Effects of Intrusion Arches on the Esthetic Smile Arc

Objective:This study investigated the flattening effects of orthodontic intrusion arches on the esthetic smile arc. Sixty one non-extraction, non-growing cases with deep overbite of at least 50% were selected. Methods:Pre- and post-treatment smile photographs, occlusal photographs and lateral cephalometric radiographs were used for the survey and measurements. Forty seven laypersons took part in the survey to evaluate smile attractiveness and smile arc appearance. Results: Indicated that intrusion mechanics appeared to flatten the smile arc in about 3 out of 10 cases. Lower utility arches demonstrated the strongest effect with a 5-to-10 ratio. Neither archform nor any cephalometric measurement was found to show any correlation with the appearance of the smile arc. The study showed that orthodontic correction of deep overbite malocclusions moderately increased the smile attractiveness and made the smile arc more acceptable. Conclusion:Although a parallel (consonant) smile arc was most favored by the public, a flat smile arc was perfectly acceptable. The public survey suggested that smiles with consonance ratios of between 0.77 and 0.89 were considered consonant.