Influence of Access Cavity Design on Root Canal Detection, Instrumentation Efficacy, and Fracture Resistance Assessed in Maxillary Molars

Introduction: The aim of this study was to assess the influence of contracted endodontic cavities (CECs) on root canal detection, instrumentation efficacy, and fracture resistance assessed in maxillary molars. Traditional endodontic cavities (TECs) were used as a reference for comparison. Methods: Thirty extracted intact maxillary first molars were scanned with micro computed tomographic imaging at a resolution of 21 assigned to the CEC or TEC group (n = 15/group), and accessed accordingly. Root canal detection was performed in 3 stages: (1) no magnification, (2) under an operating microscope (OM), and (3) under an OM and ultrasonic troughing. After root canal preparation with Reciproc instruments (VDW GmbH, Munich, Germany), the specimens were scanned again. The noninstrumented canal area, hard tissue debris accumulation, canal transportation, and centering ratio were analyzed. After root canal filling and cavity restoration, the sample was submitted to the fracture resistance test. Data were analyzed using the Fisher exact, Shapiro-Wilk, and t tests (alpha = 0.05). Results: It was possible to locate more root canals in the TEC group in stages 1 and 2 (P <.05), whereas no differences were observed after stage 3 (P >.05). The percentage of noninstrumented canal areas did not differ significantly between the CEC (25.8% +/- 9.7%) and TEC (27.4% +/- 8.5%) groups. No significant differences were observed in the percentage of accumulated hard tissue debris after preparation (CEC: 0.9% +/- 0.6% and TEC: 1.3% +/- 1.4%). Canal transportation was significantly higher for the CEC group in the palatal canal at 7 mm from the apical end (P <.05). Canal preparation was more centralized in the palatal canal of the TEC group at 5 and 7 mm from the apical end (P <.05) and in the distobuccal canal of the CEC group at 5 mm from the apical end (P <.05). There was no difference regarding fracture resistance among the CEC (996.30 +/- 490.78 N) and TEC (937.55 +/- 347.25 N) groups (P >.05). Conclusions: The current results did not show benefits associated with CECs. This access modality in maxillary molars resulted in less root canal detection when no ultrasonic troughing associated to an OM was used and did not increase fracture resistance.