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PubMed1993

Further studies on the plasma-sprayed amorphous phase in hydroxyapatite coatings and its deamorphization.

Plasma-sprayed hydroxyapatite coatings contain a quite large amount of amorphous phase. Infrared analysis shows that the plasma-sprayed amorphous phase is an oxyapatite and the coating predetermined as a hydroxyapatite is proved to be an oxyhydroxyapatite with a small quantity of hydroxyapatite. Heat treatment promotes the transformation of amorphous oxyapatite into a crystalline hydroxyapatite structure and reduces the dissolution rate of the coatings. Further studies focus on the properties of the amorphous phase, showing that amorphous oxyapatite is more soluble in 0.15 M lactic acid at 25 degrees C and that water molecules can accelerate the amorphous/crystalline transformation of the hydroxyapatite structure during the plasma-spraying process.

Crystallization↗
PubMed1996

Acidic amino acid-rich sequences as binding sites of osteonectin to hydroxyapatite crystals.

Osteonectin, an acidic noncollagenous protein of bone and dentin, has affinity to hydroxyapatite crystals. Binding sites to hydroxyapatite of this protein were determined by a proteolytic experiment and an in vitro binding experiment using synthetic peptide analogues. Osteonectin was adsorbed on hydroxyapatite crystals and digested with trypsin. A peptide was left adsorbed on the crystal even after the digestion. The peptide was identified as an amino terminal peptide containing glutamic acid-rich sequences, which have been assumed to be possible hydroxyapatite-binding sites. Poly glutamic acid sequences were synthesized as models of the binding sites. Glu6 peptide was bound to the hydroxyapatite with a dissociation constant of 2.4 microM. Peptides containing fewer glutamic acids had lower affinity to the crystal. Effects of these peptides on in vitro mineralization were examined by a gel system in microtiter plates. The Glu6 peptide had a positive effect on the mineralization in this system, whereas Asp6 peptide had a negative effect. These effects indicate the presence of an interaction between these peptides and mineral crystals.

Adsorption↗
PubMed2005

Constitutive modeling of the densification and the grain growth of hydroxyapatite ceramics.

In the present work, constitutive models for densification and grain growth were employed to investigate the sintering behavior of pure hydroxyapatite ceramics. For densification study, lattice diffusion, grain-boundary diffusion, and interface reaction mechanisms, and for grain-growth study, surface diffusion mechanism, were considered respectively. Hydroxyapatite ceramics were pressurelessly sintered. The sintering results were discussed and compared with the modeling results. Based on the constitutive models employed and the experimental results obtained, grain-boundary diffusion was identified as the dominant mechanism for the densification of the investigated hydroxyapatite. The grain-growth model provided a good prediction to the grain growth of the investigated hydroxyapatite. The activation energies for densification and grain growth of hydroxyapatite ceramics were evaluated as 1150+/-40 and 1020+/-40 KJ mol(-1), respectively.

Biocompatible Materials↗
PubMed2006

Fabrication of hydroxyapatite ultra-thin layer on gold surface and its application for quartz crystal microbalance technique.

We present a method for coating gold quartz crystal microbalance with dissipation (QCM-D) sensor with ultra-thin layer of hydroxyapatite nanocrystals evenly covering and tightly bound to the surface. The hydroxyapatite layer shows a plate-like morphology and less than 20 nm in thickness. The hydroxyapatite sensor operated in liquid with high stability and sensitivity. The in-situ adsorption mechanism and conformational change of fibrinogen on gold, titanium and hydroxyapatite surfaces were investigated by QCM-D technique and Fourier-transform infrared spectroscopy. The change of secondary structures of fibrinogen adsorbed on the surfaces depended on the adsorbed amounts of protein. The secondary structure of fibrinogen adsorbed on the surfaces changes with increasing coverage. This is explained by repulsion among fibrinogens, affecting water structure and thus the strength of fibrinogen interactions on the surface. The study indicates that the hydroxyapatite sensor is applicable for qualitative and conformational analysis of protein adsorption.

Adsorption↗
PubMed2006

Copper and zinc decontamination from single- and binary-metal solutions using hydroxyapatite.

