Physicochemical,setting, rheological,and mechanical properties of a novel bio-composite based on apatite cement,bioactive glass,and alginate hydrogel

Calcium phosphate cements (CPC) have been widely investigated as bone substitutes, owing to their attractive features in terms of physicochemical and biocompatibility properties. However, the clinical applicability of this group of biomaterials is still critically limited by its poor strength and rheological properties in terms of injectability and cohesion. The present work aims to develop novel composite cement based on calcium phosphate cement (CPC) and bioactive glass (BG), associated with sodium alginate hydrogel (Alg). The composition, microstructure, setting, rheological, and mechanical properties of this composite cement were further investigated. Evaluation of setting properties showed that BG participates crucially in the setting reaction as a calcium and phosphate provider and serves as a setting accelerator. Thus, the setting time appears lower in these cements than in the reference CPC cement: it decreases from 75 to 42 min as the BG content increases from 10 to 25 wt% and is delayed from 42 to 73 min while the Alg amount augmented from 1 to 5 wt%. The rheological evaluation revealed that injectability was slightly improved with increasing BG content compared to the injectability of CPC, reaching a value close to 100% when combined with Alg hydrogel. The anti-washout property appeared to be weak for the CPC with or without BG, which are disintegrated in solution. The cohesiveness was significantly improved by introducing Alg hydrogel; furthermore, the addition of 5 wt% of alginate hydrogel induced an increase in the compressive strength about twice (7.2 MPa) higher than that of the reference CPC (4.0 MPa). According to the above findings, the addition of BG acts as a setting accelerator leading to a fast apatite formation, while the introduction of Alg hydrogel as a rheological promoting agent improves the injectability and cohesion. The combination of BG and Alg as additives increased the compressive strength compared to the reference cement.     

纳米二氧化硅/磷酸钙复合骨水泥的力学强度和水化过程

在磷酸钙骨水泥（CPC）中添加纳米二氧化硅（nSiO2）获得了nSiO2/CPC复合骨水泥。利用维卡仪、万能压力试验机和热导式等温量热仪研究了nSiO2的添加量对nSiO2/CPC复合骨水泥的凝结时间、抗压强度和水化行为的影响,利用X射线衍射和扫描电子显微镜等技术研究添加的nSiO2对nSiO2/CPC复合骨水泥固化产物的相组成和断面形貌的影响。研究结果表明：nSiO2添加量为5%的nSiO2/CPC复合骨水泥凝结时间由16 min缩短到10 min,抗压强度由原来的（24 2）MPa增加到（33 4）MPa,提高了38%,但添加超过5%的nSiO2会影响水化产物磷灰石的生成从而使复合骨水泥的力学强度下降。在水化反应过程中,一方面nSiO2作为填料,吸附了固化液中的水导致CPC的实际固液比增大,减弱了CPC的水化进程,由于实际固化液下降也减少了水化产物的孔隙大小和数目;另一方面,nSiO2与水化产生的Ca（OH）2发生化学反应形成CSH凝胶,改善了nSiO2和CPC基体之间的界面结合。这两方面的作用结果使得添加适量的nSiO2可以提高nSiO2/CPC复合骨水泥的抗压强度,缩短其凝结时间。     

Development,characterization and optimization of a new bone cement based on calcium–strontium aluminates and chitosan-glycerin solution

Bioceramic bone cements are increasingly studied, developed, and improved to become a viable alternative to polymethyl methacrylate (PMMA)-based cements. In this regard, we aimed to develop a new cement composed of calcium aluminate (C₁₂A₇) and strontium aluminate (S₃A) powders obtained via solution combustion synthesis (SCS) and chitosan/glycerin solution. The cement properties were optimized through a design of experiments. The approach used in the optimization process was the 2^k factorial experimental design with insertion of 3 repetitions of the central point, which resulted in 11 compositions. All compositions were tested to determine the liquid/powder ratio (L/P), final setting time (ST), maximum hydration temperature (T_max), compressive strength and radiopacity. The results were statistically evaluated by analyzing the effects, Pareto diagram, ANOVA analysis and response surface plot. The models obtained in this study could precisely predict three responses: T_max, compressive strength, and radiopacity. An optimized composition for possible application as bone cement had an average T_max of 40.34 °C, compressive strength of 7.75 MPa and radiopacity of 3.76 mm Al, all above the standard requirements.     

