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PubMed1986

Mandibular augmentation with hydroxyapatite.

This study investigated the success of hydroxyapatite mandibular augmentation in nine patients, the histologic response around hydroxyapatite, and the effect of collagen in localizing hydroxyapatite. It can be concluded that hydroxyapatite is biocompatible, causes minimal inflammatory response, and can increase denture retention. However, a large number of patients develop lip paresthesia, and hydroxyapatite migrates. Paresthesia might be avoided by altering the surgical technique to avoid manipulation of the mental nerve, and collagen might be a useful binder to confine hydroxyapatite particles. Further studies are in progress to develop new methods to place the hydroxyapatite and materials to confine it.

Adult↗

PubMed1993

Thermal behaviour of hydroxyapatite intended for medical applications.

Four commercial hydroxyapatites (both natural and synthetic) were tested to assess transformations of the chemical and crystalline structure following variation of temperature from 20 to 1600 degrees C. The thermal behaviour of hydroxyapatite is relevant for biomedical applications such as plasma spraying of metallic implants. Thermogravimetric analysis showed a weight loss from each hydroxyapatite specimen, due to a release of structural H2O molecules; all the specimens up to 1300 degrees C were made of crystalline hydroxyapatite, determined by X-ray diffraction; at 1470 degrees C they were made of both hydroxyapatite and calcium phosphate, but at 1570 degrees C of calcium phosphate exclusively. The diffractograms of the hydroxyapatite coatings showed the same peaks as the original powders, so at the chosen plasma-spray procedure level no new phases were formed. The peak height was nevertheless lower in the plasma-sprayed hydroxyapatites for all interplanar spacing values, which indicated a lower degree of crystallinity, associated with a random structure derived from an alteration to the original crystalline network.

Hydroxyapatites↗

PubMed1996

Osteoinduction in porous hydroxyapatite implanted in heterotopic sites of different animal models.

Previous studies have demonstrated the induction of bone in coral-derived porous hydroxyapatite when implanted intramuscularly in baboons. This hydroxyapatite-induced bone differentiation model was used to study the effect of different animal species on heterotopic bone formation. Porous hydroxyapatite, obtained after hydrothermal conversion of the calcium carbonate exoskeleton of coral (genus Goniopora), was implanted in the rectus abdominis of adult rabbits, dogs and baboons (Papio ursinus). Specimens were harvested on day 90 after implantation and subjected to histological and histomorphometrical analysis. Minimal amounts of bone formed in hydroxyapatite specimens harvested from rabbits and dogs. Substantial bone differentiation did occur, however, in hydroxyapatite specimens harvested from the rectus abdominis of the baboons. In primates, the porous hydroxyapatite, as used in this study, may act as a solid matrix for adsorption, storage and controlled release of circulating or locally produced bone morphogenetic proteins, which locally initiate bone formation. The results of this study on heterotopic bone formation in porous hydroxyapatite underscore the importance of primate models in biomaterial research, which should be exploited for the formulation of porous substrata with intrinsic osteoinductive activity.

Animals↗

PubMed1996

Geometry of porous hydroxyapatite implants influences osteogenesis in baboons (Papio ursinus).

Coral-derived porous hydroxyapatite disks of two geometric configurations were implanted in 16 calvarial defects, 25 mm in diameter, prepared in eight subadult male baboons (Papio ursinus). To determine whether the orientation of the exoskeletal microstructures (corallites) influences bone ingrowth and osteogenesis, hydroxyapatite disks were prepared by cutting the coral either longitudinally or transversally, to obtain two distinct implant geometries defined by the orientation of the corallites. In the same animals, 16 defects were left untreated to assess the regeneration potential of the subadult baboon calvaria. Disks of both geometric configurations were also implanted in heterotopic intramuscular sites to investigate their osteoinductive potential. Histomorphometric analysis on undecalcified and decalcified sections prepared from specimens harvested on day 90 after surgery showed that greater amounts of bone formed in porous hydroxyapatites cut in the longitudinal plane when compared with hydroxyapatites cut in the transversal plane (p < 0.01). Bone formed in hydroxyapatite specimens harvested from the intramuscular sites, but no difference in bone formation was found between the two geometric configurations. Untreated defects showed limited osteogenesis, comparable with a previous series of untreated defects identically prepared in adult baboon calvariae. This finding suggests that skeletally mature, adult primates may not be a requirement for evaluation of craniofacial bone substitutes. These results in a primate indicate that hydroxyapatite disks are able to induce bone differentiation when implanted in intramuscular sites, and that the geometric configuration of the porous hydroxyapatite influences bone ingrowth and osteogenesis in orthotopic calvarial sites. This should be taken into consideration when designing porous bone substitutes for craniofacial applications.

