Canine edge width and height affect dental esthetics in maxillary canine substitution treatment

BACKGROUND: To investigate the effect of canine edge width and height on dental esthetics in maxillary canine substitution treatment. METHODS: A total of 127 canine substitution treatment cases were screened and evaluated by a panel of orthodontic experts and laypersons in the pilot study. The top five subjects with the esthetically most pleasant canine substitution were included in the study, resulting in 140 computerized images displaying only the upper dentition, with different canine edge widths (0%, 12.5%, 25%, 37.5%, 50%, 62.5%, and 75% of the central clinical width) and heights (− 0.5 mm, 0 mm, 0.5 mm, and 1.0 mm vertically relative to the central incisor edge) finally used for the esthetic evaluation by 101 observers (41 orthodontists and 60 laypersons). The ordered logistic regression analysis, the univariate analysis of variance, the chi-square, and Fisher’s exact tests were used for statistical analyses. RESULTS: The most esthetic canine shape for canine substitution was found to be a shape with the edge width of 62.5% of the central incisor width and the edge height of 0.5 mm gingival to the central incisor edge (P < 0.05). The canine edge width of 50–75% and height of 0.5–0 mm gingival to the central incisor edge were generally considered to be esthetic by all observers. Orthodontists and laypersons had the same ranking on the top two most esthetic canine shapes (edge width and height 62.5% and 0.5 mm gingival; 50% and 0 mm incisal) as well as the bottom two most unesthetic canine shape (0% and 0.5 mm gingival; 75% and 1 mm incisal). Male and female observers generally had similar esthetic grades and rankings on the canine shapes (P > 0.05). CONCLUSIONS: The most esthetic canine shape for canine substitution is a shape with the canine edge width of 62.5% of the central incisor width and the edge height of 0.5 mm gingival to the central incisor edge. The different collocations of the canine edge width and height affect dental esthetics of the canine during canine substitution treatment.