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

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.

A STRESS ANALYSIS OF THE IMPLANT: SUPPORTED OVERDENTURE USING STRAIN GAUGE / 대한치과보철학회지

Stress distribution on mandibular implants supporting overdentures were registered in vitro experimental model by means of 4 rosette gauges which were placed around the implant. The overdenture attachments used in this study were the Resilient Dolder bar, Rigid Dolder bar, Round bar, Hader bar&Dal-Ro attachment. An occlusal jig was placed on the overdenture and the loading sites were 3 points which mimicked working, balancing, and median relations. With 5 and 10kg loading, strains were measured by strain indicator(P-3500, Measurement group, Raleigh, USA), and using these data, maximum and minimum principal stresses and Von Mises stress were calculated and evaluated. The results were as follows: There was a tendency of high stress concentration in the lingual side of the implant, and in the buccal side low stress was developed regardless of the attachment systems. The resilient Dolder bar concentrated highest stress among the attachment systems, and the Round bar and the Dal-Ro attachment provided comparatively low stresses around the implant. The rigid Dolder bar concentrated high stress in the mesial side, and the Dal-Ro attachment developed tensile stress patterns in the lingual and distal sides of the implant at the balancing relation.