NMR spectroscopy of dental materials. II. The role of tartaric acid in glass–ionomer cements

Abstract

D(+) tartaric acid is incorporated into glass–ionomer cements to control the setting properties. 13C NMR spectroscopy of the fluid cement pastes have shown that tartaric acid reacts more readily than the polyacid with the glass, and hence suppresses the premature gelation of the cement. As the cements set, the pH rises from ca. 1.25 to ca. 3 when tartaric acid is fully complexed. As the polyacid reacts the pH rises further to ca. 5.

The role of poly(acrylic acid) in conventional glass polyalkenoate cements

“…(+)-Tartaric acid (5-10 wt.%) ( Figure 5A) improves the rheological properties of GPCs by extending the working time and sharpening the onset of the setting time [40]. Results of Wilson et al were confirmed by Prosser et al [87], who showed by means of 13 C Fourier transform NMR spectroscopy that tartaric acid reacts preferentially with the glass and prevents the early binding of cations to the polyanion chains, resulting in increased working time. Tartaric acid is fully complexed at pH≈3, and complexing by PAA then occurs with the pH of the set cement rising to pH≈5 [87].…”

“…Results of Wilson et al were confirmed by Prosser et al [87], who showed by means of 13 C Fourier transform NMR spectroscopy that tartaric acid reacts preferentially with the glass and prevents the early binding of cations to the polyanion chains, resulting in increased working time. Tartaric acid is fully complexed at pH≈3, and complexing by PAA then occurs with the pH of the set cement rising to pH≈5 [87]. This change in complexing species occurs due to the stability of calcium and aluminum tartrate compounds at low pH (pH≈3-4).…”

“…A modest increase in strength has also been noticed with the addition of (+)-tartaric acid. These strengthening effects have been attributed to reduction in bulk homogeneities and indirectly improving the surface of the specimen by increasing flow properties [40,86,87].…”

A long-term study on the setting reaction of glass ionomer cements by 27Al MAS-NMR spectroscopy

“…It is also known that the baseline can often hinder the reproducibility of the FTIR spectrum. In contrast, Raman [11] and 13 C NMR [9] spectroscopies only concentrate on the neutralization of COOH group in the polycarboxylic acid during the setting process.…”

“…Various techniques such as pH studies [8], 13 C MAS-NMR [9], Fourier transform infra red spectroscopy (FTIR) [10] and Raman [11] spectroscopy have been used to characterize the setting reaction of the cements. However, FTIR [10] spectroscopy is only suitable for semi-quantitative analysis, since the loss of the carbonyl group absorption band from a carboxylic acid (-COOH) during the neutralization can be masked by the asymmetric COO -salt band.…”