Dicalcium Phosphate Anhydrous Research Articles

Corrosion resistance of bioinspired DNA-induced Ca–P coating on biodegradable magnesium alloy

Bioinspired coatings with decreased corrosion rate and enhanced bond strength are at the core of future clinic applications on degradable magnesium (Mg)-based implants. The hybrid of organic and inorganic compounds offers a strategy to fabricate biodegradable, biocompatible and compact coatings on biomedical Mg alloys. Hereby, a comparison with and without DNA addition was made on the corrosion resistance and adhesion strength of Ca–P coatings fabricated on AZ31 alloy via hydrothermal deposition. The morphology, chemical composition, and crystallographic structure of the coatings were investigated by means of SEM, EDS and FTIR as well as XRD before and after corrosion tests. Corrosion resistance was evaluated via potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and hydrogen evolution tests in Hank's solution. Results show that the coatings are mainly characterized by tricalcium phosphate (TCP), dicalcium phosphate anhydrous (DCPA) and calcium-deficient hydroxyapatite (CDHA). The presence of DNA leads to the formation of Ca–P coating with improved corrosion resistance and adhesion strength. Additionally, the formation mechanism for DNA-induced Ca–P coating is proposed. The DNA-induced Ca–P coating exhibits a promising future for controlling the corrosion rate of biodegradable Mg alloys.

Degradation in vitro and in vivo of β-TCP/MCPM-based premixed calcium phosphate cement

Premixed calcium phosphate cements (CPCs) have been developed to shorten the surgical time of conventional CPCs. However, there is lack of investigation on degradation behavior of premixed CPCs in vitro and in vivo. In this study, the premixed CPCs are prepared by mixing glycerol or polyethylene glycol (PEG) with the CPC power (β-tricalcium phosphate (β-TCP) and monocalcium phosphate monohydrate (MCPM)), and their degradation performances including the microstructure, chemical composition and mechanical properties are systematically evaluated both in vitro and in vivo (subcutaneous implantations in rabbits). When the premixed CPCs aged in PBS or FBS, results show weight loss of the specimens, decreased pH value and increased calcium ion concentration of aging media. Meanwhile, the setting products convert from dicalcium phosphate dihydrate (DCPD) to dicalcium phosphate anhydrous (DCPA), and no hydroxyapatite deposit. The specimen size and the molecular weight of non-aqueous solvent can modulate the setting product of premixed CPCs. For the larger specimens, DCPA is the main setting product, for the smaller ones, the composite contained DCPD and DCPA. With the decrease of the molecular weight of the non-aqueous solvent PEG, the setting product change from both DCPD and DCPA to DCPA due to the quicker exchange rate of PEG with water. After a period of subcutaneous implantation, the surface of the grafts obviously disintegrated with the formation of porous structures, but their internal morphology do not obviously change.

The Evaluation of Setting Time and FTIR Spectroscopy of Carbonate Apatite Cement as Endodontic Sealer

The carbonate apatite (CO3Ap) cement as an endodontic sealer play an essential role for endodontics treatment due to its potential to obturate root canal system as one of the most important part in endodontic treatment. Moreover, the CO3Ap has probability of similarities with composition of root dentin. Recently, the setting time of commercial endodontic sealer has 4 hours to 1 day. Therefore, the aim of this present study is to evaluate setting time and to determine the functional group of the new material composition for endodontic sealer. CO3Ap cement sealer was prepared by mixing dicalcium phosphate anhydrous (DCPA), vaterite and calcium hydroxide [Ca (OH)2] with 0.2 mol/L Na2HPO4 containing 1% sodium carboxymethylcellulose (NaCMC) and 32 μg thymoquinone, with liquid to powder ratio of 0.6. The setting time was evaluated by Vicat needle method as describe on modification ISO 1566 for zinc phosphate cement. Five compositions of powder ratio were prepared in this study. The set CO3Ap cement sample was evaluated by Fourier Transform Infrared Spectroscopy (FTIR) to define the functional group of the sample. Setting time evaluation indicated that the average setting time of CO3Ap cement was 21 minutes of five compositions. The FTIR analyses revealed that the CO32- groups were detected, so the results could determine as B-type CO3Ap.The CO3Ap cement was considered fast setting as an endodontic sealer compared to sealers made from other base and proven to have similarities with the components of root dentin.

