Erosion Potential of Commercial Fluoride-Free Mouthwashes on Dental Hard Tissues

Mouthwashes often present acidic pH, which raises concerns about their potential contribution to erosive tooth wear. This study evaluated the erosive potential of commercial fluoride-free mouthwashes using a screening method.

A convenience sample of 81 different mouthwashes was evaluated for their erosion potential (International Organization for Standardization, ISO/FDIS 28888:2013). This method measured the pH changes (ΔpH) of 25 mL of calcium phosphate solution (baseline pH 5.05 ± 0.05; mean ± standard deviation) once the test mouthwash was added (0.25 mL). Three citric acid/citrate buffers were used, with the maximum allowable ΔpH based on the strongest buffer. Each mouthwash was tested four times, and mean values, standard deviations, and the correlation/regression between the initial and final pH were calculated.

Mouthwashes presented a baseline pH range of 3.00-9.47. The reference solutions resulted in ΔpH of 0.58 ± 0.00, 0.89 ± 0.00, and 1.20 ± 0.01, respectively. None of the mouthwashes showed ΔpH higher than the strongest standard. Several unexpected results were observed: (i) nine mouthwashes with initial pH above 5.00 caused a pH drop when added to the screening solution; (ii) one mouthwash with initial pH 4.27 caused a pH drop to 4.17; and (iii) one with initial pH 4.93 caused a pH increase to 6.18. The correlation and regression values were: r = -0.81/r² = 0.65 (p-value < 0.001).

Most mouthwashes showed no erosive potential, but unexpected pH shifts in over 10% highlight the need to refine testing methods for fluoride-free products.

Some fluoride-free mouthwashes may contribute to dental erosion due to low pH. Identifying these products helps clinicians make safer recommendations for daily use.