Influence of mechanical cycling on marginal misfit, strain and loosening torque in the implant-supported system

Author(s)

Isabella da Silva Vieira Marques

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2013-06-17

Examining board members

Marcelo Ferraz Mesquita; Karin Hermana Neppelenbroek; Valentim Adelino Ricardo Barão

• Advisor: Marcelo Ferraz Mesquita; Jessica Mie Ferreira Koyama Takahashi

Abstract

The aim of this study was to evaluate the influence of cyclic loading on loosening torque, misfit and strain transmitted to prosthesis-implant system. Ten Commercially pure titanium frameworks were casted simulating fixed partial dentures (FPD) of three elements retained by two implants and mandibular full-arch fixed prostheses (FFP) as bars retained by five implants. From the waxed and casted frameworks, models were fabricated, which resulted in three evaluation groups (n = 10): group I (pre-casting), group II (passive fit) and group III (simulated misfit), for both prosthetic designs. For each fabricated acrylic resin cast, the misfit and loosening torque analyses were assessed before and after mechanical loading (106 mechanical cycles, 2 Hz, 280 N). The initial prosthetic and mini abutment screws loosening torque were measured 24 hours after the tightening torque (10 Ncm and 20 Ncm, respectively) using a digital torque meter. The single-screw test was performed and the vertical misfit was quantified using an optical microscope. The strain after fixation was evaluated in a plaster cast using strain gauges analysis with each framework tightened to the cast with 10 Ncm standardized torque. The results were submitted to exploratory analysis followed by statistical tests such as ANOVA and Tukey (? = 0.05) when parametric data were found and Mann-Whitney and Wilcoxon when non-parametric data were obtained. For all groups, the cyclic loading had no significant difference when analyzed the prosthetic screw loosening torque, misfit and strain, but there was an increase of the mini abutment loosening torque mean values for FPD of groups II and III and for FFP of group III. The Pearson correlation test (? = 0.05) indicated a positive correlation between misfit and strain for all evaluated situations and a negative correlation between loosening torque and vertical misfit for both prostheses designs of groups II and III. Within the evaluated conditions and obtained results, it can be concluded that cyclic loading of screw-retained multiple prosthesis does not exert significant influence on loosening torque, misfit and strain. The prosthetic screws have a greater tendency to loosening in ill-fitting prosthesis, which induces higher strain values on prosthesis-implant system (AU)

• FAPESP's process: 10/13998-1 - Strain, marginal misfit and torque analysis of cyclic loaded implant-supported frameworks
• Grantee: Isabella da Silva Vieira Marques
• Support Opportunities: Scholarships in Brazil - Master