| Objective: Analyze the incidence of middle mesial root canal(MMC),as well as the root canal classification of mandibular first molars by observing the cone-beam computed tomography(CBCT)image of the mandibular first permanent molar in the population of Guizhou individuals.In order to further explore the influence of related factors such as gender,age and dental position on the incidence of the middle mesial root canal.Methods: 1.We collected the data of patients who had CBCT scanning in Hospital of Stomatology Zunyi Medical University during the period of year 2017.CBCT images of7318 patients were identified in the database of the oral radiology department.All of them met the following inclusion criteria:(i)the image is clear;(ii)the lack of teeth does not affect the judgement of tooth position;(iii)the first mandibular molar has no defect,no root canals with open apices or absorption;(iv)the post crown is not restored.We picked5504 patients out of 7318,among which 2840 were male and 2664 were female.10479 teeth counted from the 5504 patients,including 5230 left mandibular first molars and 5249 right mandibular first molars.2.After locating the mandibular first permanent molar,CBCT images were observed and analyzed from three planes: cross section,coronal plane and sagittal plane,.All the planes were observed three times to make sure no misunderstanding happens.An endodontists and a radiologist would have to pass the standard conformance test by evaluating all the images separately to obtain accurate results.When they couldn’t get a consensus of complex root canal dissection after mutual consultation,an experienced endodontics would confirm the root canal morphology and internal anatomy.According to the Vertucci classification,the root canal configuration of middle mesial root canal of mandibular first molars was classified and described.The morphology of root canals and basic information of each patient(gender,age and dental position)were recorded in detail,and finally counted.Data were recorded and analyzed by SPSS 18.0 software.3.The data of each patient includs:medical history,name,gender,age,tooth position,and root canal type.4.The results were counted according to gender(male,female),dental position(left,right)and age groups(≤20 years old,21-40 years old,41-60 years old,≥61 years old).Results: 1.There were 107 MMC of the mandibular first molars,the incidence was 1.0%(107/10479),the incidence of man is 2.4%(67/2840),which is higher than women by the chance of 1.5%(40/2664).The difference in incidence between the genders was statistically significant.The incidence of left side was 1.1%(57/5230)and right side was1.0%(50/5249).The difference was not statistically significant.2.Among 107 MMC,the incidence under 20 years old was 0.77%(9/1174),the incidence between 21 and 40 years old was 1.87%(39/2088),the incidence of between 41 and 60 age group was 2.64%(47/1780),the incidence over 61 years old was 2.60%(12/462).The incidence of chi-square trend was statistically significant among different age groups.3.According to the Vertucci classification,MMC is divided into three types,with the most additional type(3-2)accounting for 87.0%,followed by the Ⅷ(3-3)accounting for 8.3%,and finally the additional typee(3-1)accounting for 4.7%.Conclusion: 1.The incidence of mandibular first molar MMC in Guizhou was lower than in other regions.It has statistic difference between different genders.There was no significant difference in the incidence between the left and right teeth.2.The incidence of MMC increased with age in mandibular first molars,especially at the age of 20-60.3.The mandibular first molars MMC was most commonly detected as the additional type(3-2),followed by type Ⅷ(3-3),and finally the additional type(3-1). |
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