Porous hydroxyapatite‐bioactive glass hybrid scaffolds fabricated via ceramic honeycomb extrusion

The successful fabrication of hydroxyapatite‐bioactive glass scaffolds using honeycomb extrusion is presented herein. Hydroxyapatite was combined with either 10 wt% stoichiometric Bioglass^® (BG1), calcium‐excess Bioglass^® (BG2) or canasite (CAN). For all composite materials, glass‐induced partial phase transformation of the HA into the mechanically weaker β‐tricalcium phosphate (TCP) occurred but XRD data demonstrated that BG2 exhibited a lower volume fraction of TCP than BG1. Consequently, the maximum compressive strength observed for BG1 and BG2 were 30.3 ± 3.9 and 56.7 ± 6.9 MPa, respectively, for specimens sintered at 1300°C. CAN scaffolds, in contrast, collapsed when handled when sintered below 1300°C, and thus failed. The microstructure illustrated a morphology similar to that of BG1 sintered at 1200°C, and hence a comparable compressive strength (11.4 ± 3.1 MPa). The results highlight the great potential offered by honeycomb extrusion for fabricating high‐strength porous scaffolds. The compressive strengths exceed that of commercial scaffolds, and biological tests revealed an increase in cell viability over 7 days for all hybrid scaffolds. Thus it is expected that the incorporation of 10 wt% bioactive glass will provide the added advantage of enhanced bioactivity in concert with improved mechanical stability.     

Anti-washout tricalcium silicate cements modified by konjac glucomannan/calcium formate complex for endodontic applications

Although tricalcium silicate (TCS)-based cement showed a great clinical success as the dental filling material, a big challenge encountered by TCS is its poor anti-washout property. Thus, the purpose of this study is to develop a novel TCS-based cement with excellent anti-washout ability by incorporation of konjac glucomannan (KGM)/calcium formate (CF) complex. The self-setting characteristics, anti-washout ability, setting time, compressive strength, porosity, injectability and flowability of the cements were investigated. Furthermore, antibacterial property and cell cytocompatibility of TCS/CF were also assessed. The results showed that KGM could enhance the washout resistance of TCS pastes while it hindered hydration reaction. CF can further increase the anti-washout ability of TCS cement and shorten its setting time from 420 to 174 min because of the accelerating effect of CF on hydration kinetics of TCS. Compared with TCS pastes, TCS cement containing CF showed an increased compressive strength while the addition of CF decreased the injectability of pastes without an obvious effect on flowability. The antibacterial activity of TCS/CF against S. aureus increased with the amount of CF. Moreover, TCS/CF had good cell cytocompatibility. Our results suggested that incorporation of KGM/CF is a superior strategy to enhance the anti-washout ability of TCS-based dental cements, which have the potential use for endodontic applications.     

Soluble phosphate salts as setting aids for premixed calcium phosphate bone cement pastes

Recently, premixed calcium phosphate cement pastes have been proposed as biomaterials for bone tissue repair and regeneration. Use of premixed pastes saves the time and removes an extra step during a medical operation. α-Tricalcium phosphate (α-TCP) based cements set to form calcium deficient hydroxyapatite which has a moderate bioresorbtion speed. α-TCP cements require a setting aid, usually a sodium or potassium phosphate salt, to speed up the setting process. Within the current research we investigated which setting aid has significant advantage, if α-TCP is used in form of non-aqueous premixed paste. This approach offers the application of simple ingredients to produce a premixed calcium phosphate cement. The following properties of cement formulations were evaluated: cohesion, phase composition, microstructure, pH value of the liquid surrounding the cement, and compressive strength.Compositions using mixture of basic and acidic potassium phosphate salts (KH₂PO₄ and K₂HPO₄) in sufficient amounts give the best overall results (adequate cohesion and pH of the surrounding liquid, hydrolysis of starting materials within 48 h, and compressive strength of 12 ± 3 MPa). Cement prepared with basic sodium phosphate salt (Na₂HPO₄) as setting aid had considerably higher compressive strength 22 ± 1 MPa, but the pH of the surrounding liquid was basic (9.0).     

