Buffering effects of toothpastes/gels on abrasion of eroded dentin

Objectives: Evaluation of abrasion resistance of eroded and non-eroded dentin brushed with experimental toothpastes and gels of varying buffering capacities. Methods:120 human dentin specimens were distributed among six groups (A-F) according to the different buffering capacities of experimental toothpastes and gels. Th toothpastes (pH:4.5) and gels (pH:4.5) differed in fluoride content, RDA-value and buffer capacity (given as mg KOH needed for neutralization): A: 0.125%F, RDA: 77, 6mg KOH; B: 0.125%F, RDA: 125, 24mg KOH; C: 0.125%F, RDA: 129, 12mg KOH; D: 0%F,RDA: 81, 1.55mg KOH; E:1.25%F, RDA: 21, 8.5mg KOH; F: 0.125%F, RDA:7, 3.11mg KOH. Ten specimens were cycled through three alternating demineralizations (5min, citric acid)and remineralizations (1min, artificial saliva) including brushing abrasion in an automatic brushing machine (2x2000 strokes, 2.75 load, between cycles storage in artificial saliva for 8h). A mixture containing artificial saliva and the respective toothpaste or gel were used as slurry. Ten samples of each group were not eroded, but only brushed. Results: After three cycles, loss of dentin was determined by profilometry, resulting in the following values (mean±standard deviation (µm)): eroded samples: A:37.12±4.95, B:48.67±4.77, C:39.88±3.76, D:32.92±2.67, E:3.65±1.35, F:6.47±1.31; non-eroded samples: A:30.78±6.47, B:37.84±7.75, C:30.07±3.05, D:26.93±2.30, E:1.76±0.94, F:0.51±0.18. Analysis of variance revealed significantly higher abrasion values for the eroded compared to the non-eroded samples (p<0.05). Toothpastes with same pH-value, fluoride content and similar RDA-values but a higher buffering capacity exhibited significantly more abrasion than toothpastes with the lower buffering capacity. Highly-concentrated fluoride gel with higher buffering capacity lead to less abrasion values compared to the gel with low fluoride concentration and low buffering capacity. Conclusion: Abrasion behaviour of eroded dentin may be influenced by the pH-value, fluoride content, RDA-value and buffering capacity of the applied toothpaste or gel.