Toxic metals contamination of waters, soils and sediments can seriously affect plants, animals and human being. The bioavailability of metal ions can be reduced trapping them in minerals with low solubilities. This study investigated the sorption of aqueous Cu and Zn onto hydroxyapatite surfaces. Batch experiments were carried out using synthetic hydroxyapatite. The metals were applied as single or binary species, in a range of metal concentrations ranging from 0 to 8 mmol/L at 25+/-2 degrees C. The removal capacity of hydroxyapatite was 0.016-0.764 mmol of Cu/g and 0.015-0.725 mmol of Zn/g. In the Cu-Zn binary system, competitive metal sorption occurred with reduction of the removal capacity by 13-76% and 10-63% for Cu and Zn, respectively, compared to the single-metal systems. The sorption of Cu and Zn was well characterized by the Langmuir model. Heavy metal immobilization was attributed to a two-step mechanism: first rapid surface complexation and secondly partial dissolution of hydroxyapatite and ion exchange with Ca followed by the precipitation of a heavy metal-containing hydroxyapatite.

Adsorption↗
PubMed2006

Critical evaluation of the use of the hydroxyapatite as a stabilizing agent to reduce the mobility of Zn and Ni in sewage sludge amended soils.

The leachability of zinc (Zn) and nickel (Ni) was investigated in various soil types amended with sewage sludge and sewage sludge treated with hydroxyapatite. Sandy, clay and peat soils were investigated. For leachability tests, plastic columns (diameter 9 cm, height 50 cm) were filled with moist samples up to a height of 25 cm. Sewage sludge (1 kg) was mixed with 4.6 kg of clay and sandy soils and with 6.7 kg of peat soil. For sewage sludge mixtures treated with hydroxyapatite, 0.5 kg of the hydroxyapatite was added to 1 kg of the sewage sludge. Neutral (pH 7) and acid precipitation (pH 3.5) were applied. Acid precipitation was prepared from concentrated HNO(3), H(2)SO(4) and fresh doubly distilled water. The amount of precipitation corresponded to the average annual precipitation for the city of Ljubljana, Slovenia. It was divided into eight equal portions and applied sequentially on the top of the columns. The results indicated that the leachabilities of Zn in sewage sludge amended peat and clay soils were low (below 0.3% of total Zn content) and of Ni in sewage sludge amended sandy, clay and peat soil below 1.9% of total Ni content. In sewage sludge amended sandy soil, the leachability of Zn was higher (11% of Zn content). The pH of precipitation had no influence on the leachability of either metal. Treatment of sewage sludge with hydroxyapatite efficiently reduced the leachability of Zn in sewage sludge amended sandy soil (from 11% to 0.2% of total Zn content). In clay and peat sewage sludge amended soils, soil characteristics rather than hydroxyapatite treatment dominate Zn mobility.

Durapatite↗
PubMed1993

Hydroxyapatite orbital implant after enucleation--experience with 200 cases.

The recently introduced hydroxyapatite orbital implant was designed to provide improved motility of the prosthesis in patients who have undergone enucleation. To date, little has been written about the use of the hydroxyapatite orbital implant in eyes that harbored malignant neoplasms. We have performed hydroxyapatite orbital implantation in approximately 200 patients, including children as young as 1 month of age, who underwent enucleation primarily for malignant intraocular tumors. During a median follow-up of 24 months, no cases of orbital hemorrhage, orbital infection, implant extrusion, or implant migration have occurred. Three patients have had conjunctival erosion, which was successfully repaired. Motility of the socket and fornices has been excellent, and all patients have cosmetically satisfactory motility of the prosthesis. Use of the hydroxyapatite implant has had no adverse effect on the clinical course of the intraocular neoplasms, and it has not hindered postoperative evaluation for recurrent orbital tumor. Overall, the hydroxyapatite orbital implant seems to be well tolerated, provides improved motility of the prosthesis, and is associated with few complications.

Adult↗
PubMed2004

[Long term bone behavior in total primary hip arthroplasty with a fully hydroxyapatite-coated femoral stem: a continuous series of 120 cases with twelve years follow-up].

