Effect of needle insertion depth and apical diameter on irrigant extrusion in simulated immature permanent teeth

The aim of this study was to compare the amount of irrigant extrusion in simulated immature permanent teeth when the apical diameter and needle insertion depth were varied. Thirty single-rooted maxillary incisors with straight root canals were selected. The root length was standardized to a length of 9 mm. The teeth were divided into two experimental groups according to the degree of apical enlargement (n = 15). The apices were enlarged to a diameter of 1.10 mm or 1.70 mm by using a #3 or #6 peeso reamer, respectively, to simulate immature teeth. The irrigation solution was applied 2 or 4 mm short of the working length (WL) in each experimental group. The glass vial model was used for the collection of extruded irrigant beyond the root apex. A two-way repeated measures analysis of variance test showed that there was no significant difference between different needle insertion depths (2 and 4 mm short of the WL) in the group with an apical diameter of 1.70 mm (p > 0.05). In the group with an apical diameter of 1.10 mm, a 32% increase in irrigant extrusion was observed when the needle was positioned at 2 mm (p本研究旨在对比根尖直径与针头插入深度不同时，模拟年轻恒牙（simulated immature permanent teeth）的根管冲洗液根尖外溢量差异。研究选取30例根管平直的上颌单根切牙，将所有标本的牙根长度统一标准化为9mm。根据根尖扩孔程度将标本分为2个实验组（每组n=15）：分别使用#3 Peeso扩孔钻（peeso reamer）与#6 Peeso扩孔钻将根尖扩至1.10mm或1.70mm直径，以此模拟年轻恒牙形态。两组均分别以距工作长度（working length, WL）短2mm或4mm的深度施加根管冲洗液。采用玻璃小瓶模型收集根尖孔外溢出的冲洗液。双向重复测量方差分析结果显示，在根尖直径为1.70mm的实验组中，不同针头插入深度（距工作长度短2mm与4mm）对应的冲洗液外溢量无显著统计学差异（p > 0.05）。在根尖直径为1.10mm的实验组中，当针头置于距工作长度短2mm位置时，冲洗液外溢量提升32%（p ）