Correlation study on the position of mandibular third molar and the morbidity of acute pericoronitis

[Objective:] To study the relationship between the position of the mandibular third molar (M3M) and the morbidity of acute pericoronitis. [Methods:] A total of 289 patients with M3M acute pericoronitis were examined. The age, gender, angulation of partially impacted M3M, the height of eruption, the covering area of the soft tissue around the crown, the depth of pericoronal pocket, and the presence of impinging maxillary third molar were recorded. The data were analyzed statistically. [Results:] Vertical impaction molar was the most frequent (69.9%) in M3M with pericoronitis. There was significant difference in the constituent ratio of pericoronitis among different types of impaction (P<0.05). The height of eruption, the percentage of soft tissue coverage, and the depth of the retromolar pad were correlated with the pericoronitis, and the differences were statistically significant （P<0.05). [Conclusion:] High vertical impaction, 51%-75% soft tissue coverage around the crown or deep pericoronal pocket are risk factors for acute pericoronitis ,and these types of M3M are best treated prophylactically.