Dental calculus forms when calcium and phosphate ions precipitate within a maturing biofilm, producing mineral phases such as brushite, octacalcium phosphate, hydroxyapatite and whitlockite. Saliva is central to both calculus formation and enamel remineralization because its ionic composition and buffering capacity provide calcium and phosphate for mineral deposition. Agents that reduce free calcium availability in saliva—such as chelators or anti-calculus additives—may therefore influence both calculus and remineralization processes.
Soluble pyrophosphates and zinc salts are widely used anti-calculus ingredients that inhibit calcium phosphate nucleation and crystal growth. The methyl vinyl ether/maleic acid copolymer (PVM/MA, Gantrez®) is another anti-calculus agent that can reduce bacterial adhesion and decrease calcium availability. Whether anticalculus formulations alter fluoride-mediated remineralization remains unresolved: some experimental work shows no effect on fluoride uptake, whereas longer-term clinical trials have reported different caries outcomes between formulations. Given the biological role of calcium availability, assessing immediate changes in salivary calcium after toothpaste use can provide mechanistic insight into how formulations may affect mineral availability.
This randomized three-period crossover study was designed to compare short-term changes in salivary calcium after single applications of three sodium fluoride toothpastes: one containing PVM/MA (Sensodyne), one containing pyrophosphate plus zinc (Dentalux), and a sodium bicarbonate formulation without anticalculus agents (Parodontax). The primary objective was to evaluate whether changes in salivary calcium over time differ between toothpaste formulations.
The trial used a randomized, three-treatment, three-period crossover design. Ethical approval was obtained from the Ethics Committee of Witten/Herdecke University (S-324/2023) and all participants provided written informed consent. The study enrolled 48 healthy adult volunteers based on an a priori power calculation that targeted a medium effect size (f = 0.25), four repeated measurements, and 80% power.
The study was originally exploratory and focused on salivary biomarkers; it was retrospectively registered in the German Clinical Trials Register (DRKS00039385). No minors participated in the trial.
Each participant used all three commercially available sodium fluoride toothpastes in randomized order, according to one of three predefined treatment sequences. The three products differed in formulation: a PVM/MA copolymer formulation (Sensodyne), a pyrophosphate plus zinc formulation (Dentalux), and a sodium bicarbonate-containing formulation without anticalculus agents (Parodontax). Treatment periods were separated by a 2-day washout interval.
Unstimulated saliva samples were collected at four time points for each treatment period: baseline before brushing (T0), immediately after brushing (T1), 30 minutes after brushing (T2), and 60 minutes after brushing (T3). The study measured total salivary calcium concentrations in these samples.
Salivary calcium concentrations were quantified using a colorimetric assay. Data were analysed with linear mixed-effects models. Fixed effects included toothpaste formulation, measurement time, treatment sequence, and the toothpaste-by-time interaction; participant identity was modelled as a random effect to account for within-subject correlation across periods and time points.
The analysis tested main effects for formulation and time, the interaction between formulation and time, and evaluated whether treatment sequence influenced results.
The primary outcome was whether changes in salivary calcium concentration over time differed between toothpaste formulations (i.e., the toothpaste-by-time interaction). Secondary analyses compared salivary calcium concentrations across formulations at each measurement time and assessed effects of measurement time and treatment sequence.
Statistical testing revealed significant main effects of toothpaste formulation (F(2,103.35) = 42.31, P < 0.001) and measurement time (F(3,141) = 39.78, P < 0.001). The toothpaste-by-time interaction was also significant (F(6,141) = 23.91, P < 0.001). Treatment sequence did not have a significant effect (P = 0.927), indicating no detectable carryover attributable to order in this design.
Pairwise comparisons showed that the sodium bicarbonate toothpaste (Parodontax) produced significantly lower salivary calcium concentrations immediately after brushing (T1) compared with both the pyrophosphate/zinc formulation (Dentalux) and the PVM/MA formulation (Sensodyne); both comparisons reached Bonferroni-adjusted significance (P < 0.001). The differences in salivary calcium between products diminished at 30 minutes (T2) and were no longer significant at 60 minutes (T3). No significant differences between Dentalux and Sensodyne were observed at any measured time point.
These findings indicate that the largest product-level differences in total salivary calcium occurred immediately after brushing and that these differences tended to resolve within an hour.
The study demonstrates that commercially available sodium fluoride toothpastes with different formulation profiles produce distinct short-term effects on salivary calcium. The most pronounced differences were observed directly after brushing and were transient, diminishing by 30 minutes and absent by 60 minutes.
Because the tested products varied in multiple ingredients beyond their principal anticalculus agents, the observed effects should be interpreted as product-level differences rather than definitive, ingredient-specific actions. For example, although pyrophosphate chelates calcium and is expected to reduce free calcium availability, the pyrophosphate/zinc product in this study did not differ significantly from the PVM/MA product at any time point. Conversely, the sodium bicarbonate formulation produced a greater immediate reduction in total salivary calcium compared with the other two products, a finding that cannot be attributed to a single ingredient based on the study design and available data.
The clinical relevance of transient, short-term reductions in salivary calcium is not established by this physiological study. While changes in calcium availability could theoretically influence remineralization potential, this trial did not assess enamel fluoride uptake, lesion remineralization, or long-term clinical outcomes. The authors note that prior experimental and clinical literature on whether anticalculus agents affect fluoride-mediated remineralization is mixed, and they recommend further research.
A single application of different commercially available sodium fluoride toothpastes produced statistically significant, but transient, differences in total salivary calcium concentration in healthy volunteers. Differences were largest immediately after brushing and resolved within 60 minutes. Findings reflect product-level effects rather than isolated ingredient actions.
The authors recommend multicentre studies to replicate these observations and to evaluate whether short-term changes in salivary calcium translate into clinically meaningful effects on enamel remineralization or caries outcomes. Data supporting this trial are reported within the article and supporting information, and the study was funded by the Fördergemeinschaft of Witten/Herdecke University, with no reported competing interests.