Postoperative complications substantially increase morbidity and healthcare costs. Preoperative oral hygiene has been proposed to reduce postoperative complications, yet its use remains inconsistent across surgical practices.

This systematic review and meta-analysis evaluated the effect of preoperative oral hygiene on adverse postoperative outcomes. MEDLINE, Embase, Cochrane Central, and Cochrane Database of Systematic Reviews were searched for randomised controlled trials and prospective cohort studies in adults undergoing elevated-risk elective surgery. Interventions included any preoperative oral hygiene measures. Primary outcomes were pneumonia, infection (nosocomial, surgical site, respiratory, urinary tract), hospital and ICU length of stay (LOS), and all-cause mortality. Risk of bias was assessed using the Cochrane ROB tool and Newcastle-Ottawa Scale (NOS), with certainty of evidence rated using GRADE. Meta-analyses used pooled odds ratios (ORs) and mean differences (MDs) with 95% confidence intervals (CIs).

Nineteen studies (5,757 patients) were included. Preoperative oral hygiene significantly reduced pneumonia (OR: 0.42; 95% CI [0.27, 0.66], p < 0.001); nosocomial (OR: 0.56; 95% CI [0.44–0.71], p < 0.001), surgical site (OR: 0.62; 95% CI [0.42, 0.92], p = 0.02), and respiratory infections (OR: 0.62; 95% CI [0.41, 0.93], p = 0.02). Hospital LOS (MD: −1.09 days; 95% CI [−1.73, −0.45], p < 0.001) and ICU LOS (MD: −0.14 days; 95% CI [−0.27, −0.00], p = 0.04) were also reduced. No significant association was identified with urinary tract infections or mortality.

Preoperative oral hygiene significantly decreases postoperative infections and shortens hospital and ICU stay. Routine implementation in preoperative protocols may improve surgical outcomes.

PROSPERO CRD42025638150