This in vitro study performed elemental analysis of the ions absorbed into the salivary coat covering the surfaces of S-PRG resin blocks and assessed the adherence of Streptococcus sanguinis and Streptococcus mutans to these saliva-coated S-PRG resin blocks. Elemental analysis of ions absorbed into the salivary coat of resin blocks exposed to the saliva was performed using an inductive coupled plasma atomic emission spectrometer and the fluoride electrode method. Quantitative adherence of radio-labeled test bacteria to the resin blocks was determined. As the results, the saliva-coated S-PRG resin showed significantly greater amounts of absorbed B, Al, Si, Sr, and F than the saliva-coated unfilled resin. It was of particular significance that the salivary coating of the S-PRG resin reduced the adherence of S. mutans to this resin. However, in the case of S. sanguinis, no significant difference in adherence could be recognized between saliva-coated S-PRG resin and saliva-coated unfilled resin.

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The purpose of this study was to use a new scratch test and tensile test to evaluate the bond strength between artificial erosive enamel or dentin and self-adhesive resin composites as a coating material. Coronal enamel or dentin surface was exposed to an erosive cycle (artificial saliva [AS], pH:7.0 for 6.5 h and acidic carbonated beverages for 5 min, alternated 3 times per day) for the eroded-surface or stored in AS for the remineralized-surface. Two self-adhesive flowable resin composites, Fusio and LLB-CR6 (prototype), and a conventional flowable resin composite, BEAUTIFIL FLOW with self-etching primer system, Clearfil Mega Bond, were applied to enamel or dentin surfaces; and then the bond strengths were measured. For the eroded-surface, there were no significant differences in bonding strength among all materials, as assessed by the new scratch test. Thus, these self-adhesive flowable resin composites might be useful for coating materials on acid-eroded tooth surfaces.