PURPOSE OF THE STUDY: Cementless hydroxyapatite-coated total prostheses have proven their reliability for more than twenty years. The intimate contact between the receiver bone and the implant allows "union" between the inert and living material. Osteointegration is maintained over time. The purpose of this work was to study the long-term reaction of femoral bone to wear debris after insertion of cementless hydroxyapatite implants. MATERIAL AND METHODS: One hundred twenty implants constituted a continuous series of total hip arthroplasties performed since 1989 for primary joint degeneration in patients followed for at least twelve years. The same femoral implant totally coated with hydroxyapatite was used for all patients in combination with a metal cup and a polyethylene insert. Twelve years later, twenty-seven patients had died, five were contacted by telephone, and three were lost to follow-up, giving a study population of 85 total hip arthroplasties with complete review and radiographic data. Clinical and radiological findings are reported with a measure of polyethylene wear and femoral bone behavior in contact with femoral implants. RESULTS: At twelve year follow-up, there were no cases of implant loosening. Clinical outcome was satisfactory, 90% of the hips were pain free. Radiologically, mean polyethylene wear was 0.1 mm per year with calcar changes (zone VII) in 27% and trochanter changes (zone I) in 14%. There was no evidence of osteolysis extension or granuloma formation in the shaft zone. Implant survival at twelve years was 99.1% (97.2-100%). DISCUSSION: Hydroxyapatite-coated cementless implants resist well to polyethylene wear debris. At twelve years, osteolysis caused by macrophage activation remained limited to zones I and VII. There appeared to be an intimate plug between the implant and the living bone preventing wear debris migration along the implant as was visualized along the entire length of the implant. Polyethylene wear was however real and the risk of osteolysis remains a threat to implant stability. Improved survival of hydroxyapatite-coated total hip implants will thus depend on improvements in the weight-bearing couple.

Aged↗
PubMed2003

Toughness, bonding and fluoride-release properties of hydroxyapatite-added glass ionomer cement.

Improving the mechanical strength of glass ionomer cement while preserving its favorable clinical properties such as fluoride release, bonding to tooth structure and biocompatibility is desirable. In this study, hydroxyapatite was incorporated into chemically setting glass ionomer cement and its effect on the fracture toughness, bonding to dentin and fluoride release was identified. Commercial glass ionomer cement (Fuji IX GP((R)) ) was the control and base material. Eight weight percent of hydroxyapatite was added into the glass ionomer powder. Specimens were fabricated and the fracture toughness, shear bond strength and eluted fluoride ion concentration were measured. Adding hydroxyapatite into the glass ionomer cement led to significantly higher fracture toughness after 15min and 24h from mixing. The hydroxyapatite-added cement also exhibited bond strength to dentin similar to that of the control from 15min to 56 days and consistent fluoride release for 13 weeks. SEM findings showed a cohesive type of fracture in the material for all specimens in both groups. These results indicate that hydroxyapatite-added glass ionomer cement has a potential as a reliable restorative material with improved fracture toughness, long-term bonding to dentin and unimpeded ability of sustained fluoride release.

Biocompatible Materials↗
PubMed1997

Processing of hydroxyapatite via microemulsion and emulsion routes.

Hydroxyapatite powders have been prepared by reacting CaCl2 and (NH4)2HPO4 in bicontinuous microemulsion, inverse microemulsion and emulsion, which have the same components as cyclohexane, non-ionic surfactant (NP5 + NP9) and aqueous solution. The characteristics of the resulting hydroxyapatite powders, such as the particle size, particle size distribution, chemical homogeneity and the degree of particle agglomeration, are strongly affected by the structure of the reaction medium. Both bicontinuous and inverse microemulsions led to the formation of much finer hydroxyapatite powders than that prepared from the emulsion composition. The two fine hydroxyapatite powders are sintered to a relative density of >95% theoretical density at 1000 degrees C, compared with a relative density of <73% theoretical density for the emulsion-derived one. The two microemulsion-derived hydroxyapatites also exhibit a higher sintered density and are more refined in grain size than that of the emulsion-derived one when sintered at 1200 degrees C for 2h.

Ceramics↗
PubMed1999

Adsorption of glycosaminoglycans onto hydroxyapatite using chromatography.

