| Objective In the study,Cone beam computer tomography(CBCT)was used to observe the curvature and curved positions of each root canal of double-rooted mandibular second molars in the buccal-lingual,mesio-distal.The study explored the differences in the curvature of each root canal in the buccal-lingual,mesial-distal direction,and the differences in the curvature of each root canal in men and women,different age groups,and left and right sides.By measuring the buccal-lingual bone wall thickness at a distance of 3 mm from the apex of the double-rooted mandibular second molars and the root thickness in the buccal-lingual and mesial-distal directions,the differences between men and women,different age groups,and left and right sides were studied.In order to provide theoretical and imaging basis for root canal treatment and endodontic microsurgery of double-rooted mandibular second molars,and improve the success rate of endodontic surgery.Methods The CBCT imaging data taken at the Stomatology Department of Inner Mongolia Medical University Affiliated Hospital from January 2019 to January 2021 were stratified and sampled by age and gender.For each patient who meets the inclusion criteria,record their tooth position,observe the curvature and location of the root canal,and observe data such as bone wall and root thickness at a distance of 3mm from the root tip.Use SPSS24.0 statistical software to analyze all data.Results The CBCT images of180 patients met the inclusion criteria,including 360 double-rooted mandibular second molars.1.The curvature of the mesiobuccal canal(MB)of the double-root type three-canal mandibular second molar is(32.57±12.84)° in the buccolingual direction,(30.23±7.01)° in the mesio-distal direction,and the curvature in the buccolingual direction is greater than mesio-distal(P<0.05).The detection rates of the buccal and lingual bending parts of MB curved root canals located in the upper,middle and lower 1/3 of the root were 38.59%,4.03%,and 57.38%respectively;in the mesial and distal directions,the detection rates were 25.66%,72.57%,and 1.77% respectively.The mesiolingual canal(ML)curvature was(29.24±8.88)° in the buccolingual direction and(32.74±13.67)° in the mesio-distal direction.The detection rates of ML curved root canals located in the upper,middle and lower third of the root canal were 35.55%,2.26%,and 64.19%respectively;in the mesio-distal direction,the detection rates were 30.52%,66.86%,and 2.62%,respectively.The curvature of the distal canal(D)was(9.49±9.58)° in the buccolingual direction,and(3.93±7.46)° in the mesio-distal direction.The detection rates of D-curved root canals located in the upper,middle,and lower 1/3 of the root canals were 0%,68%,and 32% respectively;In the mesial and distal directions,the detection rates were 9.5%,44.3%,and 46.2%.There was no side-to-side difference in the curvature of each root canal of the double-rooted mandibular second molars(P>0.05).The mesial-distal curvature of ML root canals was greater in men than in women(P<0.05),and in the18-35-year-old group>36-53-year-old group>over 54-year-old group(P<0.05).2.The buccal bone wall thickness at 3 mm from the mesial root apex of double-rooted mandibular second molars was 6.35±2.02 mm,and 4.03±1.14 mm on the lingual side;the buccal bone wall thickness at 3 mm from the distal apex was 7.51±1.97 mm,and 3.83±1.28 mm on the lingual side.There was no side-to-side difference in buccal bone wall thickness and lingual bone wall thickness at 3 mm from the apex of the double-rooted mandibular second molars(P>0.05).In terms of age,the buccal bone wall thickness of 18-35-year-old group>36-53-year-old group>over 54-year-old group;the lingual-side bone wall thickness of over 54-year-old group>36-53-year-old group>18-35-year-old group(P<0.05).The buccal bone wall thickness was greater in males than in females(P<0.05).3.The thickness of the buccal-lingual root of the double-rooted mandibular second molar at the distance from the mesial root to the apex is4.72±0.82 mm,and the mesio-distal direction is 2.61±0.57mm;the thickness of the buccal-lingual root from the distal root to the apex is 4.23± 0.80 mm,mesio-distal is 2.39±0.44 mm.There was no side-to-side difference in root thickness at the root tip 3mm(P>0.05).There was no gender difference or age difference in the thickness of the distal root(P>0.05),but the thickness of the mesio-distal root in the mesial root was greater in males than in females(P<0.05).In terms of age comparison,the buccal-lingual root thickness of 18-35-year-old group>over54-year-old group>36-53-year-old group(P<0.05).The mesio-distal root thickness of over 54-year-old group>36-53-year-old group>18-35-year-old group(P<0.05).Conclusion 1.The curvature of MB and ML of double-rooted mandibular second molars is large,and the curvature of D is small.The curvature of each root canal is different in the buccolingual and mesial-distal directions,and the teeth with the same name and the same root canal are symmetrical in the same plane view.The bending parts of each tube are complex and changeable.2.The buccal bone wall at 3 mm from the apex of the double-rooted mandibular second molar is thick,and the lingual bone wall is thin.As we age,the buccal bone wall becomes thinner and the lingual bone wall becomes thicker.The buccal bone wall is thicker in males than in females.The tooth with the same name and the same root have symmetry.3.The buccal-lingual and mesio-distal thickness of the distal root at 3 mm from the apex of the double-rooted mandibular second molar has no side,gender and age differences,but the thickness of the mesial root is complex and variable. |
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