ABSTRACT Background: The bariatric surgery may have negative repercussions on oral conditions. Aim: To evaluate the impact of oral health educational/preventive program developed with patients submitted to gastroplasties. Method: The sample consisted of 109 patients randomly allocated to two groups: intervention group (IG), where they participated in the oral health promotion program that include multiple educational-preventive approaches; control group (CG), where they received usual care from the bariatric clinic staff, without participation in the program. The oral conditions investigated in the pre-operative and postoperative periods of one month (1M) and six months (6M) were: dental caries, periodontal disease, tooth wear, dental plaque and salivary flow. Results: After bariatric surgery, patients in IG presented: fewer changes in enamel (6M: p=0.004), dentin (6M: p=0.005) and gingival bleeding (6M: p<0.0001), reduction in plaque index (1M, 6M: p<0.0001) and increased salivary flow (6M: p=0.039), when compared with CG. Incipient tooth wear was recorded in both groups (6M: p=0.713). Conclusion: There was a positive impact of the implemented program in the prevention of the main oral health problems in patients who underwent gastroplasties, contributing to their quality of life.