β-Dicalcium silicate-based cement: synthesis, characterization and in vitro bioactivity and biocompatibility studies

Remineralizing Ability of Resin Modified Glass Ionomers (RMGICs): A Systematic Review

The selective caries removal approach leads to the need to use materials with the ability to remineralize remaining partially demineralized dentin. Among the materials proposed are resin-modified glass ionomer cements (RMGICs). The aim of this systematic review was to evaluate, based on in vitro experimental studies, whether RMGICs are suitable for remineralizing affected dentin. A systematic literature search was performed in four databases, followed by article selection, data extraction, and quality assessment. Studies assessing the remineralizing potential of RMGICs on dentin were included in our review. Studies which compared such properties between different RMGICs or with other materials were also eligible. The studies report the remineralizing ability of RMGICs, albeit with differences between different commercial products. RMGICs show a similar ability to conventional GICs to remineralize affected dentin, fulfilling the function for which they are designed. Moreover, the incorporation of additives, such as bioactive glass (BAG) or CCP-ACP, improves their remineralizing potential. The results of this review support the use of RMGICs as restorative materials after selective caries removal.

Remineralization Potential of Three Restorative Glass Ionomer Cements: An In Vitro Study

The aim of this in vitro study was to evaluate the remineralizing ability of three glass ionomers on demineralized dentin with different thicknesses and time periods. Fifty third molars were obtained and were sectioned into 1-, 2-, and 3-mm thick slices (n = 36 for each thickness). The specimens were demineralized with 18% EDTA for 2 h. From the glass ionomer cements (GICs) under study (Ketac Molar Aplicap, Equia Forte, or Riva Light Cure), 1 mm was placed over each slice, set, and preserved in PBS until observation after 1, 7, 14, and 28 days after placement. For each material, thickness, and time, three samples were prepared. Using Fourier Transform Infrared Spectrometry (FTIR), apatite formation was determined on the side opposite to that on which the material had been placed. By means of Energy Dispersive Spectroscopy (EDX), the changes in the Calcium/Phosphate (Ca/P) ratio were evaluated. These changes were compared between the different materials by means of a two-way ANOVA test, considering time and dentin thickness, for a significance level of p < 0.05. Results: FTIR showed a peak at 1420 cm^-1, evidencing the presence of carbonated hydroxyapatite in all the materials after 14 days, which indicates that a remineralization process occurred. Riva Light Cure showed the most homogeneous results at all depths at 28 days. The Ca/P ratio was maximum at 7 days in 2 mm of dentin for Riva Light Cure and Equia Forte HT (3.16 and 3.07; respectively) and for Ketac Molar at 14 days in 1 mm (3.67). All materials induced remineralization. Equia Forte achieved the greatest effect at 2 mm and Ketac Molar at 1 mm, whereas Riva Light Cure showed similar results at all depths. In terms of Ca/P ratio, Equia Forte and Riva Light Cure remineralized best at 2 mm, whereas for Ketac Molar, it was 1 mm. Carbonate apatite formation was higher at 24 h and 7 days for Ketac Molar, whereas it decreased at 14 days for Ketac Molar and peaked in Riva Light Cure and Equia Forte.

Zinc-/copper-substituted dicalcium silicate cement: advanced biomaterials with enhanced osteogenesis and long-term antibacterial properties

The development of bioactive Ca-silicate-based cements which may simultaneously suppress infection is promising for periapical therapy or alveolar bone defect repair. While these treatments are usually effective in the short term, many of these cements have not been designed to have an affinity with dental tissue in a prolonged anti-infectious manner and are only high alkaline in the early stages. This can lead to less favorable long-term outcomes, such as in bone repair or secondary therapy. Inspired by the strong antibacterial activity of zinc and copper ions, we developed a nonstoichiometric dicalcium silicate (C₂S) substituted by 5% or 10% Zn or Cu to endow it with appropriate multifunctions. It was found that the foreign ion substitution could inhibit free CaO content and increase the pH value in the initial ∼6 h. The C₂S cement only showed antibacterial activity in the early stage (6-72 h), but the C₂S displayed appreciable long-term antibacterial potential against P. aeruginosa, E. faecalis and E. coli (>6 h) and S. aureus (>72 h). Moreover, the enhanced new bone regeneration by Zn substitution in C₂S was confirmed in a maxillofacial bone defect model in rabbits. The increases in new bone formation adjacent to C₂S-10Zn and C₂S after 16 weeks of implantation were 32% and 20%, respectively. And the Tb.N values in the C₂S-10Zn and C₂S-10Cu groups (∼5.7 and 4.9 mm^-1) were over two-fold higher than in the C₂S group (∼2.0 mm^-1). It is considered that Zn- or Cu-substitution in C₂S is promising for applications to infectious bone repair.

