Objective:Objective to analyze the CBCT image data of mandibular first premolars in Shanxi area,and to explore the morphological characteristics of root and root canal of mandibular first premolars,so as to provide reference for clinical diagnosis and treatment.Methods:1、CBCT image data of patients with mandibular first premolars who were treated in the Stomatological Hospital of Shanxi Medical University from January 2015 to December 2020 were selected according to the inclusion criteria.2、The collected image data were divided into male and female groups according to gender,and grouped according to the age difference of 10 years,namely 15-24 years old,25-34 years old,35-44 years old,45-54 years old,55-64 years old and ≥ 65 years old.3 、 CBCT images of the selected subjects were processed and analyzed by one volume viewer software.For each mandibular first premolar selected,the number and length of root,whether there were root grooves,the location of root grooves,the number and shape of root canals,the location and thickness of the smallest root canal wall were recorded.Analyse and summarise the relevant data,and carry out statistical analysis.Results:1、In this study,a total of 1102 patients with mandibular first premolar CBCT image data were selected as the research object.There were 424 males and 678 females with an average age of 36.75 years old(range 17-80 years old).2、Of the 1102 mandibular first premolars,1090(98.9%)were single root,only12(1.1%)were two roots,and no 3 or more roots were found.The incidence of single root was 99.4% in female,and 98.1% in male.There was no significant difference between the two groups(P > 0.05).3、Root length: the longest was 16.25 mm,the shortest was 10.33 mm,and the average root length was 13.83 mm ± 1.29mm。The average length of male was 14.21 ±37 mm and 13.60 ± 18 mm for female,the root length of male was longer than that of female,the difference was statistically significant(t = 7.808,P < 0.05).4、According to vertucci classification,958 root canals were classified as type I,accounting for 86.9%;92 root canals were classified as type V,accounting for 8.4%;42root canals were classified as type C,accounting for 3.8%;10 root canals were classified as type III,accounting for 0.9%.In this study,no other root canal types were observed.The ratio of type I in female was significantly higher than that in male,and the ratio of type III,type V and type C in male was significantly higher than that in female(P< 0.05).There was no significant difference in the distribution of root canal configuration among different age groups(P > 0.05).5、524 teeth(47.5%,524/1102)had root grooves,most of which were located in the mesial surface(63.1%,356/564).There were root surface depression in all multiple root canal teeth.6、The average thickness of the thinnest root canal wall was 1.74 ± 0.14 mm at the junction of crown and root,1.24 ± 0.10 mm at the junction of 1 / 3 of neck and 1 / 3 of middle root,and 0.85±0.11 mm at the junction of 1 / 3 of middle root and 1 / 3 of apex.Conclusion:1、In this study,98.9% of mandibular first premolars had single root and 1.1% had double root;The most common root canal configuration was type I(86.9%),followed by type V(1-2).It is suggested that clinicians should fully understand the morphology and anatomical variation of the root and root canal system of mandibular first premolar,and pay attention to the number of root canals in clinical treatment,so as to avoid the failure of root canal treatment due to missing root canals.2、The root surface depression of mandibular first premolars is closely related to the occurrence of complex root canals and C-shaped canals,and the wall of root canals corresponding to the root groove is often thin.In the root canal treatment,we should pay attention to avoid excessive cutting of the root canal wall,resulting in lateral penetration of the root canal wall.3、CBCT can display the anatomical characteristics of root canal system in three dimensions,and provide reliable information for clinical diagnosis and treatment.It has a good application prospect in the clinical work of endodontics. |