What factors affect the severity of permanent tooth impaction?

Background The aim of this study was to investigate the association between the severity of permanent tooth impaction and a number of predefined factors, including tooth type, age, gender, tooth agenesis, microdontia of maxillary lateral incisor, and retained deciduous predecessors. Methods A sample of 2979 dental patients, aged 15 to 40 years, was surveyed by two calibrated examiners for permanent tooth impaction (excluding third molars). On panoramic radiographs, the impacted teeth were initially ranked based on their vertical, horizontal, and angular positions, and the ranking was then analysed for distribution by the predefined factors. To test the age factor, patients were divided into younger (15 to 25 yr) and older (between 25 and 40 yr) age groups. The statistical significance of the ranked vertical, horizontal, and angular positions of impacted teeth by the investigated factors was determined using the Wilcoxon-Mann-Whitney U test. Results The angular position of the impacted teeth was more severe in the older age group ( P = 0.012) and in females ( P = 0.018). The maxillary canine had more severe horizontal ( P = 0.001) and angular ( P = 0.003) impactions in females. Tooth agenesis was associated with less severe horizontal impaction ( P = 0.041) in the mandibular second premolar. In addition, microdontia of the maxillary lateral incisor was associated with more severe horizontal impaction in general, and more severe horizontal ( P = 0.024) and angular ( P = 0.010) impaction of the mandibular second premolar in particular. Finally, our results showed that a retained deciduous predecessor was linked to a less severe vertical impaction of the mandibular second premolar ( P = 0.030) and horizontal impaction of the maxillary second premolar ( P = 0.037) but more severe angular impaction of the mandibular canine. Conclusions This study suggests that the more delayed the treatment, being a female, the presence of maxillary lateral incisor with microdontia, and retained lower deciduous canines might be associated with more severe position of the impacted teeth. Because the severity of tooth impaction would follow different patterns when considering the investigated factors, it is mandatory to include such factors during dental diagnoses and the planning of preventive or interceptive interventions for young patients.