Intra-Oral Evaluation of a Two-Phase Calcium-Containing Bicarbonate Toothpaste

As part of an intra-oral study of the surface mineralizing effects of a dual-phase, calcium-containing toothpaste, we measured micro-hardness changes and evaluated changes in surface defects using SEM. Objective: To determine the effect of the calcium-containing toothpaste on the surface hardness of etched enamel. Method: Forty-one enamel cores were mounted in acrylic rods, polished flat and then etched in an acid soft drink for 70 minutes; another forty-one were brushed with a whitening toothpaste (Colgate Platinum®). One of each defect type was placed for one month in an oral prothesis in the mouth of a volunteer, and before and after placement, Knoop microhardness of the etched enamel was measured and SEM micrographs of two sites on each brushed specimen were taken. The volunteers brushed twice daily with a calcium-containing two-phase bicarbonate toothpaste (T-1), or a calcium-containing two-phase toothpaste without bicarbonate (T-2), or a conventional NaF/silica toothpaste (Crest Cavity Protection Regular®) (C-1). Results: Knoop Hardness changes were:

Toothpaste	DHK
Two-phase without bicarbonate	56.5 ± 30.4
Two-phase with bicarbonate	47.4 ± 31.3
Conventional NaF/silica	31.8 ± 30.6

The two-phase paste (T-2) without bicarbonate was significantly different from the conventional paste (C-1) (p<0.04). By SEM, all three formulations appear to produce varying effects on surface imperfections. However, only the calcium-containing toothpastes show unequivocal signs of surface mineralization on the whitening-toothpaste-prebrushed specimens. Conclusions: The calcium-containing toothpaste without bicarbonate hardens enamel to a significantly greater extent than the conventional toothpaste. The potential of the calcium-containing pastes for visibly creating new mineral in surface defects, suggests that the hardening is a result of their mineralizing power.