Investigation of the effect of different margi̇nal design on stress in periodontal ligaments, teeth, bones and infrastructure materials by finite element analysis when PEEK and PEKK infrastructure materials are used

Objective: Due to the increasing aesthetic expectations of patients in dentistry, metal-free restorations are gaining even more importance. Because at this, the use of polymers is increasing day by day. The polyaryletherketone (PAEK) family is considered as an alternative to existing restorative materials. There are 2 different types of PAEK family, namely Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK) used in dentistry. The aim of this thesis study is to investigate the effects of PEEK and PEKK infrastructure materials on the periodontal ligament, tooth, intraosseous, infrastructure and superstructure materials by using finite element analysis, as an alternative to metal-supported restorations in different marginal types, with ceramic and composite superstructure materials. Materials and Methods: In this study; PEEK, PEKK infrastructure and porcelain, composite superstructure were designed on four different marginal types in the maxillary first molar tooth. By applying oblique and vertical forces to the crown, maximum prime stress, minimum prime stress on cortical bone, cancellous bone, periodontal ligament, dentin, pulp, infrastructure and superstructure, Von mises stress findings were examined. The study was carried out by using three-dimensional finite element stress analysis method and static linear analysis. Results: The highest principle stress value in the cortical bone was observed when vertical force was applied (16.1712MPa) in group 13 (pekk infrastructure-porcelain superstructure-chamfer marginal). Group 2 (peek infrastructure-composite superstructure-shoulder 900 marginals) was also observed. The highest maximum principle stress value in the cancellous bone (1.35926MPa) was observed in group 2. The highest minimum principle stress value in the cancellous bone was observed in group 4 (peek infrastructure-porcelain superstructure-shoulder 1350 marginals) when vertical force was applied (-2.41887MPa). The highest von mises stress value was observed in group 13 when vertical force was applied (1.547746MPa). The highest von Mises stress value in dentin was observed in group 13 when oblique force (1833.63MPa) was applied. The highest von mises stress value in the infrastructure was observed in group 13 when oblique force (288,305 MPa) was applied. The highest von Mises stress value on the pavement was observed in group 15 (pekk base-porcelain-chamfer marginal) when oblique force was applied (9587.1 MPa). Conclusion: When the stresses occurring in the superstructure are evaluated, regardless which of the infrastructure, we can choose shoulder 900 or deep chamfer marginal design in both composite and porcelain superstructures. vii Keywords: Finite Element Analysis, Polyetheretherketone, Polyetherketoneketone, Marginal Design