Age Factors↗

PubMed1992

Osteogenin, a bone morphogenetic protein, adsorbed on porous hydroxyapatite substrata, induces rapid bone differentiation in calvarial defects of adult primates.

Osteogenin, a bone morphogenetic protein, in conjunction with insoluble collagenous bone matrix initiates local endochondral bone differentiation by induction in vivo. This study, by exploiting the affinity of native osteogenin for hydroxyapatite, was designed to construct a delivery system for the expression of the biologic activity of osteogenin in nonhealing calvarial defects of adult primates. After exposure of the calvaria, 64 cranial defects, 25 mm in diameter, were prepared in 16 adult male baboons (Papio ursinus). Defects were implanted with disks of porous nonresorbable and resorbable hydroxyapatite substrata obtained after hydrothermal conversion of calcium carbonate exoskeletons of corals. In each animal, one disk of each hydroxyapatite preparation was treated with osteogenin isolated and purified from baboon bone matrix after sequential chromatography on heparin-Sepharose, hydroxyapatite, and Sephacryl S-200 gel filtration columns. The remaining two defects were implanted with one disk of each hydroxyapatite preparation without osteogenin as control. Histomorphometry on decalcified sections prepared on days 30 and 90 showed superior osteogenesis in osteogenin-treated nonresorbable hydroxyapatite specimens as compared with controls. On day 90, substantial bone formation also had occurred in control nonresorbable hydroxyapatite specimens. On day 90, but not on day 30, significantly greater amounts of bone had formed in osteogenin-treated resorbable specimens as compared with resorbable controls. Overall, resorbable substrata performed poorly when compared with nonresorbable substrata, perhaps due to a premature dissolution of the implants. These results provide evidence that the biologic activity of osteogenin can be restored and delivered by a substratum other than the organic collagenous matrix, inducing rapid bone differentiation in calvarial defects of adult nonhuman primates. The adsorption strategy of osteogenin on porous inorganic nonimmunogenic substrata may help to design appropriate osteogenic delivery systems for craniofacial and orthopedic applications in humans.

Adsorption↗

PubMed1984

Fluoride enhancement of chlorhexidine uptake by hydroxyapatite and enamel powders.

The purpose of the present study was to examine the in vitro adsorption of chlorhexidine and fluoride to hydroxyapatite and tooth enamel powders. Samples of hydroxyapatite or enamel powder were suspended in aqueous solutions of chlorhexidine gluconate 2.0; chlorhexidine acetate 1.5%; sodium fluoride of various concentrations (0.2%, 1%, 2%) and mixtures of sodium fluoride and chlorhexidine. The data obtained in the study show that chlorhexidine and fluoride adsorb to hydroxyapatite and tooth enamel in vitro. Furthermore, the amount of fluoride adsorbed to hydroxyapatite is reduced in the presence of chlorhexidine in the solution. A probable explanation for this effect may be that there is a competitive adsorption of fluoride and chlorhexidine on to the same binding sites on the hydroxyapatite. Additionally, the presence of fluoride dramatically increases the affinity of chlorhexidine for hydroxyapatite. The fact that fluoride strongly enhanced the adsorption of chlorhexidine to hydroxyapatite and enamel, indicates that fluoride may be of clinical interest beyond the prevention of caries.

