The influence of sample dimensions on hydroxyl ion release from calcium hydroxide products

The purpose of this study was to compare the rate of hydroxyl ion release f rom commercially available setting and nonsetting calcium hydroxide product s. The rate of hydroxyl ion release is important, as this has been suggeste d to be the main factor in the therapeutic activity of these products. In t otal, hydroxyl ion release was measured from 1104 samples of Dycal, Life, C alasept and Hypocal in solution using in vitro titration. The rate of hydro xyl ion release was measured for up to 14 days, using two sizes of sample s urface area. The dimensions of the exposed sample surface area was found to be an important physical constraint to the hydroxyl ion release from non-s etting calcium hydroxide products, whereas this was not found to be the cas e with setting products. The range in hydroxide activity between products w as found to be 298%. In rank order of hydroxide ion release, from the most to the least active was: Hypocal, Calasept, Life and Dycal. The differences in the rate of hydroxyl ion release from these products may have some impl ications for their clinical applications. It is suggested that in cases whe re the oral healing responses have been poorer than expected, the size and seal of prepared cavities could have negatively influenced the therapeutic release of hydroxyl ions from non-setting calcium hydroxide products.