Maxillary canines are generally considered important both cosmetically and functionally. Most claims on the importance of maxillary canines, however, have been based on expert opinions and clinician-based studies. There are no scientific studies in the literature reporting on their cosmetic importance or how laypeople perceive a smile treated by maxillary canine extractions. Our objective was to investigate whether there is any difference in the perceptions of patients' smiles treated by extracting either maxillary canines or first premolars, as judged by orthodontists, dentists, and laypeople.Methods
This retrospective study included 24 participants who had unilateral or bilateral extraction of maxillary permanent canines and fixed appliances in the maxillary and mandibular arches to comprehensively correct the malocclusion, selected from orthodontic patients treated at Chesterfield Royal Hospital NHS trust in the United Kingdom over the last 20 years. The control group of patients had extraction of maxillary first premolars followed by fixed appliances and finished to an extremely high standard judged by the requirement that they had been submitted for the Membership in Orthodontics examination. The finished Peer Assessment Rating scores for this group were less than 5. The end-of-treatment frontal extraoral smiling and frontal intraoral views were presented for both groups. The photographs were blinded for extraction choice and standardized for size and brightness using computer software (Adobe Photoshop CC version 14.0; Adobe Systems, San Jose, Calif). The work file was converted to an editable pdf file and e-mailed to the assessors. The assessor panel consisted of 30 members (10 orthodontists, 10 dentists, and 10 laypeople), who were purposely selected. The measures were rated on a 10-point Likert scale.Results
The attractiveness ratings were not statistically significantly different between the canine extraction and premolar extraction groups, with a mean difference of 0.33 (SD, 0.29) points. A 1-way repeated-measures analysis of variance to test the difference in scores among the laypeople, orthodontists, and dentists (n = 30) showed no statistically significant difference (Wilks lambda = 0.835; P = 0.138), and the Bonferroni test indicated that no pair-wise difference was statistically significant.Conclusions
No statistically significant difference was found in the smile attractiveness between canine extraction and premolar extraction patients as assessed by general dentists, laypeople, and orthodontists. Further high-quality studies are required to evaluate the effect of canine extraction and premolar substitution on functional occlusion.