三根型下颌第一恒磨牙根尖解剖结构的显微CT观测

A micro-computed tomographic analysis of the apical anatomy of permanent three-rooted mandibular first molars

目的揭示三根型下颌第一恒磨牙根尖解剖特点，以期为临床进行根管治疗提供依据。方法从江苏省吴江市第一人民医院口腔科门诊采集中国汉族患者拔除的下颌第一恒磨牙122颗，选择20颗三根型下颌磨牙（三根组）及25颗双根型下颌磨牙（双根组）进行显微CT扫描及三维重建。Mimics10．01软件界面下观测根尖部的解剖结构，测量根尖狭窄的长、短径，根尖孔、根尖狭窄与根尖端的距离；两组牙齿不同根管间根尖狭窄直径及其与根尖孔、根尖端距离的比较采用单因素方差分析及LSD—t检验，以P〈0．05为差异有统计学意义。结果近颊根管根尖孔最多见于根尖远中侧（三根组10个，双根组6个），近舌根管多见于舌侧（三根组及双根组各8个）；远颊根根尖孔多位于根尖远中舌侧（10个），远舌根根尖孔常偏向颊侧（7个）；双根组远中根管根尖孔大多偏向远中（11个）。典型的沙漏状根尖狭窄出现率为53％（80／151）。三根组远颊根管根尖狭窄的长、短径分别为（0．32±0．09）、（0．25±0．05）mm，显著大于远舌根管[长、短径分别为（0．27±0．08）、（0．22±0．06）mm，P〈0．05]及近舌根管[长、短径分别为（0．24±0．06）、（0．19±0．06）mm，P〈0．01]。三根组根尖孔至根尖狭窄及根尖端的平均距离分别为（0．67±0．32）和（0．49±0．28）mm，根尖狭窄至根尖端平均距离为（1．01±0．34）mm。结论三根型下颌第一恒磨牙根尖孔往往偏离根尖端，根尖狭窄在远颊根管最宽大；根尖狭窄、根尖孔及根尖端间距的测量可以为根管治疗时确定工作长度提供参考。

Objective To investigate the anatomic features of the root apexes of permanent three-rooted mandibular first molars. Methods A total of 122 permanent mandibular first molars of Han Chinese patients were collected. Twenty three-rooted and 25 two-rooted molars were scanned by micro-CT and then reconstructed three-dimensionally. The apical anatomy of the tooth models were analyzed in software Mimics 10. 01. The long and short diameters of the apical constriction （AC） , the distances between AC, apical foramen（AF） and apex were measured. One-way ANOVA and LSD-t tests were used to compare the groups in relation to AC diameter and the distances between the AC, AF and apex. Results The AF of the mesiobuccal（MB） canals most frequently presented at the distal side of the apex （10 cases in three-rooted and 6 cases in two-rooted group ）, and of the mesiolingual （ ML ） canals, most often at the lingual side （8 cases in each group）. The AF of the distobuccal （DB） roots were frequently located at the distolingual （DL） side （ 10 cases） , and those of the DL roots and distal canals of two-rooted molars were most often at the buceal（7 cases） and distal（ll cases） sides, respectively. The percentage of the ＂ classical＂ singular AC was 53% （80/151）. The average long（D） and short（d） diameters of the AC of the DB canals were （0. 32 ± 0. 09 ） mm and （ 0. 25± 0. 05 ） ram, respectively, significantly larger than the DL canals [ D = （0.27 ±0.08） ram, d = （0.22 ±0.06） mm, P 〈0.05] and the ML canals [D = （0. 24 ±0.06） mm, d = （0. 19±0. 06） mm, P 〈 0. 01 ）. In three-rooted group, the mean distances between AC and AF, AF and apex, and AC and apex were （ 0. 67 ± 0. 32 ） , （ 0. 49 ± 0. 28 ） and （ 1.01 ± 0. 34 ） ram, respectively. Conclusions The AF of three-rooted mandibular molars frequently deviate from the root apex,and the AC of the t）B canal is wider than those of the other canals. The mean distances between AC, AF and the apex suggest that root canal therapy should terminate at 1 to 1.5 mm short of the radiographic apex.