Calcium Phosphate Cement Matrix Research Articles

Mechanical behaviour of wollastonite-based cement composites incorporating fibres and recycled rubber aggregates

Calcium phosphate cement (CPC) is a wollastonite-based inorganic cement that hardens at room temperature to a brittle cementitious material with low fracture behaviour. Recycled rubber aggregates from end-of-life tyres were incorporated up to 17.5 wt% into the CPC matrix to produce high-strength composites with improved strain capacities for structural repair purposes. Furthermore, the effects of 0.75% and 1.5% volume fibre content (Vf) of macro polypropylene, amorphous metallic and recycled carbon fibres on the flexural behaviour of CPC were studied. The synergy between the rubber aggregates and the selected corrosion-resistant fibres in improving the fracture properties of the plain CPC was investigated. The changes in other mechanical properties of CPC such as modulus of rupture, compressive and splitting tensile strength due to the inert inclusions (i.e. rubber aggregates and/or fibres) were determined. It was found that increasing the quantity of inert inclusions in the cement matrix improved the fracture energy of the plain CPC. Incorporating 1.5% Vf of macro polypropylene, amorphous metallic, and recycled carbon fibres into the CPC matrix produced cementitious composites with fracture energies that were 11.8 times, 63.4 times, and 75.8 times that of plain cement, respectively. For the rubberised fibre-reinforced CPC composites, a positive synergistic relationship was observed between rubber aggregates and macro polypropylene fibres while a negative synergistic relationship was found between rubber aggregates and the other fibres (amorphous metallic and recycled carbon fibres). The rubber aggregates decreased the flexural, compressive and splitting tensile strengths of the plain CPC, while the fibre inclusions improved these properties.

Multifunctional Three-Dimensional Printed Copper Loaded Calcium Phosphate Scaffolds for Bone Regeneration

Bone regeneration using inorganic nanoparticles is a robust and safe approach. In this paper, copper nanoparticles (Cu NPs) loaded with calcium phosphate scaffolds were studied for their bone regeneration potential in vitro. The pneumatic extrusion method of 3D printing was employed to prepare calcium phosphate cement (CPC) and copper loaded CPC scaffolds with varying wt% of copper nanoparticles. A new aliphatic compound Kollisolv MCT 70 was used to ensure the uniform mixing of copper nanoparticles with CPC matrix. The printed scaffolds were studied for physico-chemical characterization for surface morphology, pore size, wettability, XRD, and FTIR. The copper ion release was studied in phosphate buffer saline at pH 7.4. The in vitro cell culture studies for the scaffolds were performed using human mesenchymal stem cells (hMSCs). The cell proliferation study in CPC-Cu scaffolds showed significant cell growth compared to CPC. The CPC-Cu scaffolds showed improved alkaline phosphatase activity and angiogenic potential compared to CPC. The CPC-Cu scaffolds showed significant concentration dependent antibacterial activity in Staphylococcus aureus. Overall, the CPC scaffolds loaded with 1 wt% Cu NPs showed improved activity compared to other CPC-Cu and CPC scaffolds. The results showed that copper has improved the osteogenic, angiogenic and antibacterial properties of CPC scaffolds, facilitating better bone regeneration in vitro.

Physicochemical Properties, In Vitro Degradation, and Biocompatibility of Calcium Phosphate Cement Incorporating Poly(lactic-co-glycolic acid) Particles with Different Morphologies: A Comparative Study.

