Sponsorship Bias in Randomised Controlled Trials on Postoperative Pain After Third Molar Extraction: A Meta‐Research Study

BACKGROUND: To evaluate whether sponsorship influences the reporting of positive results and the occurrence of selective outcome reporting (SOR) in randomised controlled trials (RCTs) investigating pharmacologic interventions for postoperative pain management following third molar extraction. METHODS: This meta-research included RCTs comparing at least one active drug with placebo, two active drugs, or combination thereof, and reporting outcomes related to pain reduction after third molar extraction. Searches were conducted in PubMed, Scopus and Web of Science without date restrictions and last search was performed on 2024 August. Study selection was performed in Rayyan QCRI, with two independent reviewers screening titles, abstracts and full texts. Data extraction was also conducted independently by two reviewers, collecting information on year of publication, trial design, number of groups, placebo comparisons, sample size (number of patients/teeth), follow-up losses, statistical significance of results, protocol registration and funding disclosures. Selective outcome reporting was assessed by comparing registered protocols with published outcomes. Associations between sponsorship status and both SOR and positive result reporting were analysed using chi-square test (α = 0.05). RESULTS: A total of 430 RCTs were included. No association was found between sponsorship status and SOR (p = 0.861), nor between sponsorship status and the reporting of positive results (p = 0.241). CONCLUSIONS: In this sample, sponsorship was not associated with either selective outcome reporting or the likelihood of reporting positive results in RCTs on postoperative pain management after third molar extraction. SIGNIFICANCE STATEMENT: The absence of sponsorship bias in RCTs on third molar extraction suggests that industry-funded and non-sponsored studies provide comparably reliable evidence, supporting clinicians in making unbiased, evidence-based decisions for postoperative pain management in third molar surgery.