The influence of sample dimensions on fluoride ion release from a glass ionomer restorative cement

The fluoride release from a commercial, restorative glass ionomer cement wa s found to be strongly dependent on sample surface area rather than volume. This was noted for disc, cylindrical- and bar-shaped specimens over period s ranging from 1 day to 3 yr. Release from all shapes of specimen followed the established pattern of an initial non-linear region followed by one whe re release was proportional to the square root of time. If fluoride levels in the cement matrix of specimens were artificially increased by incorporat ion during the mixing then the release pattern during the first few months was altered. The initial release increased for some specimen sizes and decr eased for others. The dependency on surface area was greatly reduced for se veral months. By the time a year had elapsed the correlation between fluori de ion release and surface area had been re-established. The influence of a dditional fluoride during setting can therefore act to perturb the normal r elease pattern and may in some instances reduce the initial fluoride releas e. Release should be quoted in terms of, or with measurements of, the surfa ce area of specimens under investigation. (C) 1999 Elsevier Science Ltd. Al l rights reserved.