Differences in Lip Support with and without Labial Flanges in a Maxillary Edentulous Population – Part 3: Unblinded and Discriminatory Subjective Analysis

Purpose To study the subjective differences in direct lip support assessments and to determine if dentists and laypeople are able to discern and correctly identify direct changes in lip support between flange and flangeless dentures. Materials and Methods A random sample of 20 maxillary edentulous patients described in part 2 of the study was used for analysis. A total of 60 judges comprising 15 general dentists, 15 prosthodontists, and 30 laypeople, the majority of who were distinct from part 2 of the study, were recruited. All images used in this study were cropped at the infraorbital level and converted to black and white tone, to encourage the judges to focus on lip support. The judges were un-blinded to the study objectives and told what to look for, and were asked to rate the lip support of each of the 80 images on a 100 mm visual analog scale (VAS). The judges then took a discriminatory sensory analysis test (triangle test) where they were required to correctly identify the image with a flangeless denture out of a set of 3 images. Both the VAS and triangle test ratings were conducted twice in a random order, and mean ratings were used for all analyses. Results The overall VAS ratings of lip support for images with flangeless dentures were slightly lower compared to images with labial flanges, and this difference was statistically significant (p < 0.0001). This was true for both profile and frontal images. However, the magnitude of these differences was too small (no greater than 5 mm on a 100-mm scale) to be clinically significant or meaningful. The differences in VAS ratings were not significant between the judges. For the triangle test, judges overall correctly identified the flangeless denture image in 55% of frontal image sets and 60% of profile image sets. The difference in correct identification rate between frontal and profile images was statistically significant (p < 0.0001). For frontal and profile images, prosthodontists had the highest correct identification rate (61% and 69%), followed by general dentists (53% and 68%) and by laypeople (53% and 50%). The difference in correct identification rate was statistically significant between various judges (p = 0.012). For all judges, the likelihood of correctly identifying images with flangeless dentures was significantly greater than 1/3, which was the minimum chance for correct identification (p < 0.0001). Conclusions Removal of a labial flange in a maxillary denture resulted in slightly lower ratings of lip support compared to images with a labial flange, but the differences were clinically insignificant. When judges were forced to look for differences, flangeless dentures were detected more often in profile images. Prosthodontists detected the flangeless dentures more often than general dentists and laypeople.