A influência do acesso minimamente invasivo na instrumentação de canais ovais: análise em microtomografia computadorizada e teste de resistência à fadiga flexural

Abstract

Purpose: The present study evaluated the type of endodontic access cavity would result in greater or lesser touch on the canal walls during instrumentation, and the influence on the instrument's resistance to cyclic flexural fatigue. Methods: Extracted human mandibular incisors with oval-shaped canals were scanned by Micro-computed tomography for sample selection and distribution in two experimental groups (n = 19), according to the test cavity: Group I, minimally invasive endodontic access (MIA) and Group II, conventional endodontic access (CEA). The canals were instrumented with WaveOne Gold Medium system and irrigated with 2.5% NaOCl and 17% EDTA. After rescanning, the untouched areas were measured and analyzed by reconstructing and overlapping the images. Endodontic instruments were subjected to static flexural cyclic fatigue testing using a stainless-steel artificial canal (60° angle and 5mm radius) located 5 mm from the tip. The instruments (n= 7) were rotated to fracture, and the time in seconds to fracture was recorded using a digital timer. The number of cycles to fracture (NCF) was calculated and statistically analyzed. The data obtained in Micro–computed tomography was analyzed by the T test, Mann-Whitney and Wilcoxon tests. For cyclic fatigue data, Tukey's post-test ANOVA was used. A significance level of 5% was adopted for all analyzes. Results: There was no statistical difference between the groups regarding the walls touched and walls untouched by the endodontic instrument in relation to the variation of the access cavities (p> 0.05). The cyclic fatigue resistance test showed no statistical differences between the groups. Conclusion: Within the limitations of the research, the use of minimally invasive cavities did not interfere in the instrumentation of lower incisors with straight and oval canals, and there was no difference in the resistance to flexural fatigue of the instruments against different accesses.