Radiological and statistical analysis of impacted maxillary third molars in Korean adults.

Objectives: : This study aimed to investigate the distribution of Archer's Classification in impacted maxillary third molars in Korean adults, evaluate the effect of the buccopalatal inclination of the maxillary second molar on the position and angulation of the impacted maxillary third molar, and analyze the relationship between root involvement with the maxillary sinus.

Materials and methods: : Cone-beam computed tomography (CBCT) images of 384 impacted maxillary third molars from 277 patients who visited Dankook University Dental Hospital between March 2021 and February 2024 were analyzed. The teeth were classified according to Archer's Classification (depth and axis), and the long axis angles of the maxillary first, second, and third molars as well as root involvement with the maxillary sinus were measured. Statistical analyses were conducted using the Mann-Whitney U test, chi-square test, and logistic regression analysis, with a significance level set at 0.05.

Results: : Depth categories B and C, and axis categories mesial and vertical were the most prevalent, with no significant differences in distribution based on sex (P>0.05). A significant negative correlation was found, indicating that as the buccal inclination of the maxillary second molar increased, the impacted maxillary third molar tended to incline more palatally (Kendall's tau-b=-0.245, Spearman's rho=-0.353, P<0.001). Root involvement with the maxillary sinus was not significantly associated with depth in Archer's Classification but showed a statistically significant difference based on axis (P=0.002).

Conclusion: This study systematically evaluated the position and angulation of impacted maxillary third molars through Archer's Classification and CBCT analysis, providing a clinical predictive index for assessing extraction difficulty and determining the surgical approach. In particular, the buccopalatal inclination of the maxillary second molar was identified as an important factor in predicting the position and angulation of impacted maxillary third molars.