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PubMed1992

Histopathological reactions of calcium phosphate cement.

Calcium phosphate cement (CPC) consisting of Ca4 (PO4)2O and CaHPO4 (2H2O) was recently developed. This study evaluated in vivo aspects of CPC and CPC mixtures compared to those of commercial hydroxyapatite (HP) and several endodontic materials: Grossman's cement (GC), calcium hydroxide-iodine paste (CHP) and gutta-percha plate (GP). Biocompatibility of subcutaneous implants in Donryu rats was evaluated after one month. Results showed very slight inflammatory reactions from CPC, CPC mixtures and HP. The materials were surrounded by thin fibrous connective tissues with a small number of lymphocytes and plasma cells. Severe inflammatory reactions were provoked by GC. Granulation tissues induced by CHP resembled those of pseudoxanthomatous granuloma. The GP material was encapsulated by relatively thick fibrous connective tissues with little inflammatory reactions.

Animals↗
PubMed1993

In vitro stability of biphasic calcium phosphate ceramics.

Biphasic calcium phosphate ceramics consist of both beta-tricalcium phosphate and hydroxyapatite. This study was performed to examine the in vitro stability of biphasic calcium phosphate ceramics in deionized distilled water and in physiological solutions. Biphasic calcium phosphates of two different molar ratios and pure hydroxyapatite and pure beta-tricalcium phosphate granules were tested. X-ray diffraction data were obtained before and after immersion. Surface morphology was compared using scanning electron microscopy. The pure beta-tricalcium phosphate and the beta-tricalcium phosphate in the biphasic calcium phosphate ceramics gradually converted to apatite. Needle-like apatite crystals were observed on the surface of biphasic calcium phosphate and beta-tricalcium phosphate, but hydroxyapatite showed no change.

Biocompatible Materials↗
PubMedDate not supplied

[Calcium phosphate materials].

Calcium phosphate materials are being studied from the beginning of this century in its several dental and medical applications. There are different types depending on the origin, production procedure and its numerous commercial brandts. They have some features in common: non toxic, biocompatibility, biodegradation, bioresorption and strong bond to the bone and to the soft tissues. The differences between the materials developed so far can be found in other characteristics like density, porosoity, resistance, strength and osteogenic potential.

Animals↗
PubMed2000

Calcium orthophosphates in medicine: from ceramics to calcium phosphate cements.

Calcium phosphate (CaP) compounds are becoming of increasingly great importance in the field of biomaterials and, in particular, as bone substitutes. Recent discoveries have accelerated this process, but have simultaneously rendered the field more complicated for the everyday user. Subtle differences in composition and structure of CaP compounds may have a profound effect on their in vivo behaviour. Therefore, the main goal of this article is to provide a simple, but comprehensive presentation of CaP compounds. Reference is made to the most important commercial products.

Biodegradation, Environmental↗
PubMed1999

Effects of various adjuvants (lactic acid, glycerol, and chitosan) on the injectability of a calcium phosphate cement.

Calcium phosphate cements are well-known orthopedic materials for filling bone. Various formulations are proposed. The current challenge is to place the material in the surgical site by methods as least invasive as possible. One approach consists of making the cement injectable by incorporation of various adjuvants. However, the requirement properties of the cement must be preserved: setting times suited to a convenient delay with surgical intervention, limited disintegration in aqueous medium, and sufficient mechanical resistance. Various additives were studied: in particular, lactic acid, glycerol, chitosan, and sodium glycerophosphate. Injectability, setting time, disintegration, and toughness after 10 days were followed in vitro. Glycerol greatly improved injectability and increased setting time, but decreased mechanical properties. Lactic acid reduced setting time, increased toughness of the material, but limited the dissolution rate. After injection, the cement did not present any disintegration. The effects lactic acid were correlated with the formation of calcium complex. Its association with sodium glycerophosphate is particularly interesting. Chitosan alone improved injectability, increased setting time, and limited the evolution of the cement by maintaining the OCP phase. Only slight disintegration was observed. These first results show that is possible to transform the cement into an injectable paste by addition of adjuvants without fundamentally modifying the chemical reactions occurring during setting and hardening.

Adjuvants, Pharmaceutic↗
PubMed1989

[An in vitro study of dentin hypersensitivity using calcium phosphate cement].

