI: 10.1080/10255842.2014.903930 To link to this article: http://dx.doi.org/10.1080/10255842.2014.903930
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Computer Methods in Biomechanics and Biomedical Engineering, 2014 http://dx.doi.org/10.1080/10255842.2014.903930
Biomechanical analysis and comparison of 12 dental implant systems using 3D finite element study Rui Lianga,b1, Weihua Guoa1, Xiangchen Qiaoa, Hailin Wena,c, Mei Yua,c, Wei Tanga,c, Lei Liua,c, Yongtao Weib* and Weidong Tiana,c* a
State Key Laboratory of Oral Diseases, Sichuan University, Chengdu, P.R. China; bDepartment of Mechanical and Engineering, College of Architecture and Environment, Sichuan University, Chengdu, P.R. China; cDepartment of Oral and Maxillofacial Surgery, West China College of Stomatology, Sichuan University, Chengdu, P.R. China
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(Received 9 July 2012; accepted 10 March 2014) Finite element analysis plays an important role in dental implant design. The objective of this study was to show the effect of the overall geometry of dental implants on their biomechanics after implantation. In this study, 12 dental implants, with the same length, diameter and screw design, were simulated from different implant systems. Numerical model of right mandibular incisor bone segment was generated from CT data. The von-Mises stress distributions and the total deformation distributions under vertical/lateral load were compared for each implant by scores ranking method. The implants with cylindrical shapes had highest scores. Results indicated that cylindrical shape represented better geometry over taper implant. This study is helpful in choosing the optimal dental implant for clinical application and also contributes to individual implant design. Our study could also provide reference for choice and modification of dental implant in any other insertion sites and bone qualities. Keywords: dental implant; implant shape; finite element
1. Introduction Since it was introduced by Bra˚nemark and his colleagues in the 1970s (Adell et al. 1970), the dental implant has been widely used to replace a missing tooth. Dental implants received a great deal of attention in clinic by virtue of the improved comfort and stability, excellent biting force (Pera et al. 1998; Fontijn-Tekamp et al. 2000) and high success rate without compromising the adjacent teeth (Buser et al. 1997; Brocard et al. 2000; Testori et al. 2001). However, a number of factors may lead to the failure of dental implants (Natali and Pavan 2002; Susarla et al. 2008; Cooper 2010). Among these, poor biomechanics of implant is the major cause of failed implantation (Salvi and Bra¨gger 2009; Huang et al. 2010; Olate et al. 2010). Load transferring of an implant may be influenced by variation of implant design, bone qualities and so on. It was suggested that the shape design of a dental implant plays an important role on the implant biomechanics (Lee et al. 2005). Studies have shown that different shape designs will result in a significant difference in the distribution of stress around implants. However, there is no general agreement on the optimal shape of dental implants. It was suggested that screw-type cylindrical implant was superior to the tapered implant in biomechanics (Clelland et al. 1991). On the contrary, after a systemic comparison of a number of dental implant systems, Rieger et al. (1990) showed that tapered implants had better biomechanical properties compared
with cylindrical implants (Rieger et al. 1990). Holmgren et al. (1998) considered that stepped cylindrical implants were better than cylindrical or tapered shape in terms of their biomechanics (Holmgren et al. 1998). The conflicted conclusions may be due to the variations of bone quality, threads, implants dimensions and so on. On the other hand, the variety of commercial dental implant systems with different shapes, diameters, lengths and screws also reflected the conflicts in dental implant design. The debate about ideal design will lead to confusion in clinic (Lee et al. 2005). Hence, this study was designed to evaluate the stress and its distribution on a number of commercial available dental implants and surrounding bones. To determine the influence of implant shape on the subsequent biomechanics, only implants with similar dimensions and thread were considered. Three-dimensional finite element analysis (FEA) was carried out to analyse the selected individual implants biomechanically.
2.
2.1 Implant selection Twelve dental implant models of identical length, diameter and thread but different shapes were used (Figure 1). For each implant, the length and the diameter were 10 and 3.3 mm, respectively. Moreover, each
*Corresponding authors. Email: [email protected]; [email protected] q 2014 Taylor & Francis
Materials and methods
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Figure 1.
