| Objective:To study and analyze the differences in anatomical morphology of maxillary tuberosity in class II patients with different vertical skeletal types,in order to determine the difference of distalization limit in borderline cases of different vertical skeletal types,in order to find which skeletal type is more inclined to achieve orthodontic treatment goal through arch expansion or molar distalization rather than conventional tooth extraction,and to provide reference for improving mini-implant stability in the maxillary tuberosity.Materials and methods:A total of 60 patients with skeletal class II(ANB>4.7°)aged between 20-40 years were selected from the Orthodontics Department of Dalian Stomatological Hospital affiliated to Dalian Medical University,with unilateral or bilateral maxillary third molars completely impacted.All subjects used Ka Vo 3D e Xam Cone-Beam Computed Tomography(CBCT)for image scanning,and Invivo Dental 5.0 software was used to three-dimensionally reconstruct the DICOM data obtained from CBCT,and obtain the measurements of the required maxillary tuberosity.The sagittal section and axial section were used to measure and analyze the statistical differences in the length,width,and height of the maxillary tuberosity.The length and width were analyzed between groups.(1)According to MP-FH and MP-SN angle,60 patients were divided into three groups: high angle group(mean age 24.3±4.2years,22 cases),average angle group(mean age 25.9±5.3 years,19 cases),low angle group(mean age 25.7±4.9 years old,19 cases).SPSS25.0 software was used for analysis of variance.The difference was statistically significant when p< 0.05.(2)The length and width of the maxillary tuberosity were compared in patients(mean age 25.6 ± 3.2 years old,11 cases)with one maxillary third molar fully impacted and the contralateral third molar missing to explore whether the maxillary tuberosity bone mass is correlated to the existence of maxillary third molars.SPSS25.0 software was used for t-test analysis.When P<0.05,the difference was statistically significant.Results:(1)The width of maxillary tuberosity at different measurement positions in the low-angle group was significantly larger than that of the high-angle group and the average-angle group(P < 0.01);the average-angle group was 3.0 mm away from the maxillary second molar on the axial section.The distance between the buccal and palatal cortical plates of the maxillary tuberosity(W3)and the distance between the buccal and palatal cortical plates of the maxillary tuberosity at the furthest 4.5mm from the maxillary second molar(W4.5)were significantly greater than the high angle group(P<0.01),And on the axial section,the distance between the buccal and palatal cortical plates of the maxillary tuberosity at 6.0mm distance from the maxillary second molar(W6),and the buccal palatal cortex of the maxillary tuberosity at 7.5mm distance from the maxillary second molar There was no significant difference in the distance between the plates(W7.5)and the distance between the buccal and palatal cortical plates of the maxillary tuberosity at the furthest 9.0mm from the maxillary second molar(W9)(P>0.05).(2)The length of maxillary tuberosities in the low-angle group was significantly greater than that in the high-angle group(P<0.01),but not statistically different from the average-angle group(P>0.05).In the average angle group and the high angle group,the distance from the root of the maxillary second molar cemento-enamel junction(CEJ)6.0mm in the sagittal plane to the farthest edge of the maxillary tuberosity(L6)and,there is a statistically significant difference in the distance(L9)from the root of the maxillary second molar CEJ 9.0mm from the root of the CEJ on the sagittal plane(P<0.05),while the distance from the maxillary on the sagittal plane.There was no significant difference in the distance(L3)from the furthest root of the second molar CEJ at the root of 3.0mm to the rear edge of the maxillary tuberosity(P>0.05).(3)The width of the maxillary tuberosity of the three groups is the largest at W3,and the largest in the low-angle group(17.21mm);the length of the maxillary tuberosity at L6 and L9 is significantly longer than the length at L3,and the high-angle group is the smallest(4.01mm).(4)The length and width of maxillary tuberosity on the third molar side of the same patient were significantly greater than those on the congenital missing third molar side(P<0.01).Conclusion:The width of maxillary tuberosity in the low-angle group is significantly larger than that of the high-angle group and the average-angle group,and the length is greater than that of the high-angle group,but there is no statistical difference from the average-angle group.The width at W3 and W4.5 and the length at L6 and L9 of the average angle group are significantly larger than those of the high angle group.The length of the maxillary tuberosity of the three groups of different vertical skeletal types is the shortest at L3.The clinical decision on distalization limit should be based on the shortest length,especially for high-angle patients when the maxillary tuberosity bone volume,length,and width is analyzed.The length and width of the maxillary tuberosity on the third molar side of the same patient were significantly greater than that of the congenital missing third molar side,indicating that the bone mass,length and width of the maxillary tuberosity area may have a certain correlation with the presence of third molars. |
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