Objectives: To
investigate the hardness and chemical composition of sound, demineralized (demin)
and
remineralized
(remin) bovine enamel and their influence on demineralization and
remineralization.
Methods:
Demineralization was chemically induced in 94 bovine enamel specimens at
three different times [(24h
(n=33),
48h (n=30), 96h (n=31)]. The specimens were then pH-cycled using either 367
ppm F sodium fluoride or
deionized-water.
Surface microhardness (SMH) and energy dispersive X-ray spectroscopy
(measured-elements: Ca,P, F, C, Mg, N) were performed at three stages (sound,
demin, remin) and transverse microradiography was performed at demin and
remin. Comparisons were determined by ANOVA.
Results: SMH,
integrated mineral loss (ΔZ) and lesion depth (L) were significantly
different between stages,
demineralization
times and treatments. Surface zone mineralization (SZmax)was significantly
different between stages and treatments, but not demineralization times. The
weight% of F at the surface was significantly affected by treatment,
irrespective of demineralization time. Both fluoride and deionized-water
specimens were remineralized. For SMH, a weak positive correlation was found
between sound and demineralization (r=0.31, p=0.002), however, there was no
correlation between sound and after pH-cycling (r=0.07, p=0.49). The Ca:P
ratio remained stable at all stages.
Conclusions: Harder
specimens at the sound stage remained hard after demineralization and
pH-cycling,
respectively.
Additionally, harder lesions showed less ΔZ and L, and greater SZmax, and
were thus less susceptible to demineralization. Finally, specimens with
greater surface F weight% had greater SZmax, which in turn had less ΔZ and L,
and were therefore less susceptible to demineralization.
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