Demonstration pH Cycling Robustness, Accuracy, and Sensitivity for Evaluating Dentifrices

Objectives: Demonstrate robustness of the pH Cycling model proposed as an animal caries alternative to the requirements of the US Anticaries Monograph, as well as demonstrate its accuracy and sensitivity.
Methods: A combination of historic data mining, stability experiments, and elemental analysis was used to evaluate the allowable range of ingredient addition to key solutions, variation in incubation temperature, and critical solution stability. After these evaluations, caries-like lesions were made with various treatments over three weeks in a protocol described by Stookey et al. 2011. Those treatments included various fluoride concentrations (110, 275, 550, 850, 1100 ppm) in a silica base, commercial products (Arm & Hammer Essentials, Sensodyne Clinical White, and Crest Cavity Protection), and a known-ineffective product (NaF/calcium carbonate). Following treatment, lesions were cross-sectioned and indented using a method described by Featherstone et al. 1983.
Results: Allowable addition was determined to be ± 0.5% for solution ingredients and 2.5% for treatments based on variation in 10 historic studies. Allowable temperature deviation during incubation was determined to be 37 ± 3° C (before sample addition) and 37 ± 4° C (at termination of incubation period) following stability experiments. Unused remineralization and demineralization solutions are stable and clear for 14 days following elemental analysis, while remineralization and demineralization need to be changed after 3 cycles (days) where deviation from target formulation was < 5% and fluoride content did not rise above 0.015 ppm. A significant dose response, p<0.05, was observed for the pH cycling study while commercial products passed non-inferiority testing and the known-ineffective product failed non-inferiority testing (p<0.05, single-sided, student’s t-test vs. non-inferiority threshold).
Conclusions: The pH cycling model was demonstrated to be robust, accurate, and sensitive thus helping to prove its utility as an alternative to animal testing to substantiate fluoride efficacy in soluble fluoride containing dentifrices.