Adsorption↗

PubMed1998

A method of cranioplasty using coralline hydroxyapatite.

INTRODUCTION: Current cranioplasty materials include autologous or homologous bone grafts, wire mesh and methyl methacrylate, either alone or in combination. However, each material has its own unique disadvantages. Although hydroxyapatite has been used extensively in other specialties as a bone substitute, the coralline form has rarely been used to repair cranial bone defects. Coralline hydroxyapatite, similar to that found in bone, provides a matrix on which living tissue can form and grow. Because it is an ideal bioimplant, a method of cranioplasty using coralline hydroxyapatite was employed. METHODS: The hydroxyapatite granules are mixed with Avitene and autologous blood to form a paste which can be contoured as needed. RESULTS: Over the past few years, we have used hydroxyapatite either alone or in combination with tantalum mesh in 19 pediatric patients for a variety of conditions. The cosmetic results were good to excellent. Furthermore, postoperative CT scans have documented bony substitution of the hydroxyapatite granules. Follow-up ranged from 1 to 43 months with a mean of 26 months. CONCLUSION: In neurosurgical procedures when a bone substitute is needed, hydroxyapatite is an effective alternative to other currently available materials.

Bone Substitutes↗

PubMed1986

The influence of ossein-hydroxyapatite compound ('Ossopan') on the healing of a bone defect.

A study was undertaken in 60 adult rabbits in order to determine the effects of ossein-hydroxyapatite compound on bone healing. Standardized bony defects were produced in the distal femoral epiphyses, after which animals were randomized into four equal groups. An untreated group served as a control. One group received ossein-hydroxyapatite compound, 830 mg per day, a second group received bone mineral (ossein-hydroxyapatite compound reduced to ash, to remove organic constituents), 510 mg per day, and a third group received calcium carbonate, 650 mg per day. A series of fluorescent vital markers was administered to the animals from the 7th to the 32nd day after production of the defect. A third of the animals in each group were sacrificed 35, 56 and 84 days, respectively, after induction of the defect. Histological sections of the region of the bone defect were examined with a fluorescence microscope and resulting photomicrographs were scored with respect to degree of fluorescence, nature and degree of defect filling and structure of the newly formed bone. All three active treatment groups resulted in significantly improved mineralization as compared with the untreated control group. Treatment with ossein-hydroxyapatite compound, but not the other two active treatments, resulted in significant improvements in the pattern and quality of bone healing, particularly when assessed at 56 or 84 days after induction of the bone defect. These results indicate that ossein-hydroxyapatite compound has a beneficial effect on the process of bone healing but that this effect is lost if the organic components of the compound are destroyed or if pure calcium carbonate treatment is substituted. This strongly suggests that organic components of ossein-hydroxyapatite compound have osteogenic effects, enhancing the utilization of the mineral intake, and is consistent with previous experimental findings. It is suggested, therefore, that ossein-hydroxyapatite compound has considerable clinical potential and should be regarded as having specific, sophisticated effects on bone metabolism, rather than as a simple dietary mineral supplement.

Animals↗

PubMed1991

[Tympanoplasty with mastoid obliteration using hydroxyapatite granules for aural cholesteatoma--a clinical and experimental study].

Hydroxyapatite granules were employed for mastoid obliteration in cases of aural cholesteatoma. After eradicating a cholesteatoma by the canal-down technique, the canal wall was reconstructed with cortical bone chips, and the mastoid cavity was obliterated with hydroxyapatite granules. Tympanoplasty by this technique was performed on 48 ears with aural cholesteatoma. There was no recurrence of cholesteatoma during the follow-up period of two years after surgery. One case of residual cholesteatoma was found in the mesotympanum. There were two cases in which the hydroxyapatite granules became exposed through the posterior canal skin. An air-bone gap of less than 20 dB was achieved in 73% of all the patients. Experimental studies in guinea pigs have demonstrated that hydroxyapatite granules do not undergo morphological changes in and are tightly interdigitated with newly formed bone tissue growing from bulla bone one year after hydroxyapatite implantation in the temporal bullae. The newly-formed bone showed incomplete osteon structures. Excellent biocompatibility and bone adaptability of hydroxyapatite granules were demonstrated experimentally. It is concluded that tympanoplasty with mastoid obliteration using hydroxyapatite is safe and useful for avoiding mastoid cavity problems and for preventing the recurrence of cholesteatoma.

