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PubMed1986

Biomaterial aspects of Interpore-200 porous hydroxyapatite.

Interpore-200 is the product of over 11 years of continuous research and development. It has been investigated at over 25 research centers in a wide variety of animal and human implant settings, including alveolar ridge augmentation, periodontics, and orthognathic reconstructions. The biomaterial aspects of Interpore-200 show the following: Interpore-200 has a highly interconnected, three-dimensional porosity that is uniform and consistent. The hydroxyapatite manufactured from marine corals is biocompatible and nontoxic. Interpore-200 is essentially pure hydroxyapatite, with the balance consisting of tricalcium phosphate. Interpore-200 is approximately 55 to 65 per cent porous with nominal pore diameters of 200 micron. Unlike nonporous materials, Interpore-200 is osteoconductive and results, when placed next to a viable bone, in an advancing front of bone into the implant. From 50 to 88 per cent of the porosity within the implant is filled with woven and lamellar bone within 3 months. Moreover, the surfaces of Interpore-200 are intimately bonded with the bone tissue. The biomechanical properties of Interpore-200 blocks are similar to those of a cancellous bone graft. Once ingrown with vascularized bone tissue, the defect site is, in effect, restored. Interpore-200 adequately matches the elastic properties of bone so that stresses necessary to maintain healthy bone are transmitted throughout the regenerated region. Extensive animal and clinical studies have shown that nonporous implants or implants without interconnected porosity can result in aberrant mineralization, stress shielding, low fatigue strength, and bulk displacement. Hydroxyapatite with interconnected porosity like Interpore-200 reacts differently than materials with limited or no porosity. In animals, Interpore-200 exhibits 0 to 5 per cent biodegradation per year. Moreover, this minimal biodegradation is compensated by regeneration of bone. These studies have now been extended for 4 years. Interpore-200 and its ingrown bone are remodeled in response to the same chemical and biomechanical forces that remodel normal bone. Therefore, Interpore-200 responds in accordance to Wolff's law. Having achieved an optimal combination of biomaterial (hydroxyapatite) in an ideal porous structure (replamineform), Interpore-200 fulfills the expectation of early researchers in the basic sciences who demonstrated that an interconnected porous material is better tolerated by the body than the same material in solid form.(ABSTRACT TRUNCATED AT 400 WORDS)

Alveolar Ridge Augmentation↗
PubMed1997

Particulate bioglass compared with hydroxyapatite as a bone graft substitute.

Bioactive ceramics, notably hydroxyapatite, have been used clinically in various situations in which bone augmentation and restoration are required. Particulate material has been used either alone or in conjunction with freeze dried or autologous bone, with variable clinical success. In this study a bioactive glass, 45S5 Bioglass, has been compared with hydroxyapatite in an animal model to discover whether the 2 major disadvantages of hydroxyapatite may be overcome. These are the difficulty of placing and retaining the particulate in the defect and the length of time needed before full bony restoration is achieved. Bioglass is shown to be easy to manipulate and hemostatic and allows full restoration of bone in 2 weeks, rather than the 12 weeks needed for the particulate hydroxyapatite to produce a comparable response. The Bioglass particulate is used up in the process, and any problems that may be associated with the production of a composite of bone and biomaterial are avoided in the fully restored bone. In any procedure that requires bony augmentation, this rapid response to Bioglass is expected to provide a clinical advantage.

Animals↗
PubMed1998

[Long-term radiologic evolution of coral implanted in cancellous bone of the lower limb. Madreporic coral versus coral hydroxyapatite].