Calcium phosphate cement (CPC) is one of the most promising synthetic biomaterials for bone defect repair, but its low degradation rate and the lack of macropores restrict its repair effect. Poly(lactic-co-glycolic acid) (PLGA) is commonly used as an in situ pore forming agent in CPC, and the morphology of PLGA would affect the properties of CPC. In this study, three kinds of PLGA particles with different morphologies, including dense PLGA microspheres, dense milled PLGA particles with an irregular shape, and porous PLGA microspheres, were respectively incorporated into CPC matrix. The influences of the morphology of PLGA particles on the setting time, porosity, mechanical properties, in vitro degradation, and cytocompatibility of CPC were comparatively investigated. The results showed that the CPC composites containing dense spherical and irregularly shaped PLGA particles showed proper setting time and better compressive strength, but the CPC composite incorporating porous PLGA microspheres significantly prolonged the final setting time and dramatically decreased the compressive strength of CPC. The CPC composite containing irregularly shaped PLGA particles has shown a slightly faster in vitro degradation rate than that containing dense PLGA microspheres. In addition, the CPC composites containing dense PLGA particles were beneficial for cell proliferation. Taken together, the dense PLGA particles are suitable for use as in situ pore forming agents in the CPC matrix, and meanwhile, the dense irregularly shaped PLGA particles are more easily prepared with low cost.

A green composite material of calcium phosphate cement matrix with additions of car tire waste particles

AbstractThe car tire waste have a tremendous adverse environmental impact in nature due to the large volumes generated worldwide, which requires multiple solutions that decrease as much as possible the tires disposed in landfills. Therefore, this research proposes to use part of the unused tire waste in a construction material, phosphate cement with ground rubber waste particles. For that, up to 12wt% of tire waste has been incorporated to cement. The samples characterization was conducted with scanning electron microscope; X‐ray diffraction; compressive strength; thermal stability at 50 and 100°C; density; and Weibull statistics. Results show that this composite can be used as a building material therefore as an environmental solution for the rubber tire waste, mainly in applications requiring similar compressive strengths than concrete with ordinary Portland cement. Weibull statistics showed compression strength changing from 2.85 to 38.29 MPa, which is typical in construction materials and also it enables it to be used as building material. Density of samples was between 1.0 and 1.6 g/cm3, which open up applications for precast panels or other lightweight solutions.

Characterization and multiscale modeling of novel calcium phosphate composites containing hydroxyapatite whiskers and gelatin microspheres

In this study, novel calcium phosphate cement (CPC) composites were prepared by simultaneous incorporation of porogenic crosslinked gelatin microspheres (GMs) and reinforcing hydroxyapatite whiskers (HAWs) into the CPC matrix and the effects of the mentioned additives on the compositional characteristics, phase evolution, setting time, microstructure and mechanical properties of the CPC matrix, were thoroughly investigated. Simulation techniques and multiscale modeling were also employed to predict and compare mechanical properties of the composite formulations with those of real mechanical tests. For this purpose, composite CPCs of varying compositions were prepared by concurrent addition of GMs (5, 10 wt %) and HAWs (5–30 wt %) to the typical apatitic CPC composed of equimolar mixture of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA). Morphological observations by SEM confirmed proper dispersion of the additive materials in the CPC matrix. The results of the compositional evaluation of the composites by FTIR and XRD also revealed that the additives preferably didn’t exhibit a considerable inhibitive effect on the HA conversion during the composite CPC setting process. Porosity measurements approved that GMs could act as porogenic materials which introduced an increased total porosity of up to ∼69% to the structure of composites. The CPC sample and the composite cements also exhibited considerable specific surface area of 12.99 and 4.32–8.20 m 2 /g, respectively. Moreover, the results of compressive mechanical testing showed that the CPC control and the composites had a compressive strength of 28.1, 9.5–29.4 MPa and Young modulus of 3860 and 515–2630 MPa, respectively. However, in terms of mechanical and microstructural features, the composites containing 10 wt % of HAWs exhibited the most preferable characteristics. The mechanical results of the multiscale modeling method were also in the same range of those obtained by experimental compressive tests. Such finding was more notable for the composites with lower content of HAWs (5 and 10 wt %), when the predicted mechanical values for such samples were more than 80% accurate. In-vitro cellular tests also showed that the additives (GMs and HAWs) improved biological response of the composites, with 10 wt % of GMs and HAWs as the optimal amount. Nevertheless, depending on the bone graft requirements and the needed compromise between porosity and mechanical properties; the optimum composite can be chosen. • Successful synthesis of Gelatin Microspheres (GMs) and Hydroxyapatite whiskers (HAWs). • Incorporation of GMs and HAWs into the calcium phosphate cement (CPCs). • Designing novel composite CPC formulations with different amounts of GMs and HAWs. • Thorough characterization of CPC composites to determine optimum formulations. • Observation of reinforcing and porogenic roles by HAWs and GMs, respectively.

