Investigation into the Depth of Cure of Resin-Modified Glass-Ionomer Restorative Materials

This investigation involved an attempt at delineating the depth of cure of resin-modified glass-ionomer restorative dental materials. Samples of different thicknesses using Vitremer Core Material and Restorative 3MESPE, Fuji II LC GC America, and Photac-Fil Quick 3MESPE were evaluated as to solubility, Knoop hardness, and thermal analysis techniques that included specific heat determination as well as differential scanning calorimetry thermal scans. Specimens were evaluated at time periods that included immediately after fabrication, 24 hours, one week, one month, and at three months. Overall results found that the solubility method chosen for this investigation did not provide the necessary sensitivity for depth of cure analysis of resin-modified glass-ionomer restorative materials. Hardness and thermal analysis provided evidence of a continuing, post-photopolymerization reaction that resulted in increased hardness, specific heat, and thermal requirements over the storage times. Furthermore, the resin-modified glass-ionomer restorative materials demonstrated water storage behavior similar to conventional glass-ionomer materials, in that water gained by the materials became more bound as storage time increased. Individual instances were observed in which the physical properties of 3 mm thick specimens were similar to that observed of 2 mm specimens however, these findings were not consistent throughout the investigation. Based on the conditions of this study, it is recommended that resin-modified glass-ionomer restorative materials should not be cured in thicknesses greater than two millimeters.