Three-dimensional finite element stress analysis of single implant restoration using different fixture and abutment screw diameters

Kwon, Joo Hong; Choi, Min Ho; Kim, Yu Lee; Cho, Hye Won

Abstract

STATEMENT OF PROBLEM: As the effects of the various diameters of fixture and abutment screw on stress distribution was not yet examined, this study focused on the different design of single implant restoration using three dimensional finite element analysis. PURPOSE: This study was to compare five different fixture-abutment combinations for single implant supported restorations with different fixture and abutment screw diameters. MATERIALS AND METHODS: The five kinds of finite element models were designed by 3 diameter fixtures (O/ 3.3, 3.75, 5.0 mm) with 3 different abutment screws (O/ 1.5, 1.7, 2.0 mm). The crown for mandibular first molar was made using UCLA abutment according to Wheeler's anatomy. 244 N was applied at the central fossa with two different loading directions, vertically and obliquely (30degrees) and at the buccal cusp vertically. Maximum von Mises stresses were recorded and compared in the supporting bone, crowns, fixtures, and abutment screws. RESULTS: 1. The stresses in supporting bone and implant-abutment structure under oblique loading were greater than those under vertical or offset loading. The stresses under vertical loading were the least among 3 loading conditions regardless of the implant and abutment screw diameters. 2. The stresses in the narrow implants were greater than the wider implants. The narrow implant with narrow abutment screw showed highest stresses in the lingual crest, but the narrow implant with standard abutment screw showed highest stress in abutment screw. 3. The stresses of abutment screws were influenced by the diameter of fixtures and loading conditions. The wide implants showed least difference between two different abutment screw diameters. CONCLUSIONS: The wide implants showed lesser stresses than the narrow implants and affected least by the different abutment screw diameters. The narrow implants with standard abutment screw showed highest stresses in the lingual bony crest under oblique loading.