Methods: After assessment of their MS ratio following in-office tooth cleaning (=starting point), 60 volunteers received either an ncHA paste or a placebo paste containing dicalcium phosphate dehydrate (30 subjects per group). Subjects applied a drug-retainer containing a small amount of the test paste to their upper and lower teeth for 5 minutes daily following nighttime brushing for 1 week. MS ratios were then assessed by culture techniques from saliva samples collected at 1 week, then 1, 2, 6 and 12 months after use of the test paste, and the effect of each paste was statistically evaluated.
Results: Median MS ratios of the group using ncHA paste, measured at starting point, 1 week, then 1, 2 and 6 months after using the paste were respectively 2.94E-3, 2.72E-3, 2.28E-3, 1.50E-3 and 1.38E-3. Linear regression analyses confirmed a high correlation between use of the ncHA paste and MS ratio decrease (R2=0.72). In contrast, no such correlation between paste use and MS ratios in the placebo group was found (R2=0.39). Moreover, at 2 months after using the paste, a significant difference in MS ratio between the two groups was confirmed (P<0.01).
Conclusion: Clinical testing showed ncHA reduces subjects’ MS ratio, and therefore may help restore balance to flora in the oral cavity.