Effects of angulation on tooth color determination during color matching

Various factors influence tooth shade determination during both visual and instrumental color matching in restorative dentistry. There are concerns regarding shade tab positioning and angulation of a tooth surface using color instruments during tooth shade determination. OBJECTIVE: The purpose of this study to investigate the effects of angulation on the color determination of shade-guide tooth tabs using a non-contact measuring system. METHOD: Five tooth tabs chosen from three types of shade guides were measured using the PR705 measuring system with 30, 45, 60, 75, 90 and 105 degree on central, cervical and incisal positions each tab, and CIEL*a*b* color differences between 90 degree and every other degree were calculated. Repeated measures ANOVA analysis was performed on these five color differences. RESULTS:  Mean (± s. d.) color differences were:

Position	ΔE 30°-90°	ΔE 45°-90°	ΔE 60°-90°	ΔE 75°-90°	ΔE 105°-90°
Cervical	2.4 ± 1.3	3.5 ± 2.2	5.2 ± 2.3	4.1 ± 1.4	5.7 ± 1.9
Central	3.4 ± 2.2	3.5 ± 1.3	9.8 ± 4.2	12.2 ± 7.3	5.6 ± 1.0
Incisal	3.2 ± 0.6	3.5 ± 2.1	10.1±13.5	6.9 ± 6.7	7.2 ± 1.2

No significant difference was found between positions (P=0.379) nor its interaction with angulation (P=0.314); however, a significant difference was found between the angulations (P=0.003). CONCLUSIONS: Angulation is a real concern during the process of instrumental color matching. Color differences caused by a change in angulation are not only perceptible but also may be the cause of unacceptable color matching.

This study was supported by The Ohio State University College of Dentistry