Effect of artificial saliva and calcium on fluoride output of controlled-release devices

The purpose of this in vitro study was to assess the effect of graded concentrations of calcium in artificial saliva on the output of fluoride from HEMA/MMA controlled-release devices. After the initial release rates were determined in deionized water, the devices were assigned to five groups. The devices of one group remained in deionized water throughout the 19-day study while those of the other groups were placed in artificial saliva containing 0, 4.5, 8.0, or 12.0 mg% calcium on days 4-13. Ten devices of each group were placed in deionized water again on days 14-17 and then in 0.1 mol/l HCl on days 18-19. The five devices of each group that were not placed in deoinized water on day 14 were inspected for surface crystals and then placed in 1 mol/l KOH for 2 days. The fluoride release rates in artificial saliva were reduced by 71-90% and in proportion to the calcium concentration. The release rates in deionized water (days 14-17) approached the baseline values; they exceeded baseline rates by 13-49% while in HCl. The fluoride release rates did not differ among the groups while in KOH, but calcium output was directly related to the calcium concentration of the artificial saliva. The results indicate that fluoride release from HEMA/MMA devices is markedly reduced in artificial saliva and that the reduction is proportional to the concentration of calcium.