Dental And Basal Arch Forms Analysis In High Facial Angle With Skeletal Class Ⅱ Malocclusion Based On WALA Ridge

Objective:In this study,the WALA Ridge was used as a landmark to measure the width and length of dental arch and basal bone in patients with skeletal Class II High Angle Malocclusion,and the morphological characteristics of mandibular arch and basal bone were analyzed,so as to provide clinical guidance for the correct diagnosis and treatment design of this kind of patients before treatmentMethods:From January 2018 to December 2020,30 patients aged 20-30(mean age 25.32± 2.83)were randomly selected from the Department of Orthodontics,yijishan hospital,the First Affiliated Hospital of Wannan Medical College.Methods: 30 patients with skeletal Class II high angle(mean age 25.9 ± 2.56 years,sn-mp angle greater than40 ° and mean angle 44.47 ± 1.80 °)and 30 patients with skeletal Class II high angle(mean age 25.45 ± 2.83,sn-mp angle 29-39 ° and mean angle 35.53 ±1.89 °)were selected as the experimental group The patients were divided into two groups: control group 1 and control group 2,90 cases in total.The lateral cephalogram and the model of super anhydrite were preserved completely.The clinical crown center points of each tooth,namely FA point and Wala ridge point,were marked on the mandibular model.The length and width of dental arch and the length and width of base bone in canine area,first premolar area and first molar area were measured by electronic digital vernier caliper.All the models were fixed and measured by the author himself and another orthodontist.The reliability test was carried out between the two measurers and the measurer himself(intra group correlation coefficient > 0.8).The relevant data were retested two weeks later,and the mean value of two measurements of the two measurers was taken as the result.The distance between FA points and Wala points in bilateral first molar area,first premolar area and canine area of three groups of mandibular models were measured,that is,dw6(width of arch between first molars)and BW6(width of base bone between first molars),DW4(width of arch between first premolars)and bw4(width of base bone between first premolars),dw3(width of arch between first molars)and Wala(width of base bone between first premolars)Bw3(width of base bone between canines)was compared to explore the correlation between dental arch and base bone.Independent sample t-test was used to compare various data between the experimental group and the two control groups.P < 0.05 indicates that the difference of related items between the two groups is statistically significant,and P < 0.01 indicates that the difference of related items between the two groups is statistically significant.Results:Pearson correlation analysis showed that there was a significant positive correlation between FA distance and WALA distance in the first molar area,first premolar area and canine area of patients with skeletal Class Ⅱ high angle,skeletal Class Ⅱmean angle and skeletal class I mean angle.There was no significant difference in the length of mandibular arch between the experimental group and the control group.There was no significant difference in the width of mandibular arch between the experimental group and the control group.However,the width of mandibular arch between the experimental group and the control group was(50.39 ±)in the canine area and the first premolar area The width of dental arch was(53.00 ± 3.29)mm in control group 1,which was significantly decreased(P < 0.05).There was no significant difference in the length of mandibular basal bone between the experimental group and the group with skeletal class I malocclusion,and there was no significant difference in the width of canine area and first premolar area of mandibular basal bone between the patients with skeletal Class II malocclusion and the control group1,but the width of basal bone in the first molar area of the experimental group was(54.94± 2.61)mm compared with the control group 1(57.85 ± 2.61)mm 04)mm(P < 0.01).There was no significant difference in the length and width of mandibular arch in canine area,first premolar area and first molar area between the experimental group and the control group(P > 0.05),and there was no significant difference in the length and width of mandibular base bone in each section(P > 0.05).Conclusion:1.There was a significant positive correlation between FA and Wala curves,which suggested that Wala ridge could be used as an anatomical marker of mandibular basal bone,and it was very reliable;2.In skeletal Class Ⅱ malocclusion,the width of arch and base bone in mandibular molar area is smaller than that in skeletal class I malocclusion,which suggests that the arch of lower teeth should not be expanded easily,but should be changed on the basis of the lower base bone;3.The width of dental arch and base bone in mandibular molar area decreased compared with skeletal Class Ⅱ high angle and skeletal class I mean angle,but there was no significant difference in the shape of dental arch and base bone compared with skeletal Class Ⅱ mean angle.