Effect of setting atmosphere on apatite cement resorption: An in vitro and in vivo study

ObjectivesThe aim of this present study was to investigate the effect of setting atmosphere on replacement of apatite cement with new bone both in vitro and in vivo. Material and methodsApatite cement consisting of an equimolar mixture of tetracalcium phosphate and anhydrous dicalcium phosphate was mixed with distilled water and allowed to set at 37 °C and 100% relative humidity under 0%, 5%, and 100% CO2 atmospheres. X-Ray diffraction and Fourier Transform Infrared Spectroscopy were employed to confirm the carbonate apatite formation. Micro-CT and histological evaluation was made at 1 and 6 month(s) using twelve 10-week-old specific-pathogen-free male Wistar rats. ResultsB-type carbonate apatite was found when the apatite cement was set under 100% CO2 and 5% CO2. More carbonate apatite was formed in the case of 100% CO2 when compared with 5% CO2, and none was formed under 0% CO2. Interestingly, unreacted tetracalcium phosphate was significant when apatite cement was set under 0% CO2, indicating the formation of Ca-deficient hydroxyapatite. When a bone defect of rat tibia was reconstructed in these conditions of apatite cement and sintered hydroxyapatite, replacement of the apatite cement was confirmed 6 months after implantation, whereas no replacement was observed in the case of sintered hydroxyapatite. The amount of replacement of apatite cement with bone was greater, on the order of 100% CO2 and 5% CO2, followed by 0% CO2. ConclusionThe results obtained in the present study demonstrated that setting atmosphere clearly plays an important role in the replacement of set apatite cement with bone.

A two-step reaction to prepare a fast-hardening strontium-calcium phosphate scaffold in room temperature

Objective To evaluate a fast-hardening strontium-calcium phosphate scaffold using a two-step reaction in room temperature. Methods The original powder phase consisted of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and strontium hydrogen phosphate (DSPA). The liquid phase consisted of 20wt% citric acid and 12wt% polyvinylpyrrolidone K-30. Groups were designed as Sr-0, Sr-5, Sr-10, and Sr-20, according to the molar ratios of Sr/(Sr+Ca) being 0, 5%, 10%, and 20% in the powder phase, respectively. The ratio 0.5 mL/g in the liquid to solid phase was used for mixing. After the scaffold was prepared, its setting time, compression strength, phase composition and structural morphology, ions release and pH value of the substrates were analyzed. Results Addition of citric acid accelerated the setting reaction. Acceptable setting time was achieved by optimizing composition of the original powder and liquid phases. On the other hand, the compression strength, phase composition and structural morphology were not affected by addition of strontium. In addition, calcium and strontium ions were detected in the substrates, without any significant change in the pH value. Conclusion This two-step reaction can be used to prepare a fast hardening strontium-calcium phosphate scaffold in room temperature. Key words: Strontium; Calcium phosphates; Hydroxyapatites; Setting time

Setting time evaluation of injectable carbonate apatite cement using various sodium carboxymethylcellulose (Na CMC) concentration

