Effects of maxillary third molar impaction on the position of maxillary molars in adult patients with skeletal class Ⅱ high angle malocclusion

XU Ting-ting; WANG Bo; ZHAO Qi; DONG Zhao-xin; HAN Li-chi; JIANG Hong-tao

doi:10.19538/j.kq.2025.04.010

Abstract：Objective To analyze the impact of maxillary third molar impaction on the position of maxillary molars in adult patients with skeletal class Ⅱ high-angle malocclusion.Methods A retrospective analysis was conducted on the clinical and imaging data of 40 adult patients with skeletal class Ⅱ high-angle malocclusion who were treated in the De-partment of Orthodontics at Dalian Stomatological Hospital from 2018 to 2020.Among them,there were 20 patients with normal eruption of maxillary third molars on both sides(the eruption group),and 20 patients whose maxillary third molar crowns were fully formed but had not erupted on both sides(the impacted group).Cone beam CT(CBCT)was used to measure and analyze the angle of the maxillary first molar(A-U6),the angle of the maxillary second molar(A-U7),the inclination of the maxillary occlusal plane(FHP-MOP),the height of the maxillary first molar(FHP-U6,PP-U6),the height of the maxillary second molar(FHP-U7,PP-U7),subfacial height(ANS-ME),total length of the palatal plane(ANS-PNS),anterior palatal plane length(ANS-U6),and the ratio of ANS-U6 to ANS-PNS(A6/AP).Results The comparison of the measurement results for the angle of maxillary molars(A-U6,A-U7)and the height of maxil-lary molars(PP-U6,PP-U7,FHP-U6,FHP-U7)between the eruption group and the impacted group showed no sta-tistically significant differences(all P＞0.05).Therefore,the average values of the left and right sides of the two groups were used for inter-group comparison.A-U6,A-U7,FHP-U6 and FHP-U7 in the eruption group were all greater than those in the impacted group,while FHP-MOP,ANS-ME,ANS-U6 and A6/AP were all lower than those in the impacted group,with differences being statistically significant(all P＜0.05).There was no significant difference in PP-U6,PP-U7 or ANS-PNS between the two groups(all P＞0.05).The A6/AP of impacted group was 0.53±0.06.Conclusion In adults with skeletal class Ⅱ high angle malocclusion,compared to the eruption of the maxillary third molar,the crowns of the maxillary first and second molars in the impacted state of the maxillary third molar are tilted more distally,the height of the maxillary molars is reduced,and the inclination of the maxillary occlusal plane is greater.Maxillary posterior dentoalveolar discrepancy may lead to the impaction of the maxillary third molar.