The interfacial properties of a new calcium-silicate-based coronal restorative material (Biodentine™) and a glass-ionomer cement (GIC) with dentin have been studied by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), micro-Raman spectroscopy, and two-photon auto-fluorescence and second-harmonic-generation (SHG) imaging. Results indicate the formation of tag-like structures alongside an interfacial layer called the “mineral infiltration zone”, where the alkaline caustic effect of the calcium silicate cement’s hydration products degrades the collagenous component of the interfacial dentin. This degradation leads to the formation of a porous structure which facilitates the permeation of high concentrations of Ca²⁺, OH^-, and CO₃^2- ions, leading to increased mineralization in this region. Comparison of the dentin-restorative interfaces shows that there is a dentin-mineral infiltration with the Biodentine, whereas polyacrylic and tartaric acids and their salts characterize the penetration of the GIC. A new type of interfacial interaction, “the mineral infiltration zone”, is suggested for these calcium-silicate-based cements.

The first mention of the use of hydraulic cements in dentistry dates to the 19^th century with Portland cement used as an additive to make a paste for endodontic use. This did not gain popularity until the mid-1990s when the first patent for the use of Portland cement for root-end surgery and perforation repair was filed by Torabinejad and White and the first material marketed by Dentsply as ProRoot MTA. Even though the term mineral trioxide aggregate (MTA) is a misnomer as MTA is neither an oxide nor an aggregate, several developments have resulted in a number of materials being created for clinical endodontics. These materials are presented in various consistencies and delivery methods. Furthermore, although composed primarily of tricalcium and dicalcium silicate, the materials also include a radiopacifier, additives and an aqueous or a non-aqueous vehicle Only materials whose primary reaction is with water can be classified as hydraulic. The main features of hydraulic cements are the formation of calcium hydroxide on hydration and the interaction of these materials with the environment. The current review refers to a classification by Camilleri and the literature pertaining to specific uses of hydraulic cements in endodontics namely intra-coronal, intra-radicular and extra-radicular as this classification informs the clinician about the material interactions which are dependent on the environment the material is placed in. The literature was reviewed using PUBMED and for each clinical use, the in vitro properties such as physical, chemical, biological and antimicrobial characteristics and clinical data was extracted and evaluated. This provided the current status of these materials after which future trends and gaps in knowledge were identified. The hydraulic cements have made a difference to clinical outcomes. The main shortcoming is the poor testing methodologies employed which provide very limited information and also inhibits adequate clinical translation. Furthermore, the clinical protocols need to be updated to enable the materials to be employed effectively.

Since their introduction, calcium silicate cements have primarily found use as endodontic sealers, due to long setting times. While similar in chemistry, recent variations such as constituent proportions, purities and manufacturing processes mandate a critical understanding of service behavior differences of the new coronal restorative material variants. Of particular relevance to minimally invasive philosophies is the potential for ion supply, from initial hydration to mature set in dental cements. They may be capable of supporting repair and remineralization of dentin left after decay and cavity preparation, following the concepts of ion exchange from glass ionomers. This paper reviews the underlying chemistry and interactions of glass ionomer and calcium silicate cements, with dental tissues, concentrating on dentin-restoration interface reactions. We additionally demonstrate a new optical technique, based around high resolution deep tissue, two-photon fluorescence and lifetime imaging, which allows monitoring of undisturbed cement-dentin interface samples behavior over time. The local bioactivity of the calcium-silicate based materials has been shown to produce mineralization within the subjacent dentin substrate, extending deep within the tissues. This suggests that the local ion-rich alkaline environment may be more favorable to mineral repair and re-construction, compared with the acidic environs of comparable glass ionomer based materials. The advantages of this potential re-mineralization phenomenon for minimally invasive management of carious dentin are self-evident. There is a clear need to improve the bioactivity of restorative dental materials and these calcium silicate cement systems offer exciting possibilities in realizing this goal.