Calcium Phosphates

Renal lithiasis is a multifactorial disease. An important number of etiologic factors can be adequately modified through diet, since it must be considered that the urine composition is directly related to diet. In fact, the change of inappropriate habitual diet patterns should be the main measure to prevent kidney stones. In this paper, the relation between different dietary factors (liquid intake, pH, calcium, phosphate, oxalate, citrate, phytate, urate and vitamins) and each type of renal stone (calcium oxalate monohydrate papillary, calcium oxalate monohydrate unattached, calcium oxalate dihydrate, calcium oxalate dihydrate/hydroxyapatite, hydroxyapatite, struvite infectious, brushite, uric acid, calcium oxalate/uric acid and cystine) is discussed.

It is well known that boric acid exhibits various toxic effects on plant, animal and human beings even at very low concentrations. Thus, the development of boron-removal technique from wastewater has been intensively investigated. In this study, a new hydrothermal treatment technique was developed to recover boron as recyclable precipitate Ca(2)B(2)O(5).H(2)O from aqueous solutions. As a result, it was found that the hydrothermal treatment using calcium hydroxide as a mineralizer converted boron in the aqueous media effectively into calcium borate, Ca(2)B(2)O(5).H(2)O. In the optimal hydrothermal condition, more than 99% of boron was collected from the synthetic wastewater of 500 ppm. Thus, the present hydrothermal treatment in the presence of calcium hydroxide is recommended as one of the effective techniques to recover boron from aqueous media.

Dental implants are commonly used in daily practice; however, most surgeons do not really know the characteristics of these biomedical devices they are placing in their patients. The objective of this work is to describe the chemical and morphological characteristics of 14 implant surfaces available on the market and to establish a simple and clear identification (ID) card for all of them, following the classification procedure developed in the Dohan Ehrenfest et al (2010) Codification (DEC) system. Fourteen implant surfaces were characterized: TiUnite (Nobel Biocare), Ospol (Ospol), Kohno HRPS (Sweden & Martina), Osseospeed (AstraTech), Ankylos (Dentsply Friadent), MTX (Zimmer), Promote (Camlog), BTI Interna (Biotechnology Institute), EVL Plus (SERF), Twinkon Ref (Tekka), Ossean (Intra-Lock), NanoTite (Biomet 3I), SLActive (ITI Straumann), Integra-CP/NanoTite (Bicon). Three samples of each implant were analyzed. Superficial chemical composition was analyzed using X-ray photoelectro...

Calcium phosphate cement (CPC) has been successfully used in clinics as bone repair biomaterial for many years. However, poor mechanical properties and a low biodegradation rate limit any further applications. Magnesium phosphate cement (MPC) is characterized by fast setting, high initial strength and relatively rapid degradation in vivo. In this study, MPC was combined with CPC to develop novel calcium–magnesium phosphate cement (CMPC). The setting time, compressive strength, phase composition of hardened cement, degradation in vitro, cells responses in vitro by MG-63 cell culture and tissue responses in vivo by implantation of CMPC in bone defect of rabbits were investigated. The results show that CMPC has a shorter setting time and markedly better mechanical properties than either CPC or MPC. Moreover, CMPC showed significantly improved degradability compared to CPC in simulated body fluid. Cell culture results indicate that CMPC is biocompatible and could support cell attachment and proliferation. To investigate the in vivo biocompatibility and osteogenesis, the CMPC samples were implanted into bone defects in rabbits. Histological evaluation showed that the introduction of MPC into CPC enhanced the efficiency of new bone formation. CMPC also exhibited good biocompatibility, biodegradability and osteoconductivity with host bone in vivo. The results obtained suggest that CMPC, having met the basic requirements of bone tissue engineering, might have a significant clinical advantage over CPC, and may have the potential to be applied in orthopedic, reconstructive and maxillofacial surgery.

