Decoding the dental and skeletal factors behind mandibular second molar impaction: a retrospective cross-sectional study

BACKGROUND: Although the etiology behind the failure of second molars to erupt has not been fully elucidated, several contributing factors have been suggested. Even though a considerable number of studies have been published on second molar impaction, only a limited number have examined the influence of mandibular skeletal characteristics via panoramic and cephalometric radiographs. This study aimed to evaluate the relationships between the impaction of mandibular second molars (MM2) and various skeletal and dentoalveolar morphological parameters. METHODS: In this retrospective study, panoramic and lateral cephalometric radiographs of individuals aged 11–18 years were examined. Measurements of the study group (SG), consisting of individuals with impacted MM2, and the control group (CG), consisting of individuals with normally erupted MM2, were compared. Subgroups were formed on the basis of skeletal classifications. The primary evaluation parameters included the GoGn/SN angle, gonial angle, molar inclination angle, and ratio of MM1-ramus distance to MM2 mesiodistal crown width. A significance level of p < 0.05 was adopted for all the statistical analyses. RESULTS: There was no statistically significant difference in the GoGn/SN angle between the SG and CG. Within the study group, a significant difference in gonial angle was observed only among Class II individuals, where a decreased angle was associated with a more horizontal mandibular growth pattern. The molar inclination angle increased particularly in Class III individuals with impacted teeth, suggesting that increased mesial tipping may play a role in impaction. The most prominent finding was a significantly lower MM1-ramus distance to MM2 crown width ratio in the SG across all skeletal classes. CONCLUSIONS: MM2 impaction appears to be a multifactorial predominantly associated with local morphological limitations. Posterior space deficiency and increased mesial inclination were identified as major contributing risk factors. This study highlights the clinical value of early assessment of molar angulation and posterior space availability in preventing MM2 through appropriate orthodontic and surgical planning.