Analysis of anticaries potential of pit and fissures sealants containing amorphous calcium phosphate using synchrotron microtomography.

The aim of this study was to analyze the anticaries potential of pit and fissure sealants containing amorphous calcium phosphate (ACP) by synchrotron microtomography. Bovine enamel blocks (4×4 mm; n=50) were selected through surface hardness (Knoop) analysis. Slabs were obtained through cross-sections taken 1 mm from the border of the enamel. Five indentations, spaced 100 µm apart, were made 300 µm from the border. Ten specimens were prepared for each tested material (Ultraseal XT plus TM, Aegis, Embrace, Vitremer and Experimental Sealant). The materials were randomly attached to the sectioned surfaces of the enamel blocks and fixed with sticky wax. The specimens were submitted to pH cycling. After that, the surface hardness (SH1) was determined, and the blocks were submitted to synchrotron microcomputed tomography analysis to calculate the mineral concentration (ΔgHAp cm(-3)) at different areas of the enamel. The comparison between the SH1 and ΔgHAp cm(-3) showed a correlation for all groups (r=0.840; p<0.001). The fluoride groups presented positive values of ΔgHAp cm(-3), indicating a mineral gain that was observed mainly in the outer part of the enamel. The ACP showed mineral loss in the outer enamel compared with fluoride groups, although it inhibited the demineralization in the deeper areas of enamel. The combination of two remineralizing agents (fluoride and ACP) was highly effective in preventing demineralization.

Pressor responses to common carotid occlusion in female rats: effects of gonadectomy and treatment with gonadal steroid hormones

The pressor responses to common carotid occlusion were studied in conscious female rats throughout the estrous cycle, after gonadectomy and after gonadectomy followed by treatment with estrogen and progesterone. The initial peak pressor response was highest during proestrus and fell significantly over the remaining 3 days of the estrous cycle. The maintained pressor response was relatively unchanged throughout the cycle, except during diestrus 1 when it decreased markedly. Gonadectomy reduced and treatment with estradiol alone increased the initial pressor component, respectively. Treatment of gonadectomized rats with estradiol plus progesterone enhanced both components. These findings suggest that gonadal steroid hormones are important modulators of the pressor to common carotid occlusion