R. Liang et al.
3D models (A– L) and 2D blueprints (a– l) of 12 dental implants with different shapes.
implant has the same size of thread (ACME) at the 8 mm upper part, and no thread structure for the remaining part. The shape design was carried-out according to the published data of each commercial implant system, including OSSTEM (OSSTEM, Seoul, Korea), ERA (Sterngold Dental LLC, Carlsbad, CA, USA), Spectra (Implant Direct LLC, Calabasas Hills, CA, USA), Noble Biocare (Nobel Biocare AB, Goteborg, Sweden), ITI (Institute Straumann AG, Basel, Switzerland), MDI (3M ESPE AG, St Paul, MN, USA) and FRIADENT (Friadent GmbH, Mannheim, Germany). These dental implants were divided into 12 groups. Details of selected implant systems were listed in Table 1.
2.2
Mandibular bone model
CT data (Figure 2(a)) were obtained from a 24-year-old male volunteer. The external mandible model was generated using Mimics 10.01 (Materialisen NV, Leuven, Belgium) (Figure 2 (b)). Data of central incisors and surrounding bone were extracted from the mandible and input to Geomagic11 (Geomagic Inc., Morrisville, NC, USA). Boolean operation was carried-out in Pro/e (4.0, PTC, Needham, MA, USA), and data of mandible bone were computed using the CAD model. Likewise, 3D CAD model of each dental implant was obtained before they were assembled onto the mandibular bone model (Figure 2(c)). Assembly models of drawing or detached drawing are shown in Figure 2(c),(d).
Computer Methods in Biomechanics and Biomedical Engineering
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Table 1.
Details of selected 12 implant systems, including manufacturers, product models, number of nodes and elements.
Groups
Manufacturers
Product models
A B C D E F G H I J K L
Nobel Biocare ERA Mini OSSTEM ADIN ITI OSSTEM MDI Nobel Biocare MDI Nobel Biocare OSSTEM FRIADENT
MK III TiUnite Micro ERA GSIII ISP-X Standard Plus implants US II PLUS Collared O-Ball Noble Speedy Classic O-Ball Novle Active US III PLUS Plus Stepped Screw
Each model is composed of nine parts (Figure 2(c) (d)): namely, crown, gutta-percha, air, connecting screw, abutment, implant, cortical bone, cancellous bone and mandibular canal. The abutment and implant were connected together by connecting a screw. Screw holes were filled with gutta-percha in this study as it is the commonly used filling material for most endodontic applications (Camps and Pertot 1996). Conversion of solid model to finite elements model was carried-out using ANSYS Workbench 13.0 (Swanson Analysis, Inc., Huston, PA, USA). 2.3
3
Materials properties
Implant-borne prosthesis consisted of five parts, namely, implant, abutment, connection screw, gutta-percha and
Elements of group
918,475 902,346 922,909 915,276 919,314 917,929 895,394 895,160 897,398 916,440 915,583 915,893
631,627 623,037 634,825 630,397 632,208 631,131 616,176 616,249 618,012 630,917 630,666 630,980
crown. Each of them was made from isotropic materials. Three types of materials were involved; details of them are listed in Table 2. In contrast, as an anisotropic material, bone mechanics varies along axis, and it was distinctive between bone types (cortical or cancellous bone) (Wu et al. 2010). Details of bone mechanical properties are presented in Table 3. For all groups, linear-static analysis was carried-out.
2.4
Elements and nodes
Ten-node tetrahedral elements were previously used in quadratic displacement and modelling irregular meshes (Wu et al. 2010), therefore same method was applied in this study. Accordingly, all models were meshed with tetrahedron elements, giving the average element size of 0.35 mm for all FEA models. The mesh generation resulted in a total of about 900,000 nodes and 620,000 elements (Table 1). Considering the scale of each element, material properties can be considered constant within the element (Yang and Xiang 2007). Moreover, given implants were tightly implanted and there was no shift of implants after implantation; therefore, linear contact mode was applied in order to reduce the amount of computation, and the connection of all parts of the models was assumed to be of ‘bonded’ type.
2.5
Figure 2. Assembly of mandibular bone model and dental implant model. (a) One section from CT data. (b) The external mandible model was generated by Mimics. (c) Implant A was assembled with the mandibular bone model and crown. (d) The models consisted of nine parts: namely, crown, gutta-percha, air, connecting screw, abutment, implant, cortical bone, cancellous bone and mandibular canal.
