A Novel Optical Approach to Achieving Tooth Whitening

Objectives: To measure the in vitro tooth whitening effects of a toothpaste containing blue covarine. Methods: Extracted human teeth were cleaned and placed in sterile saliva for two hours. After rinsing with water, baseline tooth colour was measured using a chromameter. The specimens were brushed for 1 minute with a toothbrush and a slurry of toothpaste in water. The toothpaste used was either a new whitening silica toothpaste containing blue covarine (BC) or a whitening silica toothpaste control containing no blue covarine (n=8). Blue covarine is a new optical approach to altering the colour properties of teeth, giving them a yellow to blue colour shift which is one of the primary drivers of tooth whiteness perception. Following treatment, teeth were rinsed thoroughly with water and the colour remeasured. Teeth were then placed in 400ml water and the water was continuously agitated by stirring. At each time point the excess water was removed from the tooth surface, the colour of each tooth measured and then returned into water. The colour of the teeth was measured immediately after treatment and rinse, and then after 1, 2 and 5 hours of further water rinsing. Changes in tooth colour were calculated in terms of Delta b* (yellow-blue) and a previously described tooth whiteness index (WIO). Results: Mean colour parameter changes (s.e.) are shown below.

Toothpaste	Colour Parameter	Time in water rinse (hours)
		0	1	2	5
BC	Delta b*	-0.47 (0.10)	-0.40 (0.10)	-0.41 (0.10)	-0.48 (0.11)
Control	Delta b*	0.21 (0.08)	0.23 (0.13)	0.36 (0.19)	0.35 (0.21)
BC	Delta WIO	1.87 (0.38)	2.00 (0.46)	1.95 (0.34)	1.73 (0.56)
Control	Delta WIO	-0.78 (0.33)	-0.68 (0.82)	-0.91 (0.73)	-1.24 (0.97)

The BC toothpaste gave a reduction in tooth yellowness and an increase in tooth whiteness. Statistical analysis (Student t-test) showed that the BC and control toothpaste were significantly different at each time point (p<0.05) for both Delta b* and Delta WIO. Conclusions: The BC toothpaste gave a statistically significant reduction in tooth yellowness and an increase in tooth whiteness compared to the control toothpaste. The optical effect was not removed following water rinsing for up to 5 hours.