Physicochemical and biological properties of composite bone cement based on octacalcium phosphate and tricalcium silicate

Biocompatible tricalcium silicate (C₃S) bone cement is widely used as dental and bone repair material; however, its long setting time, poor injectability and low initial mechanical properties limit clinical applications. In order to improve C₃S silicate bone cement and its derivatives to play a more important role in tooth restoration, bone defect repair, implant coating and tissue engineering scaffolds, a novel C₃S and octacalcium phosphate (OCP) composite bone cement (OCP/C₃S) was prepared and evaluated for setting time, injectability, anti-flocculation, pH, microstructure, bioactivity and cytotoxicity. The setting time of the OCP/C₃S composite bone cement was controlled within the clinically operable time range (8.3–13.7 min); the cement exhibited good compressive strength, injectability (93.54%), and anti-collapse performance. The 20% OCP/C₃S composite bone cement had a compressive strength of 28.94 MPa, 93% stronger than pure C₃S (14.98 MPa). An in vitro immersion test showed that the composite bone cement had excellent hydroxyapatite forming ability, proper degradation rate, and a low pH value. Cellular experiments confirmed the low cytotoxicity of the composite bone cement and its great capacity for cell proliferation. These results indicate that 20% OCP/C₃S composite bone cement is a promising biomaterial.     

Role of iron on physical and mechanical properties of brushite cements,and interaction with human dental pulp stem cells

Improving the physical, mechanical and biological properties of brushite cements (BrC) is of a great interest for using them in bone and dental tissue engineering applications. The objective of this study was to incorporate iron (Fe) at different concentrations (0.25, 0.50, and 1.00 wt%) to BrC and study the role of Fe on phase composition, setting time, compressive strength, and interaction with human dental pulp stem cells (hDPSCs). Results showed that increase in Fe concentration increases the β-tricalcium phosphate (β-TCP)/dicalcium phosphate dihydrate (DCPD) ratio and prolongs the initial and final setting time due to effective role of Fe on stabilizing the β-TCP crystal structure and retarding its dissolution kinetic, in a dose dependent manner where the highest setting time was recorded for 1.00 wt% Fe–BrC sample. Addition of low concentrations of Fe (0.25 and 0.50 wt%) did not have adverse effect on compressive strength and strength was in the range of 5.7–7.05 (±~1.4) MPa; however, presence of 1.00 wt% Fe decreases the strength of BrC from 7.05 ± 1.57 MPa to 3.12 ± 1.06 MPa. Interaction between the BrCs and hDPSCs was evaluated by cell proliferation assay, scanning electron microscopy, and live/dead staining. Low concentrations of 0.25, and 0.50 wt% of Fe did not have any adverse effect on cell attachment and proliferation; while significant decrease in cellular activity was evident in BrC samples doped with 1.00 wt %. Together, these data show that low concentrations of Fe (equal or less than 0.50 wt %) can be safely added to BrC without any adverse effect on physical, mechanical and biological properties in presence of hDPSCs.     