Adolescent↗

PubMed1989

[Histological investigation of improvement of mandibular atrophy for application of hydroxyapatite dental implant].

UNLABELLED: The purpose of this study was to investigate the possibility of applying the hydroxyapatite dental implant to the atrophic mandible after alveolar ridge augmentation using hydroxyapatite granules. The lower P3, P4 and M1 of 3 mongrel dogs were extracted. At 30 weeks, alveolar ridge augmentation was performed with porous hydroxyapatite granules. Sixteen weeks later, hydroxyapatite dental implants were applied to the area. And 4 weeks later, the specimens were taken out and fixed by 10% formalin alcohol. They were embedded in polyester resin and prepared into undecalcified sections. And the sections were stained with toluidine blue to observe the surrounding tissue of the dental implants histologically under light microscopy. RESULTS: 1) Bone formation was seen in most part of the intergranular spaces. However, in the buccal area, there were some spaces in which bone formation was entirely not observed. 2) At 4 weeks after implantation, almost all of the surface of the hydroxyapatite dental implants was attached to the surrounding osseous tissues. But in some parts of the implant surface, especially the buccal, fibrous connective tissue was seen. 3) These results provide a basis for the technique of hydroxyapatite dental implantation with porous hydroxyapatite granules in the atrophic mandibles after alveolar ridge augmentation.

Animals↗

PubMed1991

Clinical and radiographic experience with a hydroxyapatite-coated titanium plasma-sprayed porous implant.

The use of bioactive materials recently has given increased hope to achieving adequate fixation in cementless total hip arthroplasty. Hydroxyapatite, one of the most biocompatible materials known, interacts with surrounding bone and forms a chemical bond with the bone, rather than a mechanical microinterlock via bioingrowth. There is direct bonding of bone and the hydroxyapatite, as opposed to the development of an intervening fibrous tissue layer between the implant and the bone. Recent use of hydroxyapatite-coated implants has shown that very strong bonds with living bone occur within a relatively short period of time. In this article, 53 primary, cementless total hip arthroplasties, all performed by or under the direction of a codesigner of the prosthetic system, are reviewed. The average age of the patients at arthroplasty was 51 years; the follow-up period averaged 17 months. The preliminary results achieved in this group of patients were compared with those achieved in 50 patients who received the identical porous coated implant without hydroxyapatite. The preoperative diagnoses, Harris Hip Scores, and patient demographics were similar for both groups. A comparison of clinical results showed that patients with the hydroxyapatite-coated femoral implants experienced more rapid clinical improvement in the first 6 to 10 weeks after arthroplasty than the patients with the identical prosthesis without hydroxyapatite coating. Radiographically, in the hydroxyapatite group, there have been no femoral or acetabular component failures, and no instances of femoral component subsidence or acetabular component migration.

Female↗

PubMed1979

SnF2 treatment of enamel, hydroxyapatite or brushite at 37 degrees C and 50 degrees C: an infra-red investigation.

The effect of 4% SnF2 on brushite, hydroxyapatite and powdered bovine enamel applied for short, 15 or 30 minute, periods was investigated using infra-red spectroscopy. It was found that brushite was converted into a fluoridated hydroxyapatite, a reaction which was both time and temperature dependent. The reactions of hydroxyapatite and powdered enamel with SnF2 were similar. There was a drop in the OH- peak intesities. X-ray diffraction analysis of these samples showed that F- ions occupied mainly OH positions in the hydroxyapatite lattice structure. In all reactions an increase in temperature from 37 degrees C to 50 degrees C increased the reaction speed by at least a factor 2. The most probable result of in vivi SnF2 application on sound enamel is the formation of a fluoridated hydroxyapatite together wity stannous complexes and amorphous CaF2. In demineralized areas some of the brushite is converted into a fluoridated hydroxyapatite as is some of the remaining hydroxyapatite. In the more protected area of an enamel lesion these reactions may well continue for some time after the topical fluoride application; Sn2F3PO4 may also therefore be formed.