Interfacial characterization of poly (vinyl alcohol) fibers embedded in a calcium phosphate cement matrix: An experimental and numerical investigation

Because of their chemical similarity to the mineral phase of bone and teeth, calcium phosphate cements (CPCs) are extensively investigated for applications in biomedicine. Nevertheless, their applicability in load-bearing anatomical sites is restricted by their brittleness. Reinforcement of calcium phosphate cements with polymeric fibers can overcome this mechanical limitation provided that the affinity between these fibers and the surrounding matrix is optimal. To date, the effects of the fiber-matrix affinity on the mechanical properties of fiber-reinforced calcium phosphate cements are still poorly understood. The goal of this study is therefore to investigate the interfacial properties and bond-slip response between the CPC matrix and polymeric fibers. To this end, we selected poly (vinyl alcohol) (PVA) fibers as reinforcing agents because of their high strength and stiffness and their effective reinforcement of cementitious matrices. Micromechanical pull-out experiments were combined with numerical simulations based on an dedicated constitutive interfacial law to characterize the interfacial properties of PVA fibers embedded in a CPC matrix at the single fiber pull-out level. The computational model developed herein is able to predict all three main phases of pull-out response, i.e. the elastic, debonding and frictional pull-out phases. The resulting interfacial constitutive law is validated experimentally and predicts the pull-out response of fibers with different diameters and embedded lengths. Statements of SignificanceTo date, the effects of the fiber-matrix affinity on the mechanical properties of fiber-reinforced calcium phosphate cements are still poorly understood. In this study, we present a novel experimental protocol to investigate the affinity between poly (vinyl alcohol) PVA fibers and the calcium phosphate cement (CPC) matrix by means of single-fiber pull out tests. We determine the critical embedded length for PVA fibers with two different diameters; and we design a numerical FE model including a distinct representation of fiber, matrix and interface with a predictive interfacial constitutive law which is capable of capturing all three main phases of single-fiber pull-out, i.e. elastic, debonding and frictional stages. The resulting interfacial constitutive law is validated experimentally and predicts the pull-out response of fibers with different diameters and embedded lengths.

Enhancement of mechanical and biological properties of calcium phosphate bone cement by incorporating bacterial cellulose

ABSTRACTLow mechanical strength of calcium phosphate cement (CPC) limits its clinical application as a bone replacement. Herein, for the first time, we selected bacterial cellulose (BC) fibres to reinforce CPC. The BC-reinforced CPC (BC/CPC) composites with varying BC content were prepared and compared in terms of microstructure, compressive strength and cellular responses. Scanning electron microscope (SEM) images revealed the uniform dispersion of BC in CPC matrix. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results confirmed the interfacial coordination interaction between BC and CPC. It was found that the introduction of BC enhanced the compressive strength of CPC, and the optimal BC content was 2 wt.%. Moreover, cell studies showed that BC/CPC composites exhibited better cell performance than bare CPC. The results have demonstrated that a new CPC composite with enhanced mechanical performance and cellular responses may be developed by using BC as reinforcement.

Effect of ultrafine poly(ε-caprolactone) fibers on calcium phosphate cement: in vitro degradation and in vivo regeneration.

