The Study Of Pulp Chamber Size And Root Canal Orifice Morphology Of The Second Primary Mandibular Molars By Using Cone Beam Computed Tomography

Objectives:This study measured the pulp chamber size and root canal orifice morphology types of the second primary mandibular molars(SPMMs),including mesial pulp horn and distal pulp horn,the max distance between buccal and lingual pulp chamber wall A(B-L),the max distance between medial and distal pulp chamber wallA(M-D),the height of pulp chamber(H)and the thickness of pulp chamber floor(T)by using Cone Beam Computed Tomography(Cone Beam CT,CBCT).Study the SPMMs anatomy regulation and characteristic of the size range of pulp chamber and root canal orifice morphology classification,which could provide the theory evidences of SPMMs for dental education and clinic treatments,avoid iatrogenic pulp exposure,root canal perforation and pulp chambe wall perforation.Avoid failure of root canal treatment failured due to missing with root canal for the SPMMs.Methods:Children aged 4-9-year-old,referred to the Affiliated Stomatology Hospital of Kunming Medical University,from March 2015 to August 2017 were enrolled in this study.In order to ensure the integrity of the original morphology of the root canals and pulp chamber,SPMMs that were fully developed with no periapical lesions,no obvious root absorption,and were untreated were included.Finally,71 children including 42 males and 29 females and 127 SPMMs with clear images of root and canal morphology were enrolled.Each child's object file number,name,gender,age and dental position were enrolled before experiment started.CBCT images were opened by NNT software.Measure pulp chamber of SPMMs and analyze the relationship between mesial pulp horn and distal pulp horn,and measure the max distance between buccal and lingual pulp chamber wall A(B-L),and the max distance between medial and distal pulp chamber wall A(M-D),the height of pulp chamber(H),the thickness of pulp chamber floor(T).Each data was measured three times.Last,observe root and canal morphology of SPMMs.The data were statistically analyzed by software SPSS 19.0.Results:1 The relationship betw een mesial pulp horn and distal pulp horn23.5%of mesial pulp horn of the left SPMMs were higher than that of the distal pulp horn,58.8%of distal pulp horn were higher than that of the mesial pulp hom,17.7%of distal pulp horn and mesial pulp horn were the same.27.1%of mesial pulp hom of the left SPMMs were higher than that of the distal pulp horn,47.5%of distal pulp horn were higher than that of the mesial pulp horn 25.4%of distal pulp horn and mesial pulp horn were the same.2 The size of the pulp chamberThe max distance between medial and distal pulp chamber wall A(M-D)of leftSPMMs was 4.06±0.44mm,the max distance between buccal and lingual pulp chamber wall A(B-L)was 3.69±0.39mm,and the height of pulp chamber(H)was 1.0610.34mm.The thickness of pulp chamber floor(T)was 1.99±0.29mm;The maxdistance between medial and distal pulp chamber wall A(M-D)of right SPMMs was4.04±0.43mm,the max distance between buccal and lingual pulp chamber wall A(B-L)was 3.7210.37mm,and the height of pulp chamber(H)was 1.17±0.33mm.The thickness of pulp chamber floor(T)was 1.99±0.31mm;3 The number and morphology variants of root canal orificesIn total,there were five different types of root canal orifices for SPMMs.Four of them were detected in left SPMMs including type 1211(13.2%),type 1212(69.1%),type 1213(4.4%),type 1222(13.2%).Five of them were detected in the right SPMMs including type 1211(18.6%),type 1212(59.3%),type 1213(1.7%),type 1222(18.6%),type 1223(1.7%).4 Comparison of the relationship between mesial pulp horn and distal pulp horn,size of the pulp chamber,and number and morphology variants of root canal orifices for left and right SPMMsThe max distance between buccal and lingual pulp chamber wall A(B-L),the max distance between medial and distal pulp chamber wall A(M-D),the height of pulp chamber(H)and the thickness of pulp chamber floor(T)were all measured.The distribution was normal.The paired T test was used to compare the mean;The height relationship of pulp horn and root canal orifices typing were used as count data.Chi-square test was used to compare the constituent ratios.It was verified that at the level of ?=0.05,the height of pulp chamber,the relationship between mesial pulp horn and distal pulp horn,and the root canal orifices classification had difference on different sides.All have statistical differences(p>0.05);A(M-D)values,A(B-L)values and T values had not statistically difference on different sides(p<0.05).5 Comparison of the relationship between mesial pulp horn and distal pulp horn,size of the pulp chamber,and the number and morphology variants of root canal orifices for sexual distinctionMetrological data were analyzed using an independent sample T-test,grouped according to sex;count data using chi-square test.After testing,at the level of a=0.05,there was no statistical difference in the measurement results of different genders(p>0.05).Conclusion:The relationship between mesial pulp horn and distal pulp horn of the SPMMs was that:the ratio of the distal pulp horn was higher than that of the mesial pulp horn.The root system of the SPMMs was highly variable.In the mesial parts of the SPMMs,there were two root canals of a root,while in the distal part,there could be one or two roots,and the root canal can be one or more.The max distance between medial and distal pulp chamber wall>the max distance between buccal and lingual distal pulp chamber wall>the thickness of pulp chamber floor>the height of chamber.There was no significant difference in A(M-D)values,A(B-L)values and T values between the right and left of SPMMs.However,there was statistical difference in the relationship between the mesial pulp horn and distal pulp horn,the shape of the root canal orifice,and the H values.There was no statistical difference in the measurement results of different genders.