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Quintessence Publishing: Journals: ORTHODONTICS
ORTHODONTICS
The Art and Practice of Dentofacial Enhancement

Formerly World Journal of Orthodontics

Edited by
Rafi Romano, DMD, MSc (Editor-in-Chief)

ISSN 2160-2999 (print) / ISSN 2160-3006 (online)

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Publication:
Yearbook 2013
Volume 14 , Issue 1

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Relationship between crown-root angulation (collum angle) of maxillary central incisors in Class II, division 2 malocclusion and lower lip line

Bhadrinath Srinivasan, MDS/Vignesh Kailasam, MDS/Arun Chitharanjan, MDS/Arthi Ramalingam, MDS


DOI: 10.11607/ortho.841

Aim: The present study aimed to measure the magnitude of the collum angle (crown-root angulation) of maxillary central incisors present in Class II, division 2 malocclusion and to relate the changes in its magnitude with variations in the lower lip line. Methods: A set of 120 conventional lateral cephalograms were selected and divided into three groups of 40 each based on the type of malocclusion presented: Class II, division 2 (group 1); Class II, division 1 (group 2); and Class I (group 3). The collum angle of the maxillary central incisor was measured, and the lower lip line was recorded. Results: Analysis of variance (ANOVA) revealed that the mean collum angle was statistically significantly different in the three groups. The mean collum angle was greatest in Class II, division 2 malocclusion (group 1). The mean collum angles were 3.24 4.69 degrees, 0.95 1.06 degrees, and 1.05 1.50 degrees in groups 1, 2, and 3 respectively. In χ2 test comparison of the location of the lower lip line (incisal, middle, or apical third of the central incisor) among the three groups, the lower lip line was found to contact the middle third of the central incisor most frequently in Class II, division 2 malocclusion. ANOVA followed by Tukey honestly significant difference (HSD) test showed that the mean collum angle is significantly increased when the lower lip is in the middle third (P < .05) of the central incisor. Conclusion: Variations in magnitude of the collum angle with the change in the lower lip line suggest a probable etiologic role of the lower lip line in the development of the collum angle. ORTHODONTICS (CHIC) 2013; 14:e66e74. doi: 10.11607/ortho.841

Key words: collum angle, lower lip line

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