We incorporated ultrafine polymer fibers into calcium phosphate cement (CPC) to improve the resorption rate of CPC with fiber degradation. Different weight percentages of electrospun poly(ε-caprolactone) fibers (0%, 3%, and 7%, named as ultrafine fiber-incorporated CPC0 [UFICPC0], UFICPC3, and UFICPC7) were included into preset CPC specimens for in vitro immersion in lipase phosphate-buffered solution and long-term in vivo implantation in the femoral condyle of rabbits. The effect of the ultrafine poly(ε-caprolactone) fibers with a diameter ranging from nanometer to micrometer on CPC degradation was evaluated by measuring the pH of the medium, mass loss, porosity, and physiochemical properties. For the in vivo evaluation, histomorphometrical analysis as well as three-dimensional (3D) reconstruction was applied to assess the osteogenic properties of the CPC composite. After in vitro immersion and in vivo implantation, the total porosity and macroporosity as well as the bone formation and ingrowth increased significantly during time in the fiber-incorporated CPC specimens. After 24 weeks of implantation, the degraded space was occupied by newly formed bone, and the UFICPC3 and UFICPC7 composites showed ~3.5 times higher fraction of bone volume than that of the pristine CPC (UFICPC0). In vitro and in vivo results proved that the introduction of ultrafine degradable fibers within a CPC matrix can be used to improve macroporosity efficiently and enhance CPC degradation and bone ingrowth largely.

Size matters: effects of PLGA-microsphere size in injectable CPC/PLGA on bone formation

The aim of this study was to evaluate the effect of PLGA microsphere dimensions on bone formation after injection of calcium phosphate cement (CPC)/PLGA in a guinea pig tibial intramedullarly model. To this end, injectable CPC/PLGA formulations were prepared using PLGA microspheres with either a small (~25 µm) or large (~100 µm) diameter, which were incorporated at a 20:80 ratio (wt%) within apatite CPC. Both CPC/PLGA formulations were injected into a marrow-ablated tibial intramedullary cavity and, after an implantation period of 12 weeks, histology and histomorphometry were used to address bone formation. The results demonstrated bone ingrowth throughout the entire scaffold material for both CPC/PLGA formulations upon PLGA microsphere degradation. More importantly, bone formation within the CPC matrix was > two-fold higher for CPC-PLGA with 25 µm PLGA microspheres. Additionally, the pattern of bone and marrow formation showed distinct differences related to PLGA microsphere dimension. In general, this study demonstrates that PLGA microsphere dimensions of ~25 µm, leading to pores of ~25 µm within CPC, are sufficient for bone ingrowth and allow substantial bone formation. Further, the results demonstrate that PLGA microsphere dimensions provide a tool to control bone formation for injectable CPC/PLGA bone substitutes. Copyright © 2013 John Wiley & Sons, Ltd.

In vitro degradation, biocompatibility, and in vivo osteogenesis of poly(lactic‐co‐glycolic acid)/calcium phosphate cement scaffold with unidirectional lamellar pore structure

The aim of this study was to investigate the in vitro degradation, cytocompatibility, and in vivo osteogenesis of poly(lactic-co-glycolic acid) (PLGA)/calcium phosphate cement (CPC) scaffold with unidirectional lamellar pore structure. CPC-based scaffold was fabricated by unidirectional freeze casting, and PLGA was used to improve the mechanical properties of the CPC-based scaffold, which covered the surface of the pore wall as coating. The in vitro degradation results demonstrated that the PLGA/CPC scaffold had good degradability. The degradation of PLGA film on the surface of the scaffold made the CPC matrix exposed, which facilitated cell response and osteogenesis. Rat bone mesenchymal stem cells (rMSCs) were seeded on the PLGA/CPC composite scaffold. Cell viability, proliferation, and differentiation on the PLGA/CPC composite scaffold were evaluated. The results showed that viable rMSCs attached on the surface of pore wall gradually penetrated into the internal pores of the scaffold as prolongation of culture time. In addition, the rMSCs seeded on the scaffold exhibited good proliferation and growing alkaline phosphatase activity. The scaffold was implanted in the defects in distal end of femora of New Zealand white rabbits. Histological evaluation indicated that the PLGA/CPC scaffold with unidirectional lamellar pore structure had good biocompatibility and effective osteogenesis. These results suggest PLGA/CPC composite scaffold with unidirectional lamellar pore structure is a promising scaffold for bone tissue engineering.

