Purpose:  Although matching the tooth color for a ceramic prosthesis is usually done by subjective visualization, spectroscopic instruments are gradually making inroads in dental offices.  The purpose of this investigation was to compare the color measurements made with two spectrophotometers used by two operators and an imaging software.

Methods: A total of 26 shade tabs from a Vitapan 3-D Master shade guide (Vita) were used to make the CIE L*a*b* measurements with Minolta Chromameter 3000 (Minolta America) [Chroma] and Easyshades spectrophotometer (Vita) [Easy].  Two operators (A,B) made three measurements each on the shade tabs.  Similar measurements were made on the images of the shade tabs obtained from a scanner using imaging software (Adobe Photoshop) [Scan].  The data were analyzed using t-test and Pearson's Correlation (r).

Results:  Tables 1 and 2 show the t-test and Pearson r values for various comparisons.   Table 1

Statistical Test	A Chroma : Easy			B Chroma : Easy			Chroma A : B			Vita A : B
	L*	a*	b*	L*	a*	b*	L*	a*	b*	L*	a*	b*
t-Test (p < )	0.001	0.001	0.001	0.001	0.001	0.001	0.10	0.46	0.03	0.00	0.00	0.00
Pearson (r)	0.89	0.92	-0.12	0.93	0.97	0.59	0.89	0.89	0.11	0.95	0.91	0.57

Table 2

Statistical Test	A Chroma : Scan			A Easy : Scan			B Chroma : Scan			B Easy : Scan
	L*	a*	b*	L*	a*	b*	L*	a*	b*	L*	a*	b*
t-Test (p < )	0.69	0.57	0.67	0.00	0.02	0.00	0.10	0.86	0.04	0.00	0.02	0.00
Pearson (r)	0.71	0.81	0.49	0.42	0.78	0.76	0.19	0.66	0.29	0.42	0.78	0.76

 

Conclusion:  The inter-operator agreements for Chroma and Easy are significantly high for L* and a*  but not for b*.  The Scan values appear to compare more closely with Chroma than with Easy.