ImportanceDental caries and periodontal disease are common adult oral health conditions and potentially amenable to primary care screening and prevention.ObjectiveTo systematically review the evidence on primary care screening and prevention of dental caries and periodontal disease in adults to inform the US Preventive Services Task Force.Data SourcesMEDLINE, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews (to October 3, 2022); surveillance through July 21, 2023.Study SelectionDiagnostic accuracy studies of primary care screening instruments and oral examination; randomized and nonrandomized trials of screening and preventive interventions; cohort studies on primary care oral health screening and preventive intervention harms.Data Extraction and SynthesisOne investigator abstracted data; a second checked accuracy. Two investigators independently rated study quality. Diagnostic accuracy data were pooled using a bivariate mixed-effects binary regression model.Main Outcomes and MeasuresDental caries, periodontal disease, morbidity, quality of life, harms; and diagnostic test accuracy.ResultsFive randomized clinical trials, 5 nonrandomized trials, and 6 observational studies (total 3300 participants) were included. One poor-quality trial (n = 477) found no difference between oral health screening during pregnancy vs no screening in caries, periodontal disease, or birth outcomes. One study (n = 86) found oral health examination by 2 primary care clinicians associated with low sensitivity (0.42 and 0.56) and high specificity (0.84 and 0.87) for periodontal disease and with variable sensitivity (0.33 and 0.83) and high specificity (0.80 and 0.93) for dental caries. Four studies (n = 965) found screening questionnaires associated with a pooled sensitivity of 0.72 (95% CI, 0.57-0.83) and specificity of 0.74 (95% CI, 0.66-0.82) for periodontal disease. For preventive interventions no study evaluated primary care counseling or dental referral, and evidence from 2 poor-quality trials (n = 178) of sealants, and 1 fair-quality and 4 poor-quality trials (n = 971) of topical fluorides, was insufficient. Three fair-quality trials (n = 590) of persons with mean age 72 to 80 years found silver diamine fluoride solution associated with fewer new root caries lesions or fillings vs placebo (mean reduction, −0.33 to −1.3) and decreased likelihood of new root caries lesion (2 trials; adjusted odds ratio, 0.4 [95% CI, 0.3-0.7]). No trial evaluated primary care–administered preventive interventions.Conclusions and RelevanceScreening questionnaires were associated with moderate diagnostic accuracy for periodontal disease. Research is needed to determine benefits and harms of oral health primary care screening and preventive interventions.