Reinforcement of calcium phosphate cement by incorporating with high-strength β-tricalcium phosphate aggregates

Calcium phosphate cement (CPC) sets to form hydroxyapatite after implantation and has been used in orthopedic and dental procedures. However, the brittleness and low strength of CPC prohibit its use in many stress-bearing locations, and so the improvement of the compressive strength is one of the focuses of research on CPC. In this study, a novel way was used to improve the mechanical performance of CPC by dispersion of high-strength degradable β-tricalcium phosphate (β-TCP) granules sized between 200 μm and 450 μm in the cement as aggregates. Intimate bonding was formed between the aggregates and CPC matrix after hydration. The results showed that, by addition of 20 wt % the as-prepared β-TCP aggregates, the compressive strength of the calcium phosphate cement was increased by about 70%, while the paste of the CPC concrete still maintained injectable, and the heat release decreased obviously (about 25%) in the hydration process. The high strength or high rigidity of the β-TCP aggregates and good interfacial bonding between the aggregates and the CPC matrix seemed to contribute to the significant improvement in the mechanical performance.

Calcium phosphate combination biomaterials as human mesenchymal stem cell delivery vehicles for bone repair

A new class of biomimetic, bioresorbable apatitic calcium phosphate cement (CPC) was recently developed. The handling characteristics, and the ability to harden at body temperature in the presence of physiological saline, make this material an attractive clinical bone substitute and delivery vehicle for therapeutic agents in orthopedic applications. The major challenge with the material is formulating an injectable paste with options for cell delivery, in order to regenerate new bone faster and with high quality. In this study, three different additives and/or viscosity modifiers (carboxymethylcellulose, silk, and alginate) were incorporated into a CPC matrix. Injectability, cell viability, cell proliferation, surface morphology, and gene expression for osteogenesis of hMSCs were all evaluated. Injectable CPC-gel composites with cell protection were achieved. The CPC modified with alginate provided the best results based on cell proliferation, ALP and collagen production, and osteogenic transcript increases (for ALP, type I collagen, BSP, and OP). Furthermore, osteogenic analysis indicated lineage-specific differentiation of hMSCs into osteogenic outcomes. The results suggest that CPC mixed with alginate can be used as a cell delivery vehicle for bone regeneration.

Reinforcement of calcium phosphate cement with multi-walled carbon nanotubes and bovine serum albumin for injectable bone substitute applications

This paper presents the development of novel alternative injectable calcium phosphate cement (CPC) composites for orthopaedic applications. The new CPC composites comprise β -tri-calcium phosphate ( β -TCP) and di-calcium phosphate anhydrous (DCPA) mixed with bovine serum albumin (BSA) and incorporated with multi-walled carbon nanotubes (MWCNTs) or functionalized MWCNTs (MWCNTs–OH and MWCNTs–COOH). Scanning electron microscopy (SEM), compressive strength tests, injectability tests, Fourier transform infrared spectroscopy and X-ray diffraction were used to evaluate the properties of the final products. Compressive strength tests and SEM observations demonstrated particularly that the concomitant admixture of BSA and MWCNT improved the mechanical properties, resulting in stronger CPC composites. The presence of MWCNTs and BSA influenced the morphology of the hydroxyapatite (HA) crystals in the CPC matrix. BSA was found to act as a promoter of HA growth when bounded to the surface of CPC grains. MWCNT–OH-containing composites exhibited the highest compressive strengths (16.3 MPa), being in the range of values for trabecular bone (2–12 MPa).

Self‐setting collagen‐calcium phosphate bone cement: Mechanical and cellular properties

