Copyright @ 2010 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited. Implant Platform Switching: Biomechanical Approach Using Two-Dimensional Finite Element Analysis Lucas Fernando Tabata, DDS, PhD,* Wirley Gon 0alves Assun 0a ˜ o, DDS, PhD,* Valentim Adelino Ricardo Bar a ˜ o, DDS, MSc,* Edson Antonio Capello de Sousa, PhD,Þ E ´ rica Alves Gomes, DDS, MSc,* and Juliana Aparecida Delben, DDS, MSc* Abstract: In implant therapy, a peri-implant bone resorption has been noticed mainly in the first year after prosthesis insertion. This bone remodeling can sometimes jeopardize the outcome of the treatment, especially in areas in which short implants are used and also in aesthetic cases. To avoid this occurrence, the use of plat- form switching (PS) has been used. This study aimed to evaluate the biomechanical concept of PS with relation to stress distribution using two-dimensional finite element analysis. A regular matching diameter connection of abutment-implant (regular platform group [RPG]) and a PS connection (PS group [PSG]) were simulated by 2 two-dimensional finite element models that reproduced a 2-piece implant system with peri-implant bone tissue. A regular implant (prosthetic platform of 4.1 mm) and a wide implant (prosthetic platform of 5.0 mm) were used to represent the RPG and PSG, re- spectively, in which a regular prosthetic component of 4.1 mm was connected to represent the crown. A load of 100 N was applied on the models using ANSYS software. The RPG spreads the stress over a wider area in the peri-implant bone tissue (159 MPa) and the implant (1610 MPa), whereas the PSG seems to diminish the stress distribution on bone tissue (34 MPa) and implant (649 MPa). Within the limitation of the study, the PS presented better biomechanical behavior in relation to stress distribution on the implant but espe- cially in the bone tissue (80% less). However, in the crown and retention screw, an increase in stress concentration was observed. Key Words: Dental implants, platform switching, implant supported prosthesis, finite element analysis, stress distribution, crestal bone loss (J Craniofac Surg 2010;21: 182Y187) S ince the introduction of osseointegration, new alternatives of prosthetic treatment were available to patients based on the placement of endosseous titanium implants in edentulous areas. The replacement of missing teeth by means of implants has become a predictable treatment modality for both complete and partial eden- tulous patients. 1Y3 Ten-year surveys of fixed prostheses on natural teeth reveal a survival rate of approximately 75%. 4,5 In contrast, success rates for endosseous implants have been shown to be greater than 90%. 6,7 As these success rates have been achieved, treatment options have expanded to include immediate and early delayed im- plant placement and loading after tooth extraction. However, conven- tional 2-step surgical and delayed loading techniques are still relevant in certain circumstances. 8 One aspect of implant therapy that can be most challenging is the placement and subsequent restoration in the aesthetic zone, 5 in which the level of peri-implant bone support and the soft-tissue dimensions are factors suggested to be critical for the aesthetic out- come. 9 Numerous techniques within surgical hard-tissue and soft- tissue management are available today to assist in achieving an ideal aesthetic treatment result. The current view is that the long-term preservation of healthy peri-implant tissues is of primary import- ance for ensuring function and aesthetics over an extended period. 10 Nevertheless, after implant insertion and loading, the crestal bone usually undergoes remodeling and resorption during the first year after prosthetic restoration in 2-piece implants. 10,11 Radio- graphic observations have shown that, after abutment connection, remodeling of bone takes place, which is manifested in diminished bone dimensions, both horizontally (1.3Y1.4 mm) 8,12 and vertically (1.5Y2 mm), at the facial aspect of the implant. This crestal bone loss generally coincides with the level of the first thread of the implants 9 and can jeopardize the treatment outcome, especially in aesthetic cases in which facial soft-tissue deficiencies create a crown that appears longer than desired, 5 because the gingival papilla sup- port depends on the crestal bone level underneath. 8 It is also crit- ical in areas where short implants are used, 10 in which the bone resorption would represent a decrease in bone-to-implant contact surface that could lead to implant or osseointegration failure. The factors involved in the mechanisms of the bone resorp- tion and deposition around dental implants are not yet completely known, 13 and several theories try to explain the changes observed in crestal bone height after implant restoration. 14 The establishment of a biologic width, 10,15Y17 the location of the inflammatory cell infiltrate, 14,18 the distance of implant-abutment junction (IAJ) from the crestal bone, 17,19,20 gingival biotype, 21 and stress concentration due to occlusal loading 6,13,22Y27 are some of those hypotheses. 10 It has been reported that the platform switching (PS) seems to reduce or eliminate the expected postrestoration crestal bone re- modeling. The concept of PS presented by Lazzara and Porter 14 consists in the placement of smaller-diameter prosthetic compo- nents on wider-diameter implants and was based on a description SCIENTIFIC FOUNDATION 182 The Journal of Craniofacial Surgery & Volume 21, Number 1, January 2010 From the *Department of Dental Materials and Prosthodontics, Ara0atuba Dental School, and the †Department of Mechanical Engineering, Bauru Engineering School, Sa ˜o Paulo State University (UNESP), Sa ˜o Paulo, Brazil. Received May 7, 2009. Accepted for publication May 30, 2009. Address correspondence and reprint requests to Wirley Gon0alves Assun0a ˜o, DDS, PhD, Department of Dental Materials and Prosthodontics, Ara0atuba Dental School (UNESP), Jose ´ Bonifa ´cio, 1193, Ara0atuba, Sa ˜o Paulo, Brazil 16015-050; E-mail: wirley@foa.unesp.br The authors claim that they did not receive funding for research on which their article is based from any of the following organizations: National Institutes of Health, Wellcome Trust, Howard Hughes Medical Institute, or others. Copyright * 2010 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0b013e3181c50eb8