PURPOSE: The study aimed to compare two successive series of procedure using first pieces of natural madreporic coral, then coralline hydroxyapatite in traumatology. The goal of this work was to evaluate long term radiological features of absorption and influencing factors. MATERIAL: Within six years, 65 pieces were used; only impaction articular fracture on the lateral tibial plateau (31) and calcaneum fractures (23) were included 21 cases completed inclusion criteria. As there were 3 secondary infections, 18 had therefore, an aseptic evolution and were included in this series. METHODS: Absorption was evaluated in five degrees according to the volume of the remaining piece on X-rays. We also took into consideration the position of the pieces and the amount of surfaces in contact with cancellous bone. RESULTS: Among the 18 pieces followed up for more than 19 months (average 40), there were 4 sequestrations (1 tibia, 3 calcaneum), all were natural madreporic coral, the others presented osteointegration. Only natural madreporic coral pieces were absorbed, but never completely and the absorption was slow (3 to 7 years) and never complete. A radiolucent line was present in 7 out of 10 pieces of madreporic coral and none around coralline hydroxyapatite. Three developed favorably. Four were sequestred. Number of surfaces in contact with cancellous bone was correlated with osteointegration. DISCUSSION: The calcium carbonate which makes up the natural madreporic coral pieces is the site of destruction by osteoclasts. The radiolucent line is the specific witness of this biochemical activity. The radiolucent line proceeds sequestrations. No substitute of coralline hydroxyapatite has presented the same sign of peripheral absorption or sequestration. Coralline hydroxyapatite could be the correct coralline material to fill cancellous defect after elevation of an articular depression. In every case, the piece of coral must be fitted in contact with the cancellous bone in the depth of the bone. Conditions of osteoconduction of madreporic coral must be reconsidered. The degree and speed of peripheral absorption must be controlled before weight bearing is allowed.

Adult↗
PubMedDate not supplied

Reconstruction of the frontal sinus and frontofacial skeleton with hydroxyapatite cement.

OBJECTIVE: To evaluate the efficacy of a newly developed biomaterial, hydroxyapatite cement, for use in frontal sinus and anterior craniofacial skeletal reconstruction. DESIGN: A nonrandomized patient cohort that was compared with historical controls of standard treatment with methyl methacrylate implants. SETTING: Craniofacial reconstructive surgery services at 3 referral health care centers. Eligible patients had frontal-cranial defects limited to a maximum size of 25 cm2. Patients were randomly selected volunteers with preexistent, acute traumatic or acute surgically induced defects of the frontal sinus and anterior craniofacial skeleton. All patients provided informed consent, and the study was approved by the 3 institutional review boards. Forty patients underwent reconstruction of defects of the anterior craniofacial region, and 38 of these patients were evaluable at 24 months. MAIN OUTCOME MEASURES: Hydroxyapatite cement was used to reconstruct full-thickness anterior craniofacial skull defects. Standard surgical techniques were used to place all implants. The primary outcome measurement was maintenance of implant volume determined at 24 months by computed tomography and clinical examination. Secondary outcome measures included incidence of complications and infections necessitating implant removal. RESULTS: Of the 38 evaluable patients, 31 had successful reconstructions at the end of the study, for an overall success of 82% for frontal sinus and frontofacial region reconstruction. Seven patients underwent explantation, 5 for surgical access to the site. Two implants were removed because of infection in the wound, for an overall incidence of approximately 5%. Explant biopsy specimens confirmed implant osseointegration and vascularization. CONCLUSIONS: Hydroxyapatite cement successfully reconstructs full-thickness defects of the frontal sinus and frontofacial region at 24 months. Hydroxyapatite cement appears to be superior to acrylic implants for frontal-cranial reconstruction and by allowing implant osseointegration with improved biocompatibility.

Adult↗
PubMed1999

Postoperative rotation of hydroxyapatite enucleation implants.

OBJECTIVE: To determine the incidence of postoperative rotation of flattened hydroxyapatite enucleation implants. METHODS: A retrospective review of patients receiving flattened hydroxyapatite enucleation implants was performed to determine the incidence and severity of postoperative implant misalignment. RESULTS: Flattened hydroxyapatite implants had been placed in 16 patients. Five were noted to have postoperative implant rotation, which was detected between 11 and 60.3 months following enucleation. The malposition was mild, inconsistent, and clinically insignificant in 2 patients. The remaining 3 patients demonstrated marked implant misalignment, which likely would have been functionally significant had motility pegs been placed. CONCLUSIONS: Postoperative rotation of flattened hydroxyapatite implants may occur late after enucleation. Such implant modification should not be performed in patients with preexisting strabismus, who have a higher incidence of this complication.

Coated Materials, Biocompatible↗
PubMed1998

Thermal processing of hydroxyapatite for coating production.

