Selective outcome reporting bias is highly prevalent in randomized clinical trials of nonsurgical periodontal therapy.

Selective outcome reporting (SOR) is a type of bias that can compromise the validity of results and affect evidence-based practice. SOR can overestimate the effect of an intervention and lead to conclusions that a treatment is effective when it is not. This study aimed to investigate the prevalence of SOR in publications of RCTs on nonsurgical periodontal therapy (NSPT) and to verify associated factors. The protocols were searched and selected on the www.clinicaltrials.gov platform up to January 16, 2022. Corresponding publications were identified, and data extraction and discrepancy analysis were performed. The risk of bias was assessed according to the RoB2 tool. One hundred forty-five studies (174 publications) were included. The prevalence of SOR was 49.7% and was unclear in nearly one third of studies (27.6%). Only 31.7% of the primary outcomes were completely described in the publications. The overall risk of bias was high in 60% of the included studies. SOR was associated with statistical significance (p < .001), and multiple publications of the same study (p = .005). Our study demonstrated the high prevalence of SOR, highlighting the need to improve the quality of reporting of RCTs on NSPT studies.