Aim: Lips-Dentition relationships play a special role during smile. Present study compared the relationship of lips and teeth during posed smile in subjects with normal occlusion, class 1 malocclusion and non-extraction treated cases.
Materials and methods: 20 cases with normal occlusion according to Andrews' and without facial malformation (N), 22 cases with moderate crowding (C 1) and 12 well treated patients without any extraction and facial malformation (T) with the age between 15 — 20 years old were selected. One photograph in rest position and another in posed smiling were taken in standard position. 12 variables on photos were measured by use of a smile mesh. ANOVA and Krukal-wallis tests were used for analysis.
Results: Commissure width and Smile width was significantly greater in group N than groups Cl and T (P<0.001). Upper lip curvature in non-extraction treated group was concave but in others were convex (P<0.022). Inter-canine width in group N was significantly higher than treated patients (P<0.03).
Conclusion: There is a direct relation between anatomic form of lips in rest and in smiling. Orthodontic treatment can cause some changes in lips form during smiling (IJO 2006; 1:163-7).