Thermally processed hydroxyapatite coatings used on dental implants and hip prostheses for enhanced fixation may typically consist of a number of chemical and structural phases. These phases affect coating performance and tissue attachment. Hydroxyapatite was plasma sprayed to examine the phase evolution during processing. Coatings were examined with X-ray diffraction and elemental analysis. Results indicate that phase transformations are produced by (a) preferential removal of hydroxyl and phosphate leading to a change in melt composition, and (b) the high cooling rate due to the thermal spray process. Hydroxyl group removal promotes the amorphous phase and oxyapatite. Further heating produces a less viscous melt facilitating decomposition of hydroxyapatite to tricalcium and tetracalcium phosphate. Phosphate removal during flight produces a more calcium-rich melt preferring tetracalcium phosphate and calcium oxide formation. A proposed model shows the phase location within the lamellae of these coatings. Coating processes must thus prevent removal of hydroxide and phosphate during processing to maximize the hydroxyapatite content.

Biocompatible Materials↗
PubMed1999

Chemical characterization of silicon-substituted hydroxyapatite.

Bioceramic specimens have been prepared by incorporating a small amount of silicon (0.4 wt %) into the structure of hydroxyapatite [Ca10(PO4)6(OH)2, HA] via an aqueous precipitation reaction to produce a silicon-substituted hydroxyapatite (Si-HA). The results of chemical analysis confirmed the proposed substitution of the silicon (or silicate) ion for the phosphorus (or phosphate) ion in hydroxyapatite. The Si-HA was produced by first preparing a silicon-substituted apatite (Si-Ap) by a precipitation process. A single-phase Si-HA was obtained by heating/calcining the as-prepared Si-Ap to temperatures above 700 degrees C; no secondary phases, such as tricalcium phosphate (TCP), tetracalcium phosphate (TeCP), or calcium oxide (CaO), were observed by X-ray diffraction analysis. Although the X-ray diffraction patterns of Si-HA and stoichiometric HA appeared to be identical, refinement of the diffraction data revealed some small structural differences between the two materials. The silicon substitution in the HA lattice resulted in a small decrease in the a axis and an increase in the c axis of the unit cell. This substitution also caused a decrease in the number of hydroxyl (OH) groups in the unit cell, which was expected from the proposed substitution mechanism. The incorporation of silicon in the HA lattice resulted in an increase in the distortion of the PO4 tetrahedra, indicated by an increase in the distortion index. Analysis of the Si-HA by Fourier transform infrared (FTIR) spectroscopy indicated that although the amount of silicon incorporated into the HA lattice was small, silicon substitution appeared to affect the FTIR spectra of HA, in particular the P-O vibrational bands. The results demonstrate that phase-pure silicon-substituted hydroxyapatite may be prepared using a simple precipitation technique.

Biocompatible Materials↗
PubMed2000

Quantitative comparison of bone growth behavior in granules of Bioglass, A-W glass-ceramic, and hydroxyapatite.

The hypothesis that bioactive glass particulate increases the rate of bone proliferation over that of synthetic hydroxyapatite and bioactive glass-ceramic was tested in these experiments. Three types of bioactive particles-45S5 Bioglass(R), synthetic hydroxyapatite, and A-W glass-ceramic-were implanted in 6-mm-diameter holes drilled in the femoral condyles of mature rabbits. Bone growth rate was measured using an image processor. 45S5 Bioglass(R) produced bone more rapidly than either A-W glass-ceramic or hydroxyapatite. At the later time periods, 45S5 Bioglass(R) was resorbed more quickly than A-W glass-ceramic. Synthetic hydroxyapatite was not resorbed at all. Backscattered electron imaging suggested that the resorption process occurred by solution-mediated dissolution, which produced chemical changes in the enclosed particulate. It was concluded that the rate of bone growth correlates with the rate of dissolution of silica as the particles resorb.

Animals↗
PubMed2006

Effects of interconnecting porous structure of hydroxyapatite ceramics on interface between grafted tendon and ceramics.