Strontium-Substituted Dicalcium Silicate Bone Cements with Enhanced Osteogenesis Potential for Orthopaedic Applications

Incorporating Sr element in biomaterials for bone implants is an effective way to improve their biological performance, as Sr element has been proved to enhance bone regeneration and depress bone resorption activity. In the present study, we developed a Sr-incorporated dicalcium silicate (C2S) bone cement as a potential candidate for bioactive self-setting bone cement in orthopaedics and stomatology. The Sr-C2S powders containing 0.3–6.8% Sr in molar ratio were prepared by means of chemical co-precipitation, and the results of XRD analysis indicated the incorporation of Sr element into the lattice of C2S. Sr-C2S bone cements, as prepared by mixing the powders with water, have a final setting time of 570 to 594 min, and compressive strength higher than that of C2S bone cement within certain incorporation range. The Sr-C2S bone cements possessed good in vitro bioactivity by inducing apatite formation in simulated body fluid (SBF) within 7 days. Moreover, the proliferation activity of human bone marrow mesenchymal stem cells (hBMSCs) with Sr-C2S bone cements was significantly higher than that with C2S bone cement, and the alkaline phosphatase (ALP) activity of hBMSCs was also enhanced with addition of Sr element in Sr-C2S groups. The Sr-C2S might therefore be a bioactive self-setting material with enhanced biological performance and holds the prospect for application in the bone regeneration area.

In vivo evaluation of the subchronic systemic toxicity of akermanite bioceramic for bone regeneration following ISO standard methods

Although the akermanite (Ca₂MgSi₂O₇) bioceramic has been confirmed to possess favorable osteogenic activity, until now little was known about its in vivo subchronic systemic toxicity, which is important for determining the biocompatibility and the clinical applications of the material in bone implants. In this study, the subchronic systemic toxicity of akermanite bioceramic was for the first time investigated according to well-accepted ISO standard methods. Following the method, healthy adult Wistar rats were injected with certain amounts of extracts of akermanite bioceramic that was intended to simulate the ionic product during the degradation of the material when implanted into the body. At day 28 after injection, the general body conditions, blood cytology, blood biochemistry and histology of all important organs of the rats were examined. The results showed that there was no significant difference in the hemoglobin concentration, red blood cell count, platelet count and white blood cell count between the rats with injection of akermanite bioceramic extracts and the saline control. The indicators of liver function, including aspartate aminotransferase and alkaline phosphatase, and kidney function, including blood urea nitrogen and creatinine, did not show significant difference between the two groups (P > 0.05). In addition, the results of histological examination showed that the extract of akermanite bioceramic did not cause any pathological changes to important organs such as the heart, liver and kidneys. These findings demonstrated that the ionic product derived from the degradation of akermanite bioceramic did not cause in vivo subchronic systemic toxicity. The results of the current study provided more strengthened evidence for the biosafety of akermanite bioceramic and suggest that this material with desirable biocompatibility may be a potential candidate for orthopedic clinical applications.

This study demonstrated that the extracts of akermanite bioceramic did not cause in vivo subchronic systemic toxicity and suggested that Ca₂MgSi₂O₇ with desirable biocompatibility may be a potential candidate for orthopedic clinical applications.

Dicalcium Silicate Induced Proinflammatory Responses through TLR2-Mediated NF-κB and JNK Pathways in the Murine RAW 264.7 Macrophage Cell Line

