To evaluate the validity of Recurring Esthetic Dental proportion in natural dentition.

Background: Different proportions are described in the literature for smile designing, such as Golden proportion, Golden percentage, Preston's proportion, and recently, Recurring Esthetic Dental (RED) proportion.

Aims And Objectives: To evaluate the existence of RED proportion in natural dentition. To determine the relative height of maxillary lateral incisor and canine occurring in natural dentition so that it can be used in any of the above proportions.

Materials And Methods: Fifteen male subjects and 15 female subjects in each of the different age groups of 18-23 years, 24-29 years and 30-35 years were selected for this study (total 90). Photographs of the subjects were taken using Nikon D200 camera with 135 mm lens and analyzed using Adobe Photoshop CS4 extended software. The height and width of maxillary central incisors, lateral incisors and canines were found out using the measuring tool provided in the software.

Results: Average width ratio and height ratio of maxillary lateral incisor to central incisor and maxillary canine to lateral incisor were calculated to check the existence of RED proportion in natural dentition. Average lateral incisor to central incisor height ratio for "small"- and "medium"-sized teeth was found to be 88% and for "tall"-sized teeth was found to be 84%. Average canine to lateral incisor height ratio for "small"- and "medium"-sized teeth was found to be 106% and for "tall"-sized teeth was found to be 105%.

Conclusions: Within the limitations of the study, RED proportion was not seen in natural dentition.