Proteoglycans are known to play an important role in the mineralization process, acting either as promoters or inhibitors. In this study the binding affinity of a variety of constituent glycosaminoglycan to hydroxyapatite was studied. Glycosaminoglycans (10-1000 microg ml(-1) in 0.02 M sodium acetate (pH 6.8) were constantly circulated through a hydroxyapatite column for 1 h. The total amount of glycosaminoglycan bound was determined by dimethylmethylene blue assay. The relative affinities of the different glycosaminoglycans remaining bound to hydroxyapatite was investigated by examining their release in a 0-1 M sodium phosphate gradient. Differences were noted between the desorption profiles of dermatan sulfate with two elution peaks and chondroitin 4-sulfate and chondroitin 6-sulfate each with a single peak. Dermatan sulfate and chondroitin 6-sulfate had a higher affinity for hydroxyapatite than chondroitin 4-sulfate possibly due to the presence of differing di-sulfated disaccharide ratios in the glycosaminoglycan chains. These findings suggest the presence of a variety of binding forms of each glycosaminoglycan or the differing orientation of these forms to yield different complexes with hydroxyapatite. The Ca2+ co-ordinates of the glycosaminoglycans are known to vary and may in part explain these findings.

Adsorption↗
PubMed2000

Preparation and characterisation of monoclinic hydroxyapatite and its precipitated carbonate apatite intermediate.

Five 100 g batches of a carbonate apatite (the intermediate) were produced by heating an aqueous slurry of CaCO3 and CaHPO4 with an overall Ca/P mole ratio of 5/3 with vigorous stirring. Each intermediate produced by boiling off water was heated in vacuum at 1100 degrees C to remove carbonate, then steamed at 900 degrees C to ensure complete hydroxylation. Comparison of calculated and observed X-ray diffraction patterns showed final products containing 50-100 wt% monoclinic hydroxyapatite (remainder hexagonal). Rietveld refinements in P6(3)/m gave structures similar to several hydroxyapatite standards, including NIST SRM 2910, although there was no evidence from X-ray diffraction that the latter was in the monoclinic form. Refinements from standards and final products were slightly different from published single crystal data for Holly Springs hydroxyapatite. This is attributed to known impurities in mineral hydroxyapatite and indicates that parameters from the Rietveld refinements are closer to the true values for pure hydroxyapatite. Rietveld refinements for intermediates showed small, but significant differences from the final product, the largest being in O1x, O2x and O(H)z. All P-O bond lengths were shorter than in the final product, resulting in a 3.2% lower PO4 tetrahedron volume. The occupancies of P and Ca(2) were reduced. These differences are attributed to partial replacement of PO4(3) by CO3(2-) ions.

Apatites↗
PubMed2000

Comparison of artificial eye amplitudes with acrylic and hydroxyapatite spherical enucleation implants.

PURPOSE: To compare artificial eye amplitudes in patients who randomly received either a hydroxyapatite or an acrylic, scleral-covered spherical implant after enucleation. DESIGN: Randomized, controlled trial. PARTICIPANTS: Thirty-four consecutive patients who underwent enucleation because of an intraocular melanoma and 21 healthy control participants from the hospital staff. METHODS: Eligible patients randomly received a hydroxyapatite or an acrylic, scleral-covered spherical orbital implant. Fourteen patients were fitted with a hydroxyapatite implant, and 16 were fitted with an acrylic implant. We measured horizontal and vertical saccadic amplitudes of both the artificial eye and the healthy eye. Measurements were performed with the magnetic search coils technique. Saccadic amplitudes of the artificial eye were compared with the healthy eye of the patient. The amplitudes of the healthy eyes were compared with saccadic amplitudes of control participants. The interval from surgery to measurements was at least 3 months in all patients. Saccadic gain (artificial eye and eye amplitude divided by target amplitude) and saccadic symmetry (artificial eye amplitude divided by healthy eye amplitude) were calculated. MAIN OUTCOME MEASURES: Saccadic gain and saccadic symmetry. RESULTS: The gain in the healthy eyes of the patients was comparable with the gain of the control eyes. Saccadic symmetry was 1.0 in control participants. In patients, it was 0.334 in horizontal saccades and 0.577 in vertical saccades. However, saccadic symmetry did not differ significantly between the acrylic group and the hydroxyapatite group (P: > 0.1 for any saccadic direction). Equivalence was detectable with a power more than 90% for horizontal saccades and more than 80% for vertical saccades. Curvilinearity was rejected for both patient groups and for all saccadic directions (P: > 0.5). CONCLUSIONS: When no motility peg is placed, acrylic and hydroxyapatite spherical implants yield comparable saccadic amplitudes of the artificial eye. Artificial eye amplitudes were markedly more restricted horizontally than vertically. In all saccadic directions, the relation between target amplitude and artificial eye amplitude was linear.

