Abstract
A simple and rapid test of saliva for caries activity by Resazurin Discs was investigated. The Resazurin Disc method has a characteristic color reaction developing within 15 min at 32-37°C. The composition of Resazurin Discs was 0.0275% resazurin sodium salt, 0.2% PVA and 10% sucrose, and these were impregnated in a filter paper with 8 mm diameter. The color of these discs changed from blue to bluish violet, reddish violet, and then to red or colorless with saliva.
Experiments were demonstrated to examine the effect on color reaction of resazurin with saliva and representative strains. Resazurin Discs were highly sensitive to gram-positive microorganisms such as S. mutans, S. mitis, S. faecalis, S. aureus, L. casei and B. subtilis. The sensitivity was correlated with the number of S. mutans and Lactobacilli in saliva.
Furthermore, from the data of the spectrum analysis of color changes caused by bacterial and Salivary substrate, it was apparently shown that the visible and flurescence spectrum of resazurin coincided with the spectrum of the solution based on chemical reduction and not coincided with acid origin. These results suggested that the color reaction of saliva and bacteria was due to a chemical reaction (oxdation-reduction rate) and not to a pH effect.
The use of Resazurin Discs might be a useful caries activity test and they might also be used advantageously for a screening in dental health instruction.
