Elemental and micromorphological analysis of bioactive restorative material/tooth interface

Abstract Aim The aim of this study was to analyze mineral ions deposition and micromorphological formation of apatite-like crystals at the bioactive restorative material/tooth interface at different pH of saliva. Patients and methods A total of 24 sound-extracted human molars were embedded in self-curing acrylic resin. Class V cavities were prepared at the cervical third of the buccal surface of the crowns of the samples above the cemento-enamel junction. These cavities were prepared as box-shaped with dimensions (3 mm long × 4 mm wide × 2 mm deep). The samples were randomly divided into two groups based on the type of restorative materials used: group I Alkasite restorative material (cention forte) and group I resin-modified glass ionomer ( Fuji II LC). Each main group was randomly divided into two subgroups (n = 6), subgroup A (the samples were immersed in artificial saliva with pH = 6.57 for 30 days) and subgroup B (the samples subjected to pH-cycling with pH = 5 for 30 days). The crown of each sample was buccolingually sectioned at the center into two halves. One-half of each sample was subjected to elemental analysis using energy dispersive radiography analysis, the data was collected and statistically analyzed. While the remaining half was sputter coated with gold and underwent micromorphological analysis of the restoration/tooth interface using SEM. Results The statistical analysis showed insignificant differences in both calcium and phosphorus levels among the tested restorative materials. Regarding the mean values of Ca level in enamel and dentin of the tested groups in subgroup A and subgroup B there was no significant difference between the tested groups either at subgroup A or subgroup B with P values in enamel equal 0.160 and 0.155, respectively. While in dentin P values recorded 0.694 and 0.104, respectively. Regarding the mean values of P level in enamel and dentin of the tested groups in subgroup A and subgroup B there was no significant difference between the tested groups either at subgroup A nor at subgroup B with P values in enamel equal 0.523 and 0.655, respectively. While in dentin P values equal 0.759 and 0.625, respectively. Ca and P levels showed a slight insignificant increase in all tested restorative materials after exposure to pH-cycling. But there was a significant increase in Ca levels within resin-modified glass ionomer restorative material/dentin interface with P value 0.004. The micromorphological analysis of the restoration/tooth interfaces showed nodules of hydroxyapatite crystals in both tested restorative materials as shown in SEM images. Conclusion It was concluded that Cention Forte and Fuji II LC, which are represented as a bioactive restorative material released ions and formed hydroxyapatite crystals. Thus, the claim of manufacturers that Alkasite restorative materials have the ability of releasing ions was accepted. Also, the null hypothesis of this study was accepted since no significant difference was recorded between the tested restorative materials.