Calcium phosphate remineralizing slurry (CPRS), consisting of an equimolar mixture of tetracalcium phosphate (TTCP) and dicalcium phosphate dihydrate (DCPD), has previously been shown to form hydroxyapatite (HAp) spontaneously at physiological pH. Since considerable amounts of HAp may be formed in situ by CPRS, it may be effective for desensitizing hypersensitive dentin by obturating exposed dentinal tubule openings. In the present study, the effects of topically applied CPRS to etched dentin surfaces were investigated. The samples were randomly divided into 3 groups: (1) the control specimens were soaked in a saliva-like (SL) solution (2) the specimens received either 10-minute or 1-hour treatment with CPRS and (3) the specimens were treated with viscous CPRS, containing carboxymethyl cellulose (CMC) gel, for 8 hours. The SEM observations revealed that the control specimens were covered with a thin layer of plate-like crystals indicative of octacalcium phosphate (OCP). No significant penetration of the crystals into the dentinal tubules was detected. In CPRS group, the 10-minute treatment produced a 10 to 15 microns thick dense layer of precipitation consisting of needle-, rod-, and plate-like crystals. The 1-hour treatment produced a similar precipitation except that the crystals were mostly needle-like. A cross section view of the samples indicated remarkable penetration of the crystals into the tubules, thus providing significant obturation of tubule openings. Samples in the CMC-gel group were covered with an even more impervious layer of precipitation consisting of crystals of a variety of morphologies.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Phosphates↗
PubMed2006

Injectable and rapid-setting calcium phosphate bone cement with dicalcium phosphate dihydrate.

Calcium phosphate cement (CPC) sets in situ with intimate adaptation to the contours of defect surfaces, and forms an implant having a structure and composition similar to hydroxyapatite, the putative mineral in teeth and bones. The objective of the present study was to develop an injectable CPC using dicalcium phosphate dihydrate (DCPD) with a high solubility for rapid setting. Two agents were incorporated to impart injectability and fast-hardening to the cement: a hardening accelerator (sodium phosphate) and a gelling agent (hydroxypropyl methylcellulose, HPMC). The cement with DCPD was designated as CPC(D), and the conventional cement was referred to as CPC(A). Using water without sodium phosphate, CPC(A) had a setting time of 82 +/- 6 min. In contrast, CPC(D) exhibited rapid setting with a time of 17 +/- 1 min. At 0.2 mol/L sodium phosphate, setting time for CPC(D) was 15 +/- 1 min, significantly faster than 40 +/- 2 min for CPC(A) (Tukey's at 0.95). Sodium phosphate decreased the paste injectability (measured as the paste mass extruded from the syringe divided by the original paste mass inside the syringe). However, the addition of HPMC dramatically increased the paste injectability. For CPC(D), the injectability was increased from 65% +/- 12% without HPMC to 98% +/- 1% with 1% HPMC. Injectability of CPC(A) was also doubled to 99% +/- 1%. The injectable and rapid-setting CPC(D) possessed flexural strength and elastic modulus values overlapping the reported values for sintered porous hydroxyapatite implants and cancellous bone. In summary, the rapid setting and relatively high strength and elastic modulus of CPC(D) should help the graft to quickly attain strength and geometrical integrity within a short period of time postoperatively. Furthermore, the injectability of CPC(D) may have potential for procedures involving defects with limited accessibility or narrow cavities, when there is a need for precise placement of the paste, and when using minimally invasive surgical techniques.

Biocompatible Materials↗
PubMed1994

Post-deposition heat treatments for ion beam sputter deposited calcium phosphate coatings.

Calcium phosphate coatings produced using the ion beam sputter deposition process are amorphous. To produce crystalline coatings, a series of different post-deposition heat treatments were conducted. Heat treatments conducted at temperatures less than 500 degrees C did not produce crystalline phases in the coatings. A 500 degrees C post-deposition heat treatment provided the energy required to produce a hydroxyapatite (HA)-type coating as determined using X-ray diffraction and Fourier transform IR spectroscopy (FTIR). Although post-deposition heat treatments can reduce the adhesion of a coating to its substrate, the 500 degrees C heat treatment did not decrease the coating bond strength. Heat treatments conducted at 600 degrees C were found to produce crystalline HA-type coatings but these heat treatments significantly reduced the coating bond strength. Cracks were observed on the surface of the 600 degrees C heat treated coatings. FTIR analysis revealed a new absorption band at 820 cm-1 for the 600 degrees C heat treated coatings, suggesting the formation of a new phase.

Calcium Phosphates↗
PubMed2007

Mechanical and biocompatible influences of chitosan fiber and gelatin on calcium phosphate cement.

