Untitled

Abstract

The water-sorption characteristics of two commercial resin-modified glass-ionomer dental cements (Baseline VLC, ex. Detrey Dentsply, and Vitremer lining cement, ex. 3M Dental Products) have been studied in more detail than previously. Water sorption in both cements proved to be rapid, reaching equilibrium at approximately 48 h for Baseline VLC and at approximately 10 d for Vitremer. Over the first 8 h or so, absorption was shown to follow Fick's law, with a diffusion coefficient of 1.56x10(-7) cm2 s(-1) for Baseline VLC (cured for 20 s) and 5.09x10(-7) cm2 s(-1) for Vitremer (also cured for 20 s). As expected, sorption of water was found to be faster in specimens cured for shorter cure times and slower for those cured for longer times. In the presence of sodium chloride, both at 0.9% and at 1 M, diffusion coefficients were significantly greater than in pure water, but did not vary significantly with sodium chloride concentration, being approximately 3.3x10(-7) cm2 s(-)1 for Baseline VLC and 8.0x10(-7) cm2 s(-1) for Vitremer. This is attributed to conformational changes in hydrophilic segments of the polymer on absorption of aqueous sodium chloride in which the molecules form more compact coils than in the presence of pure water. They thus create a microstructure that is more permeable to water. Sorption in salt solutions became non-Fickian much sooner than in pure water, i.e. at 3-4 h for both cements. This is probably due to concentration changes of salt within the cement, suggesting that these materials possess a degree of permselectivity. Finally, equilibrium water uptakes varied with salt concentration, being least in 1 M NaCl, which reflects the different chemical potentials of water in the various storage media.

Avaliação da solubilidade e sorção em água de alguns materiais restauradores diretos

“…Para estes materiais, o equilíbrio de absorção de água pode estar relacionado ao potencial químico da água no meio circundante. O potencial químico da água pura é maior do que em soluções de cloreto de sódio, por exemplo, portanto a força motriz termodinâmica para SR de água é maior em água pura do que em soluções de sais 23 .…”

Evaluation of Water Sorption and Solubility of Nano Titania Enriched Glass Ionomer Cement Considering the Storage Solution and Time

“…Most researchers studied the adsorption after immersion in water [12], artificial saliva [13], ethanol/water solution [14], and sodium chloride [15]. Since literature is spare in evaluating the effect of alcohol-containing mouthwash on the sorption of GICs, residence time in the storage environment may be crucial in assessing the clinical durability of restorative materials.…”