The purpose of this study was to evaluate histologically and biomechanically the interface between porous hydroxyapatite ceramics and a tendon grafted into ceramics, and to compare the interface in two ceramics with different porous structures: interconnected porous calcium hydroxyapatite ceramics (IP-CHA) with an effective porosity index (interpore diameter > 20 microm) of 63.6%, and porous calcium hydroxyapatite ceramics with less interconnection (HA-L) with an effective porosity index of 5.5%. The tendon-IP-CHA complex and the tendon-HA-L complex were implanted into the bone defects made in both knees of rabbits. With IP-CHA, abundant fibrous tissue, including vessels and collagen fiber continuity, was observed inside interface-region pores. The amount of osseous tissue in interface-region pores increased over time, and at 24 weeks after operation, the tendon was in direct contact with the osseous tissue in IP-CHA. With HA-L, the amount of fibrous tissue in interface-region pores was low and did not increase. The results of biomechanical analysis revealed that the maximum tendon pull-out load from IP-CHA was significantly higher than that from HA-L. With the porous hydroxyapatite ceramics having highly interconnecting porous structure, a bioactive interface was achieved between ceramics and grafted tendon. On the basis of these results, we conclude that bone defects, including tendon insertion, can be reconstructed using IP-CHA.

Animals↗
PubMed1996

Osteogenic potential of allogeneic rat marrow cells in porous hydroxyapatite ceramics: a histological study.

Hydroxyapatite ceramics facilitate osteogenesis but cannot induce bone formation by themselves. We studied the feasibility of bone formation supported by allogeneic bone marrow cells in porous hydroxyapatite ceramics. Coralline hydroxyapatite discs were soaked in a marrow cell suspension harvested from either ACI (RT1a), Lewis (RT1(1)), or Fischer 344 (RT1(1v)) male rats, and these discs were implanted subcutaneously into 56 male Fischer 344 rats. FK-506 (tacrolimus hydrate), an immunosuppressant, or saline was injected intramuscularly into the recipients every day for 2 weeks after surgery, and additional injections were given to 19 of the rats every 2 days for 2 more weeks. Neither of the mismatched major (ACI rat) or minor (Lewis rat) marrow cell transplants showed any bone formation without administration of FK-506. However, in rats treated with FK-506, bone formed in the pores of all the three types of ceramics implanted, which each contained the marrow cells from one of the three kinds of rats used. There were no differences among the three groups of donors with regard to the bone formation ratio. We previously reported that subcutaneous implantation of porous hydroxyapatite combined with isogeneic marrow cells resulted in consistent bone formation, even at ectopic sites. Since it would be difficult to harvest a large number of autologous marrow cells in clinical cases, we attempted to use allogeneic marrow cells and have shown the allogeneic murine marrow cells to have osteogenic potential.

Animals↗
PubMed2002

Sintering mechanism of the CaF2 on hydroxyapatite by a 10.6-l microm CO2 laser.

BACKGROUND AND OBJECTIVES: Laser has been reported as a heat source for melting and re-crystallization. Occurring at about 1100 degrees C, the melting of surface dental enamel along with re-crystallization might have an assistant role in the therapy of hypersensitive tooth, apical sealing of endodontic surgery in dentistry, preventive dentistry for pit and fissure sealing, and fluoridation. For laser to be accepted in clinical applications, it is desired that, studies must show the incorporation of CaF(2) into hydroxyapatite could reduce the sintering temperature for the sake of safety. STUDY DESIGN/MATERIALS AND METHODS: In this study, the Sharplan 20XJ CO(2) laser with 10.6- microm wavelength was set under the following parameters: power, 5 W; repetitive mode, 0.1 second; beam, focused. Fluorite was added to hydroxyapatite as a synthetic compound to lower the sintering temperature. Human dental enamel without caries was used for in vitro sintering test. Scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier transforming infrared spectroscopy (FTIR), and differential thermal analysis/thermogravimetric analysis (DAT/TGA) were used for the investigation of sintering mechanism of CaF(2). RESULTS: Fusion between hexagonal shape crystals and cubic shape crystals (CaF(2)) were observed under SEM study. Hexagonal shape crystals indicated the formation of fluorapatite under XRD analysis. Under FTIR study, we examined reductions of water (3445 cm(-1)) and hydroxyl bands (3567 and 627 cm(-1)) in irradiated compounds. From the DTA pattern of synthetic compound, it showed the endothermic reaction reaching its peak point around 1180 +/- 20 degrees C. It was attributed to the phase transformation and/or initial melting. CONCLUSIONS: In this study, we proposed the interrelationship of the eutectics between initiator (CaF(2)) and the reaction product (calcium hydroxide) that reduced the sintering temperature. It appeared that the co-eutectics interacted to reduce the sintering temperature of hydroxyapatite below 800 degrees C and that the key eutectic was calcium hydroxide. The clinical feasibility of the melting and re-crystallization of hydroxyapatite under 10.6-microm CO(2) laser would be therefore enhanced.