Introduction: The injectable calcium phosphate cement has the advantage to be used in the bone defect with the limited access which supports a minimally invasive surgical technique. These Injectability properties of calcium phosphate cement can be modified by adding a sodium carboxymethylcellulose (Na CMC). The aim of this present study is to investigate the setting time of injectable bone cement based on CO3Ap using various Na CMC concentration. Methods: Vaterite (a polymorph of CaCO3) and Dicalcium Phosphate Anhydrous (DCPA) as powder phase mixed with 0.2 mol/L Na2HPO4 solution containing 1% polyethylene glycol (PEG) and various concentration of Na CMC as followed 0.5%, 1%, 1.5%, and 2%, respectively. Each concentration groups was consisting of 5 samples from total 20 samples. Powder and liquid phase was mixed with a spatula at a liquid to powder (L/P) ratio of 0.4. The setting time of CO3Ap cement was evaluated according to the modification method standardized by ISO 1566 for dental zinc phosphate cement using a custom fabricated Vicat needle apparatus. The cement was maintained at 37ºC and 100% relative humidity as a standard requirement. Results: The mean value of setting time cement was as followed 0.5% Na CMC 35:06 minutes, 1% Na CMC 38:48 minutes, 1.5% Na CMC 40:06 minutes, and 2% Na CMC 41:30 minutes. The result is statistically significant (p<0.05) with the group of 0.5% Na CMC compared to others group. Conclusion: Increasing the concentration of Na CMC could prolong the setting time of CO3Ap cement.

Characterization of hybrid light-cured resin composites reinforced by microspherical silanized DCPA/nanorod HA via thermal fatigue

The mechanical and self-mineralized properties of nanohybrid composite resins used for the dental restoration of class V caries are investigated. The nanorod hydroxyapatite (Nr-HA) hybrid and the microspherical granular dicalcium phosphate anhydrate (DCPA) after silanization were mixed and used as fillers in different kinds of composite resins (abbreviated as DCPA, DCPA+5Nr-HA, and DCPA+10Nr-HA). Their composite strengths were measured via 3-point flexure. Their properties were characterized from environmental samples after water immersion for 24 h and exposure to thermal fatigue between 5 and 55 °C for 600 and 2400 cycles. The resin reinforced with high amounts of Nr-HA (DCPA+10Nr-HA) showed a significant increase in mineralization of the sample surfaces, which consequently enhanced microhardness. The presence of Nr-HA also increased the residual energy of samples during preparation and enhanced their capacity to reprecipitate after immersion and through thermal fatigue. However, the presence of Nr-HA also resulted in high ductility and early failure of the sample, especially in the reinforced group with the highest amount of Nr-HA (DCPA+10Nr-HA). The appropriate additive Nr-HA (DCPA+5Nr-HA) balanced the properties with less difference of strength and residual energy compared with the DCPA group. The additive showed superior capability in enhancing the release of ions and initiating mineralization after immersion with thermal fatigue in vitro. This newly developed composite resin may provide an excellent combination of stress bearing, improved residual energy before the sample fracture, enhanced mineralization capacity, and improved caries-inhibiting capabilities.

A STUDY FOR SYNTHESIS OF DICALCIUM PHOSPHATE FROM VARIOUS GRADES OF PHOSPHATIC MATERIALS

Anhydrous dicalcium phosphate with monetite structure plays a significant biological importance for the mineralization of bones and teeth. This compound can reconstruct the hard tissues due to its high solubility in the body than other calcium phosphate compounds. Di calcium phosphate is being used as a food - additive supplying calcium and phosphate for humans and animals. Due to the high effective P2O5 content, this compound is also used efficiently as a slowly soluble fertilizer in agriculture for all soil and crop types. This paper presents results of synthesis of di calcium phosphate monetite from Ca(OH)2 and phosphoric acid and di calcium phosphate brushite from the resulting solution after enriching of type II - Lao Cai apatite ore by phosphoric acid. The samples were examined by volumetric titration methods, XRD, SEM and EDS.

Novel treatment of in-office tooth bleaching sensitivity: A randomized, placebo-controlled clinical study.

