Determinação da angulação das paredes axiais dos preparos dentários para coroas totais em clínica simulada

Abstract

Introduction: The rehabilitation with dental-supported fixed prosthesis is sometimes preferred to implant-supported, since it could represent a less traumatic and less costly procedure and might even fix or protect the abutment teeth. The clinical success of the implant is related to its holding capacity and permanence in the oral cavity. The tooth preparation is the most reliable way to get the required retention. It is important to consider that the fundamental unit of retention is the angle that two opposite walls form together named convergence angle. It is recommended that the walls present a convergence angle between 2 and 6 degrees. However, it appears that most dental preparations analyzed do not respect this value, due to access difficulties, visualization errors and aspects inherent to the remaining tooth, such as height, width, position and morphology. Objectives: Validate an instrument that helps to determine the convergence angle during tooth preparation. Materials and Methods: First it was necessary to improve and manufacture an existing instrument designed to determine the convergence angle of tooth preparation. Subsequently a sample of 140 mesiodistal and buccolingual convergence angles of dental preparations for crowns performed on Frasaco® teeth was evaluated by 5th year students of Dental Degree of the Portuguese Catholic University. The observations were statistically compared with the control group with SPSS® (IBM Corp. Released in 2011. SPSS Statistics for Windows, Version 20.0. Armonk, NY: IBM Corp.), applying correlation (Pearson Coefficient test) and comparison of means tests (Student’s t-test). It was considered a significance level of 1%. Results: There were no significant differences between the means of the observed values and the control group whereas t(139) = - 1,524 and p = 0.130. Additionally, it was possible to demonstrate that the values were typically correlate with 0,30 < r(138) < 0,5 and p < 0,01. Conclusion: It was possible to check that the analyzed preparations showed convergence angles consistent with what is described in literature. Under the experimental conditions the developed instrument was considered valid to help determine the convergence angle of tooth preparations of Frasaco® teeth in simulated clinical environment.

Date of Award	2013
Original language	Portuguese
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Helder José Martins Esteves (Supervisor)