Micro-CT assessment of an experimental pediatric reciprocating file and an experimental bioceramic-based, resorbable material for shaping and filling of primary teeth

Background This micro-CT study evaluated and compared the shaping performance of a pediatric rotary file and an experimental pediatric reciprocating file in primary molars. Additionally, it compared the efficacy of syringe delivery (SD) and and SD+ultrasonic activation on the filling efficacy of an experimental bioceramic-based root canal filling material, in relation to the file system used. Methods Forty extracted primary molars were randomly divided into two groups: (1) a pediatric rotary file system (AF Baby; Fanta Dental, Shanghai, China), and (2) an experimental reciprocating file system. Following instrumentation, all canals were obturated using an experimental bioceramic-based root canal filling material, delivered via syringe or syringe combined with ultrasonic activation. Comparative analyses were conducted to evaluate changes in canal volume, surface area, structure model index (SMI), uninstrumented canal surface, apical transportation, filling volume, obturation percentage, intersection surface area, and porosity. Statistical evaluation was performed using the Mann-Whitney U test and Wilcoxon signed-rank test, with significance set at p < 0.05. Results Compared with the rotary file system, instrumentation with the reciprocating files resulted in significantly less volumetric change and a reduction in surface area ( p < 0.001 and p = 0.009), with no significant differences in uninstrumented area or apical transportation ( p = 0.602 and p > 0.05, respectively). In the syringe delivery group, the rotary system showed higher filling volume, obturation percentage and intersection surface ( p < 0.001), while no significant differences were observed in the ultrasonic group. Conclusions The experimental reciprocating file system achieved effective canal preparation with significantly less canal enlargement. Ultrasonic activation may enhance filling efficacy of the experimental bioceramic sealer in conservatively prepared files.