| Objective:The purpose of this study is to study root number,root canal morphology,root length and the age-related changes of physiological absorption of maxillary primary molars by CBCT data,so as to provide more theoretical basis for the treatment of maxillary primary molars.Methods:Part 1:From July 2018 to March 2021,417 maxillary deciduous molars were selected from 186 children aged 4-8 who were taken CBCT in the Department of Radiology,Stomatological Hospital of Shandong University.NNT Viewer software was used to record the basic information of the children such as name.The root number,root canal type of each root,the distance between the two root canal orifices when the root canal type was type Ⅳ,and the distance from the root canal bifurcation to the horizontal plane of pulp chamber bottom when the root canal type was type V were measured.Then the relationship between the above measurement indexes and gender,left and right sides,tooth position was analyzed.Part 2:From July 2018 to March 2021,720 maxillary deciduous molars were selected from 261 children aged 4-12 who were taken CBCT in the Department of Radiology,Stomatological Hospital of Shandong University.There were 274 teeth whose apical and medial absorption were less than 1/3.NNT Viewer software was used to record the basic information of the children such as name and measure the root length of maxillary primary molars whose apical and medial absorption were both less than 1/3.The relationship between the root length and gender,left and right sides,tooth position and root number was analyzed.Then the degree of root apical absorption and root medial absorption of all maxillary primary molars were measured,and the difference between them were analyzed.Results:1.Maxillary deciduous molars usually have two or three roots,and maxillary second deciduous molars occasionally have four roots.There are gender differences and tooth position differences in root number,but there is no difference between left and right sides.2.Most of the distal buccal root and palatal root of maxillary primary molars are type Ⅰ root canals,while type Ⅳ or Ⅴ root canals can be found in the mesiobuccal root,but the root canal types are different among different tooth positions.The root canal types of maxillary first deciduous molars have no gender and left-right differences,while the root canal types of maxillary second deciduous molars have no gender differences but left-right differences.3.The distance between the furcation of V-shaped mesiobuccal root canal and the horizontal plane of pulp chamber floor of maxillary first deciduous molar is about 2.5mm.There is no gender difference,and there is left-right difference.The distance between the furcation of V-shaped mesiobuccal root canal and the level of pulp chamber floor is about 2.1 mm.There is gender difference,but there is no difference between left and right sides.4.The length of mesiobuccal root,distal buccal root and palatal root of male maxillary first deciduous molars are about 8.2±1.3mm、6.1±2 mm and 5.8 mm±0.9mm respectively;while for women,these values are about 8.3±0.9mm、5.7±2 mm and 5.4 mm±1.0mm respectively.The length of the mesiobuccal root,distal buccal root,and palatal root of male maxillary first deciduous molars are approximately 9.8±1.1mm,8.1±1.6mm,and 9.1±1.6mm;while for women,these values are approximately 9.2±1.1mm,7.9±1.3mm and 8.3±1.7mm.5.There are gender differences,root number differences and tooth position differences in the root length of maxillary primary molars,but there is no difference between left and right sides.6.The root apical and medial resorption of maxillary first primary molars are less than 1/3 when they are under 6 years old;The root apical and medial resorption of maxillary second primary molars are less than 1/3 at the age of 7 years and below.7.The trend of apical and medial root resorption of maxillary primary molars is basically the same,but the degree of medial root resorption is always greater than that of apical resorption.Conclusion:There are many variations in the root and root canal types of maxillary primary molars.Root canal therapy can be performed on maxillary first deciduous molars when they are 6 years old and below,and on maxillary second deciduous molars when they are 7 years old and below.The trend of apical and medial root resorption is similar but not synchronous.This study enriches the relevant data of anatomy and physiological root resorption of maxillary primary molars with age,and provides a theoretical basis for the selection of root canal treatment cases and prognosis evaluation of maxillary primary molars. |
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