Ability of Experimental Resin Modified Glass Ionomer Cements (RMGICs) to Remineralise and Form Apatite on Immersion

Abstract

ABSTRACT Background: Dental caries is one of the most common dental diseases that causing damage to the tooth structure. The best caries management strategy focuses on methods to improve the remineralising process. Several studies suggested that some dental materials have the ability to form apatite and remineralise the carious tissue. Glass ionomer cements (GICs) have been extensively researched and explored as apatite forming materials. Resin modified glass ionomer cements (RMGICs) have similar structure to GIC with addition of water compatible polymerising resin. However, the apatite formation by RMGIC requires further research to explore remineralising potential of the material. Aim: The study's goal was to assess the ability of the resin modified glass ionomer cements (RMGICs) to remineralise using new experimental RMGICs samples with and without bioactive glass as well as containing varying concentrations of polyacrylic acid (PAA) on immersion in artificial saliva. Materials and methods: The experimental RMGICs were made from two types of powders including ionomer glass powder and bioactive glass powder (10% by weight of the total glass powder) in addition to three different liquids with different PAA concentrations (25%, 10%, 0%). The cements were immersed in artificial saliva (pH=6.5) at four immersion periods (2-weeks, one- month, three-months and six-months). Fourier-transform infrared (FTIR), X-ray diffraction (XRD) and Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) spectroscopy were used to assess the ability of the experimental cements to form the apatite. Moreover, Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES) and Fluoride-Ion Selective Electrode (F-ISE) were used to determine the ion release to the immersion media. Commercial product Fuji II LC was used as a control for the study. Result: The FTIR, XRD and MAS-NMR characterisation techniques showed that all the experimental cements had strong signs of apatite formation and the amount of apatite increased over time. Nevertheless, Fuji II LC cements displayed no signs of apatite formation even after a 6-months immersion period. In term of the ions releasing from the experimental RMGICs into the immersion media after immersion, the F-ISE determined that the fluoride release among all the samples was increasing with increasing the time of immersion, and the commercial cements (Fuji II LC) solution had the highest concentration of fluoride. While the ICP-OES determined that in the experimental RMGIC with bioactive glass, ion release data revealed consumption of calcium and phosphorus from the immersion solution. The release of silicon was higher in the samples with bioactive glass. Conclusion: Apatite was found in high concentrations in all experimental RMGICs samples with and without BAG and at different PAA concentrations. The addition of bioactive glass plays an important role in increasing the amount of apatite formation as well as ion release. In terms of the effect of PAA concentration, there was no effect on apatite formation in the presence or absence of bioactive glass.