Distal radius fracture often presents a metaphyseal void which is more extended in elderly, osteoporotic patients. Bone graft and bone substitutes are reported to be beneficial in maintaining metaphyseal reduction. We performed a prospective study on 52 menopausal, osteoporotic women with unstable intra-articular distal radius fractures to compare the outcome of percutaneous pinning and immobilisation in a cast for 6 weeks with that using injectable calcium phosphate bone cement (Norian Skeletal Repair System, SRS) to supplement pin and screw fixation and immobilisation in a cast for 3 weeks. All patients were reviewed 2 years (range 21-29 months) after surgery. Patients treated with SRS had better functional outcome, restoration of movement and grip strength ( p<0.001). In this group there was 1 mm loss of radial length, 3 degrees loss of radial inclination and 7 degrees loss of palmar tilt. In the control group radial length decreased 3 mm, radial inclination decreased 11 degre...

The influence of ionic substituents in calcium phosphates intended for bone and tooth replacement biomedical applications is an important research topic, owing to the essential roles played by trace elements in biological processes. The present study investigates the mechanical and biological evaluation of ionic doped hydroxyapatite/β-tricalcium phosphate mixtures which have been prepared by a simple aqueous precipitation method. Heat treating the resultant calcium phosphates in a carbonated atmosphere led to the formation of ionic doped carbonated hydroxyapatite/β-tricalcium phosphate mixtures containing the essential ions of biological apatite. The structural analysis determined by Rietveld refinement confirmed the presence of hydroxyapatite as the main phase, together with a considerable amount of β-tricalcium phosphate. Such phase assemblage is essentially due to the influence of substituted ions during synthesis. The results from mechanical tests proved that carbonate substitutions are detrimental for the mechanical properties of apatite-based ceramics. In vitro proliferation assays of osteoblastic-like cells (MC3T3-E1 cell line) to powders revealed that carbonate incorporation can either delay or accelerate MC3T3 proliferation, although reaching the same proliferation levels as control cells after 2 weeks in culture. Further, the powders enable pre-osteoblastic differentiation in a similar manner to control cells, as indirectly measured by ALP activity and Type-I collagen medium secretion.

Many studies of calcium phosphate precipitation have been made using relaxation techniques in which the concentrations of the lattice ions are allowed to decrease as equilibrium is approached. Since the nature of the phases that form depend markedly on the solution composition, this decrease can lead to concomitant phase transformations during the crystallization experiments. The results of the present constant composition (CC) studies show that defect apatites may be formed under conditions of sustained supersaturation with a non-stoichiometric coefficient dependent on the pH of the growth medium. An important factor in analyzing these experiments is the initial surface modification and ion-exchange processes involving H+ and Ca2+ ions after inoculation of the supersaturated solutions. Thereafter, active growth sites may be eliminated as the crystals undergo lattice perfection. Transformation of dicalcium phosphate dihydrate to octacalcium phosphate, involving dissolution and subsequent nucleation and growth of the new phase, is also influenced by surface roughening of the initial phase. Typical inhibitors that reduce the rate of growth of seed crystals in supersaturated solutions may actually induce the nucleation of calcium phosphate phases when immobilized on inert surfaces. This may be a factor in the modulation of crystal growth in many biological systems.

The effect of the elasticity of various pharmaceutical materials on the interfacial adhesion in bilayer tablets was investigated. The elastic properties of five pharmaceutical products were characterized by their total elastic recovery. To test the interfacial strength of the bilayer tablets a new flexural test was proposed. Thanks to the test configuration, the experimental breaking force is directly correlated with the interfacial layer strength. Depending on the materials, the fracture occurred over the interface or in one of the two layers. In most cases, the highest breaking forces were obtained when the materials had close elastic recovery. On the contrary, for materials with different elastic recovery, the breaking forces were reduced. The observed changes in the interfacial mechanical strength were statistically analyzed. Such an approach has an importance in the growing interest in the Quality by Design (QbD) concept in pharmaceutical industry.

