| Background and objectivesIt is essential to master root anatomy and canal configuration before dental pulp therapy.The first molar is the earliest eruption of permanent teeth,and its caries prevalence is highest.Due to large destruction,pulpitis or periapical periodontitis and so,the first molar often needs to be conducted with root canal therapy.The successful root canal therapy includes the appropriate establishment of root canal pathway,chemo-mechanical preparation to remove infectious substances,and then three-dimensional root canal filling to seal root canal system.It can be seen that it is important to be familiar with the anatomical structure of root canal system.Any variation of root canal configuration should be confirmed before or during root canal therapy.Omission of root canal is a common cause of failure of root canal therapy.The root canal system of first molar is complex.The distolingual root of mandibular first molar and the second mesiobuccal root canal(MB2)of maxillary first molar may exist.What’ s more,the variability of root canal appeared great.Sometimes it is narrow and/or curved,and is made positioning very difficult.All above are the difficulties of root canal treatment for the first molar,which easily lead to endodontic failure.Cone-beam computed tomography(CBCT)is easier to obtain data and conduct classified study than vitro study when we observe the morphology of the root canal.Compared with periapical film,panoramic radiography or CT,CBCT has more advantages,such as low radiation dose,high image resolution,three-dimensional reconstruction,easy operation and so on.Meanwhile,it can be analyzed by computer software,and show the sagittal,coronal and axial surface at the same time.CBCT is more suitable for oral clinical needs.Furthermore,it can provide the clinical first-hand reliable imaging information.The aim of this study was to observe and analyze CBCT images of the first molar in a southern Chinese subpopulation in order to provide effective evidence for clinical pulp treatment.Materials and methods1.We collected data of patients who had CBCT scanning in Department of Stomatology,Nanfang Hospital between January 2014 and December 2015.CBCT images of 924 mandibular first molars from 500 patients(aged 34.2±12.8 years)and 953 maxillary first molars from 588 patients(aged 45.5 ±15.4 years)were identified in the database of the oral radiology department.All of them met the following inclusion criteria:(ⅰ)without periapical lesions;(ⅱ)the teeth involved had not been endodontically treated;(ⅲ)no root canals with open apices or absorption;(ⅳ)the CBCT images were of good quality and without artifacts;and(ⅴ)the ancestral home was in South China,and the Han nationality.2.Two endodontists who had passed the standard conformance test to obtain accurate results evaluated all the images separately.When they couldn’t get a consensus of complex root canal dissection after mutual consultation,the third assessor(endodontics expert)would confirm the root canal morphology and internal anatomy.3.The data of each patient included:medical history,name,sex,age,tooth position,root number,root canal number,root canal type,MB2 of maxillary first molar,distolingual root of mandibular first molar root canal calcification,the distance between root canal orifice of distolingual and distobuccal.Data were recorded and analysed using the SPSS 20.0 software.Results1.Of 424 patients who had bilateral homonymous teeth in mandibular first molars,the bilateral symmetry of root canal configuration is 76.2%.Among all the mandibular first molars,76.7%had double roots and 23.3%had three roots,i.e.the incidence of distolingual root was 23.3%.According to Vertucci’s classification,71.97%of the mesial roots were type IV,23.70%were type II.49.35%of the distal roots were type I,31.82%of them were type IV.When distolingual roots exist,the distance between root canal orifice of distolingual and distobuccal was 2.94 ±0.27 mm.The incidence of calcified canal in mandibular first molars was positively correlated with age.2.Of 365 patients who had bilateral homonymous teeth in maxillary first molars,the bilateral symmetry of root canal configuration is 52.6%.Among all the maxillary first molars,more than 97%had 3 separate roots,more than 99%of the teeth had 3 canals or 4 canals.the incidence of MB2 is 68.3%.The root canal configuration of the MB root of maxillary first molars when MB2 was present was 36.3%type IV,28.4%type II,18.6%type V and 14.1%type III,others were type VI or VII.The incidence of calcified canal in maxillary first molars was positively correlated with age.ConclusionsThe root canal configuration of first molar in a southern Chinese subpopulation is various.CBCT is an effective tool for detecting additional distolingual roots and provides a favorable tool for diagnosis in root canal therapy for dental practitioners. |
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