Nodes of group
Boundary conditions and loads
For all groups, same boundary conditions and loads were used (Figure 3). The degrees of freedom were constrained at the nodes of buccal and lingual areas (Figure 3(B)). Vertical intrusion (along the axis of implant) was 200 N (Figure 3(a)) and the shear force (opposed to the buccal – lingual axis) was determined to be 100 N (Figure 3(b)).
2.6
Ranking by scores
As von-Mises stress and total deformation are two of the most important factors in dental implant systems, selected
4 Table 2.
R. Liang et al. Mechanical properties of titanium, porcelain and gutta-percha.
Titanium Porcelain Gutta-percha
Table 3.
E (MPa)
V
Reference
Implant, abutment, connection screw Crown Gutta-percha
1.10E þ 05 6.89E þ 04 0.69
0.35 0.28 0.32
Kong et al. (2008) Kong et al. (2008) Ausiello et al. (2001)
Mechanical properties of cortical and cancellous bones.
Cortical Cancellous
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Parts
Ex (MPa)
Ey (MPa)
Ez (MPa)
Vxy
Vyz
Vxz
Gxy (MPa)
Gyz (MPa)
Gxz (MPa)
12,700 210
17,900 1148
22,800 1148
0.18 0.055
0.28 0.322
0.31 0.055
5000 68
7400 434
5500 68
dental implants were ranked according to their mechanical properties under external loads as elsewhere described (Reiger et al. 1990). Briefly, von-Mises stress and total deformation of cortical/cancellous bone around implants were determined in the presence of vertical or shear force of each implant system. A total of eight measurements for each implant were determined. For each measurement, the 12 implants were re-arranged according to their biomechanical behaviours from excellent to poor, scores of 12– 1 were given to each implants under each measurement accordingly. Average scores of eight measurements for each implant were determined, where the implant shape with the highest average score is decided to be the optimal design.
3.
Results
Contour plots of stress and deformation are shown in Figures 4– 6. The stress and deformation of neighbouring bone were measured under vertical load and shear (Table 4). The stress and deformation of cortical and cancellous bones were subsequently scored and are listed in Table 5 and Figure 7(i), and the ranking of them is shown in Figure 7(a) – (h).
3.1
Von-Mises equivalent (EQV) stress of bones
Table 4 shows the stress difference between cancellous bone and cortical bone by orders of magnitude. Figures 4 and 5 show the von-Mises stress (MPa) distribution of
Figure 3. Fixed support from buccal and lingual bone surface (B) the red arrows (A) indicates the direction of force under vertical load 200 N (a) and shear load 100 N (b).
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Computer Methods in Biomechanics and Biomedical Engineering
Figure 4.
The von-Mises stress distribution (MPa) on cortical bone around implant under vertical load (A– L) and shear load (a –l).
cortical and cancellous bones, respectively. The figures show that the stress concentration area for cortical bone was located at the cortical bone around the neck of implant. This was identical for all dental implant systems. Moreover, it was shown that under vertical load, the stress transferring of cancellous bone along the cylindrical shape and hemispheroidal dental implants was shorter than the tapered implants. For the former two types of implants, the stress was close to zero at the bottom, while it was noticeable at the bottom of tapered implants. Under shear load, load transferring along buccal side went deeper than lingual side regardless of shapes. In Figures 4 – 6, (A)– (L) are under vertical load and (a)– (l) are under shear. Ranking of the maximal stress with either vertical load or shear load is given in Figure 7(a),(c),(e),(d).
3.2
5
Total bone deformation
The total deformation of cortical bone and cancellous bone is given in Figure 6. There was no order of magnitude difference of deformation for the two types of bones under vertical or shear load (Table 4).
However, with vertical load, the deformed area was clustered at the neighbouring bones near the neck of implants for all models, while the deformation of models A, C and E was less and more evenly distributed than others at the middle and lower parts as shown in Figure 6. When the shear load was applied, the deformation was clustered at similar area to the deformation under vertical load, and only the maximal deformed area was observed at the middle part of the model B. The ranking of deformation of all models is listed in Figure 7(b),(d),(f),(h).