Calcium phosphate cement (CPC) is a widely used bone substitute in the clinic; however, the low strength of CPC limits its utilization. In this study, we investigated mechanical influences of chitosan fiber combined with gelatin on CPC, and examined the biocompatibility of the new composite with rat bone marrow stromal cells. Compared to the fiber impregnated in phosphate buffered saline (80.5 MPa), our study showed that tensile strength of chitosan fiber increased 106 and 114% with the impregnation of gelatin at the mass fraction 5 and 10%, although this increase was not statistically significant. It was demonstrated by Fourier transform infrared spectroscopy that the characteristic absorption bands of chitosan were changed with the addition of gelatin. The optimal flexural strength enhancement was obtained when CPC was reinforced with fiber at volume fraction of 30% and gelatin at mass fraction of 5% (maximum: 12.31 MPa). The fiber morphology was more compact when the chitosan fibers impregnated with gelatin at mass fraction of 5 or 10% than chitosan alone. The fracture analysis showed that the new CPC-chitosan fiber-gelatin composite presented many remnants of CPC adhered to fibers. Short minimum essential medium extract test showed no cell growth inhibition after the addition of the new composite. Rat bone marrow stromal cells retain the ability to spread and grow on the composite. Our studies demonstrated that the flexural strength is greatly increased by using CPC incorporated with proper ratio of CF and gelatin. More over, the new composite demonstrated biocompatibility in vitro.

Animals↗
PubMed2000

Physicochemical evaluation of bioactive polymeric composites based on hybrid amorphous calcium phosphates.

Amorphous calcium phosphate (ACP)-filled methacrylate composites were recently found to effectively remineralize in vitro caries-like enamel lesions. Their inferior mechanical properties compared to glass-filled composites, however, limit their use as a dental restorative material. In this study, the feasibility of introducing glass-forming elements (tetraethoxysilane or zirconyl chloride) during the low-temperature synthesis of ACP was investigated. Composites based on such hybrid fillers (mass fraction, 40%) were evaluated to establish whether hybridization strengthened the composites via improved interfacial interactions with the polymer phase without compromising the release of the mineral ions. Two types of visible-light cured resins were prepared: BTHZ resin from 2, 2-bis[p-(2'-hydroxy-3'-methacryloxypropoxy)phenyl]propane (BisGMA), triethylene glycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA) and zirconyl methacrylate (ZrM), and TP resin from TEGDMA and pyromellitic glycerol dimethacrylate (PMGDM). Hybridized fillers and BTHZ- and TP-based composites were characterized by the IR spectroscopy, X-ray diffraction, dissolution/transformation kinetic studies, and biaxial flexure strength (BFS) testing before and after immersion in buffered saline solutions. The feasibility of improving the BFS via hybridization, while retaining, if not enhancing the remineralizing potential was demonstrated for BTHZ-based composites. Both BFS and remineralizing ability of the TP-composites, however, deteriorated upon their exposure to an aqueous environment. Therefore, hybridized ACP-filled BTHZ composites have a potential for utilization in more demanding restorative, sealant, and adhesive applications.

Calcium Phosphates↗
PubMed2001

Effect of mechanical grinding of MCPM and CaO mixtures on their composition and on the mechanical properties of the resulting self-setting hydraulic calcium phosphate cements.

Calcium bis-dihydrogenophosphate monohydrate (or monocalcium phosphate monohydrate, MCPM) is often used as the acid calcium phosphate in hydraulic calcium phosphate cement formulations. But commercial MCPM is not pure; it contains a small amount of orthophosphoric acid and moisture. Consequently, MCPM is difficult to mill and the powder is sticky and presents aggregates. Because granularity influences the mechanical properties of the hardened cements, a possible way to get around this difficulty that has been proposed is to premix it with other materials before grinding. We therefore ground commercial MCPM with CaO. A rapid decrease in the amount of MCPM was observed during mechanical grinding by a solid-solid reaction with calcium oxide. The final products were anhydrous or dihydrate dicalcium phosphate and/or hydroxyapatite or calcium-deficient hydroxyapatite depending on the initial calcium-to-phosphate (Ca/P) ratio. The mechanical properties (compressive strength and setting time) of cements made from MCPM and CaO were affected whatever the Ca/P ratio as a consequence of the change in composition of the starting materials. Storage at different temperatures of MCPM and CaO mixtures manually ground in a mortar for only 2 min and without mechanical grinding did not affect their composition, but a decrease was observed in the compressive strength of cements made from these mixtures.

Journal Article↗
PubMed1988

Serum magnesium, calcium, phosphate and PTH following long-term beta-blockade in ischaemic heart disease.