Aim of this clinical trial was to investigate the effect of a calcium phosphate based desensitizer paste applied prior to in-office tooth whitening on bleaching sensitivity (BS). This crossover study was designed as randomized double-blinded, placebo-controlled trial. The desensitizer paste Teethmate AP (TAP) contains tetracalcium phosphate and dicalcium phosphate anhydrous in glycerol and polyethylene glycol, whereas placebo (PLA) is a calcium phosphate free analog. Fifty patients with sound maxillary incisors and canines were enrolled. Tooth shades were determined with a Vitapan Classic Shade guide. Randomly, TAP and PLA were applied to the left or to the right anterior teeth. After rinsing and air-drying the bleaching gel (Opalescence Boost PF 40%) was applied and left on the labial surfaces for 15 minutes. Sensitivity was recorded using a 10 cm visual analog scale (VAS) before, at 5, 10, and 15 minutes during, and at 1 hour, 1, 2, and 7 days after bleaching. Tooth whitening was determined with the shade guide after 1 day and 1 week. Prebleaching desensitization with TAP reduced BS significantly when compared with PLA. Between 1 and 7 days the average sensitivity scores were close to zero, whereas the average scores for PLA were significantly higher during this time interval. Independent from the desensitizing treatment after 1 and 7 days the medians of the shades were between 5 and 3.5 units brighter. Prebleaching desensitization with TAP was effective in reducing BS during and after tooth whitening treatment and had no adverse effect on the bleaching result. Prebleaching topical application of a calcium phosphate containing compound reduced significantly bleaching sensitivity during a single 15 minutes treatment and up to one week with a 40% hydrogen peroxide containing gel without compromising tooth whitening.

Fabrication of Carbonate Apatite Cement as Endodontic Sealer

Carbonate Apatite (CO3Ap) cement has been widely used for bone substitute. It is known that CO3Ap crystals have the close composition to natural bone. It is expected that CO3Ap cement may play an essential role in endodontics treatment, particularly as an endodontic sealer due to its potential to obturate root canal system to a more hermetic and stable environment. Therefore, the aim of this study is to fabricate CO3Ap cement as a new material for endodontic sealer. The CO3Ap cement sealer was prepared by mixing dicalcium phosphate anhydrous (DCPA), vaterite and calcium hydroxide [Ca(OH)2] with 0.2 mol/L Na2HPO4 containing 1% sodium carboxymethyl cellulose (NaCMC) and 32 µg thymoquinone, with liquid to powder ratio of 0.6. The set cement was incubated at 37°C under 100% relative humidity for 72 h. In this study, five compositions of powder ratio were prepared. The diametral tensile strength (DTS) evaluation indicated that CO3Ap cement made of 60% DCPA, 30% Vaterite and 10% Ca(OH)2 has the highest mechanical strength compared with the other compositions. X-ray diffraction (XRD) analysis of the set cement with the highest DTS value indicated that CO3Ap crystals were successfully formed. The set cement with the highest DTS value showed the highest density compared with the other compositions evidenced from scanning electron microscope (SEM) images. In conclusion, the CO3Ap cement was successfully fabricated by mixing DCPA, vaterite and Ca(OH)2. The CO3Ap cement prepared from 60% DCPA, 30% Vaterite and 10% Ca(OH)2 demonstrated the highest DTS value compared with the other compositions.

Evaluation of Carbonate Apatite Cement in Inducing Formation of Reparative Dentin in Exposed Dental Pulp

Carbonate apatite (CO3Ap) cement is a biocompatible material with the ability to induce osteogenesis and is widely studied as the bone substitute material. The similarity of bone to tooth structure in their organic and inorganic composition offers a good prospect of the application of CO3Ap for regeneration of dentin and pulp tissue repair. This study is a sequel of the previous study in the development of CO3Ap cement for dental application, particularly in pulp capping treatment. In this study, the CO3Ap cement is used to cover an exposed dental pulp in rats and histological evaluation was carried out to evaluate the formation of reparative dentin, which is one of the signs of positive pulp capping treatment outcome. The CO3Ap cement was made by combining 60% dicalcium phosphate anhydrous (DCPA) and 40% vaterite with 1 mol/L Na2HPO4 aqueous solution at liquid to powder ratio of 0.5 and conventional calcium hydroxide [Ca(OH)2], which is the golden standard for pulp capping material was used for control. The coronal part of dental pulp in Wistar Rat was exposed with a small dental bur until bleeding were visible. The CO3Ap cement was applied to the exposed pulp and covered with light cured glass ionomer cement. The same protocol was applied to the control groups using Ca(OH)2. The Evaluation of formation of reparative dentin was done in 3 weeks after application by histological observation. Reparative dentin was histologically visible for all samples in CO3Ap group, as well as in the Ca(OH)2 groups. None of the dental pulps were necrotic and the pulp showed no heavy chronic inflammation. The CO3Ap cement was able to maintain the vitality of the pulp with no sign of chronic inflammation. The formation of reparative dentin was observable in 3 weeks of evaluation. Investigation on other properties and in vivo studies in different types of perforation and animal are to be carried out for further development of this material in dental application.

