Enamel Hardening Properties of Two Dental Pastes

Dental tooth pastes and topical pastes with remineralizing properties have been introduced to the market to help prevent demineralization that eventually may result in dental caries or erosion.

Objective: To determine the effect of two types of remineralizing paste on the microhardness of demineralized human enamel.

Methods: Eighteen extracted teeth were mounted on acrylic-cylinders so that the occlusal surface was exposed. The surface was polished using SiC paper. A groove was made on the acrylic rings to divide exposed enamel of each tooth into two halves. Thirty-six enamel surfaces were available. Twelve surfaces were randomly assigned for treating with WhiteLasting Tooth Whitening gel (WL: Frontier Pharmaceutical, NY, USA) containing calcium lactate, trisodium phosphate and fluoride, a PROSPEC™ MI paste (MI: GC America, IL, USA) containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), or water as a control. Remineralizing treatment was applied for 20 minutes twice daily for three days. Knoop microhardness was determined at three areas at 500 microns from the edge with a microhardness tester (FM-7, Future-Tech, Tokyo, Japan) on three opportunities:  prior treatment, after 15 hours immersion in Diet Coke^®, and after treatment with the pastes. The data were statistically analyzed using paired t-test and one-way ANOVA/Tukey's test (a = 0.05).

Results: Means (SD) for Knoop microhardness are as follows [identical letters indicate no statistical differences (p>0.05)]:

	Baseline	After Demineralization	After Treatment
WL	260a (31)	121d (34)	211b (40)
MI	253a (27)	134cd (22)	206b (35)
Water	259a (26)	135cd (24)	167c (26)

Conclusion: Within the limitations of this study, both pastes tested showed significant increase in microhardness of the demineralized enamel; however, the increase in the hardness of the enamel did not reach the pre-demineralization levels.