3.3 Ranking of dental implants As previously mentioned, all groups had similar vonMises stress distribution and total deformation. Therefore, the optimum implant was determined by the maximum stress/deformation. Table 5 lists the maximum stress and deformation of each dental implant, where they were individually marked with a digit from 1 to 12 according to their mechanical properties under external loads as elsewhere described (Reiger et al. 1990). Subsequently, implants were compared with others by their scores, before
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Figure 5.
R. Liang et al.
The von-Mises stress distribution (MPa) on cancellous bone around implant under both vertical load (A– L) and shear load (a– l).
they were then arranged in Figure 7(a) –(h), sequentially. Considering the stress and deformation magnitude and distribution, implants A, G and E were thought to be optimal in this condition. 4. Discussions In this study, 12 commercially available dental implants with different shapes and with the same length, diameter and thread were analysed by means of three-dimensional linear elastic FEA. Both cortical and cancellous bones were considered, and the influence of vertical load and shear load on the mandibular central incisor segment was determined. Most of the previous work studied the influence of thread, dimensions of implant or bone quality (Bumgardner et al. 2000; Steigenga et al. 2003; Bozkaya et al. 2004) on the biomechanics of dental implants; however, as an important aspect of dental implant design, shapes of implants have significant effect on their biomechanics (Lee et al. 2005). The shapes of commercial available dental implants varied from cylindrical, coniform, tapered or stepped. Few studies have systemically
investigated the influence of shapes on the biomechanics implants. This work indicated that the adjacent alveolar bones of models A, G and E have smaller and more even stress distribution than others. As the upper parts of these three implants were cylindrical, it may suggest that cylindrical shape is the optimal geometry for the bone model. Both cortical and cancellous bones adjacent to the dental implant models A and E received the least deformation under either vertical load or shear load compared with the remaining models. It implied that the cylindrical shape of dental implant represents the optimal shape for dental implant, which was consistent to the design of the most commercial dental implants. However, our conclusion is different from elsewhere stated by Holmgren et al. (1998) who suggested that stepped cylindrical implant type was better than straight cylindrical implant using a twodimensional comparative study. It may be attributed to the variation of methods. Moreover, we observed that the stresses on the alveolar bone in models K and L were less than models B and D, which is again different from previous work by Quaresma et al. (2008), where stepped cylindrical implant was suggested to produce greater
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Computer Methods in Biomechanics and Biomedical Engineering
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Figure 6. The deformation distribution (mm) of cortical bone and cancellous bone around implant under both vertical load (A– L) and shear load (a– l).
stresses on the alveolar bone than the conical implant. Baggi et al. (2008) studied five dental implants with variations of shapes, lengths, diameters, abutments and Table 4.
connection methods from ITI, Ankylos and Branemark implant systems. Although it was suggested that the stress on the neighbouring bone of implant systems had a large
The maximum value of stress and deformation of the cancellous and cortical bones. Cortical Vertical
A B C D E F G H I J K L
Cancellous Shear
Vertical
Shear
EQV (MPa)
Deformation (mm)
EQV (MPa)
Deformation (mm)
EQV (MPa)
Deformation (mm)
EQV (MPa)
Deformation (mm)
35.14 39.57 36.99 55.3 30.6 35.29 37.68 35.67 33.38 41.21 38.4 46.42
1.87 2.57 2 2.23 1.92 1.88 1.73 1.99 2.02 1.94 2.2 2.21
151.78 147.97 154.39 152.85 113.48 151.89 112.59 119.55 131.39 155.26 136.99 138.65
4.48 5.75 4.68 5.07 4.51 4.49 4.45 4.85 4.86 4.77 5.15 4.72
4.68 2.96 2.59 2.49 5.47 4.8 5.39 2.83 3.02 2.43 2.25 4.91
1.63 2.37 1.78 2.01 1.66 1.64 1.58 1.79 1.82 1.79 2 1.95
4.28 6.05 3.44 4.65 4.8 4.36 5.17 3.78 3.68 3.6 3.87 9.47
1.87 3.35 2.05 2.38 1.82 1.87 1.87 2 2.04 2.23 2.36 2.42
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R. Liang et al.
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Table 5.