Synthesis and Characterization of a Novel SCPC-CO<sub>3</sub>Ap Cement for Pulp Capping Application in Dentistry

Silica-calcium phosphate composite (SCPC) and carbonate apatite (CO3Ap) have several superior properties as they are bioactive, bioresorbable and elicit excellent tissue response. The CO3Ap surface layer and hydrated silica developed on the surface of the SCPC may be a key factor for achieving dentin regeneration. On the other hand, calcium hydroxide [Ca(OH)2] have antibacterial properties and biocompatible to dental tissue. Therefore, the combination of CO3Ap, SCPC, and Ca(OH)2 in a bone cement may be favorable as a pulp capping agent that enhances pulp tissue formation and dentin regeneration. The aim of the present study is to synthesize and characterize a novel SCPC-CO3Ap cement for pulp capping application in dentistry. The cement is composed of dicalcium phosphate anhydrous (DCPA), vaterite, Ca(OH)2 and SCPC. The set cement was further characterized by Fourier transform infrared (FT-IR). The microstructure of set cement was examined by scanning electron microscopy (SEM) and the mechanical strength was evaluated by diametral tensile strength (DTS). The FT-IR analyses revealed that the additional bands of carbonate were detected in each sample. The SEM samples of set cement showing more compact surface microstructure of group II compared to other groups. Furthermore, the combination of 5% SCPC and 5% Ca(OH)2 in the cement facilitated a compact structure with superior mechanical strength. The novel SCPC-CO3Ap cement has great potential to be used for pulp capping to facilitate dentin regeneration.

STUDY ON CAUSE-EFFECT RELATIONS AND OPTIMIZATION OF TABLETS CONTAINING AQUILARIA CRASSNA SPRAY-DRIED EXTRACT

Objective: The aim of this study was to develop and optimize the formulation of tablets containing Aquilaria crassna extract using the direct compression method.Methods: D-optimal design based on three independent variables was applied to evaluate the cause-effect relations and optimize the A. crassna tablet formulation. The weight variation (Y1), disintegration time (Y2), hardness (Y3) and friability (Y4) were investigated with respect to three independent variables including % dicalcium phosphate anhydrous (DCPA) in filler (X1), % filler (X2) and % croscarmellose sodium (CCNa) (X3). The dissolution study of the optimized A. crassna tablets were investigated in simulated gastric fluid (SGF) (pH 1.2) using a validated high-performance liquid chromatography (HPLC) method for mangiferin analysis.Results: All investigation factors were found to have significant effects on the physical properties of A. crassna tablet. The tablet hardness and the disintegration time increased in positive relations with the ratios of DCPA. The results exhibited the negative relations between disintegration time and the percentages of CCNa. The optimized A. crassna tablet formulation which included 35 % (w/w) DCPA in filler, 60 % (w/w) filler and 7% (w/w) CCNa possessed the weight variation of 1.38 % (w/w), the disintegration time of 6.29 min, the hardness of 85.63 N and the friability of 0.41 % (w/w). The optimized A. crassna tablet formulation was experimentally examined which demonstrated a good agreement between the experimental and predicted values. Mangiferin was found to release completely from the optimized A. crassna tablets within 30 min.Conclusion: The cause-effect relations and optimization of A. crassna tablet formulation were investigated and reported for the first time. The A. crassna spray-dried extract could be formulated into tablet by direct compression method with good mechanical properties and acceptable release profile.

