Elemental and micromorphological analysis of ion releasing restoration/carious dentin interface

The objective of the current study was to evaluate elemental analysis and micromorphological patterns at the interfaces between tooth substrates either sound or demineralized dentin and ion-releasing restorations, including conventional glass ionomer and ion-releasing composite. The evaluation was conducted immediately (after 24 h) and after six months of artificial saliva storage. A total of 48 sound human premolars were used in this study. The premolars were randomly divided into two groups based on substrate type: sound and demineralized dentin (n = 24). Each substrate group was further subdivided into two subgroups according to restoration type: a conventional glass ionomer (Equia Forte HT) and an ion-releasing composite (ACTIVA-Bioactive Restorative) (n = 12). Each restoration subgroup was further divided according to aging condition: whether tested immediately after 24 h or after storage for six months in artificial saliva (n = 6). Specimens were sectioned buccolingually and longitudinally into two halves. For elemental analysis, one-half of each sectioned specimen was investigated using energy dispersive X-ray spectroscopy (EDX). Four elements (Ca, P, Al, and Si) were specifically examined at three different sites: dentin, hybrid layer, and restoration. For micromorphological patterns, two representative specimens from the second half of sectioned teeth were randomly selected to be observed under scanning electron microscope (SEM). EDX data were tabulated and subjected to statistical analysis, with a significance level set at p < 0.05. Kruskal-Wallis test revealed no statistically significant differences in distribution of the four elements across different tooth substrates or aging times. However, significant differences were observed based on the site factor. SEM micrographs revealed an ion-exchange zone in aged Equia Forte specimens and crystal-like structure deposition in artificially carious dentin bonded to ACTIVA. It has been concluded that both conventional glass ionomer restorative material and ion-releasing composite highlighted their bioactive behavior by demonstrating their potential ability to remineralize the demineralized dentin, reinforcing their promise as effective restorative options for dentin remineralization.