Characterization of a high strength hydroxyapatite cement with dual chelate-setting using phytic acid and citric acid

With the development of biomaterials, a hydroxyapatite (HA) bone cement based on chelation has gradually attracted attention. This paper presents an investigation on the micromorphology and mechanical property of HA bone cement prepared by HA powders modified by inositol hexaphosphate (IP6, phytic acid). With the citric acid monohydrate (CA) solution used as setting liquid, scanning electron microscopy (SEM) and universal testing machine were employed to investigate the influence of parameters including concentrations of CA as well as powder–liquid ratio on the properties of HA bone cement. In addition, the setting mechanism of chelating cement was analyzed. The results showed that when CA concentration was more than 20 wt.%, the curing products of IP6/CA dual chelating HA cement contained calcium citrate tetrahydrate and tricalcium phosphate (TCP) besides HA. The compressive strength of dual chelated cement increased with the CA concentration. With 10 000 ppm-IP6-HA used as the starting powder, the maximum compressive strength of bone cement prepared with 40 wt.% CA as the setting liquid was up to 57 MPa. Furthermore, the temperature, pH, antibacterial activity measurement, and cell studies in vitro were carried on, suggesting that chelate-setting HA cement has potential development in orthopedic materials.     

Setting properties,mechanical strength and in vivo evaluation of calcium phosphate-based bone cements

Calcium phosphate cement (CPC) is a promising material for use in minimally invasive surgery for bone defect repair due to its similarity to the mineral phase of bone, biocompatibility, bioactivity, self-setting characteristics, low setting temperature, adequate stiffness and ease of shaping in complicated geometrics. In this study, we systematically investigate the influence of preparation variables on the final properties of CPCs. We determined the effects of CPC composition, accelerators, seed hydroxyapatite and reaction temperatures on the setting times and compressive strength of CPCs based on tetracalcium phosphate (TTCP), dicalcium phosphate dehydrate (DCPD), dicalcium phosphate anhydrous (DCPA), and α-tricalcium phosphate (α-TCP). The three types of CPCs (TTCP/DCPD, TTCP/DCPA, and TTCP/α-TCP-based bone cements) were prepared by varying the amounts of seed hydroxyapatite and citric acid used as a hardening accelerator. After 24 h of incubation, all three types of bone cements exhibited the characteristic peaks attributable to hydroxyapatite (HA) without characteristic peaks of unreacted raw materials. These results indicated that the bone cements were completely converted to HA. TTCP/DCPD-based bone cements showed faster setting times than TTCP/DCPA and TTCP/α-TCP-based bone cements. As citric acid concentrations in the liquid phase increased, the setting times of all three types of bone cements gradually decreased. However, the concentrations of seed HA in the cements were not related to significant changes in setting time. The compressive strengths of CPCs were significantly influenced by composition and reaction temperature. We also studied the effects of immersion time in physiological solution on the properties of the various CPCs. In the results of in vivo tests, subjects with bone defects implanted with CPCs exhibited more bone formation than control subjects that did not receive implantations of CPCs.     

Synergistically reinforcement of a self-setting calcium phosphate cement with bioactive glass fibers

Calcium phosphate cements (CPCs) are highly promising for clinical uses due to their in situ-setting ability, excellent osteoconductivity and bone-replacement capability. However, the low strength limits their uses to non-load-bearing applications. In the present research, first, bioactive glass fibers (BGFs) in the ternary SiO₂-CaO-P₂O₅ system were prepared, and then the fiber composites with compositions based on CPC and BGFs were prepared and characterized. Then, the effect of structure and amount of BGF incorporation into the CPC system, and the effect of mechanical compaction on the fiber-modified system were investigated. The results showed that the compressive strength of the set cements without any BGFs was 0.635 MPa which was optimally increased to 3.69 MPa by applying 15% BGF and then decreased by further addition of it. In addition, both the work-of-fracture and elastic modulus of the cement were considerably increased after applying the fibers in the cement composition. Also, the setting time slightly decreased by applying the fibers. In summary, processing parameters were tailored to achieve optimum mechanical properties and strength. The prepared composite may be useful in surgical sites that are not freely accessible by open surgery or when using minimally invasive techniques.     