Acrylic Resins↗
PubMed2002

Primary banked scleral patch graft in the prevention of exposure of hydroxyapatite orbital implants.

PURPOSE: The most frequently reported complication of hydroxyapatite orbital implantation is exposure of the implant, which may result in infection or extrusion of the implant. This study describes the use of banked sclera patch grafts to prevent implant exposure. DESIGN: A retrospective noncomparative interventional case series. PARTICIPANTS: The procedure was performed on 110 patients over a 2-year period. Hydroxyapatite implantation was performed either at the time of enucleation or as a secondary procedure to correct postenucleation socket syndrome. INTERVENTION: A banked scleral patch graft from the second eye of the same donor was placed over a scleral-wrapped hydroxyapatite implant at the time of operation. The case records were reviewed retrospectively. OUTCOME MEASURES: The primary outcome measure was the number of patients who developed exposure of their hydroxyapatite implant. The number of patients who had a postoperative conjunctival wound dehiscence was also recorded. RESULTS: No patients developed exposure of the implant. A significant percentage of patients developed conjunctival wound dehiscence (33%). Further surgery was not required in any of these cases, because the dehiscence spontaneously reconjunctivalized over the surface of the scleral patch graft. CONCLUSIONS: Insertion of a banked scleral patch graft at the time of hydroxyapatite orbital implantation is an effective means of preventing implant exposure, even in more complex cases. It thereby reduces the morbidity resulting from the procedure and obviates the need for further surgery when there is breakdown of the conjunctival wound postoperatively.

Adolescent↗
PubMed1997

Complications of motility peg placement for the hydroxyapatite orbital implant.

PURPOSE: The hydroxyapatite implant is an ocular motility implant designed to provide natural movement of the artificial eye. The movement of the prosthesis is maximized when the implant is coupled to the prosthesis via a peg. The purpose of this study is to determine the complications of the hydroxyapatite motility peg and the factors related to those complications. DESIGN: Retrospective review of 47 cases over 5 years. METHODS: A retrospective review was performed on all cases of hydroxyapatite motility peg placement. The technique of hydroxyapatite and peg placement, follow-up details, and complications of the peg were recorded. RESULTS: The complications of peg placement included peg extrusion in 26% (12 of 47), nonspecific conjunctivitis in 6% (3 of 47), audible click in 6% (3 of 47), temporary excessive conjunctival edema in 4% (2 of 47), and temporary excessive postoperative pain in 4% (2 of 47). There were no cases of infection, persistent pain, persistent edema, or discharge at peg site. The median time interval from peg placement to extrusion was 16 months (range, 1-52 months). The only statistically significant factor related to peg extrusion was age over 50 years (P = 0.04). There was a trend toward peg extrusion with use of a nonsleeved peg (versus sleeved peg) (P = 0.10). The extrusion rate was 32% (12 of 38) for nonsleeved pegs and 0% (0 of 9) for sleeved pegs. Factors unrelated to peg extrusion were patient sex, prior ocular surgery or radiotherapy, presence of giant papillary conjunctivitis, time interval from enucleation to peg placement, and degree of implant vascularization on magnetic resonance imaging. Of the 12 nonsleeved pegs that extruded, a sleeved peg system was subsequently successfully placed in 5 patients, a nonsleeved peg in 1 patient, and 6 patients remained without a peg system. CONCLUSIONS: Hydroxyapatite motility pegs have relatively few complications except for extrusion. The rate of extrusion can be minimized by employing a sleeved peg rather than a nonsleeved peg system.

Adolescent↗
PubMed1999

Aspergillus mycetoma in a secondary hydroxyapatite orbital implant: a case report and literature review.

OBJECTIVE: The authors describe the first case report of a fungal abscess within a hydroxyapatite orbital implant in a patient who had undergone straightforward secondary hydroxyapatite implant surgery. DESIGN: Case report and literature review. INTERVENTION: Four months postoperatively after pegging and 17 months after original implant placement, chronic discharge and socket irritation became evident. Recurrent pyogenic granulomas were a problem, but no obvious area of dehiscence was present over the implant. The peg and sleeve were removed 31 months after pegging (44 months after original placement of the implant). The pain and discharge did not resolve, and the entire hydroxyapatite orbital implant was removed 45 months after sleeve placement and 58 months after initial implant placement. The pain and discharge settled rapidly. MAIN OUTCOME MEASURES: Cultures and histopathology. RESULTS: Results of bacterial cultures were negative. Results of histopathologic examination of the implant disclosed intertrabecular spaces with multiple clusters of organisms consistent with Aspergillus. CONCLUSIONS: Persistent orbital discomfort, discharge, and pyogenic granulomas after hydroxyapatite implantation should cause concern regarding potential implant infection. The authors have now shown that this implant infection could be bacterial or fungal in nature. This is essentially a new form of orbital Aspergillus, that of a chronic infection limited to a hydroxyapatite implant.