Animals↗

PubMed1993

Treatment of extensive cranial bone defects using computer-designed hydroxyapatite ceramics and periosteal flaps.

We performed cranioplasty using hydroxyapatite ceramics and periosteal flaps in three patients with extensive cranial bone defects. These defects were left after post-brain surgery infection forced the removal of cranial bone. Hydroxyapatite ceramics made by using computer-aided design from three-dimensional computed tomographic image data were implanted in these patients. The defects were relatively large (the largest was 16.5 x 7.5 cm) and had a high degree of curvature. Three pieces were required in one patient, although one piece was sufficient in the other two patients. The surgical technique consisted of removal of the epidural granulation tissue, exposure of the cranial bone defect site, and shaping of the hydroxyapatite ceramics to fit the defect entirely, followed by the implantation of the hydroxyapatite ceramics. In anticipation of induction of the bone to hydroxyapatite, we covered the hydroxyapatite ceramics with periosteal flaps of cranial bones; however, based on only these three patients, our knowledge of the ossification-promoting effect is incomplete. More clinical cases should be investigated to evaluate further the clinical efficacy of this method for treatment. As we have reported here, the treatment of cranial bone defects by using computer-designed hydroxyapatite ceramics and a periosteal flap is safe and highly effective.

Adult↗

PubMed1995

[Bone formation and mechanical properties of the cancellous bone defect site filled with hydroxyapatite granules].

We investigated the co-relationships of the granule size of hydroxyapatite with the amount of new bone formation and with mechanical properties at the bone defect site filled with hydroxyapatite granules. In this experimental study, cylindrical bone defects 6.4 mm in diameter and about 1 cm in depth were prepared in the bilateral femoral condyles and in the tibial condyles of large albino rabbits (body weight 5.1-7.3 kg), filled with three types of hydroxyapatite granules 0.3-0.6 mm, 0.6-1.0 mm, and 1.0-2.0 mm in diameter, and examined after 2, 4, and 8 weeks after sacrificing the animals. Two animals (4 limbs) each were examined for the same granule size and the same period after filling. Undecalcified sections of the tibia at the defect site were examined histologically, and the volume and surface of hydroxyapatite, the volume of new bone, the surface of the new bone in contact with hydroxyapatite, and the percent of this surface relative to the entire surface of hydroxyapatite were determined. Columnar specimens 6.0 mm in diameter and 5.0 mm in length were prepared from the defect sites of the femur, compressed at a deformation rate of 2.4 mm/min, and the failure stress, stiffness, and energy absorption were calculated from the load-deformation curve. The normal cancellous bone from 2 unoperated animals (4 limbs) and bone defect sites not filled with hydroxyapatite granules of 2 animals (4 limbs) were examined as controls. A greater amount of new bone was formed as the granule size was smaller. After 8 weeks, the failure stress and energy absorption were higher as the granule size was smaller, and the mechanical properties of the bone defect sites filled with 0.3-0.6 mm granules were similar to those of normal cancellous bone.

Animals↗

PubMed2002

Hydroxyapatite deposition by electrophoresis on titanium sheets with different surface finishing.

Hydroxyapatite coatings are commonly applied to metallic biomedical implants to accelerate osseointegration. These coatings, usually produced by plasma spray techniques, can be obtained by alternative processes, like biomimetic process, electrolytic deposition, or electrophoretic process as well. Electrophoretic deposition of hydroxyapatite exhibits several advantages like simplicity and low cost. In this article, titanium sheets with three different surface finishing were coated with hydroxyapatite by using electrophoresis. Surface treatments include: (1) abrading with SiC paper; (2) abrading with SiC paper plus electrolytic etch with H3PO4 solution; and (3) blasting with alumina powder followed by etch with a solution containing H2O2 and HF. Stoichiometric hydroxyapatite was used to coat titanium sheets. Blasted samples were also coated using a calcium-deficient hydroxyapatite. SEM, XRD, and FTIR were employed to characterize titanium substrates and coatings produced. Results show that electrophoretic process can produce a uniform thin layer, satisfactorily adhered, of hydroxyapatite on treated titanium samples. Furthermore, sintering at 800 degrees C do not promote the decomposition of calcium-deficient hydroxyapatite.

