In vitro effect of human saliva on the output of fluoride from controlled-release devices

This study was designed to determine the in vitro fluoride output from controlled-release devices in stimulated, whole human saliva, and to assess changes in the salivary calcium concentration following immersion of the devices. Twenty fluoride (F) controlled-release devices of the hydroxyethyl methacrylate (HEMA)/methyl methacrylate (MMA)-type were employed. Each was designed to release 1-2 mg F per day. All devices were placed individually in 10.0 ml of deionized water for 3 days to assess baseline F output. Seven devices with markedly high or low output were discarded. During days 4-13, three of the remaining 13 devices were placed individually in 10.0 ml of stimulated, whole saliva donated by three volunteers. All devices were returned to deionized water during days 14-17. All solutions were replaced daily with fresh solutions, and each test tube was inverted once every 24 hr. The study was conducted at 19-21 degrees C. Fluoride concentration of the deionized water and human saliva was assessed by ion-specific electrode; calcium concentration of the saliva was assessed pre- and postimmersion by flame atomic absorption spectrometry. The fluoride output of the devices placed in saliva decreased to 36% of their baseline rates (P < 0.001). The calcium concentration of the human saliva decreased from a mean preimmersion value of 3.58 mg/100 ml (+/- 0.63 SD) to a postimmersion value of 2.64 (+/- 1.12 SD; P < 0.001). These results suggest an interaction between the fluoride released by the devices and calcium in the saliva.(ABSTRACT TRUNCATED AT 250 WORDS)