To evaluate, using conventional in vitro procedures, the abrasivity, enamel polishing properties, and stain removal effectiveness of various commercial dentifrices that have a variety of compositions and are marketed for cleaning, whitening, and/or polishing capabilities, and to examine their relationships between stain removal and abrasivity. The Relative Dentin Abrasivity (RDA) method was used to measure abrasivity, and the Pellicle Cleaning Ratio (PCR) procedure was used to evaluate stain removal performance. A Cleaning Efficiency Index (CEI) was calculated using the RDA and PCR values. Enamel polish was determined on bovine enamel specimens using a reflectometer. All treatments were performed on a V-8 cross-brushing machine using aqueous dentifrice slurries and standard nylon-bristle toothbrushes. A total of 26 dentifrices, purchased at retail, were tested against the American Dental Association (ADA) calcium pyrophosphate reference standard. All dentifrices removed extrinsic st...

The Stylcam 100R, a rotary press simulator, was designed to simulate speed profiles of rotary tablet presses. Such a simulator was qualified by numerous laboratories and, actually, its ability to be used for studying the behaviour of powders under pressure should be examined. Then, the purpose of this work was to investigate the performances of the Stylcam 100R for characterizing the compaction behaviour and the tabletting properties of pharmaceutical powders. The compressibility of three pharmaceutical excipients (microcrystalline cellulose, dicalcium phosphate dihydrate and α-lactose monohydrate) was studied. Four compression speeds were used on the compaction simulator. Force–displacement cycles were associated with two energy parameters, the specific total energy (Estot) and the specific expansion energy (Esexp). The mean yield pressure was calculated from Heckel's plots obtained with the in-die method. The diametral tensile strength of compacts was measured in order to evaluate mechanical properties. To evaluate the accuracy of all these parameters, a comparative study was carried out on an eccentric instrumented press. The values of energy parameters and tensile strengths of tablets are close between the eccentric press and the compaction simulator, whatever the compression speed on the latter. The mean yield pressure values obtained using the two presses are different. Finally, the Stylcam 100R seems to be a good tool for characterising tabletting properties of powders, except for the Heckel's model probably due to an unadapted equation of deformation and a lack of accuracy of the displacement transducers. Future improvements should allow correcting these two points. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2874–2885, 2010

The exceptional progress made in orthopaedic and dental applications have increased the demand of calcium phosphate bioceramics due to their chemical similarities to the inorganic component of hard tissues. Low cost production of calcium phosphate bioceramics could be achieved by using pure natural biogenic materials by relatively simple methods. In this study calcium phosphate powders were produced from ostrich (Struthio camelus) eggshell powder at a moderate temperature of 80oC by relatively simple process of low temperature heating by hot plate (HP) and hot platting while agitation with ultrasonication (HPUS) hence introducing mechanical activation. The product structure and compositions were studied with FTIR, SEM, DTA/TCA, XRD and ICP techniques. The results showed that calcium deficient hydroxyapatite and dicalcium phosphate were obtained from HP and HPUS methods. Poorly crystalline calcium deficient hydroxyapatite was converted into whilockite after calcining at 800oC. The re...

In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases after mixing form a viscous paste that after being implanted sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA) or brushite, sometimes blended with un-reacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with a newly forming bone), self-setting calcium orthophosphate cements represent a good correction technique of non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities, and easy manipulation. Nearly perfect adaptation to the tissue surfaces in bone defects and a gradual bioresorption followed by new bone formation are additional distinctive advantages of calcium orthophosphate cements. Besides, reinforced formulations are available; those are described as calcium orthophosphate concretes. Furthermore, formulations with high viscosity, such as pastes and putties are also known. The discovery of self-setting formulations has opened up a new era in the medical application of calcium orthophosphates; several commercial compositions have already been introduced as a result. Many more formulations are in experimental stages. In this review, an insight into the self-setting calcium orthophosphate formulations, as excellent biomaterials suitable for both dental and bone grafting applications, has been provided.