Abscess↗
PubMed1999

Complications associated with pegging hydroxyapatite orbital implants.

OBJECTIVE: Prior studies of hydroxyapatite orbital implant complications have primarily focused on complications of the implant itself with only occasional mention of the complications associated with the peg system. This in part may be because of a low rate of pegging and, thus, a small sample size to evaluate. Therefore, a full range of complications that can occur with pegging has not been presented. The objective of this study was to determine the complications associated with pegging and to discuss ways to manage them. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS/INTERVENTION: The authors analyzed all of the complications associated with pegging 165 of a possible 275 hydroxyapatite implants implanted by 2 surgeons over 7 years. MAIN OUTCOME MEASURES: The following data were recorded: type of surgery performed, size of implant used, type of hydroxyapatite used, peg system used, time of pegging, follow-up duration, problems encountered, and treatment. RESULTS: Sixty-two (37.5%) of the 165 patients who had pegged implants were found to have problems with their pegs. Twenty-one (33.8%) of the 62 patients with peg problems had more than 1 peg-related problem. Complications associated with pegging included discharge (37%; 23 of 62), pyogenic granulomas (30.6%; 19 of 62), peg falling out (29%; 18 of 62), poor transfer of movement (11.2%; 7 of 62), clicking (11.2%; 7 of 62), conjunctiva overgrowing peg (4.8%; 3 of 62), poor-fitting sleeve (4.8%; 3 of 62), part of sleeve shaft visible (4.8%; 3 of 62), peg drilled on an angle (4.8%; 3 of 62), hydroxyapatite visible around peg hole (3.2%; 2 of 62), peg drilled off-center (3.2%; 2 of 62), popping peg (3.2%; 2 of 62), and excess movement of peg (3.2%; 2 of 62). The most serious complication occurring in two individuals (3.2%) was implant infection requiring implant removal. CONCLUSION: There are several potential complications that can occur after pegging the hydroxyapatite implant. These problems are generally of a minor nature but often require additional patient visits that would not ordinarily have been required if the peg was not in place. The most serious peg problem is implant infection, which may necessitate implant removal. These potential peg problems should be reviewed with the patient before the procedure is performed.

Adolescent↗
PubMed1998

Nanocrystals of magnesium and fluoride substituted hydroxyapatite.

Hydroxyapatite nanocrystals synthetized in the presence of different concentrations of magnesium and fluoride ions in solutions--1, 5 and 10 at.% have been submitted to a structural and chemical characterization. The syntheses were carried out in the presence of low molecular weight polyacrylic acid, which has been verified to inhibit hydroxyapatite crystallization. The polyelectrolyte is adsorbed into the crystals during the synthesis and provokes a reduction of the mean crystal sizes. The reduction is greater along the direction orthogonal to the c-axis, suggesting a preferential adsorption of the polyelectrolyte on the crystalline faces parallel to the c-axis. Both magnesium and fluoride can be incorporated into the hydroxyapatite structure. On the basis of the values of the lattice constants and of the magnesium relative content of the solid phase, it can be suggested that probably just a part of magnesium is substituted for calcium, the remainder being adsorbed on the crystal surface. However, magnesium destabilizes the apatitic structure favouring its thermal conversion into beta-tricalcium phosphate, and displays an inhibiting effect on the crystallization of hydroxyapatite. This last effect is enhanced by the simultaneous presence of polyacrylic acid. Fluoride substitution for hydroxyl ions into hydroxyapatite structure induces a slight increase of the crystal sizes along the c-axis direction. The data indicate that the experimental approach can be successfully used to prepare nanoapatite with crystallinity, crystal dimensions, composition, structure and stability very close to those characteristics of biological apatites.

Durapatite↗