Effect of a calcium phosphate and fluoride paste on prevention of enamel demineralization.

This study aimed to examine the anti-demineralization capacities of (a) tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) and 950 ppm fluoride paste, (b) casein phosphopeptide amorphous calcium phosphate paste and (c) 950 ppm fluoride solution using optical coherence tomography (OCT). Enamel blocks were cut from the bovine incisors and treated using one of the above-mentioned three materials or deionized water as control (n=10). All samples were subjected to a demineralization gel for 1 h followed by a remineralization solution for 23 h. This experimental cycle was repeated for 28 days. The specimens were imaged using OCT at baseline and at four stages and measured lesion depth using image analysis software (ImageJ). Repeated measures ANOVA revealed that demineralization time, material and their interaction significantly affected the optical lesion depth (p<0.001). TTCP and DCPA and 950 ppm fluoride paste and 950 ppm fluoride solution showed significantly lower lesion progress compare to other groups (p<0.05).

A compressibility based model for predicting the tensile strength of directly compressed pharmaceutical powder mixtures

A new model to predict the compressibility and compactability of mixtures of pharmaceutical powders has been developed. The key aspect of the model is consideration of the volumetric occupancy of each powder under an applied compaction pressure and the respective contribution it then makes to the mixture properties. The compressibility and compactability of three pharmaceutical powders: microcrystalline cellulose, mannitol and anhydrous dicalcium phosphate have been characterised. Binary and ternary mixtures of these excipients have been tested and used to demonstrate the predictive capability of the model. Furthermore, the model is shown to be uniquely able to capture a broad range of mixture behaviours, including neutral, negative and positive deviations, illustrating its utility for formulation design.

Peculiarities in thermal evolution of precipitated amorphous calcium phosphates with an initial Ca/P ratio of 1:1.

Thermal evolution of amorphous calcium phosphate (ACP) powder from a fast nitrate synthesis with a Ca/P ratio of 1:1 were studied in the range of 20-980 °C. The powder consisted of amorphous dicalcium phosphate anhydrate (CaHPO4) after heating to 200 °C. CaHPO4 gradually condensed to amorphous calcium pyrophosphate Ca2P2O7 (CPP) between 200 to 620 °C. Amorphous CPP crystallized at 620-740 °C to a metastable polymorph α'-CPP of the high-temperature phase α-CPP and β-CPP. The α'-CPP/ β-CPP phase ratio reached a maximum at 800 °C (60 wt% α'-CPP/40 wt% β-CPP), and α'-CPP gradually transformed to β-CPP at a higher temperature. Some β-TCP occurred at 900 °C, so that a three-phasic mixture was obtained in the powder heated to 980 °C. The occurrence of metastable α'-CPP is attributed to Ostwald's step rule, and a mechanism for β-TCP formation is proposed. The advantages of prospective biomaterials from these powders are discussed.

Preparation of Dicalcium Phosphate Anhydrous (Monetite) Biological Coating on Titanium by Spray-Drying Method

Titanium and its alloys have been widely used in the manufacture of endosseous implants due to excellent biocompatibility, low elastic modulus, and good chemical stability. However, the titanium based metals are essentially bioinert materials. In order to improve their bioactivity, biological coatings are usually applied. Recent studies found that, compared with hydroxyapatite coating, dicalcium phosphate anhydrous (DCPA, Monetite) coating maybe more bioactive due to higher solubility and release of Ca and P ions. In this work, DCPA coating was prepared through a novel and simple method. Briefly, high concentration DCPA solution was sprayed onto superhydrophilic titanium and the specimens were dried fast in an air-circulating oven. After repeating the process over 100 times, a compact coating was fabricated. The microstructure, chemical composition, wettability, and in vitro bioactivity of the coating were analyzed and evaluated. Results showed that the coating fully covered the substrate and consisted of a large number of uniformly sized DCPA granules that packed together closely. The coating showed good wettability and could keep the property for a long time. After immersion in simulated body fluid for 2 weeks, a large amount of bone-like apatite with low crystallinity was induced implying a good bioactivity.

