Effect of cavity designs on instrumentation, obturation and fracture resistance of mandibular first premolars with Vertucci V canal.

Introduction: This study aimed to assess the effect of cavity designs on instrumentation, obturation and fracture resistance for mandibular first premolars with Vertucci V canal.

Methods: Mandibular first premolars with Vertucci V canal were scanned with micro-CT. 20 teeth with moderately curved canal were prepared with conservative endodontic cavity (CEC/M) or traditional endodontic cavity (TEC/M), and 30 with severely curved canal were prepared with CEC (CEC/S), modified CEC (MCEC/S) or TEC (TEC/S). CECs and MCEC were prepared using dynamic navigation system. TECs were prepared freehand. Canals were prepared with WaveOne Gold, irrigated and then obturated with single-cone technique using iRoot SP sealer and WaveOne Gold gutta-percha cones. After restoration, all teeth were submitted to fracture resistance test. Removal of peri-cervical dentin (PCD), volume of dentin removal, area of untouched canal wall, accumulated hard tissue debris, centering ability, voids in canal filling and load at fracture were evaluated.

Results: MCEC and CEC groups preserved more PCD above the alveolar bone level, and more fracture resistance than TEC groups. At 3mm from apical foramen, lower centering ability in mesio-distal direction was found in buccal canal of CEC/S group. More voids were found in lingual canal for CEC/S compared with TEC/S (P<0.05).

Conclusions: CEC and MCEC prepared with dynamic navigation system could preserve more dentin above the alveolar bone and fracture resistance than TEC prepared freehand. For teeth with severely curved V canal, MCEC showed similar ability in instrumentation and obturation as TEC.