Laypeople's perceptions of frontal smile esthetics: A systematic review

INTRODUCTION: The emphasis on dental esthetics has increased in recent years. There are, however, differences in esthetic perceptions among professional and lay groups. The aim of this comprehensive review was to update previous reviews and answer the following research question: Can lay thresholds for acceptance of smile esthetic anomalies be defined? METHODS: A systematic search in the medical literature (PubMed, PMC, NLM, Embase, Cochrane Central Register of Controlled Clinical trials, Web of Knowledge, Scopus, Google Scholar, and LILACs) was performed to identify all peer-reviewed articles reporting data regarding evaluations of laypeople's perceptions of dental esthetic factors. RESULTS: Of the 6032 analyzed articles, 66 studies were selected for the final review process. Among the selected articles investigated perceptions of diastema, 15 analyzed modifications in tooth size and shape, 8 considered incisor positions, 15 evaluated midline discrepancies, 16 investigated buccal corridors, 26 analyzed gingival display and design, 3 considered lip height, and 20 investigated miscellaneous factors. Threshold values were identified for the following features: diastema (0-2 mm), tooth size and shape of incisor position, midline discrepancy (0-3 mm), buccal corridors (5-16 mm), gingival exposure (1.5-4 mm), occlusal canting (0°-4°), and overbite (2-5 mm). Furthermore, few other smile characteristics were found to be significantly associated with perception of smile aesthetics, even though any threshold could be detected. CONCLUSIONS: On the basis of the obtained results, threshold values for the main features of smile and dental esthetics could be identified. Limitations of the present study were the heterogeneity of data which made it impossible to perform a meta-analysis, and the lack of information about sample selection and selective outcome reporting.