Cytocompatibility,bioactivity and mechanical strength of calcium phosphate cement reinforced with multi-walled carbon nanotubes and bovine serum albumin

This paper reports on the in vitro cytotoxicity, bioactivity behaviour and mechanical properties of novel injectable calcium phosphate cement filled with hydroxylated multi-walled carbon nanotubes and bovine serum albumin (CPC/MWCNT-OH/BSA). To predict the in vitro bioactivity of the calcium phosphate composites, we investigated apatite formation on CPC/MWCNT-OH/BSA composites after soaking in simulated body fluid (SBF) for up to 28 days. Compressive strength tests, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and cell culture experiments with human CCD-18Co fibroblasts cell lines were performed to evaluate the effect of SBF pre-treatment on the mechanical, structural and biological properties of the CPC/MWCNT-OH/BSA composites. Although apatite formation increased significantly with SBF immersion period, the results showed that all soaked CPC/MWCNT-OH/BSA composites exhibited up to 2.5 times lower compressive strength (13–20 MPa), which were however higher than values reported for the strength of trabecular bone (2–12 MPa). Cell culture experiments showed that low concentrations (6.25 and 12.5 μg/ml) of bio-mineralised CPC/MWCNT-OH/BSA composites led to cell proliferative rather than cytotoxic effects on fibroblasts, evidenced by high cell viabilities (104–113%). The novel CPC/MWCNT-OH/BSA composites presented in this study showed favourable cytocompatible and bioactive behaviour along with high compressive strength (13–32 MPa) and are therefore considered as an attractive bone filling material.     

Implications of unconventional setting conditions on the mechanical strength of synthetic bone grafts produced with self-hardening calcium phosphate pastes

This work presents the effects of several factors on the mechanical strength of a calcium phosphate cement (CPC) based on alpha tricalcium phosphate and correlates the results with the microstructure and percentage of conversion to hydroxyapatite. Conversion rate increased by raising the setting temperature in the studied range (4–90 °C), but the strength exhibited an increasing-decreasing trend due to changes in the morphology of hydrated crystals. Plate-like crystals were formed in the range of 22–60 °C, mechanically reinforcing the material, whereas the formation and refinement of needle-like crystals at higher setting temperature decreased the strength. Moreover, cements with dissimilar particle sizes had different optimal hydrolysis temperatures that resulted in the maximum strength. The finest powder led to higher strength at lower setting temperature due to the formation of a more compact crystal network and higher conversion. Therefore, optimization of powder particle size may allow to achieve the highest possible strength at room temperature, being beneficial for the production of the strongest pre-set CPC-based implants without the use of energy. Furthermore, the particle size can be also engineered to produce formulations that develop the highest strength at physiological temperature, with application as injectable bone grafts. The incorporation and crosslinking of gelatine further increased the mechanical strength of pre-set cements by bridging the hydroxyapatite crystals, the setting temperature showing a similar effect to that of gelatine-free cements. In contrast, moisture decreased the strength and reduced the brittleness by solvating intramolecular association between hydroxyapatite crystals and between gelatine molecules. Moreover, large cement bodies were slightly weaker than small ones, but the size effect was not statistically significant.     

Polymeric calcium phosphate cements incorporated with poly‐γ‐glutamic acid: Comparative study of poly‐γ‐glutamic acid and citric acid

Polymeric calcium phosphate cements (PCPC) derived from biodegradable poly‐γ‐glutamic acid (γ‐PGA) were prepared in an attempt to improve the mechanical strength of calcium phosphate cement (CPC). The characteristics of the PCPCs were compared with those of cement incorporated with citric acid. The diametral tensile and compressive strengths of the CPC incorporated with γ‐PGA were significantly higher than that of cement incorporated with citric acid at equivalent concentrations (P < 0.05). The maximal diametral tensile and compressive strengths of the CPC incubated for 1 week in physiological saline solution were approximately 18.0 and 50.0 MPa, respectively. However, the initial setting time of the PCPC was slower than that of CPC incorporated with citric acid. The formation of ionic complexes between calcium ions and γ‐PGA was observed using FTIR spectroscopy. Hydroxyapatite (HA) formation was retarded by γ‐PGA incorporation according to scanning electronic microscopy (SEM) and powder X‐ray diffraction (XRD) observations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The effect of carboxylic acids and phosphate salts additives on the properties of chondroitin sulfate calcium phosphate cements

