[Differences between laypersons and orthodontists in recognizing the light reflection zone on the maxillary central...

The light reflection zone (LRZ) is a new parameter that may serve as a tool for the diagnosis of smile esthetics. It is a bright white dot or area that appears on the surface of the maxillary central incisors and/or the gingiva of the front teeth, visible in intra-oral and smile extra-oral photographs. Recently it was found that the general population defines a nicer smile when the LRZ is located in the gingival area of the upper central incisors' surface rather than the incisal third. The aim of this study was to find out in two populations that are not aware of this new parameter, laypersons and orthodontists, whether there is a difference in the identification of the LRZ and the importance of the LRZ in determining the quality of the smile. Twelve pairs of facial photographs, including 10 of ordinary smiling persons and 2 of smiling models, were presented to 108 laypersons and 30 orthodontists. The only difference between each pair was the location of the LRZ that was moved, compared to the original photograph, gingivally or incisally respectively, using Photoshop (Adobe). Each participant was asked to mark whether he/she noticed a difference between the 2 pictures, and if so, to score the nicer smile. Data analysis was carried out using Chi square test and Fisher's exact test (SPSS v17). The results showed that both populations had difficulty in recognizing the differences between the pictures that were based solely on the LRZ parameter. However, when differences were recognized, most of the participants in both populations pointed on the smile where the LRZ was located gingivally as the nicer one. The orthodontic population recognized the difference between the two pictures, in which only the LRZ was changed, to a lesser extent compared to the laypersons populations. This result was with statistical significance (p = 0.007).