Risk factors for delayed-onset infection after lower third molar surgery: a retrospective case-control study

Delayed-onset infection (DOI) is an uncommon postoperative complication of lower third molar surgery, typically occurring around one month after the procedure. This study aimed to identify risk factors for DOI to support improved prevention and management.

A retrospective case-control study was conducted using records from patients who underwent lower third molar surgery between January 2015 and December 2022. Seventy-four cases of DOI were identified and matched to 296 controls in a 1:4 ratio. Univariable and conditional multivariable logistic regression analyses were employed to identify significant risk factors.

The incidence of DOI was 0.66%, with a mean onset of 36.5 days postoperatively. Univariable analysis revealed nine potential risk factors, mesioangular and horizontal impaction, including Pell & Gregory classification Class III, Position B and C, Nolla's stage ≤ 8, Ganss ratio ≤ 0.5, bone retention, and postgraduate/experienced operator. However, multivariable analysis identified three independent predictors: Pell & Gregory classification Class III (OR = 5.89, 95% CI: 1.52-22.79), Pell & Gregory classification Position B (OR = 4.19, 95% CI: 1.70-10.31), and postgraduate/experienced operator (OR = 4.54, 95% CI: 1.59-12.98).

Postgraduate/experienced operator, Pell & Gregory class III, and position B were identified as significant risk factors for DOI in our institution. Although the incidence is low, the potential impact on patient quality of life highlights the importance of early recognition, risk stratification, and close postoperative follow-up in high-risk individuals.