Plaque Zinc Concentration after Brushing with 2% Zinc-citrate Trihydrate Toothpaste

Method: The concentration of total zinc in plaque was measured before and after brushing with 2%ZCT/hydroxyapatite toothpaste or standard zinc-free toothpaste; both toothpastes contained fluoride (1450ppm). The study had a randomised, controlled, cross-over design.

Healthy adult subjects (males/females) were accepted onto the study on the basis of inclusion/exclusion criteria. This study comprised of two visits - baseline and 18h visit. Subjects brushed their teeth with zinc-free toothpaste at home for 1w before attending the baseline visit. At baseline, the pre-brushing plaque sample was collected (all tooth surfaces) and subjects brushed with 1.5g of test/control paste for 1min. No oral hygiene was performed for the following 18h. After this, the post-brushing (18h) plaque sample was taken. The level of zinc-ion in the samples was determined by Inductively Coupled Plasma (ICP) Atomic Emission Spectrometry. The protocol was approved by an independent Research Ethics Committee.

 Results: 58 subjects completed the study. The mean zinc concentrations in plaque were:

The test toothpaste with 2% ZCT increased zinc-ion concentration in plaque by 10.8ppm (82%), p<0.001. No significant increase was found in the control group. The difference in plaque zinc-ion concentration between the test and control group after 18h was 8.3ppm (52%), p<0.001.

Conclusion: Zinc-ion concentration in plaque was significantly increased 18h after brushing with toothpaste containing 2%ZCT compared to a standard toothpaste. This increased level is sufficiently high to exert efficacy against oral bacteria.