保守开髓洞型及One Curve根管预备对下颌第一磨牙近中根管危险区的影响

Effect of contracted endodontic access cavity and root canal preparation by One Curve on danger zone of mesial root canal in mandibular first molars

目的研究使用One Curve预备系统时,保守开髓洞型对下颌第一磨牙近中根管危险区的侧穿风险的影响,为临床选择更优的髓腔入路提供依据。方法选择符合纳入标准的20颗因严重牙周病拔除冠根完整、近中根具有近颊根管与近舌根管2个独立根管,弯曲度为0°~20°的下颌第一磨牙,根据髓腔通路设计随机分为2组:传统开髓洞型组与保守开髓洞型组。传统开髓洞型髓室顶完全去除,保守开髓洞型尽可能多地保留髓室顶及颈周牙本质,使用One Curve单支锉行根管预备。对预备前后的离体牙进行锥形束CT扫描,定位近中根根分叉下方0~7.0 mm位置,以1 mm为间隔确定测量截面。测量各截面中根管近远中侧最小根管壁厚度。结果①20颗下颌第一磨牙近中根预备前CT测量结果示:危险区位于根分叉下0~4 mm,近颊根管近中侧平均厚度为1.18 mm,远中侧为1.08 mm。近舌根管近中侧平均厚度为1.28 mm,远中侧为1.07 mm。②传统开髓洞型组与保守开髓洞型组的下颌第一磨牙的近中根管的危险区的根管壁厚度减少量比较无显著差异(t=1.319,P=0.19)。③传统开髓洞型的近颊根管根尖偏移更偏向近中,保守开髓洞型更趋向于远中侧。而两组在近舌根管的偏移趋势均偏向远中。结论使用One Curve预备系统时,临床上使用基于微创理念的保守开髓洞型不会增加下颌第一磨牙近中根管危险区的穿通风险。

Objective To explore the influence of a contracted endodontic access cavity on the risk of canal transportation in the danger zone of the mesial root canal of mandibular first molars(MFMs)using a one-curve preparation system,and to provide an experimental basis for the clinical selection of a better pulp approach.Methods Twenty MFMs extracted for severe periodontal disease that met the inclusion criteria,including intact coronal roots,mesial roots with two separate root canals,mesiobuccal canal(MB)and mesiolingual canal(ML),and a curvature of 0°to 20°,were selected.Subsequently,these MFMs were randomly divided into two groups based on the endodontic access design,including the traditional endodontic access cavity(TEC)group and the contracted endodontic access cavity(CEC)group.In the TEC group,the pulp chamber roof of the tooth was completely removed,while in the CEC group,the pulp chamber roof and peri-cervical dentin were preserved as much as possible.Then,the One Curve single file was adopted to conduct root canal preparation.Next,cone beam computed tomography(CBCT)was performed on extracted teeth before and after preparation,and the measurement sections were located at 0-7.0 mm below the root bifurcation of the mesial root canal at 1 mm intervals.The minimum wall thickness on the mesial and distal aspect of the root canal was measured in each section.Results(1)Prepreparation CT measurements of 20 MFMs showed that the danger zone in the range 0-4 mm under root bifurcation,a mean thickness of 1.18 mm on the mesial aspect of the MB root canal and 1.08mm on the distal aspect.The mean thickness of the ML root canal was 1.28 mm on the mesial aspect and 1.07 mm on the distal aspect.(2)Compared with that of the traditional endodontic access cavity,no significant difference in the decrease of wall thickness was observed in the danger zone of mesial root canal of MFMs in the contracted endodontic access cavity(t=1.319,P=0.19).(3)In the mesiobuccal canal,compared with the apical transportation of the traditional endodontic access cavity,which tends to be more mesial side,the apical transportation of contracted endodontic access cavity tends to the distal side.In the mesiolingual canal,both apical transportation groups tended to be on the distal side.Conclusion When using the One Curve file,compared with traditional endodontic access,the contracted endodontic access cavity based on the minimally invasive concept does not increase the risk that the mesial root canal of mandibular first molars is transported.