RESUMEN
OBJECTIVE: The purposes of this study were to evaluate the nasolabial angle changes between closed lip position at centric occlusion and relaxed lip position at which the bite is open so that the lips do not touch and to elucidate the significance of the relaxed lip position for dentofacial diagnosis. METHODS: The subjects consisted of 60 (35 Males, 25 Females) skeletal Class III malocclusion adult patients (mean age 23.3 years) with anterior crossbite. RESULTS: In Class III malocclusion adult patients, there were significant differences in the nasolabial angle changes between closed lip position and relaxed lip position. Using the cluster analysis, the subjects were divided into three groups according to the pattern of nasolabial angle change: Group 1 (N = 27, 45%, -8 ~ 1), Group 2 (N = 30, 50%, 2degrees ~ 17), and Group 3 (N = 3, 5%, over 18). CONCLUSION: The results showed that the pattern of the nasolabial angle change between closed lip position and relaxed lip position varies in skeletal Class III malocclusion patients. Thus, relaxed lip position should be taken into account when diagnostic records are obtained and analyzed to accurately to evaluate the facial soft tissues and predict facial esthetics after surgical-orthodontic treatment.