To evaluate the outcomes of transcrestal sinus floor elevation (tSFE) performed with a minimally invasive procedure (Smart Lift technique) combined with the additional use of deproteinized bovine bone mineral (DBBM) or β-tricalcium phosphate (β-TCP). In a multicenter randomized controlled trial, 38 sites in 38 patients were treated with the Smart Lift technique in association with DBBM (n = 19) or β-TCP (n = 19). The extent of the sinus lift (SL) and the height of the graft apical to the implant apex (aGH) were assessed on periapical radiographs taken immediately after surgery and at 6 months following surgery. (i) Substantial aGH and SL were observed immediately after surgery and at 6 months, with no significant differences between DBBM and β-TCP groups; (ii) a significant graft remodelling was observed from post-surgery to 6-months in the β-TCP group and (iii) limited incidence of complications as well as limited post-operative pain and discomfort were associated with the use of both graft materials. The Smart Lift technique in conjunction with the additional use of either DBBM or β-TCP may provide a substantial elevation of the maxillary sinus floor along with limited post-surgical complications and post-operative pain/discomfort.

Abstract –  Background:  Apical barrier formation and root strengthening procedures have been extensively described in the literature. This systematic review attempts to establish where the effects of interventions using multi-visit apexification, single visit apical plug techniques and root strengthening procedures are consistent and where they may vary significantly.Objectives:  To evaluate the relative effectiveness of apexification and apical plug techniques as well as root strengthening procedures for treating traumatized necrotic immature permanent anterior teeth through a systematic review of randomized controlled trials. Reported immediate and/or long-term adverse events and effects of the materials and techniques are also evaluated.Search strategy & selection criteria:  Structured electronic and hand search was performed with no restriction on the language of publication. Only randomized controlled trials comparing different apical barrier formation techniques and root strengthening procedures in traumatized necrotic immature anterior teeth were assessed.Results:  Two hundred studies were identified but only two were suitable for inclusion. Included studies investigated multi-visit apexification techniques using calcium hydroxide and tricalcium phosphate. There were no eligible studies investigating root strengthening procedures or any other intervention for apical barrier formation in necrotic immature anterior teeth. No reliable information was available on long-term adverse effects of the reported interventions or cost implications.Conclusions:  Based on two included studies, there is weak evidence supporting the use of either calcium hydroxide or tricalcium phosphate for apical barrier formation in necrotic immature anterior teeth employing multi-visit apexification techniques. The evidence is insufficient to provide guidelines for practice. There was no reliable evidence on adverse events or long-term effects after the use of calcium hydroxide or tricalcium phosphate justifying caution in their use in apical barrier formation techniques.

In early 1980-s, researchers discovered self-setting calcium orthophosphate (CaPO4) formulations (initially known as calcium phosphate cements), which were bioactive and biodegradable grafting bioceramics in the form of a powder and a liquid. After mixing, both phases formed pastes of variable viscosity, which set and hardened forming most commonly a bone-like non-stoichiometric calcium deficient hydroxyapatite (CDHA) or brushite and rarely monetite with possible admixtures of un-reacted components. Since all these compounds were found to be biocompartible, bioresorbable and osteoconductive (therefore, in vivo they could be replaced with a newly forming bone), the self-setting CaPO4 formulations appeared to be very promising bioceramics for bone grafting purposes. Furthermore, due to their unique properties such as an easy shaping, moldability and injectability these formulations possess both an easy manipulation and a nearly perfect adaptation to the complex shapes of bone defects, followed by gradual bioresorption and new bone formation, which are additional distinctive advantages. Moreover, their low-temperature setting reactions and intrinsic porosity allow loading them by drugs, biomolecules and even cells for tissue engineering applications. However, due to the ceramic origin, the ordinary self-setting CaPO4 formulations exhibit both a brittle nature and a low bending/tensile strength, prohibiting their use in load-bearing sites; therefore, reinforced formulations have been introduced, which might be described as CaPO4 concretes. Thus, the discovery of self-setting properties opened up a new era in the medical application of CaPO4 and many commercial trademarks have been introduced as a result. Many more formulations are still in experimental stages. In this review, an insight into the self-setting CaPO4 formulations, as excellent bioceramics suitable for both dental and bone grafting applications, has been provided.