Calcium phosphate cement (CPC) can conform to complex bone cavities and set in-situ to form bioresorbable hydroxyapatite. The aim of this study was to develop a CPC-collagen composite with improved fracture resistance, and to investigate the effects of collagen on mechanical and cellular properties. A type-I bovine-collagen was incorporated into CPC. MC3T3-E1 osteoblasts were cultured. At CPC powder/liquid mass ratio of 3, the work-of-fracture (mean +/- sd; n = 6) was increased from (22 +/- 4) J/m(2) at 0% collagen, to (381 +/- 119) J/m(2) at 5% collagen (p < or = 0.05). At 2.5-5% of collagen, the flexural strength at powder/liquid ratios of 3 and 3.5 was 8-10 MPa. They matched the previously reported 2-11 MPa of sintered porous hydroxyapatite implants. SEM revealed that the collagen fibers were covered with nano-apatite crystals and bonded to the CPC matrix. Higher collagen content increased the osteoblast cell attachment (p < or = 0.05). The number of live cells per specimen area was (382 +/- 99) cells/mm(2) on CPC containing 5% collagen, higher than (173 +/- 42) cells/mm(2) at 0% collagen (p < or = 0.05). The cytoplasmic extensions of the cells anchored to the nano-apatite crystals of the CPC matrix. In summary, collagen was incorporated into in situ-setting, nano-apatitic CPC, achieving a 10-fold increase in work-of-fracture (toughness) and two-fold increase in osteoblast cell attachment. This moldable/injectable, mechanically strong, nano-apatite-collagen composite may enhance bone regeneration in moderate stress-bearing applications.

Calcium phosphate cement reinforced by polypeptide copolymers

Water-based calcium phosphate with bone repairing capability was reinforced by polypeptide graft copolymers and micelles that were formed by polypeptide copolymers. The mechanical studies showed that the compression strength and fracture energy of the calcium phosphate cement (CPC)/polypeptide composites are appreciably higher than those of CPC. The molecular structure of the polypeptide graft copolymers and the association form of the polypeptide copolymers exhibit a marked effect on the mechanical properties of CPC/polypeptide composites. The polypeptide copolymers with more hydrophilic side chains and with core-shell micelle forms have more effective reinforcement effect. The morphological studies based on the scanning electron microscope (SEM) observations revealed that both polypeptide graft copolymers and polypeptide copolymer micelles are well dispersed in CPC matrix. According to the obtained experimental results, reinforcement mechanism was suggested.

Preliminary report on the biocompatibility of a moldable, resorbable, composite bone graft consisting of calcium phosphate cement and poly(lactide-co-glycolide) microspheres

We have assessed the biocompatibility of a new composite bone graft consisting of calcium phosphate cement (CPC) and poly(lactide-co-glycolide) (PLGA) microspheres (approximate diameter of 0.18–0.36 mm) using cell culture techniques. CPC powder is mixed with PLGA microspheres and water to yield a workable paste that could be sculpted to fit the contours of a wound. The cement then hardens into a matrix of hydroxyapatite microcrystals containing PLGA microspheres. The rationale for this design is that the microspheres will initially stabilize the graft but can then degrade to leave behind macropores for colonization by osteoblasts. The CPC matrix could then be resorbed and replaced with new bone. In the present study, osteoblast-like cells (MC3T3-E1 cells) were seeded onto graft specimens and evaluated with fluorescence microscopy, environmental scanning electron microscopy and the Wst-1 assay (an enzymatic assay for mitochondrial dehydrogenase activity). Cells were able to adhere, attain a normal morphology, proliferate and remain viable when cultured on the new composite graft (CPC–PLGA) or on a control graft (CPC alone). These results suggest that our new cement consisting of CPC and PLGA microspheres is biocompatible. This is the first time that a `polymer-in-mineral' (PLGA microspheres dispersed in a CPC matrix) cement has been formulated that is moldable, resorbable and that can form macropores after the cement has set.

Calcium phosphate cement containing resorbable fibers for short-term reinforcement and macroporosity

