RESUMEN
BACKGROUND: The Oral Behaviours Checklist (OBC) is a valid 21-item instrument quantifying the self-reported frequency of oral behaviours. An Italian version (OBC-It) has been released recently. Anxiety and oral behaviours are known to be associated in individuals with oro-facial pain due to temporomandibular disorders (TMD). However, information about this relationship in pain-free individuals is still limited. OBJECTIVES: The aim of this study was to test the reliability of the OBC-It and its reduced version (OBC-It 6), focusing on tooth clenching-related wake-time oral behaviours, and the effect of patient instructions on reliability. A second aim was to test the association between trait anxiety and oral behaviours in pain-free individuals. METHODS: Two hundred and eighty-two TMD-free students, divided into 2 groups (Group A, n = 139, mean age ± SD = 22.6 ± 5.4 years; Group B, n = 143, 23.7 ± 4.2 years), filled in the State-Trait Anxiety Inventory and the OBC-It. Group B received instructions about the OBC-It, while Group A did not. After 2 weeks, both groups filled in the OBC-It again. However, Group B was further divided into 2 subgroups, B1 and B2 . The first received the same instructions again, while B2 did not. RESULTS: The test-retest reliability of the OBC-It (A: ICC = .87; B1 : ICC = .94; B2 : ICC = .95) and OBC-It 6 (A: ICC = .85; B1 : ICC = .89; B2 : ICC = .93) was excellent in all groups. Trait anxiety was weakly associated with OBC-It only in women (R2 = .043, P = .021). CONCLUSIONS: The OBC-It is a reliable tool but further subjects' instructions might be needed. Trait anxiety has a limited effect on oral behaviours in TMD-free subjects.