The use of liquid phase additives is a strategy to improve the physicochemical, mechanical, and biological properties of calcium phosphate cements. In this study, TTCP and α-TCP particles were synthesized using the solid-state reaction method. Apatite cements were prepared by mixing TTCP/DCPD/α-TCP powders and liquid phases containing chondroitin sulfate with various additives of carboxylic acids and phosphate salts. The formation of hydroxyapatite and consumption of raw materials as well as the acceleration and deceleration periods through cementation process were investigated by XRD and DSC experiments, respectively. In addition, the morphology, setting time, porosity, compressive strength, degradation, in-vitro bioactivity and cytotoxicity were studied. The results showed that the approximate amount of hydroxyapatite resulting from the cementation process was divergent in the presence of liquid phase additives. The use of phosphate salt additives presented better results compared to carboxylic acid ones regarding hydroxyapatite cement product formation, compressive strength, hardening, setting, and cytotoxicity. All cements showed, generally a similar tendency to form dense hydroxyapatite on their outer surfaces through immersion in the simulated body fluid. The cement containing Na₂HPO₄ salt exhibited the lowest cytotoxicity and highest strength. The ALP assay and the morphological behavior of MG63 cells indicated the good activity and proper cell adhesion of this cement.     

A cohesive premixed monetite biocement

Sodium alginate was successfully utilized to improve cohesion and limit particulate debris of a premixed calcium phosphate cement (pCPC) that following the exchange of water set to form monetite. Modified pastes using glycerol and 2 wt% alginate exhibited initial and final setting times of 60 ± 9 and 1355 ± 105 minutes, respectively. Despite these setting times being significantly longer than clinically recommended the improved washout resistance of this formulation would allow for wound closure during setting. Set monetite pastes exhibited a maximum compressive strength of 8.6 ± 3.5 MPa with a corresponding porosity of 59% compared to 15.6 ± 5.8 MPa and 25% for the unmodified aqueous brushite cement. Storage of the pCPC paste at 4°C for 14 days was shown to significantly (P<0.05) increase the compressive strength of the harden matrix (13.2 ± 1.5 MPa), however, subsequent deterioration was observed after 90 days storage. Methylene blue was utilized to visualize perfusion into the matrix during setting, demonstrating that the use of glycerol altered mass transport and ultimately shifted the crystallization kinetics in favor of monetite. Samples >20 mm did not reach full saturation after 10 days of immersion, which for the first time suggests an upper volume limit that will form a homogeneous cement highlighting an important consideration for clinical translation of pCPCs.     

Investigation of biocompatible nanosized materials for development of strong calcium phosphate bone cement: Comparison of nano-titania,nano-silicon carbide and amorphous nano-silica

The present paper deals with the effect of adding SiC, TiO₂ and SiO₂ nanoparticles on setting time, mechanical strength and hydraulic reactions of calcium phosphate cements (CPCs). The initial and final setting times of CPC increased by adding both nano-SiC and nano-TiO₂ additives but decreased by using nano-silica. Nano-titania and nano-silica had great effect on compressive strength of as-set CPC whereas slight changes were found by using nano-SiC. Although a sharp increase in compressive strength of all cements was observed by soaking them in physiological solution, the soaked additive-free cements and nano-SiO₂-added ones exhibited the greatest strength values. The results showed that adding these nano-additives did not influence on conversion rate of cement reactants to apatite phase during soaking in physiological solution period but the morphology of the formed phase was almost different. Overall, the results determined that nano-SiO₂ and nano-TiO₂ particles were appropriate additives to improve short-term mechanical strength of CPCs a(s-set CPCs), though nano-SiO₂ was found more effective because it improves the long-term mechanical strength of CPC (after soaking) too.     