In 40 patients with ischaemic heart disease the serum levels of magnesium, parathyroid hormone (PTH), phosphate, calcium, and ionized calcium remained unchanged and within normal limits following treatment for 12 months with alprenolol (n = 20) or placebo (n = 20). No changes occurred during a 2 week withdrawal period. The clinical implication is that the non-cardioselective betablocker alprenolol can be given to patients with ischaemic heart disease without the risk of inducing potentially cardiotoxic disturbances in serum magnesium and serum calcium levels. Whether this applies to cardioselective beta-blockers remains to be established.

Adrenergic beta-Antagonists↗
PubMed2003

Fiber-enriched double-setting calcium phosphate bone cement.

Calcium phosphate bone cements are useful in orthopedics and traumatology, their main advantages being their biocompatibility and bioactivity, which render bone tissue osteoconductive, providing in situ hardening and easy handling. However, their low mechanical strength, which, in the best of cases, is equal to the trabecular bone, and their very low toughness are disadvantages. Calcium phosphate cement compositions with mechanical properties more closely resembling those of human bone would broaden the range of applications, which is currently limited to sites subjected to low loads. This study investigated the influence of added polypropylene, nylon, and carbon fibers on the mechanical properties of double setting alpha-tricalcium phosphate-based cement, using calcium phosphate cement added to an in situ polymerizable acrylamide-based system recently developed by the authors. Although the addition of fibers was found to reduce the compression strength of the double-setting calcium phosphate cement because of increased porosity, it strongly increased the cement's toughness (J(IC)) and tensile strength. The composites developed in this work, therefore, have a potential application in shapes subjected to flexure.

Biocompatible Materials↗
PubMedDate not supplied

[Calcium phosphates in otologic surgery. III. The role of fibrin glue in the integration of calcium phosphate implants. Experimental study].

Obliteration of the mastoid cavity has been realized with calcium phosphates associated to heterologous fibrin glue in otologic surgery. 22 artificially created epitympanic and 65 femoral defects in 22 rabbits were closed by means of dense or porous granulates of hydroxyapatite with homologous fibrin glue. Follow-up was for three weeks to 6 months. Osteo-integration of the implants was significantly delayed in the first weeks, comparing the integration of the same phosphates without fibrin glue.

Animals↗
PubMed1985

Calcium phosphate adjuvanted allergens.

Calcium phosphate has been used for many years as an adjuvant for vaccines. Results of field trials using calcium phosphate in several countries have been published and demonstrate high immunogenicity and the absence of untoward reactions. This paper presents preliminary results of studies on the use of calcium phosphate, instead of aluminum compounds, for preparing adsorbed allergens. These were performed with purified house dust, mite, and grass pollen extracts. Immunotherapy with house dust and mite extracts gave a high rate (70%) of satisfactory therapeutic results. Efficacy was compared with immunization carried out with fluid preparations under the same conditions. It was found that satisfactory results were of the same order, but elicited a higher number of injections. Immunotherapy with calcium phosphate adjuvanted allergens was also equal, as with aluminium adjuvanted allergens, according to published data. Good tolerance was noted for adsorbed grass pollen extracts, but clinical evaluation of results can only be reported after treatments during at least three seasons.

Adjuvants, Immunologic↗
PubMed2007

Gamma-radiation-induced changes in structure and properties of tetracalcium phosphate and its derived calcium phosphate cement.

The purpose of the present study was to investigate the gamma-radiation effect on the structure and properties of the single-phase tetracalcium phosphate (TTCP) powder and its derived calcium phosphate cement (CPC). Experimental results show that low-dosed (0-30 kGy) CPC has a setting time of 10-12 min, while high-dosed (40-120 kGy) CPC has a setting time of 8-10 min. The low dose gamma-radiation does not significantly change porosity volume fraction or compressive strength of the CPC. The pH values of all CPC samples fell in a relatively narrow band, with a band width of 8.5-9.1 (in terms of pH value). With a dose of 10 or 20 kGy gamma-radiation, the TTCP-apatite conversion ratio does not change much. With 30 kGy the conversion ratio significantly increases and reaches a maximum value. With further increases in dose, the conversion ratio quickly declines. With increasing gamma-ray dose, the CPC morphology becomes more porous/loose and apatite particles become larger in size. When exposed to a high dose (120 kGy) of gamma-radiation, TTCP structure is radiation-damaged, and gamma-ray-induced formation of apatite is confirmed by transmission electron microscopic/selected-area diffraction/lattice imaging analyses.

Bone Cements↗