Methods: This study used a double-blind, parallel-group design, consisting of 2-week pre-trial and trial phases separated by a washout period. A partial-mouth technique was used where a toothshield protected lower anterior teeth from brushing and doubled as an applicator for undiluted dentifrice twice daily. These teeth were scaled/polished before each 2-week phase. Subjects brushed with regular dentifrice (Aim®, Unilever) during the washout period. Calculus was measured on labial/lingual surfaces of 6 lower anterior teeth by the Volpe-Manhold Index (VMI). Subjects used a non-tartar-control dentifrice during the pre-trial phase to determine calculus formation rates, and these VMI scores were used as baseline data for random allocation to the following products for the trial phase: 1) Control dentifrice - hydrated silica base (Crest®, Procter & Gamble). 2) Test dentifrice - 0.5% zinc citrate trihydrate in sodium bicarbonate and sodium percarbonate base. VMI data from the trial phase were analyzed by ANCOVA using pre-trial scores as covariates.
Results: After 2 weeks of treatment, VMI calculus scores (mean ± SE) were 1) 27.39 ± 1.78 (N = 23) and 2) 20.96 ± 1.74 (N = 24). The VMI mean for the zinc citrate dentifrice group was 23.5% lower than the control group, and this difference was statistically significant (p = 0.01).
Conclusion: A sodium bicarbonate dentifrice containing 0.5% zinc citrate trihydrate significantly reduced calculus formation in a short-term human model which has been shown previously to be predictive of the outcome of long-term clinical trials. [Supported by Church & Dwight Co.]