A B C D E F G H I J K L
Scores of dental implant systems.
a
b
c
d
e
f
g
h
Average scores
11 1 6 2 9 10 12 7 5 8 4 3
10 4 7 1 12 9 6 8 11 3 5 2
11 1 8 3 9 10 12 5 4 6 2 7
5 6 2 3 11 4 12 10 9 1 8 7
11 1 8 2 9 10 12 7 5 6 3 4
5 7 9 10 1 4 2 8 6 11 12 3
10 1 6 3 12 9 11 8 7 5 4 2
7 2 12 5 4 6 3 9 10 11 8 1
8.75 2.875 7.25 3.625 8.375 7.75 8.75 7.75 7.125 6.375 5.75 3.625
arrangement in his work, given the amount of variations, the most effective factor may be missed in his work. Moreover, the deformation of bone was dependent on the external stress and its own mechanical properties. When the bone quality was assumed to be the same, the deformation was proportional to the stress. Therefore, the least obvious deformation of bone was observed when the smallest stress was applied to models A, G and E, indicating that the models A, G and E were suggested to be the optimal shapes of dental implants. In conclusion, this FEM study indicated that the shapes of Nobel Biocare MK III, MDI Collared O-Ball and ITI Standard Plus implants are the optimal designs for mandibular incisor segment. This work provided an
Figure 7. Twelve implants were ranked according to their von-Mises stress (a, c, e and g) and deformation (b, d, f and h) on cortical (a– d) or cancellous bones (e– h), where the vertical load (a, b, e, f) and shear load (b, d, g, h) were applied, respectively. Their average score were calculated and ranked (i).
Computer Methods in Biomechanics and Biomedical Engineering experimental support for choosing an optimal dental implant system in clinic, and design or modification of dental implants. Last but not the least, it also provided a method to adjust the design of dental implant systems in the remaining insertion sites with variation in bone quality.
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Funding This work was supported by grants from the National High Technology Research and Development Program of China [No. 2011AA030107], National Basic Research Program of China (973 Program) [No. 2010CB944800], the Doctoral Foundation of Ministry of Education of China [Nos 20110181120067 and 20110181110089], the Key Technology R&D Program of Sichuan Province [Nos 2012SZ0013 and 2012SZ0035], Basic Research Program of Sichuan Province [No. 2011JY0125] and Youth Foundation of Sichuan University [No. 0040305505064]. Conflict of interest statement: The authors declare no competing financial interests.
Note 1.
These authors contributed equally to this work.
References Adell R, Hansson BO, Bra˚nemark PI, Breine U. 1970. Intraosseous anchorage of dental prostheses. Scand J Plas Reconstr Surg Hand Surg. 4(1):19 – 34. Anitua E, Orive G, Aguirre JJ, Ardanza B, Andı´a I. 2008. 5-Year clinical experience with BTI dental implants: risk factors for implant failure. J Clin Periodontol. 35(8):724 –732. Ausiello P, Apicella A, Davidson CL, Rengo S. 2001. 3D-finite element analyses of cusp movements in a human upper premolar, restored with adhesive resin-based composites. J Biomech. 34(10):1269– 1277. Baggi L, Cappelloni I, Maceri F, Vairo G. 2008. Stress-based performance evaluation of osseointegrated dental implants by finite-element simulation. Simul Model Pract Theory. 16 (8):971 – 987. Bozkaya D, Muftu S, Muftu A. 2004. Evaluation of load transfer characteristics of five different implants in compact bone at different load levels by finite elements analysis. J Prosthet Dent. 92(6):523– 530. Brocard D, Barthet P, Baysse E, Duffort JF, Eller P, Justumus P, Marin P, Oscaby F, Simonet T, Benque´ E, Brunel GA, et al. 2000. Multicenter report on 1,022 consecutively placed ITI implants: a 7-year longitudinal study. Int J Oral Maxillofac Implants. 15(5):691– 700. Bumgardner JD, Boring JG, Cooper RC, Gao C, Givaruangsawat S, Gilbert JA, Misch CM, Stefik DE. 2000. Preliminary evaluation of a new dental implant design in canine models. Implant Dent. 9(3):252– 260. Buser D, Mericske-Stern R, Bernard JP, Behneke A, Behneke N, Hirt HP, Belser UC, Lang NP. 1997. Long-term evaluation of non-submerged ITI implants. Part 1: 8-year life table analysis of a prospective multi-center study with 2359 implants. Clin Oral Implants Res. 8(3):161– 172. Camps JJ, Pertot WJ. 1996. Young’s modulus of warm and cold gutta-percha. Endod Dent Traumatol. 12(2):50– 53.