Biocompatible Materials↗
PubMed1999

Preparation of Polymer Particles Coated with Hydroxyapatite.

Polymer particles coated with hydroxyapatite were prepared by treating Pd0 immobilized polystyrene-co-acrylic acid particles in aqueous CaCl2 and NaH2PO2 solutions. Hydroxyapatite coating took place at neutral to alkaline pH conditions, and the homogeneous growth of the hydroxyapatite layer on the surface of polymer particles was observed at relatively low temperature (30-50 degrees C). The thickness of the hydroxyapatite layer increased with reaction time. Copyright 1999 Academic Press.

Journal Article↗
PubMed2004

[Mechanical failure of porous hydroxyapatite ceramics 7.5 years after implantation in the proximal tibial].

The treatment of osseous defects is widely established in the elderly. The number of positive reports on the successful application of bovine as well as coralline hydroxyapatite ceramics has continuously increased during the last few years. In trauma surgery hydroxyapatite ceramics are most commonly applied in metaphyseal defects evoked by traumatic fractures of the long bones. The bovine and coralline materials applied are biocompatible and exhibit an interconnecting porous system. Good osteoconductive properties of such materials have repeatedly been demonstrated. Due to possible harmful effects caused by abrasion of the material, intra-articular application should be strictly avoided. Biological degradation of the materials does not occur even during long-term follow-up. The application of hydroxyapatite ceramics was introduced at our institution in 1992. Since then, no adverse events have been observed and only a few relevant complications were described in the literature. We report on a patient revealing a mechanical failure of a bovine hydroxyapatite (Endobon) 7.5 years after implantation into a metaphyseal defect of the proximal tibia caused by a traumatic fracture.

Athletic Injuries↗
PubMed1999

Effects of recombinant amelogenin on hydroxyapatite formation in vitro.

To determine the role of amelogenin in the mineralization of dental enamel, the effects of the recombinant mouse amelogenin rM179 on in vitro hydroxyapatite formation have been studied. In a steady-state agarose gel assay for hydroxyapatite nucleation, rM179 lacked significant activity at concentrations up to 300 microgram/ml. In an autotitration assay for inhibition of de novo hydroxyapatite formation, rM179 had no significant activity at concentrations up to 30 microgram/ml. Using selected-area dark-field electron microscopy, it was shown that rM179, at concentrations up to 30 microgram/ml, did not significantly affect the length of hydroxyapatite crystals formed in steady-state agarose gels. These findings suggest that amelogenins do not possess the specific crystal-modulating properties characteristic of certain acidic mineralized tissue proteins proteins.

Amelogenin↗
PubMed2000

Effects of phytate and pyrophosphate on brushite and hydroxyapatite crystallization. Comparison with the action of other polyphosphates.

This is a comparative study of the effects of phytate and pyrophosphate and other polyphosphates on the crystallization of hydroxyapatite and brushite, the most frequent calcium phosphates involved in calcium oxalate urolithiasis. Brushite and hydroxyapatite crystal formation was studied in synthetic urine, through kinetic-turbidimetric measurements that allowed evaluation of the inhibitory effects on crystallization of insoluble salts. The effectiveness in preventing brushite crystallization decreases in the sequence phytate > polyphosphate > EDTPO > etidronate > pyrophosphate > triphosphate > medronate; whereas the order of effectiveness in preventing hydroxyapatite crystallization was EDTPO > etidronate = pyrophosphate > triphosphate > medronate > polyphosphate > phytate. Phytate, a natural inhibitor in urine, most effectively blocked brushite precipitation (1.21x10(-5) M prevented crystallization during time periods of at least 1 h), and pyrophosphate was the natural inhibitor that most effectively blocked hydroxyapatite precipitation (2.87x10(-6) M prevented crystallization during time periods of at least 1 h). This demonstrates that low excretion of these substances would pose a risk of renal lithiasis.

Calcium Phosphates↗
PubMed2005

Interfacial interaction of tartaric acid with hydroxyapatite and enamel.

