Formation of calcium deficient hydroxyapatite at near-physiological temperature

Fulmer, Mark; Martin, Roger I.; Brown, Paul

doi:10.1007/bf00705297

Cited by 84 publications

(62 citation statements)

References 13 publications

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“…The kinetics of HAp formation at 37.4°, 45°, 55°, and 75°C were monitored using isothermal conduction calorimetry 17 and by determining the variations in pH during reaction. In isothermal calorimetry, heat evolved during TCP hydrolysis is conducted across thermopiles that surround the calorimetric cell in which the reaction is occurring.…”

Section: Methodsmentioning

confidence: 99%

Fluoride uptake by hydroxyapatite formed by the hydrolysis of ?-tricalcium phosphate

Leamy

Brown

TenHuisen

et al. 1998

J. Biomed. Mater. Res.

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Although there is interest in forming synthetic analogs of hard tissues at physiologic temperature, significant gaps in knowledge exist with respect to the mechanisms by which precursor solids convert to apatites and also with respect to the apatite compositions that may be formed. In this study calcium-deficient HAp [Ca9(HPO4)(PO4)5OH] was prepared by hydrolysis of tricalcium phosphate (TCP), alpha-Ca3(PO4)2. The kinetics of HAp formation were studied as a function of temperature by isothermal calorimetry. TCP hydrolyzed completely within about 12 h, and the hydrolysis reaction evolved 133 kJ/mol of HAp formed. Although the kinetics of hydrolysis exhibited a strong temperature dependence, the mechanistic path taken appeared independent of temperature. The fluoridation of hydroxyapatite compositions having Ca/P ratios higher than 1.59 previously has been investigated. However, little work has been done on the fluoridation of more calcium-deficient hydroxyapatite. Ca9(HPO4)(PO4)5OH was formed at temperatures between 37.4 degrees and 55 degrees C to vary its morphology. These preparations then were reacted in NaF solution and the kinetics of fluoride incorporation studied. Solution chemical analyses were used to determine the amounts of fluoride incorporated. The extent of hydroxyl replacement by fluoride ranged from 17 to 72% and correlated with the surface area of the parent HAp.

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Section: Methodsmentioning

confidence: 99%

Fluoride uptake by hydroxyapatite formed by the hydrolysis of ?-tricalcium phosphate

Leamy

Brown

TenHuisen

et al. 1998

J. Biomed. Mater. Res.

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“…These values also fall on the curve reported by Williams [6] relating compressive strength to volume porosity~ Aoki [9] found transgranular fracture occurs below 4 vol % and intergranular fracture occurs above 9 vol % in sintered hydroxyapatite. Recently it has become possible to produce phase-pure hydroxyapatite by chemical reaction at low temperature [10,11]. Low temperature formation has typically resulted in hydroxyapatite monoliths which exhibit relatively poor mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Mechanical properties of hydroxyapatite formed at physiological temperature

Martin

Brown

1995

J Mater Sci: Mater Med

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121

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The mechanical properties of monoliths of calcium-deficient and carbonated hydroxyapatite formed by dissolution-precipitation reactions at 38 °C have been determined. Particulate solid reactants were mixed at liquid-to-solid weight ratios of 0.11 and 0.2 and pressed into various configurations on which mechanical tests were carried out. Testing was performed on wet specimens which had been allowed to react for 8 h by which time phase-pure hydroxyapatite had formed. Calcium-deficient hydroxyapatite produced at a liquid-to-solids ratio of 0.11 exhibited a tensile strength as high as 18 MPa, an average compressive strength of 174 MPa and a Young's modulus of 6 GPa. These values were lower when a larger proportion of water (liquid-to-solid 0.2) was used in sample preparation. However, the compressive strengths of calcium-deficient hydroxyapatite prepared at 38 °C are comparable to the compressive strengths of sintered hydroxyapatite containing an equivalent total porosity. Carbonated hydroxyapatite showed mechanical properties inferior to those exhibited by calcium-deficient material. These differences appear to be related to the microstructural variations between these compositions.

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“…Os biomateriais empregados neste estudo foram obtidos pelo método de síntese via úmida, e foi demonstrado por Fulmer, Martin & Brown (1992), que a hidroxiapatita obtida por este método possui características similares às do tecido ósseo e dentá-rio, diferentemente da hidroxiapatita sintetizada à altas temperaturas. Aos 60 dias, a HA demonstrou moderado preenchimento de lacunas osteocíticas e neoformação de tecido ósseo, e leve presença de osteoclastos e formação de tecido mieloide, indicando boa osteoindução e boa capacidade osteorregenerativa.…”

Section: Discussionunclassified

Neoformação óssea e osteointegração de biomateriais micro e nanoestruturados em ovinos

et al. 2015

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Bone replacement is often required in veterinary clinics and hospitals routine, even because fractures, bone tumors or any orthopedic disease that entail in bone loss. In this sense, biomaterials capable of promoting this substitution, avoiding the use of bone grafts or transplants have been searched. The aim of this study was evaluated the osteoregenerative capacity of biomaterials in different compositions, implanted in sheep's tibia. Eight female, mongrel sheeps, 12 months old, weighting 28,5±7,4kg were obtained for this study. Three bone defects, 6mm each, in both tibias, a total of six bone defects, were produced, being four of them treated with four different types of biomaterials and two with autogenous bone grafts, as a control group. The biomaterials implanted were: hydroxyapatite (HA), beta-tricalcium phosphate (TCP-β), hydroxyapatite/beta-tricalcium phosphate 60:40 (HA/TCP-β 60:40) and the nanocomposite hydroxyapatite and alumina (HA/Al 2 O 3 5%). The animals were allocated in two groups: Group 60 (n=04), in which the animals were euthanized sixty days after the implantation of the biomaterials and Group 90 (n=04), in which the animals were euthanized ninety days after the procedure. Were performed radiograph images on the preoperative period, immediate postoperative and at 30, 60 and 90 days of postoperative period, to excluded any previously disease or postoperative complications that could compromise this research. After euthanasia, the tibias were collected for macro and microscopic evaluation, which was accessed by scanning electron microscopy (SEM) and optic microscopy. The results suggest that HA, TCP-β and HA/TCP-β present a great osteoregenerative capacity. The last one seems to be better for a long-term outcome, due its best control in the solubilization and releasing of calcium and phosphates ions through the biological environment during bone formation. The nanocomposite HA/Al 2 O 3 5% didn't show a good response on this study, and we suggest new researches to better evaluate the potential and applicability of this new biomaterial. We concluded that HA, TCP-β and HA/TCP-β 60:40 presented excellent capacity of bone repair, and could be used as bone substituts; the association HA/TCP-β (60:40) is superior due his intermediary velocity of absortion comparing to HA and TCP-β isolated, providing adequate supporting to the neoformed tissue; the HA/Al 2 O 3 5% showed incompatibility, 1 Recebido em 26 de junho de 2014.Aceito para publicação em 21 de dezembro de 2014.

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Formation of calcium deficient hydroxyapatite at near-physiological temperature

Cited by 84 publications

References 13 publications

Fluoride uptake by hydroxyapatite formed by the hydrolysis of ?-tricalcium phosphate

Fluoride uptake by hydroxyapatite formed by the hydrolysis of ?-tricalcium phosphate

Mechanical properties of hydroxyapatite formed at physiological temperature

Neoformação óssea e osteointegração de biomateriais micro e nanoestruturados em ovinos

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