Randomized Clinical Dose-Response Study to Evaluate Plaque Removal by Three Experimental Sodium Bicarbonate Toothpastes Using a Single Brushing Model

Objectives: This randomized, examiner-blind, crossover clinical study compared the plaque removal efficacy of three experimental toothpastes containing 20%, 35%, and 50% w/w sodium bicarbonate (NaHCO3) with commercial toothpastes containing 67% and 0% w/w NaHCO3 (positive and negative controls, respectively).

Methods: Fifty-six adults with a mean Turesky Modification of the Quigley-Hein Plaque Index (TPI) score of = 2.00 at screening and at the first treatment visit (pre-brushing) were randomized to a supervised single, timed (one minute) brushing with a 0%, 20%, 35%, 50%, or 67% w/w NaHCO3-containingtoothpaste. TPI was measured pre- and post-brushing. Participants completed five treatment visits, separated by a four- to six-day washout, and brushed once with each toothpaste. The primary efficacy analysis was change in whole mouth TPI score from pre- to post-brushing between the positive and negative control toothpastes (validation step). Secondary analyses were comparisons between each experimental toothpaste and the control toothpastes. Change in TPI score was analyzed using a mixed effect analysis of covariance.

Results: The difference in adjusted mean TPI change from pre- to post-brushing between the 67% and 0% w/w NaHCO3 toothpastes was -0.01 points (95% CI -0.06, 0.04), with no statistically significant difference between them (p = 0.6674). As such, study validity was not attained. Differences in adjusted mean change from pre- to post-brushing between each experimental toothpaste and the positive and negative controls ranged from 0.00 to -0.02 points. Twenty-two treatment-emergent, treatment-related adverse events, all oral, were reported by 17 participants (30.4%). These were spread uniformly across test toothpastes and controls. No serious adverse events were reported.

Conclusions: There was no statistically significant difference in change in mean TPI score between toothpastes containing 67% w/w NaHCO3 and 0% w/w NaHCO3 following a single timed brushing. This unexpected observation may be attributed to lower than expected reduction in overall plaque and a possible Hawthorne effect. As study validation was not met, no further conclusions can be made. The study products were generally well tolerated.