Objectives: In recent years, there has been a significant increase in the demand for tooth bleaching, yet objective data for color changes obtained by tooth bleaching based on a precise color measuring methodology is not available. The purpose of this study was to analyze the effectiveness of tooth bleaching by spectrophotometric measurement.  

Methods: This study included 32 subjects who have an intact natural dentition in the maxillary anterior sextant and have not been subjected to bleaching. Tooth bleaching (Opalescence 10% PF, Ultradent, USA) was performed for 14 days according to manufactures’ standards. Tooth color for 3 areas (1/3 of incisal, body and cervical) of the maxillary central incisor (I) and canine (C) was measured by a spectrophotometer (MSC-2000, Olympus, Japan) prior to and after bleaching. Color difference dE and color coordinates of dL*, da* and db* were calculated based on the CIELAB color system. Scheff’s multiple comparison test and Student t-test were utilized for the statistical analysis. Results:

	dE-I	dL*-I	da*-I	db*-I	dE-C	dL*-C	da*-C	db*-C
Incisal	8.7	4.3	-3.9	-5.7	9.1	5.4	-3.9	-5.2
Body	8.1	3.1	-3.0	-6.2	9.9	4.2	-4.1	-7.7
Cervical	9.3	3.8	-3.7	-7.3	11.2	5.4	-5.2	-7.9

L* values increased and both values of a* and b* were decreased. Color changes varied in mean of color difference dE from 8.1 to 11.2. There was a significant difference for mean dE and dL* values between incisor and canine at the body and the cervical regions (p<0.01). Mean values of dE for canine at the body and the cervical regions were significantly greater than the incisal region (p<0.05). Conclusions: Spectrophotometric measurement showed statistically significant differences for effectiveness of bleaching depending on the region and tooth type. It was also concluded that colorimetric effectiveness by this bleaching system indicated a very distinguishable color changes.