The purpose of this study was to investigate the interfacial interaction of tartaric acid with hydroxyapatite and enamel. Hydroxyapatite particles were mixed with 15% (w/v) alcohol-aqueous (1:1) solution of tartaric acid for 72 h. After the mixture, the filtrate was separated from the solid. The filtrate, the solid, hydroxyapatite, and tartaric acid were dried for FTIR and XRD analysis. Enamel disks etched with tartaric acid for 60 s were analyzed by attenuated total reflectance (ATR). Enamel disks etched with 15% tartaric acid for 15, 30, 60, 120 s were analyzed by SEM. FTIR spectra showed carboxylate in the solid and in subtraction spectra. ATR spectra revealed carboxylate on the enamel surfaces. XRD data indicated the formation of calcium tartrate and calcium hydrogen phosphate after the reaction of tartaric acid with hydroxyapatite. SEM observations revealed typical decalcification of the periphery of the enamel rods due tartaric acid etching. It is concluded that tartaric acid can decalcify and chemisorb onto HA simultaneously, hence, tartaric acid could be used as etchant and ingredient of self-etching primers in adhesive dentistry.

Acid Etching, Dental↗
PubMed2006

Cytotoxicity study of plasma-sprayed hydroxyapatite coating on high nitrogen austenitic stainless steels.

Stainless steel has been frequently used for temporary implants but its use as permanent implants is restricted due to its low pitting corrosion resistance. Nitrogen additions to these steels improve both mechanical properties and corrosion resistance, particularly the pitting and crevice corrosion resistance. Many reports concerning allergic reactions caused by nickel led to the development of nickel free stainless steel; it has excellent mechanical properties and very high corrosion resistance. On the other hand, stainless steels are biologically tolerated and no chemical bonds are formed between the steel and the bone tissue. Hydroxyapatite coatings deposited on stainless steels improve osseointegration, due their capacity to form chemical bonds (bioactive fixation) with the bone tissue. In this work hydroxyapatite coatings were plasma-sprayed on three austenitic stainless steels: ASTM-F138, ASTM-F1586 and the nickel-free Böhler-P558. The coatings were analyzed by SEM and XDR. The cytotoxicity of the coatings/steels was studied using the neutral red uptake method by quantitative evaluation of cell viability. The three uncoated stainless steels and the hydroxyapatite coated Böhler-P558 did not have any toxic effect on the cell culture. The hydroxyapatite coated ASTM-F138 and ASTM-F1586 stainless steels presented cytotoxicity indexes (IC50%) lower than 50% and high nickel contents in the extracts.

Animals↗
PubMed2006

In-situ hardening hydroxyapatite-based scaffold for bone repair.

Musculoskeletal conditions are becoming a major health concern because of an aging population and sports- and traffic-related injuries. While sintered hydroxyapatite implants require machining, calcium phosphate cement (CPC) bone repair material is moldable, self-hardens in situ, and has excellent osteoconductivity. In the present work, new approaches for developing strong and macroporous scaffolds of CPC were tested. Relationships were determined between scaffold porosity and strength, elastic modulus and fracture toughness. A biocompatible and biodegradable polymer (chitosan) and a water-soluble porogen (mannitol) were incorporated into CPC: Chitosan to make the material stronger, fast-setting and anti-washout; and mannitol to create macropores. Flexural strength, elastic modulus, and fracture toughness were measured as functions of mannitol mass fraction in CPC from 0% to 75%. After mannitol dissolution in a physiological solution, macropores were formed in CPC in the shapes of the original entrapped mannitol crystals, with diameters of 50 microm to 200 microm for cell infiltration and bone ingrowth. The resulting porosity in CPC ranged from 34.4% to 83.3% volume fraction. At 70.2% porosity, the hydroxyapatite scaffold possessed flexural strength (mean +/- sd; n = 6) of (2.5 +/- 0.2) MPa and elastic modulus of (0.71 +/- 0.10) GPa. These values were within the range for sintered porous hydroxyapatite and cancellous bone. Predictive equations were established by regression power-law fitting to the measured data (R(2) > 0.98) that described the relationships between scaffold porosity and strength, elastic modulus and fracture toughness. In conclusion, a new graft composition was developed that could be delivered during surgery in the form of a paste to harden in situ in the bone site to form macroporous hydroxyapatite. Compared to conventional CPC without macropores, the increased macroporosity of the new apatite scaffold may help facilitate implant fixation and tissue ingrowth.

Aging↗