Influence of Apical Diameter on Filling Material Extrusion during Retreatment - A Micro-CT and CBCT evaluation

Abstract Aim: To investigate whether foraminal widening performed at primary treatment has an effect on the amount of apically extruded obturator material during retreatment and to evaluate the sensitivity of cone beam computed tomography (CBCT) in detecting extruded obturator material. Methods: Forty palatal roots of maxillary molars were selected based on micro-CT and divided into two groups (n=20): with foraminal widening (WE) and without foraminal widening (NE). To standardize the apical foramen, all specimens were instrumented to the foramen using the Protaper Next system, up to instrument X3. The WE group was instrumented to the foramen up to instrument X5, and the NE group was instrumented 1 mm lower. The canals were obturated 1 mm below the apical foramen with gutta-percha and AH Plus and stored for 7 days at 37 °C and 95% humidity. Roots were fixed in microtubes filled with 1.5% agar gel. The obturation material was removed with Reciproc R50. Scans of the teeth and agar were performed using micro-CT and CBCT. Comparison between groups and between methods was performed using Mann-Withney test (p ≤0.05). Results: No statistical difference was found when comparing the extruded material between groups using micro-CT (p = 0.589) or CBCT (p = 0.953). CBCT measured a greater volume of extruded material than micro- CT (p = 0.0004). Conclusion: Foraminal widening had no effect on the extrusion of filling material during retreatment. The CBCT favored the evaluation of apically extruded filling material.

研究目的：探讨初次根管治疗时实施的根管孔扩大（foraminal widening）对根管再治疗过程中根尖挤出充填材料的体积是否存在影响，并评估锥形束计算机断层扫描（CBCT）检测根尖挤出充填材料的灵敏度。
研究方法：基于显微计算机断层扫描（micro-CT）筛选40颗上颌磨牙腭根样本，将其分为两组（每组n=20）：根管孔扩大组（WE）与非根管孔扩大组（NE）。为统一根尖孔预备标准，所有样本均采用Protaper Next根管预备系统进行根管预备，直至器械X3到达根尖孔。其中WE组进一步采用Protaper Next系统预备至器械X5以实现根管孔扩大，NE组则将预备终止位置低于根尖孔1mm。随后采用牙胶尖与AH Plus根管封闭剂将根管充填至根尖孔下1mm处，将所有样本置于37℃、相对湿度95%的恒温恒湿环境中保存7天。将牙根固定于装有1.5%琼脂凝胶的微量离心管内，使用Reciproc R50根管器械去除根管内的充填材料。分别采用显微计算机断层扫描（micro-CT）与锥形束计算机断层扫描（CBCT）对样本牙齿及琼脂凝胶进行扫描。采用曼-惠特尼检验（Mann-Whitney test）进行组间及两种扫描方法间的统计学比较，检验水准设定为p≤0.05。
研究结果：无论是采用显微计算机断层扫描（p=0.589）还是锥形束计算机断层扫描（p=0.953）进行组间比较，两组根尖挤出充填材料的体积均无统计学差异。锥形束计算机断层扫描测得的挤出材料体积显著高于显微计算机断层扫描（p=0.0004）。
研究结论：初次根管治疗时的根管孔扩大对根管再治疗过程中的根尖充填材料挤出无显著影响。锥形束计算机断层扫描更适用于根尖挤出充填材料的影像学评估。