Correlation between collum angle and lower lip position in different Class II malocclusions - A retrospective cephalometric study

ABSTRACT Purpose: Significance of analysing collum angle in class II malocclusions with respect to lip position may lend greater credibility to variable torque brackets (mainly in the anteriors) that are fast gaining traction. Determine the magnitude of collum angle of maxillary central incisors in Class II division 1, division 2 malocclusions and changes in measurement brought about by variations in lower lip position and incisal contact. Materials and methods: 154 lateral cephalograms were divided into three groups- 55(Angle’s class I), 52 (Angle’s class II division 1) and 47 (Angle’s class II division 2). The collum angle was measured along with lower lip line (in Class II division 2) and lower lip contact (in Class II division 1) malocclusions. Results: The mean collum angles were 2.12 ± 1.43°, −0.84 ± 0.87° and 4.67 ± 2.23° in Groups 1, 2, and 3, respectively. Mean collum angle is significantly increased when the lower lip was found to contact the middle-third of the central incisor(in Group 3)and significantly decreased when the anterior one-third of the lower lip was in contact with the incisal edge of the central incisor (in Group 2). ANOVA followed by Tukey HSD test was carried out to determine statistically significant differences (p < 0.05). Conclusion: Collum angle is significantly decreased in Class II division 1 malocclusions necessitating variable torque prescriptions and segmental mechanics of maxillary anteriors. Appropriate alveolar bone support must be assessed prior to en-masse retraction and intrusion respecting the cortical boundaries. KEY MESSAGES: Variable torque brackets are rapidly gaining credence for their ability to provide sufficient alveolar bone support in different clinical scenarios. In this study, we have emphasized upon utilizing similar mechanics to treat class II malocclusions by utilizing the lower lip position as a reference guide.