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 Ca(2+), OH(-), and CO(3) (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.

ObjectiveSince 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.MethodsThis 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.ResultsThe 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.SignificanceThe 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.

No abstract

The purpose of this study was to test nickel titanium (NiTi) instrument performance under different surrounding temperatures. Twenty-four superelastic NiTi instruments with a conical shape comprising a 0.30-mm-diameter tip and 0.06 taper were equally divided into 3 groups according to the temperature employed. Using a specially designed cyclic fatigue testing apparatus, each instrument was deflected to give a curvature 10 mm in radius and a 30° angle. This position was kept as the instrument was immersed in a continuous flow of water under a temperature of 10, 37, or 50 °C for 20 s to calculate the deflecting load (DL). In the same position, the instrument was then allowed to rotate at 300 rpm to fracture, and the working time was converted to the number of cycles to fracture (NCF). The statistical significance was set at p = 0.05. The mean DL (in N) and NCF (in cycles) of the groups at 10, 37, and 50 °C were 10.16 ± 1.36 and 135.50 ± 31.48, 13.50 ± 0.92 and 89.20 ± 16.44, and 14.70 ± 1.21 and 65.50 ± 15.90, respectively. The group at 10 °C had significantly the lowest DL that favorably resulted in the highest NCF. Within the limitations of this study, the surrounding temperature influences the cyclic fatigue resistance and DL of the superelastic NiTi instruments. Lower temperatures are found to favorably decrease the DL and extend the lifetime of the superelastic NiTi instrument. Further NiTi instrument failure studies should be performed under simulated body temperature.

Background Hydraulic materials are used in Endodontics due to their hydration characteristics namely the formation of calcium hydroxide when mixing with water and also because of their hydraulic properties. These materials are presented in various consistencies and delivery methods. They are composed primarily of tricalcium and dicalcium silicate, and 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. Objectives Review of the classification of hydraulic materials by Camilleri and the literature pertaining to specific uses of hydraulic cements in endodontics namely intra‐coronal, intra‐radicular and extra‐radicular. Review of the literature on the material properties linked to specific uses providing the current status of these materials after which future trends and gaps in knowledge could be identified. Methods 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 were extracted and evaluated. Results A large number of publications were retrieved for each clinical use and these were grouped depending on the property type being investigated. Conclusions The hydraulic cements have made a difference in 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.

Atmeh AR, Hadis M, Camilleri J. Real-time chemical analysis of root filling materials with heating: guidelines for safe temperature levels. International Endodontic Journal, 53, -708, 2020. Aim To investigate the chemical changes affecting different types of gutta-percha and endodontic sealers during heating, and correlate changes with the heating capacity of different heat carriers. Methodology The heating capacity of three endodontic heat carriers was evaluated using thermocouples to produce heat profiles. The devices were activated at different temperature set-ups, in continuous or cut-out modes. Chemical changes of six brands of gutta-percha and four types of sealers were assessed in real time during heating using micro-Raman spectroscopy equipped with a heating stage. Raman spectra of each tested material were averaged and compared at different temperature levels. The sealers were further assessed by Fourier transform infrared (FT-IR) spectroscopy. Results None of the tested heat carriers achieved the temperature levels that were set by the devices and recommended by the manufacturer. The use of continuous heating mode resulted in higher rises in temperature than the 4 s cut-out mode that reached 110°C. The various brands of gutta-percha exhibited different chemical changes in response to heat. Some changes even occurred below temperature levels generated by the heating devices. All sealers revealed changes in their chemical composition upon heating. Changes in epoxy resin-and zinc oxide-eugenol-based sealers were detectable at 100°C, with structural alterations beyond that temperature and irreversible changes after cooling. Water loss was irreversible in BioRoot, but its chemical structure was stable as well as for the TotalFill. Conclusions The heating capacity of endodontic heat carriers needs to be standardized, so that the temperatures delivered by the tips are the same as that set on the dial. Practitioners should be aware of the actual temperatures generated by these devices, and the suitability of sealers to be used at the temperature levels achieved. 698

Two-photon fluorescence microscopy, in combination with tetracycline labelling, was used to observe the remineralising potentials of a calcium silicate-based restorative material (Biodentine(TM) ) and a glass ionomer cement (GIC:​Fuji​IX) on totally demineralised dentine. Forty demineralised dentine discs were stored with either cement in three different solutions: phosphate buffered saline (PBS) with tetracycline, phosphate-free tetracycline, and tetracycline-free PBS. Additional samples of demineralised dentine were stored alone in the first solution. After 8-week storage at 37 °C, dentine samples were imaged using two-photon fluorescence microscopy and Raman spectroscopy. Samples were later embedded in PMMA and polished block surfaces studied by 20 kV BSE imaging in an SEM to study variations in mineral concentration. The highest fluorescence intensity was exhibited by the dentine stored with Biodentine(TM) in the PBS/tetracycline solution. These samples also showed microscopic features of matrix remineralisation including a mineralisation front and intra- and intertubular mineralisation. In the other solutions, dentine exhibited much weaker fluorescence with none of these features detectable. Raman spectra confirmed the formation of calcium phosphate mineral with Raman peaks similar to apatite, while no mineral formation was detected in the dentine stored in cement-free or PBS-free media, or with GIC. It could therefore be concluded that Biodentine(TM) induced calcium phosphate mineral formation within the dentine matrix when stored in phosphate-rich media, which was selectively detectable using the tetracycline labelling.

No abstract