Basic Properties of Novel Bioactive Cement Based on Silica-Calcium Phosphate Composite and Carbonate Apatite

Silica-calcium phosphate composite (SCPC) and carbonate apatite (CO3Ap) are resorbable bioactive materials with the ability to adapt to bone structure and to induce bone regeneration. Considering the similarity between bone and dental structure, where both are mainly composed of calcium deficient carbonate containing hydroxyapatite, we hypothesize that a SCPC-CO3Ap bone cement might also be favorable for the regeneration of dentin and pulp tissue. Therefore, in the present study we report on the effect of composition and structure of SCPC-CO3Ap cement on the morphology, setting and mechanical properties of the material. The novel bioceramics cement composed of vaterite, dicalcium phosphate anhydrous (DCPA) and SCPC. The powder cement ratio divided into 5 groups: group 1 (60% DCPA : 40% vaterite : 0% SCPC) as a control, group 2 (60% DCPA : 10% vaterite : 30% SCPC), group 3 (60% DCPA : 20% vaterite : 20% SCPC), group 4 (60% DCPA : 30% vaterite : 10% SCPC), and group 5 (60% DCPA : 0% vaterite : 40% SCPC). Each group was mixed by 1M Na2HPO4 aqueous solution at liquid to powder ratio of 0.5 and hardened at 37°C and 100 % of relative humidity for 72 hours. Set cement was examined by X-Ray diffraction (XRD), scanning electron microscopy (SEM) and the mechanical strength was evaluated by diametral tensile strength. XRD patterns revealed that the apatite formation was formed after 72 hours, however the intensity of apatite varied based on the SCPC content. The DTS evaluation indicated that group 3 has the highest mechanical strength compared to others. This was supported by SEM analysis of set cement showing more compact surface microstructure of group 2 and 3 compared to other different ratio and control group. The novel bioceramics cement was successfully made using vaterite, DCPA and SCPC. This new cement is currently being investigated for dental application to induce dentinogenesis.

Size Control in Porosity of Hydroxyapatite Using a Mold of Polyurethane Foam

The optimum sized polyurethane foam (PUF) was used as a mold for the formation of porous hydroxyapatite, HAp (calcium phosphate cement-base). Four PUFs of different formulations were selected based on their cell size and the percentage of open cell structure. In the preparation of porous HAp, tetracalcium phosphate and dicalcium phosphate anhydrous were mixed at a molar ratio of 1:1 in the presence of a cement setting solution namely, sodium phosphate. The effects of the morphology and the cell size of PUF on the HAp morphology were analyzed with a scanning electron microscope. Based on the analysis, it was observed that only PUFs with an average cell size of approximately 600 μm and a 95 % open cell structure could optimally generate porous HAp. This result showed 35 % enhancement in porosity compared to the reported values. This porous HAp fulfiled the two criteria for an ideal porous implant which include a cell size of more than 100 μm and a high percentage of open cell content (>50 %).

New polymorph of CaHPO4 (monetite): synthesis and crystal structure

A novel form of anhydrous dicalcium phosphate CaHPO4 (monetite) is synthesized hydrothermally and characterized by single crystal X-ray diffraction. It crystallizes in the orthorhombic space group Ccm21 with a = 6.242(1) A, b = 6.994(2) A, c = 7.003(3) A, V = 305.73(16) A3 and it has four independent unit formulas in the unit cell (Z = 4). A three-dimensional crystal structure can be described by {HPO4}n infinite zigzag chains linked by Ca–O bonds. The comparison to the crystal structures of other polymorphs is given.