Proinflammatory responses are important aspects of the immune response to biomaterials, which may cause peri-implantitis and implant shedding. The purpose of this study was to test the cytotoxicity and proinflammatory effects of dicalcium silicate particles on RAW 264.7 macrophages and to investigate the proinflammatory response mechanism induced by C₂S and tricalcium phosphate (TCP). C₂S and TCP particles were characterized using scanning electron microscopy (SEM), energy spectrum analysis (EDS) and X-ray diffraction (XRD). Cytotoxicity and apoptosis assays with C₂S and TCP in the murine RAW 264.7 cell line were tested using the cell counting kit-8 (CCK-8) assay and flow cytometry (FCM). The detection results showed that C₂S and TCP particles had no obvious toxicity in RAW 264.7 cells and did not cause obvious apoptosis, although they both caused an oxidative stress response by producing ROS when the concentrations were at 100 μg/mL. C₂S particles are likely to induce a proinflammatory response by inducing high TLR2, TNF-α mRNA, TNF-α proinflammatory cytokine, p-IκB, and p-JNK1 + JNK2 + JNK3 expression levels. When we added siRNA-TLR2-1, a significant reduction was observed. These findings support the theory that C₂S particles induce proinflammatory responses through the TLR2-mediated NF-κB and JNK pathways in the murine RAW 264.7 macrophage cell line.

A New Biphasic Dicalcium Silicate Bone Cement Implant

This study aimed to investigate the processing parameters and biocompatibility of a novel biphasic dicalcium silicate (C₂S) cement. Biphasic α´_L + β-C₂S_ss was synthesized by solid-state processing, and was used as a raw material to prepare the cement. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid (SBF) and human adipose stem cell cultures. Two critical-sized defects of 6 mm Ø were created in 15 NZ tibias. A porous cement made of the high temperature forms of C₂S, with a low phosphorous substitution level, was produced. An apatite-like layer covered the cement’s surface after soaking in SBF. The cell attachment test showed that α´_L + β-C₂S_ss supported cells sticking and spreading after 24 h of culture. The cement paste (55.86 ± 0.23) obtained higher bone-to-implant contact (BIC) percentage values (better quality, closer contact) in the histomorphometric analysis, and defect closure was significant compared to the control group (plastic). The residual material volume of the porous cement was 35.42 ± 2.08% of the initial value. The highest BIC and bone formation percentages were obtained on day 60. These results suggest that the cement paste is advantageous for initial bone regeneration.

Design and evaluation of multifunctional antibacterial ion-doped β-dicalcium silicate cements favorable for root canal sealing

Cu or Zn-doping dicalcium silicate-based cements exhibit multifunctional physiochemical and biological performances and meet some challenging criteria in root canal treatment.

Systematic investigation of β-dicalcium silicate-based bone cements in vitro and in vivo in comparison with clinically applied calcium phosphate cement and Bio-Oss®

Herein we systematically investigated the biological performance of a β-dicalcium silicate (β-C₂S)-based bone cement in comparison with the clinically used calcium phosphate cement (CPC) and Bio-Oss®.

Macrophage-mediated osteogenesis activation in co-culture with osteoblast on calcium silicate cement

The use of calcium silicate (CS) cement holds great promise for bone substitute biomaterials. However, the effects of CS on osteoblast and macrophage cells are not fully understood. This study examines cell proliferation and differentiation of mono- or co-cultured MC3T3-E1 and Raw 264.7 cells on CS cement. Very few studies to date have looked at the effects of osteoblast and macrophages on biomaterial-regulated osteogenesis. In this study the proliferation and differentiation of MC3T3-E1, Raw 264.7 and co-cultured MC3T3-E1/Raw 264.7 on CS cements have been analyzed using a PrestoBlue kit and ELISA. In addition, the effect of macrophages on CS-coordinated osteogenesis of MC3T3-E1 has been investigated. Results show that MC3T3-E1, Raw 264.7 and co-cultured MC3T3-E1/Raw 264.7 adhere to and proliferate well on the CS cement. In a co-culture, the CS cements inhibit receptor activator of nuclear factor kappa B ligand expression of both genes and proteins in Raw 264.7 cells when compared to those grown in mono-cultured system. Ca deposition of MC3T3-E1 in the co-culture is higher than that of cells in a mono-culture. Bone morphogenetic protein 2 (BMP2) is also significantly up-regulated by the CS cement stimulation, indicating that macrophages may participate in the CS stimulated osteogenesis. Interestingly, when macrophage are cultured with BMP2 receptor-blocking MC3T3-E1 on the CS cements, the osteogenesis differentiation of the cells is significantly inhibited, indicating the important role of macrophages in biomaterial-induced osteogenesis via BMP2 receptors. It is assumed that it is an increase in the secretion of the BMP2 from the Raw 264.7 cell that is primarily involved in the promotion of the osteogenesis of the MC3T3-E1. These results provide valuable insights into both the mechanism of CS-stimulated osteogenesis, and strategies to optimize the evaluation system for the in vitro osteogenesis capacity of bone substitute biomaterials.