Avaliação do comportamento mecânico de raízes fragilizadas submetidas a diferentes estratégias restauradoras e carregamentos oclusais

Abstract

The selection of the most adequate post system or technique for each case is the key to the success and longevity of the treatment planned, although the best approach to restoring teeth with weakened roots remains controversial. This in vitro study aims to evaluate the fracture resistance of weakened roots, restored with three different restoration strategies (cast post and core, anatomic post, flared root resin composite reanatomization), under edge to edge or cingule load, through mechanical cyclic aging and further submission to static load till fracture. Seventy-two incisors bovine teeth were used in this experiment. The specimens were randomly divided into six groups (n=12) according to the restorative approach (cast post and core, anatomic post and flared root resin composite reanatomization) and the load place (cingule load and edge to edge load). All specimens received metal crowns. A mechanical cycling of 1.200.000 cycles (100N; ±37ºC; 4hz; 45º) was applied with further submission to static load till fracture. The present article also classified the failure mode as repairable and nonrepairable. To analyze the relationship between the posts and load places different statistical tests were applied (Paired t- test, Wilcoxon, Oneway anova, Kruskal-Wallis) and in order to verify the relationship between load site and failure another tests were used (Chi-square test, Fisher´s exact test). The cast post and core promoted higher mean values of fracture load at weakened roots and higher levels of unfavorable fractures for both type of loads. Nevertheless, the other groups promoted more repairable fractures for both type of loads and an average fracture strength with stastical similar values. When evaluated the site of occlusal load all posts presented a higher mean fracture strength at cingule load compared to edge to edge load. According to the results, weakened roots at incisors presenting edge to edge load produce higher risk of fracture in comparison to incisors presenting cingule load. When comparing the posts, it can be concluded that despite cast post and core produce higher fracture strength values, the anatomic post and the flared root composite reanatomizarion groups are better options considering the average fracture strength values produced that are still higher than the phisiological forces produced at cingule load and also because of the incidence of more repairable fractures.