Effect of Canal Preparation on Fill Length in Straight Root Canals Obturated with Real Seal 1 and Thermafil Plus

Introduction: A common adverse effect when using thermoplasticized obturators is overextension. A canal preparation allowing for predictable obturation length would be of clinical value. This study compared straight canals instrumented to a size 40 file by evaluating the extension of 2 thermoplastic obturation systems, a 0.04 standardized taper preparation (STP) and a varied taper preparation (VIP), by evaluating the extension of 2 thermoplastic obturation systems, RealSeal 1 (RS-1) and Thermafil Plus (TP). Methods: Eighty extracted mature human premolars with single straight canals were randomly divided into 4 experimental groups (n = 20). Groups 1 and 2 were instrumented to size 40/04 at working length with SIP. Groups 3 and 4 were instrumented to size 40/02 at working length with VIP. Groups 1 and 3 were obturated with RS-1, and groups 2 and 4 were obturated with TP. All groups were obturated per manufacturer's instructions. Extension of material was evaluated and assessed ordinally. Statistically significant differences were determined by logistic regression with significance level set at P < .05. Results: Significant differences in extrusion existed between groups 2 and 4 when controlling for type of material (P = .026) and all groups for extrusion of TP compared with RS-1 when controlling for type of preparation (P < .001). Conclusions: The results indicate that when filling with RS-1 obturators, the canal can be instrumented to an SIP or VIP with a low likelihood of excessive extrusion. If the clinician prefers to use TP obturators, this study validates a VIP to decrease the occurrence of overextension. (J Endod 2012;38:1380-1382)