The study objective was to determine cementum-dentin wall thickness along the furcation groove in maxillary bifurcated first premolars after preparation with three successively larger, 0.04 tapered, nickel titanium rotary files. Pre-instrumentation and post-instrumentation imaging was accomplished utilizing Cone Beam Computed Tomography. All data was analyzed using an ANOVA. Instrumentation resulted in a significant reduction in dentin-cementum wall thickness (p < .001). At mid-groove, predicted dentin-cementum wall thickness (95% CI) was equal to or less than the proposed standard (0.50 mm) for apical file sizes 30, 35, and 40 respectively. Instrumentation of the mid-groove in maxillary first premolars reduces dentin-cementum wall thickness to levels that may be insufficient to ensure tooth integrity.

The purpose of this study was to compare the thickness of dentin removed from the buccal root of bifurcated maxillary first premolars (BMFP) in the area of furcation groove after instrumentation with WaveOne and LightSpeed LSX files utilizing limited field cone beam computerized tomography. All data was analyzed using repeated-measured mixed-model ANOVA and differences were described using Tukey’s multiple comparison procedure. The thickness of dentin removed with LightSpeed LSX files (0.1 mm) was significantly less than the thickness of dentin removed with WaveOne files (0.2 mm). To conclude, LSX files remove a more predictable and consistent thickness of dentin from the buccal root of BMFP, irrespective of the pre-instrumentation thickness of dentin and the file size when compared to WO files that remove a more variable thickness of dentin.