| Objective: The purpose of this study was to measure and analyze the retromolar space in maxilla of patients with different vertical facial types by CBCT,so as to provide reference and guidance for the design of orthodontic treatment plans for such patients in clinical practice.Research methods: From October 2017 to October 2019,60 patients with skeletal class Ⅱ malocclusion(mean age 25.48 ±3.43y)met the inclusion criteria of the experimental group,and 60 patients with skeletal class Ⅰ(mean age 26.07 ±1.80y)met the criteria of the control group,whoes CBCT images were selected from the Department of Orthodontics,Stomatological Hospital of Lanzhou University.According to the classification standard of vertical facial types of patients,the experimental group and the control group were individually divided into high-angle group,mean-angle group and low-angle group.Three-dimensional reconstruction was performed by CBCT images through Invivo dental 5 software,and the images were calibrated according to the measurement method.After confirming the key points,the length(RL/mm),width(RW/mm),height(RH/mm)of the maxillary retromolar space and the maxillary length(ML/mm)were measured.The measurement results were analyzed by t-test and analysis of variance(LSD test was used when the analysis of variance involved pairwise comparison).Research results:1.In control group and the experimental group,the width of the maxillary retromolar space in the low-angle group was larger than that in the high-angle group,and the difference was statistically significant(P<0.05).2.Compared with the control group,the width of the maxillary retromolar space of the high-angle and low-angle patients in the experimental group was significantly lower than that in the control group(P<0.05).There was no significant difference in the average angle between the experimental group and the control group.3.Independent sample analysis of the measured values of patients of different genders showed that the width of retromolar space and the length of maxilla in male patients were significantly larger than those in female patients(P<0.05).There was no significant difference in the length and height of retromolar space.4.The third molars and the missing side of the third molars were divided into two groups,and the results showed that the average values of all measurement items in the third molars group were higher than those in the third molars deletion group,and the difference was statistically significant(P<0.05).Research conclusion:1.The maxillary retromolar space of skeletal class I and skeletal class II low angle group was wider than that of high angle group,which provided a reference for clinical patients with middle and low angle to push molars distally.2.There was no significant difference in the length and height of the maxillary retromolar space between the skeletal class I patients and the skeletal class II patients,but the width of the skeletal class II patients was smaller than that of the skeletal class I patients,so the skeletal class II patients should pay special attention to prevent the occurrence of bone fenestration and bone cracking in the retromolar area during the distal push of the maxillary molars.3.Gender has a certain influence on the width of the retromolar space and the length of the maxilla.The width of the retromolar space in females is smaller than that in males.Therefore,in the process of pushing the maxillary molars distantly in female patients,it is also necessary to prevent the occurrence of bone fenestration and bone cracking in the retromolar area.4.The third molar can promote the growth of the postmolar space to a certain extent,and the influence of the third molar on this space should not be ignored in patients who can adopt the scheme of pushing the maxillary molars distally. |
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