Abstract
BACKGROUND: Sinus perforation (SP) is a relatively common complication during upper third molars (UTMs) extractions. However, previous studies included a broad range of UTM extractions, potentially underestimating the true incidence of SP by incorporating unrelated cases. This study investigated the risk factors for SP. during the extraction of UTMs that were closely adjacent to or protruded into the maxillary sinus. METHODS: This retrospective cohort study was conducted at the General Dentistry and Fifth Division of Peking University School of Stomatology from January 2019 to May 2025. The study included partially or fully impacted UTMs, classified according to the extent of protrusion into the sinus, depth of impaction, and type of inclination. Data were analyzed using chi-square tests and binary logistic regression, with statistical significance set at p < 0.05. RESULTS: A total of 141 UTMs from 120 patients were included. SP occurred in 24 sites, yielding an SP rate of 16.5%. Of these, 7 perforations were iatrogenic, with all UTMs being mesially or horizontally impacted (p < 0.05). SP was not detected when less than half of the root tip protrude into the sinus. Most of the SP were repaired successfully with a modified trapezoid flap after reliable primary wound closure. Postoperative oral-antral fistula was detected in 1 case. Chi-square analysis revealed a significant correlation between the mesially inclined UTMs and the incidence of total and iatrogenic SP (p < 0.05). Binary logistic regression showed that meisal impaction (OR 4.12) and the type Ⅱc protrusion (OR 6.03) were significantly related to SP. CONCLUSIONS: For the UTMs that closely related to sinus floor, mesially inclined UTMs was identified as the primary risk factor for intra-operative SP. Additionally, a modified trapezoid flap is recommended for optimal wound closure. TRIAL REGISTRATION: The research has been registered in the Chinese Medical Research Registration and Filing System with registration number MR-11-25-019459 on March 4(th), 2025.