OBJECTIVE To identify the risk factors for periodontal changes in adult patients during orthodontic treatment by evaluating the periodontal status of banded second molars using the gingival index (GI). METHODS The sample consisted of 100 adult patients divided into two groups: the Orthodontics group, undergoing corrective treatment with fixed appliances and bands cemented to the four second molars, and the Control group, with no prior history of orthodontic treatment, age and sex matched. Group GI values were compared using the Wilcoxon test. Additionally, a multivariate logistic regression was performed to study the risk factors for increases in the GI. RESULTS Individuals in the Orthodontics group showed a significantly higher GI than those in the Control group. Logistic regression revealed that among the risk factors found to increase GI, the following proved significant (in order of importance): plaque index, subgingival encroachment of the cervical margins of bands, probing depth, and length of orthodontic treatment. CONCLUSIONS Banded second molars of adult patients during orthodontic treatment showed more clinical signs of gingival inflammation than those of untreated individuals. Moreover, major risk factors identified included the presence of plaque and the presence of subgingival band margins.