Background: The present study was conducted to assess effect of different malocclusions on lip – tooth relationships during smiling and speech. Materials & Methods: The present study was conducted on 85 subjects and were made to pronounce few words starting from ‘che’, ‘fa’, ‘se’, ‘chee’, ‘tee’ and ‘mee’. The height and width of an upper central incisor and the height-to width ratio was calculated. Gingival display of the upper central incisor, interlabial gap, philtrum height, left and right commissure heights, smile width or outer commissure width and the smile index was recorded. Smile arc and most posterior maxillary tooth visible were recorded too. Results: Out of 85 patients, males were 30 and females were 55. Class I comprised of 10 males and 15 females, class II had 18 males and 34 females and class III had 2 males and 6 females. The mean buccal corridor ratios in posed smile arc in class I patients was 0.12, in class II was 0.15 and in class III was 0.16. In unposed smile arc, in class I patients was 0.11, in class II was 0.14 and in class III was 0.12. There was no- difference in poised and unposed smile arch patient, in class I and II whereas class III showed significant difference (P< 0.05). A significant contingency in the smile arc type between the posed and unposed smiles (Contingency coefficient: .702, p < 0.001). This means that the smile arc was the same among the posed and unposed smiles in about 75 per cent of the subjects. Conclusion: Authors found that the buccal corridor ratio during the posed smile was more than that during the unposed smile. The smile arc did not differ in different malocclusions.
Key words: Smile, Lips, Malocclusion