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 fluori de from HEMA/ MMA controlled-release devices. After the initial releas e rates were determined in deionized water, the devices were assigned to five groups. The devices of one group remained in deionized water t hroughout 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 d ays 4-13. Ten devices of each group were placed in deionized water aga in on days 14-17 and then in 0.1 mol/l HCl on days 18-19. The five dev ices of each group that were not placed in deoinized water on day 14 w ere inspected for surface crystals and then placed in 1 mol/l KOH for 2 days. The fluoride release rates in artificial saliva were reduced b y 71-90% and in proportion to the calcium concentration. The release r ates in deionized water (days 14-17) approached the baseline values; t hey exceeded baseline rates by 13-49% while in HCl. The fluoride relea se rates did not differ among the groups while in KOH, but calcium out put was directly related to the calcium concentration of the artificia l saliva. The results indicate that fluoride release from HEMA/MMA dev ices is markedly reduced in artificial saliva and that the reduction i s proportional to the concentration of calcium.