9
Clelland NL, lsmail YH, Zaki HS. 1991. Three-dimensional finite element stress analysis in and around the Screw-Vent implant. Int J Oral Maxillofac Implants. 6(4):391 – 398. Cooper LF. 2010. Factors influencing primary dental implant stability remain unclear. J Evid Based Dent Pract. 10(1):44–45. Fontijn-Tekamp FA, Slagter AP, Van Der Bilt A, Van ’T Hof MA, Witter DJ, Kalk W, Jansen JA. 2000. Biting and chewing in overdentures, full dentures, and natural dentitions. J Dent Res. 79(7):1519– 1524. Holmgren EP, Kilgren LM, Mante F. 1998. Evaluating parameters of osseointegrated dental implants using finite element analysis – a two-dimensional comparative study examining the effects of implant diameter, implant shape, and load direction. J Oral Implantol. 24(2):80 – 88. Huang HL, Hsu JT, Fuh LJ, Lin DJ, Chen MY. 2010. Biomechanical simulation of various surface roughnesses and geometric designs on an immediately loaded dental implant. Comput Biol Med. 40(5):525– 532. Kong L, Sun YY, Hu KJ, Liu YP, Li DH, Qiu ZH, Liu BL. 2008. Selections of the cylinder implant neck taper and implant end fillet for optimal biomechanical properties: a three-dimensional finite element analysis. J Biomech. 41(5):1124– 1130. Lee JH, Frias V, Lee KW, Wright RF. 2005. Effect of implant size and shape on implant success rates: a literature review. J Prosthet Dent. 94(4):377– 381. Natali AN, Pavan PG. 2002. A comparative analysis based on different strength criteria for evaluation of risk factor for dental implants. Comput Methods Biomech Biomed Eng. 5(2):127 – 133. Olate S, Lyrio MC, Moraes M, Mazzonetto R, Moreira RW. 2010. Influence of diameter and length of implant on early dental implant failure. J Oral Maxillofac Surg. 68(1):414–419. Pera P, Bassi F, Schierano G, Appendino P, Preti G. 1998. Implant anchored complete mandibular denture: evaluation of masticatory efficiency. Oral function and degree of satisfaction. J Oral Rehabil. 25(6):462– 467. Quaresma SE, Cury PR, Sendyk WR, Sendyk CA. 2008. A finite element analysis of two different dental implants: stress distribution in the prosthesis, abutment, implant, and supporting bone. J Oral Implantol. 34(1):1 –6. Reiger MR, Adams WK, Kinzel GL. 1990. A finite element survey of eleven endosseous implants. J Prosthet Dent. 63 (4):457 – 465. Salvi GE, Bra¨gger U. 2009. Mechanical and technical risks in implant therapy. Int J Oral Maxillofac Implants. 24(9): 69 – 85. Steigenga JT, Shammari KF, Nociti FH, Misch CE, Wang HL. 2003. Dental implant design and its relationship to long-term implant success. Implant Dent. 12(4):306– 317. Susarla SM, Chuang SK, Dodson TB. 2008. Delayed versus immediate loading of implants: survival analysis and risk factors for dental implant failure. J Oral Maxillofac Surg. 66 (2):251 – 255. Testori T, Wiseman L, Woolfe S, Porter SS. 2001. Prospective multicenter clinical study of the osseotite implant: four-year interim report. Int J Oral Maxillofac Implants. 16(2):193–200. Wu T, Liao WH, Dai N, Tang C. 2010. Design of accustom angle dabutment for dental implants using computer-aided design and nonlinear finite element analysis. J Biomech. 43(10): 1941– 1946. Yang J, Xiang HJ. 2007. A three-dimensional finite element study on the biomechanical behavior of an FGBM dental implant in surrounding bone. J Biomech. 40(11):2377– 2385.
