Cone-Beam Computed Tomography Evaluation of Rotary MM Files vs Manual K Files in Primary Molars: An In Vitro Study.

Abstract

Rotary instrumentation in pediatric dentistry is an emerging concept, thus this study was performed to evaluate the remaining dentine thickness (RDT), canal transportation, centering ability, quality of obturation using cone-beam computed tomography (CBCT), and the time efficiency of rotary versus manual instrumentation in mandibular second primary molars. Forty mandibular primary second molars (160 canals) were randomly and equally allocated to four groups. Instrumentation was done using K files in groups I and II; in each group, the obturation was done by two different obturation techniques; incremental technique and disposable syringe technique, respectively. MM rotary files (Innovative Material and Devices, Inc. [IMD], Shanghai, China) were used in groups III and IV; in each group, the obturation was done by incremental technique and disposable syringe technique. Preoperative and postoperative CBCT scans were performed and evaluated for the RDT, centering ability, canal transportation, and the canal filling quality, which was assessed as (underfill, optimal fill, and overfill). Instrumentation time was recorded for groups I and II collectively (manual instrumentation), and groups II and III collectively (rotary instrumentation). Statistical analysis was done using Chi-square, ANOVA, and post hoc Tukey tests, at p < 0.05). The MM rotary file removed a significantly less amount of dentine at all levels specifically at the middle section (p = 0.003). The canal transportation was significantly higher in the manual group at the cervical level (p = 0.022). In all sections, the rotary group had significantly higher values of centering ratio than the manual group (p < 0.05), which means a lower deviation of rotary instruments. For both types of files, there was no significant difference between different obturation techniques (p > 0.05). Instrumentation time was significantly lower in the rotary group (p < 0.001). Regarding the dentine removal and the shaping ability of MM files acceptable results were obtained; however, no significant difference between the different obturation techniques. Notable time efficiency was reported in the rotary files as well. The use of rotary files resulted in better conservation of tooth structure, better canal centering, and obturation quality as well as less canal transportation and less instrumentation time compared to manual K files.