Micro-CT evaluation of root canal preparation with rotary instrumentation on prototyped primary incisors

Abstract This study aimed to evaluate the endodontic instrumentation outcomes with asymmetrical files compared to reciprocating and hand files (HFs) in 3D-printed prototypes of upper primary incisors using micro-computed tomography (micro-CT). For this purpose, 50 prototypes were randomly divided (n = 10) according to the instrumentation technique as follows: HFs, a reciprocating file (WaveOne® Gold [WOG]), and three asymmetrical movement files: XP-Endo® Shaper (XPS), XP-Endo® Finisher (XPF), and XP Clean (XPC). The specimens were scanned and, after registration of the baseline and instrumented volumes, changes in the root canal volume (RCV), debris accumulation, removed root material volume (RRMV), non-instrumented areas, and the presence of cracks/perforations were quantified. Data were analyzed by analysis of variance and Student’s t-test, while the effect size was calculated for statistically significant outcomes. All groups showed an increase in RCV after instrumentation (p &lt; 0.05), but this was higher with HFs (p &lt; 0.05). Accumulated debris was higher for WOG and XPS (p &lt; 0.05), but WOG exhibited more in the medium and apical third areas. HFs showed the highest RRMV (p &lt; 0.05), especially at the apical third. The non-instrumented areas were lower for HFs and XPC than for the other systems (p &lt; 0.05). Cracks were present in a few WOG (n = 2) and HF specimens (n = 3) and in this group, one of the cracked specimens and two others showed perforations. The asymmetric systems resulted in conservative dentin removal and fewer cracks/perforations as compared to HFs and a reciprocation file in prototyped primary upper incisors. XPC showed the best compromise between RRMV and non-instrumented areas with a low accumulation of debris.摘要 本研究旨在借助显微计算机断层扫描（micro-computed tomography, micro-CT）技术，对比评估不对称根管锉、往复式根管锉与手用根管锉（Hand Files, HFs）在3D打印上颌乳前牙模型中实施根管预备的临床效果。为此，将50个上颌乳前牙模型按根管预备技术随机分为5组（每组n=10）：手用锉组、往复式锉组（WaveOne® Gold [WOG]），以及3种不对称运动根管锉组——XP-Endo® Shaper（XPS）、XP-Endo® Finisher（XPF）与XP Clean（XPC）。对所有标本进行扫描，在记录基线体积与预备后体积后，定量分析根管容积（Root Canal Volume, RCV）变化、碎屑堆积量、牙根去除材料体积（Removed Root Material Volume, RRMV）、未预备区域面积以及裂纹/穿孔的发生情况。数据采用方差分析与Student t检验进行统计学分析，并对具有统计学显著性的结果计算效应量。所有实验组的根管容积在预备后均显著升高（p<0.05），但手用锉组的升高幅度最为显著（p<0.05）。往复式锉组与XPS组的碎屑堆积量更高（p<0.05），其中WOG组在根管中段与根尖段的碎屑堆积更为明显。手用锉组的牙根去除材料体积最高（p<0.05），尤以根尖段为甚。手用锉组与XPC组的未预备区域面积显著低于其余各组（p<0.05）。仅少量WOG组（n=2）与手用锉组（n=3）的标本出现裂纹，其中手用锉组的1例裂纹标本与另外2例标本同时存在穿孔。与手用锉组及往复式锉组相比，不对称预备系统在模拟上颌乳前牙模型中可更保守地去除牙本质，且产生的裂纹与穿孔更少。XPC组在牙根去除材料体积与未预备区域面积之间实现了最优平衡，且碎屑堆积量较低。