锥形束CT分析下颌第一磨牙近中第三根管弯曲度

目的利用锥形束CT（CBCT）扫描并研究下颌第一磨牙近中第三根管发现率及其根管弯曲度。方法对我院口腔科就诊的1600名患者的下颌第一磨牙进行CBCT扫描，将发现近中第三根管的患者分为5组（A组：18~29岁；B组：30~39岁；C组：40~49岁；D组：50~59岁；E组：60~80岁）。对纳入的所有图像均采用Planmeca Romexis CBCT机的图像重建系统进行三维重建并测量，并采用改良的Schneider 法对根管弯曲度、弯曲部位进行测量，进一步研究根管形态并对其根管系统进行分析。结果1600 个患者的2856 颗下颌第一恒磨牙，有168 例存在近中第三根管（5.88%），发现率分别为：A组37.50%、B组17.80%、C组14.88%、D组19.64%、E组10.12%；A组近远中向根管弯曲度中度大于其他各组，差异有统计学意义（P<0.05）；5组根管近远中向根管弯曲度差异有统计学意义（P<0.05），且A组近远中向根管弯曲度>C、D、E组，差异有统计学意义（P<0.05）；5组根管颊舌向弯曲度相比较，差异无统计学意义（P>0.05）；近远中向和颊舌向弯曲部位在根中1/3处的发现率显著高于根冠1/3处与根尖1/3处，差异有统计学意义（P<0.01）。结论下颌第一磨牙近中第三根管发现率会随年龄增大而降低，根管弯曲度会随年龄增长而增加，特别是在30岁之后出现较为明显的下降趋势；下颌第一磨牙近中第三根管系统复杂且多变，大多数都会出现近远中向及颊舌向明显的弯曲且弯曲多发生在根中1/3处；CBCT能为临床治疗提供有效的指导，减少临床实际操作的失败率。

Cone-beam computed tomography for determination of mesial root canal curvatures ofhuman mandibular first molars

Objective To investigate mesial root canal curvatures of human mandibular first molars using cone-beamcomputed tomography (CBCT). Methods CBCT was performed for scanning the mandibular first molars of 1600 Chinesesubjects, among whom the subjects identified to have middle mesial canals were divided into 5 age groups, namely group A(18-29 years), group B (30-39 years), group C (40-49 years), group D (50-59 years), and group E (60-80 years) for furtheranalysis. All the CBCT images were reconstructed using Planmeca Romexis CBCT image reconstruction system, and thecurvature of the mesial root was measured using the Schneider method. Results A total of 2856 CBCT images were obtainedfrom the 1600 subjects, among whom 168 (5.88%) were found to have middle mesial canals in the mandibular first molars. Theprevalence of middle mesial canals was 37.50% in group A, 17.80% in group B, 14.88% in group C, 19.64% in group D, and10.12% in group E. The moderate of the curvature in the mesiodistal direction was significantly higher in group A than in theother groups (P<0.05); the curvature in mesiodistal direction differed significantly among the 5 groups (P<0.05), and was thegreatest in group A followed by group C and group D, and was the smallest in group E. The curvature in the buccolingualdirection was similar among the 5 groups. The incidence of mesiodistal and buccolingual curvature of the middle mesial canalswas significantly higher in the middle 1/3 of the root canal than in the upper 1/3 and apical 1/3 of the root canal. ConclusionsThe incidence of middle mesial canals in the mesial root of the mandibular first molars decreases with age. The middle mesialcanal system of the mandibular first molar is complex and variable, and most of the first molars have obvious curvature in themesiodistal and buccolingual directions. CBCT can provide reference for clinical treatment to reduce the treatment failure rate.