Robocasting and surface functionalization with highly bioactive glass of ZrO2 scaffolds for load bearing applications

This work is a proof of concept for making load bearing implants with osseointegration and bone bonding ability. Yttria-stabilized zirconia (YSZ) scaffolds with a percentage of macro porosity of about 70% were fabricated by robocasting. Although a maximum solids volume fraction of 50 vol.% could be achieved, the 3D-printing process revealed to be more reliable when using inks with 48 vol.% solids. The sintered porous structures exhibited an average compressive strength of ~236 MPa. After some preliminary coating experiments, an ethanol slurry of fine bioactive glass (BG) particles (10 wt.%) stabilized with polyvinylpyrrolidone was used to deposit a uniform surface coating onto the filaments, followed by glazing at 850°C. The functionalized scaffolds showed a relatively uniform surface coverage by the bioactive glass. The results of in vitro testing by immersing the scaffolds in simulated body fluid (SBF) showed remarkable morphological surface changes and an extensive deposition of hydroxyapatite layer. The overall results demonstrate the viability of producing porous YSZ scaffolds with excellent bioactivity, which are promising for bone tissue engineering under load bearing applications.     

Fabrication and characterization of bioactive glass (45S5)/titania biocomposites

Bioactive glass (BG) (45S5) has been used successfully as bone-filling material in orthopedic and dental surgery but its lean mechanical strength limits its applications in load-bearing positions. Approaches to strengthen these materials decreased their bioactivity. In order to realize the optimal matching between mechanical and bioactivity properties, bioactive glass (45S5) was reinforced by introducing titania (TiO₂) in anatase form and treated at 1000 °C to form new bioactive glass/titania biocomposites. The prepared biocomposites were assessed by XRD, FT-IR, mechanical properties and SEM. The results verified that the increase of titania percentage to BG powder enhanced gradually the mechanical data of the prepared biocomposites. SEM and FT-IRRS confirmed the presence of a rich bone-like apatite layer post-immersion on the composite surface. It has been found that the new BG/titania biocomposite materials especially those containing high content of titania have high bioactivity properties and compressive strength values comparable to cortical bone. Therefore, these biocomposite materials are promising for medical applications such as bone substitutes especially in load-bearing sites.     

Hydration reactions and physicochemical properties in a novel tricalcium-dicalcium silicate-based cement containing hydroxyapatite nanoparticles and calcite: A comparative study

The mineral trioxide aggregate (MTA) is Portland type cement whose main application in dentistry is retrograde filling. The purpose of this study was to analyze hydration reactions and physicochemical properties of a new tricalcium-dicalcium silicate-based cement containing nanocrystalline hydroxyapatite (nHAp) and calcite. The new formulation was compared with Biodentine™ and MTA-Angelus™ as control samples.Hydration reactions were monitored by Raman spectroscopy, X-ray diffraction, radiopacity, pH, setting time, and compressive strength. The compressive strength reaches its higher value at 7 days following the sequence: Biodentine™ (104.8 MPa) > Cement + 5% nHAp (59 MPa) > MTAAngelus™ (27.3 MPa), in agreement with the pH values measured at 24 h: Biodentine™, Cements + nHAp or + calcite (10.6–11.6) > MTA-Angelus™ (9.7). Mean setting times was around 30 min and no significative differences (p = 0.0001) were observed. In the Biodentine™ control samples, Ca₃SiO₅ diminishes until disappear at 28 days of hydration. On their turn, calcium silicate hydrate (CSH) increases continuously in the range of time analyzed. The present results suggest that the physicochemical properties were improved for the new cement with nanosized hydroxyapatite nanoparticles and relevant information on chemical properties is of valuable importance for testing predictive models for Biodentine™ and MTA-Angelus™.