The immediate effects of aligners and aesthetic fixed appliances on smiling and perceptions in young adults

AIMS • To evaluate, in young adults, the immediate effect of clear aligners (CAs) and aesthetic fixed appliances (AFAs) on the magnitude of rest to natural and rest to maximal smile • To evaluate, in young adults, the immediate effect of CAs and AFAs on intra-session reproducibility of rest to natural and rest to maximal smile • To evaluate, in young adults, the immediate perception of CAs and AFAs MATERIALS AND METHODS Forty Caucasian subjects (20 females, 20 males), aged between 18 and 25 years, with a Class I incisor relationship and no history of orthodontic treatment were recruited. 3D stereophotogrammetric images were captured of each subject without appliances and separately, in random order with either CAs or AFAs (Session 1), at rest, natural and maximum smile (Capture A). Following a rest period of 15 minutes, the images were retaken both without and with appliances (Capture B) to assess intra-session reproducibility. Four weeks later (Session 2), the same protocol was adopted as per Session 1, except that subjects who had been randomised to the CAs were allocated to the AFAs and vice versa. All images had 26 landmarks placed by 1 operator. The landmarking identification error was calculated by re-landmarking 10 percent of the original sample one month after initial images were landmarked and determining the difference in landmark placement. The mean magnitude of movement and reproducibility with each expression, rest to natural and rest to maximal smile, were compared and analysed across both genders. Four weeks after Session 2, a questionnaire was issued via email to all subjects to evaluate the immediate perception of CAs and AFAs. RESULTS The landmark identification error was 0.50 +/- 0.08 mm. For rest to natural smile, there was no significant difference in magnitude of movement with and without CAs (p = 0.6964). In contrast, for rest to maximal smile, the magnitude of movement differed significantly with and without CAs (p = 0.0001), with significantly greater movement recorded with the latter. For rest to natural and rest to maximal smile, there was a significant difference in magnitude of movement with and without AFAs (p = 0.0024 and p = 0.0002 respectively). Significantly greater mean movement occurred with AFAs, than with CAs, for both expressions. The mean magnitude for each smile was greater in males than in females (p = 0.0109). The order of randomisation of appliances made no difference to the mean magnitude of movement from rest to natural and rest to maximal smile (p = 0.0939). Without appliances, there was no significant difference in intra-session reproducibility of the magnitude of rest to natural and rest to maximal smile (p = 0.3601) but significant differences existed in intra-session reproducibility of the mean magnitude of each expression with appliances (p = 0.0290). Although statistically significant differences were recorded between appliances in magnitude and intra-session reproducibility for both expressions, these are unlikely to be of any clinical significance. Seventy-six percent of subjects preferred CAs to AFAs as they were deemed to be more discrete (43 percent) and more comfortable (33 percent). All subjects indicated the appearance of CAs was good or very good. Ninety percent of subjects indicated that they were likely or very likely to recommend CAs. CONCLUSIONS • Except for rest to natural smile with CAs, both appliances had an immediate and significant impact on the mean magnitude of movement for both expressions • CAs and AFAs had a significant immediate effect on intra-session reproducibility of rest to natural and rest to maximal smile • Young adults’ immediate perception was preference for CAs as they were reckoned to be more discrete and comfortable