Effect of External Light Conditions During Matching of Tooth Color

Visual assessment of tooth color is a highly subjective process and underlies several determination factors such as lighting conditions, examiner perception or tooth anatomy.

Aims: To investigate whether a color-matching process comparable with that used in routine dental practice under window daylight conditions is equivalent to color matching under a daylight lamp with standardized optimum light conditions (2000 lux, D65).

Methods: Twenty-nine preclinical students (31% male, mean age 26 years) underwent a theoretical and practical training program for standardization of knowledge. Then they matched randomly chosen shade tabs, using a shade-guide system, (3D-Master®,Vita Zahnfabrik, Bad Säckingen, Germany) under daylight lamp and window daylight conditions presented with the help of a standardized device. The difference (ΔE) between the color of the presented and selected shade tab was calculated. Statistical differences were explored by bivariate analysis (paired t-test) and multivariate analysis, exploring light conditions, lightness group of the respective shade tab, and sex simultaneously.

Results: Mean ΔE with daylight lamp was 2.5 (1.0 to 4.3) and that with daylight was 3.4 (0.9 to 7.4). This difference was statistically significant (p<0.001). Multivariate analysis confirmed the significantly smaller ΔE in the daylight lamp setting (p<0.001). Gender differences in color matching could not be detected (p=0.106).

Conclusion: Within the limitations of this study, use of a daylight lamp with spectral radiance corresponding to daylight and well defined light intensity helps to standardize light conditions and significantly improves the ability to match colors. It should, therefore, be considered for implementation in daily dental practice.