Effect of marginal misfit, welding type and screw material on the strength of the detorque prosthetic screws and stress induced the abutments

Author(s)

Sabrina Alessandra Rodrigues

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2012-04-27

Examining board members

Marcelo Ferraz Mesquita; Luis Geraldo Vaz; Rafael Leonardo Xediek Consani

• Advisor: Marcelo Ferraz Mesquita

Abstract

The aim of this study was to evaluate the stress induced to analogs of prosthetic abutment using strain gauges and to analyze the detorque strength of prosthetic screws (gold and titanium) of frameworks casted in commercially pure titanium (cp Ti) before and after laser and TIG (tungsten inert gas) welding procedures. Twenty frameworks were made simulating a three-element fixed prosthesis. Twenty index models with modified analogs of prosthetic abutments were obtained for stress analyses and twenty index models with conventional analogs of prosthetic abutments for welding (laser e TIG) and detorque analyses of the prosthetic screws. Both index models were made with 200 'mi'm vertical marginal misfit. An optic microscope was used to measure the vertical marginal misfit following the single-screw test protocol. The welding parameters were the following: laser welding (370V/9ms), TIG welding (3: 36A/2: 60ms). The stress induced on the analogs was evaluated through of the extensometric analysis using strain gauges (before and after welding). The torque of gold and titanium screws was performed with torque (10 Ncm) and retorque (10 Ncm) after 10 minutes. The detorque of the prosthetic screws was performed 10 minutes after the retorque using a digital torquemeter. The results were statistically analyzed (ANOVA/Tukey test (?=0.05)/ Pearson correlation test). A decrease in the levels of vertical marginal misfit was observed after the welding procedures (laser and TIG). Regarding the stress, after the welding procedures, stress levels were lower using laser welding than the TIG. The detorque values were lower for the gold screws than the titanium ones, which presented increased destorque values after welding procedures. There was no correlation between marginal misfit, stress and detorque strength. Thus, it can be concluded that the laser welding procedure was more effective for the improvement of adaptation of three-element implant-supported frameworks, when compared to TIG; and that titanium prosthetic screws can be considered more stable than the gold prosthetic screws when torqued in prostheses that present adaptation satisfactory (AU)

• FAPESP's process: 09/13294-7 - The effect of misfit level, welding type and screw material on preloaded torque of implants screws
• Grantee: Sabrina Alessandra Rodrigues
• Support Opportunities: Scholarships in Brazil - Master