Zinc Delivery and Plaque Acid Reduction from 2%Zinc-Citrate-Trihydrate Toothpaste

Objectives: To measure zinc concentration and lactate generation in plaque after brushing with toothpaste containing 2% zinc citrate trihydrate (ZCT).

Methods: Study 1: Zinc concentration in plaque.  Whole-mouth plaque samples were taken 12h after tooth brushing, following 1 week in-home use (2/day) of toothpaste without zinc. Subjects then used the 2% ZCT toothpaste for 1 week and plaque was sampled 12h after brushing. Forty-four subjects completed the study. Total zinc concentration was determined by ICP Atomic Emission Spectroscopy and expressed as ppm (micro-g Zn/g wet plaque). Data were analysed by ANCOVA. Study 2: Plaque lactate generation. The study had a randomised, parallel, controlled, double-blind design with three groups using a paste with either 2%ZCT or 2%ZCT/0.3%Triclosan or no active.  Subjects rinsed with a slurry of one of the three pastes and 10min later consumed a defined amount of cake as a source of food-derived carbohydrate. Plaque samples were taken 8 min after eating and concentration of lactic acid measured by capillary electrophoresis. Data (ppm lactate in wet plaque) were analysed by ANOVA.

Results: Study 1. Mean (se) total zinc concentration was 19.0 (3.8) ppm in baseline plaque and 183.7 (22.9) ppm in plaque 12h after brushing. The difference between baseline and 12h samples was statistically significant (p<0001). Study 2. Mean (se) plaque lactate concentration in the 2%ZCT group (n=23) was 16.3 (1.5) ppm; in the 2%ZCT/0.3%Triclosan group (n=24) it was 19.2 (1.7) ppm; in the control group (m=26) it was 26.8 (2.3) ppm. The means of the 2%ZCT paste groups were significantly lower than the control group mean (p<0.01); the difference between the two 2%ZCT containing paste groups was not statistically significant.

Conclusion: The 2% ZCT toothpaste delivered significant levels of zinc to plaque and reduced food-induced lactate production in plaque.