Assessing shade differences in acrylic resin denture and natural teeth

Four experiments in this study assess shade differences in acrylic resin denture and natural teeth. The first two examine the perceptual errors made by experienced dentists in their use of a manufacturer-provided shade guide for acrylic resin denture teeth. In the first of four experiments, dentists examine whether the numbering of a selected shade guide corresponds to the arrangement of the tabs from light to dark. In the second experiment, a visual discrimination task determines whether dentists can distinguish shade guide tabs from one another. The results from these two experiments revealed that the numbered progression of the shade tabs does not correspond to a light-to-dark order, that dentists have difficulty discriminating between several shade tabs, and that the shade tabs can be rearranged on an empirical basis. The third experiment demonstrated how the shade of natural teeth varies by age, gender, and complexion. The Biotone shade guide, rearranged in the manner suggested by the second experiment, was used to make these assessments. The fourth experiment examined whether the shades used for complete dentures were similar to shades found in natural teeth. The results from the last two experiments showed that shade selection can be facilitated by use of a rearranged set of shade guide tabs. The results also reveal that natural teeth significantly and clinically darken with age; however, selections made for denture teeth tend to be relatively constant in color, despite the age of the patient. Differences for gender and complexion do not appear to be clinically significant.