Calcium phosphate cement (CPC) sets to form hydroxyapatite and has been used in medical and dental procedures. However, the brittleness and low strength of CPC prohibit its use in many stress-bearing locations, unsupported defects, or reconstruction of thin bones. Recent studies incorporated fibers into CPC to improve its strength. In the present study, a novel methodology was used to combine the reinforcement with macroporosity: large-diameter resorbable fibers were incorporated into CPC to provide short-term strength, then dissolved to create macropores suitable for bone ingrowth. Two types of resorbable fibers with 322 μm diameters were mixed with CPC to a fiber volume fraction of 25%. The set specimens were immersed in saline at 37°C for 1, 7, 14, 28 and 56 d, and were then tested in three-point flexure. SEM was used to examine crack-fiber interactions. CPC composite achieved a flexural strength 3 times, and work-of-fracture (toughness) nearly 100 times, greater than unreinforced CPC. The strength and toughness were maintained for 2–4 weeks of immersion, depending on fiber dissolution rate. Macropores or channels were observed in CPC composite after fiber dissolution. In conclusion, incorporating large-diameter resorbable fibers can achieve the needed short-term strength and fracture resistance for CPC while tissue regeneration is occurring, then create macropores suitable for vascular ingrowth when the fibers are dissolved. The reinforcement mechanisms appeared to be crack bridging and fiber pullout; the mechanical properties of the CPC matrix also affected the composite properties.

Effect of an Acid Environment on Leakage of Root-End Filling Materials

One hundred fifty-six single-rooted human extracted teeth received root canal treatment, apicoectomy, and ultrasonic root-end preparations. The roots were divided into six groups of 24 teeth. The groups were filled with Amalgam, Geristore, Super-EBA, Mineral Trioxide Aggregate (MTA), Calcium Phosphate Cement (CPC), or MTA with CPC matrix, respectively. Immediately after root-end filling, 12 teeth from each group were exposed to a pH of 5.0 for 24 h, and 12 teeth were exposed to a pH of 7.4 for 24 h. Twelve teeth served as controls. All teeth were exposed to Pelikan Ink for 5 days and cleared. Linear dye leakage was recorded. Data were statistically analyzed. An acid pH significantly reduced dye leakage of Geristore (0.67 vs. 3.93 mm) and MTA with CPC matrix (0.54 vs. 2.41 mm), whereas leakage of all other materials was not affected by pH. In conclusion an acid environment did not hinder the sealing ability of any of the materials tested, and enhanced the sealing ability of Geristore and MTA with CPC matrix.

An in vitro study of furcation perforation repair using calcium phosphate cement

Furcation perforations created in the pulpal floors of 30 extracted human molars were repaired with either light-cured glass ionomer cement (GI), calcium phosphate cement (CPC), or light-cured glass ionomer cement placed over a CPC matrix (M). After the cement was set, the teeth were immersed in India Ink for 48 h, dried, and sectioned longitudinally. Dye penetration into the furcation repair was independently evaluated by three board-certified endodontists. There was no significant difference in the mean extent of dye leakage among the three experimental groups. The use of CPC, with its enhanced biocompatibility, potential for osteoconduction, and sealing ability, may improve the prognosis of teeth with furcation perforations.

Hydrothermal Cement/Metal Interfaces

We investigated the adherence of two cementitious materials, calcium phosphate cement (CPC) and silica flour‐filled class G cement (CGC), to metal substrates, such as cold‐rolled steel (CRS), stainless steel (SS), electroplated zinc‐coated steel (EZS), and zinc phosphate‐coated steel (ZPS) after autoclaving at 200°C. In CPC/metal joints, the γ‐AlOOH phase, which segregated from the hydroxyapatite phase of the CPC matrix, was preferentially precipitated on the CRS and SS surfaces and also mixed with the reaction products formed at the interfaces between CPC and EZS or ZPS. Precipitation of γ‐AlOOH caused the formation of a weak boundary layer at the interfacial transition zones, thereby resulting in a low shear‐bond strength. Although CGC accelerated the rate of corrosion of CRS and SS surfaces, the growth of Fe2O3 clusters, formed as the corrosion products of metals at interfaces, aided the anchoring effect of xonotlite crystals as the major phase of CGC matrix, thereby conferring a high shear‐bond strength. The EZS and ZPS surfaces were susceptible to alkali dissolution caused by the attack of the high‐pH interstitial fluid of CGC pastes to the Zn and zinc phosphate coatings. Thus, the bond strengths of the CGC/EZS and /ZPS joints were lower than those of the joints made with CRS and SS.