Digital videographic measurement of tooth display and lip position in smiling and speech: reliability and clinical application.

INTRODUCTION: Tooth display and lip position in smiling and speech are important esthetic aspects in orthodontics and dentofacial surgery. The spontaneous smile and speech are considered valuable diagnostic criteria in addition to the posed social smile. A method was developed to measure tooth display in both smile types and speech. METHODS: The faces of 20 subjects were individually filmed. Spontaneous smiles were elicited by a comical movie. The dynamics of the spontaneous smile were captured twice with a digital video camera, transferred to a computer, and analyzed on videoframe level. Two raters were involved. Posed social smiles and speech records were also included. Reliability was established by means of the generalizability theory. It incorporated rater, replication, and selection facets. RESULTS: Generalizability coefficients ranged from .99 for anterior teeth to .80 for posterior teeth. The main sources of error were associated with rater and selection facets. The replication facet was a minor source of error. CONCLUSIONS: This videographic method is reliable for measurement of tooth display and lip position in spontaneous and posed smiling and speaking. Application of the method is warranted especially when obtaining an emotional smile is difficult, such as cleft lip and palate or disfigured patients