Transition of RDA Dentin Abrasion Data to Clinical Relevance

Objectives: The RDA dentin abrasion method was developed to assess the safety of dentifrice use. Clinical effects of dentifrice use were not an objective in RDA method design. This study was designed to determine the effect of brushing with saliva rather than water upon results with RDA Method. Methods: The ISO 11609 abrasion method was used with profilometric measurement of dentin surface change. The toothpaste was brushed using a Sabri flat cross brushing machine with 150 gm. brush head load on Oral-B reference toothbrush at 40 strokes/min. Tap water or fresh, pooled, stimulated saliva was mixed with the selected toothpaste with silica or phosphate abrasive systems. A 4 X 4 Latin Square Design was used with four dentin specimens for the two toothpastes and the two diluents. Mahr-Federal Surfanalyzer 5000 Profilometric System was used for surface characterization. This system had software to measure surface loss and characteristics. Digital photography with Bioquant Image Analysis System complemented the profilometry measurements. Results: Loss of dentin surface measured as the integrated area under the line between the two reference areas reported as µm2 brushed with water and saliva for phosphate paste was 0.09±0.01 and 0.06±0.02 for water and saliva, respectively. Abrasive wear with silica paste was 2.37±0.63 and 0.99±0.12 for water and saliva, respectively. Surface roughness reported at Ra in µm for the phosphate paste was 0.03±0.01 and 0.03±0.01 for water and saliva. Ra for silica was 0.19±0.05 and 0.11±0.03 for water and saliva respectively. Digital analysis of surface brightness confirmed this substantial reduction in surface change when dentin was brushed with saliva compared to water. The difference in surface wear and roughness were statistically significant for the silica, but not for phosphate toothpaste. Conclusion: Apparent abrasion as measured by RDA Method was substantially reduced in a non-linear relationship with simulated oral use.