Demineralized bovine enamel slabs (n = 5) were remineralized in vitro for 24 h at 37 ¡ãC with artificial saliva (AS) containing 0-0.74 % POs-Ca to adjust the Ca/P ratio to 0.4-3.0, then sectioned and analysed by transversal microradiography (TMR). The data were analysed by Scheffe's post hoc test. The Ca/P ratio with most remineralization was used to investigate the effect of calcium on enamel remineralization (n = 11). The demineralized slabs were treated with AS with calcium-chloride- (CaCl2-) or POs-Ca with an identical calcium content, and sectioned for TMR and wide-angle X-ray diffraction (WAXRD) analyses to evaluate the local changes in hydroxyapatite (HAp) crystal content. The data were analysed using the Mann-Whitney U-test.
The highest mineral recovery rate resulted from addition of POs-Ca to adjust the Ca/P to 1.67. At this ratio, the mineral recovery rate for AS containing POs-Ca (24.2 ¡À 7.4 % ) was significantly higher than that for AS containing CaCl2 (12.5 ¡À 11.3 % ) (mean ¡À SD, p < 0.05). The recovery rate of HAp crystallites for AS containing POs-Ca (35.7 ¡À 10.9 % ) was also significantly higher than that for AS containing CaCl2 (23.1 ¡À 13.5 % ) (p < 0.05). The restored crystallites were oriented in the same directions as in sound enamel.
POs-Ca effectively enhances enamel remineralization with ordered HAp at a Ca/P ratio of 1.67.