Influence of Minimally Invasive Access Cavity Designs on the Fracture Resistance of Endodontically Treated Mandibular Molars Subjected to Thermocycling and Dynamic Loading.

INTRODUCTION: The aim of this study was to investigate the fracture resistance of endodontically treated and restored permanent mandibular molars with minimally invasive access cavities subjected to thermocycling and dynamic loading. METHODS: Forty first and second mandibular molars were randomly assigned to 4 groups (n = 10/group) as follows: group 1, control (intact teeth); group 2, traditional access cavity (TradAC); group 3, conservative access cavity (ConsAC); and group 4, truss access cavity (TrecAC). After endodontic treatment, teeth were restored with SDR core (Dentsply Caulk, Milford, DE) and subjected to thermocycling followed by dynamic and static loading with a multiaxial fatigue testing machine (Instron, Canton, MA). The maximum load to fracture and pattern of failure (restorable/unrestorable) were recorded. Data were evaluated with analysis of variance and the Tukey post hoc test for multiple comparisons. RESULTS: Fracture resistance of the samples in the control group were higher than those in the experimental groups (P < .005). TradAC exhibited the least resistance to fracture (P < .005). There was no statistically significant difference in the fracture resistance of ConsAC and TrecAC (P = .361) Unrestorable fractures were more frequent in the TradAC group compared with all other groups. CONCLUSIONS: Mandibular molars with ConsAC and TrecAC exhibited superior fracture resistance compared with TradAC. TradAC had the highest number of unrestorable fractures.