Study on the relationship among impacted depth of maxillary third molar, molar angulation and trend of anterior open bite

Objective: To explore the relationship among impacted depth of maxillary third molar, angulation of maxillary first and second molars and anterior open bite.Methods: In this study, 125 adult patients were selected and divided into high group(43 patients), middle group(37 patients)and low group(45 patients)according to the high, middle and low impacted depth of maxillary third molar.The relative indexes of anterior open bite and the angulation of maxillary first and second molars were measured by taking lateral cephalometric films and CBCT.Results: Compared with middle group and low group, overbite depth indicator(ODI)value of patients was smaller in high group, and the angulation of maxillary incisors (U1-SN), SNB angle and below height (ANS-Me) values were larger (P＜0.05).Correlation analysis showed that ODIwas negatively correlated with the impacted depth of the maxillary third molar (P＜0.01), while SNB, ANS-Me and U1-SN were positively correlated with the impacted depth of maxillary third molar (P＜0.01).The first and second molar angulation of patients in high group was larger and more mesial compared with middle group and low group (P＜0.01).The mesial angulation of maxillary molar was positively correlated with the impacted depth of maxillary third molar(P＜0.01).Additionally, the angulation of maxillary first molar (U6) and the angulation of maxillary second molar (U7) were negatively correlated with ANB and ODI(P＜0.01), while positively correlated with SNB, APDI(anterior-posterior dissonance indicator) and U1-SN (P＜0.01).Conclusion: The impacted depth of maxillary third molar, the angulation of maxillary first and second molars are closely related to anterior open bite.The higher the impacted depth of maxillary third molar is, the greater the mesial angulation of the maxillary molar is, and the more obvious the trend of anterior open bite is.