RESUMO
OBJECTIVES: The purpose of this study was to determine the influence of platform switching on stress distribution of two different implant systems using three-dimensional (3D) finite element models. MATERIALS AND METHODS: Six 3D finite element models were created to replicate two different implant systems with peri-implant bone tissue, in which six different implant-abutment configurations were represented: model XiVE-a: 3.8-mm-diameter implant and 3.8-mm-diameter abutment; model XiVE-b (platform-switching model): 4.5-mm-diameter implant and 3.8-mm-diameter abutment; model XiVE-c: 4.5-mm-diameter implant and 4.5-mm-diameter abutment; model 3i-a: 4.0-mm-diameter implant and 4.1-mm-diameter abutment; model 3i-b (platform-switching model): 5.0-mm-diameter implant and 4.1-mm-diameter abutment; model 3i-c: 5.0-mm-diameter implant and 5.0-mm-diameter abutment. vertical and oblique loads of 100 were applied to all models. RESULTS: While the pattern of stress distribution was similar for both loading situations, oblique loading resulted in higher intensity and greater distribution of stress than axial loading in both cortical bone and implant-abutment- interface. Stress distribution at peri-implant bone was almost identical with similar magnitudes for all six models. In both implant systems, platform-switching models demonstrated lower maximum von Mises stress in cortical bone than conventional models. However, in both implant systems and under both loading situations, platform-switching models showed higher stresses at the implant-abutment interface than conventional models. CONCLUSION: In both implant systems, platform switching design reduced the stress concentration in the crestal bone and shifted it towards the area of implant-abutment interface.
RESUMO
Our objective was to determine the association between keratinized mucosa width and the health status of the supporting tissue around implants supporting overdentures. Sixty-six functioning dental implants were examined. Periodontal parameters measured included gingival index, plaque index, bleeding on probing, probing depth, mucosal recession, periodontal attachment level, radiographic bone level, and width of keratinized mucosa. A negative correlation was found between keratinized mucosa width and mucosal recession and periodontal attachment level. When data were dichotomized by keratinized mucosa width, the mean gingival index score, plaque index score, and bleeding on probing were significantly higher for those implants with a narrow zone (< 2 mm) of keratinized mucosa. A wider mucosal band (> or = 2 mm) was associated with less mucosal recession and periodontal attachment loss compared with a narrow (< 2 mm) band. The absence of adequate keratinized mucosa around implants supporting overdentures was associated with higher plaque accumulation, gingival inflammation, bleeding on probing, and mucosal recession.