Biocompatible Materials↗

PubMed1994

Comparative effect of calcium hydroxide and hydroxyapatite on the cellular activity of human pulp fibroblasts in vitro.

When, in vivo, calcium hydroxide [Ca(OH)2] or hydroxyapatite are used as dental pulp-capping agents, a reparative dentine bridge is observed. New hard tissue is formed directly on the hydroxyapatite, whereas a characteristic necrotic area appears under Ca(OH)2. The differing pulpal reactions to these two capping agents suggest differing cell responses. After isolation and selection of human pulp fibroblasts in vitro, the cells were characterized by their morphology, their high alkaline phosphatase specific activity, and their synthesis of type I and III collagens and fibronectin. They were then incubated in the presence of either hydroxyapatite (1 mg/ml) or Ca(OH)2 (0.8 mg/ml). With Ca(OH)2, the cells exhibited dramatical alterations in morphology, DNA synthesis, alkaline phosphatase activity and protein synthesis, in accordance with the necrosis observed in vivo. With hydroxyapatite, phagocytic activity of pulpal fibroblasts toward hydroxyapatite particles (< 10 microns) was seen. As a consequence, DNA synthesis was affected. This inhibitory effect was not due to cell damage, as demonstrated by increased [3H]-proline and [3H]-leucine incorporation by the cells. There was also an inhibitory effect of hydroxyapatite on alkaline phosphatase activity, suggesting that the pulp fibroblasts were not in a differentiation stage. In conclusion, compared to the effects of Ca(OH)2 on human pulp fibroblasts, these data are consistent with the biocompatibility of hydroxyapatite previously described in vivo and testify to the occurrence of a biological response elicited by this synthetic biomaterial.

Adolescent↗

PubMed2006

Hydroxyapatite grafting promotes new bone formation and osseointegration of smooth titanium implants.

Titanium is the ideal metal for intra-osseous dental implants. It permits the natural formation of an oxide layer on its surface and thereby it prevents the release of potentially toxic molecules. New formation of bone around implants, partially placed into the bone marrow cavity, is a gradual process that runs from the endosteum to the surface of the implant. Deposition of hydroxyapatite crystals on collagen type I fibrils is initiated by acidic proteins and leads to bone mineralization. This study analyzed the effects of hydroxyapatite upon peri-implant bone formation after insertion of smooth titanium implants. Screw-shaped smooth titanium implants of 3.75 mm thickness and 8.5 mm length were inserted into the metaphysis of rabbit tibia, either together with bovine hydroxyapatite into the right tibia or in controls without hydroxyapatite into the left tibia. Polyfluorochrome tracers (alizarin complex, calcein, tetracycline) were injected subcutaneously at different time intervals after implantation to evaluate the time frame of bone new formation over a period of 8 weeks. All samples were processed for histology and analyzed by fluorescence and polarizing microscopy. Our results showed a higher quantity of mature type I collagen fibers around implants and an acceleration of bone formation in the presence of hydroxyapatite. Mainly immature organic matrix was formed at the surface of implants in controls. The presence of hydroxyapatite seems to promote the maturation of collagen fibers surrounding the titanium implants and to support osteoconduction. Moreover, new formation of bone was faster in all samples where implants were inserted together with hydroxyapatite.

Animals↗

PubMed2005

Plasma transglutaminase factor XIII induces microvessel ingrowth into biodegradable hydroxyapatite implants in rats.

Coagulation factor XIII is a member of the transglutaminase-family. Transgluaminases cross-link either fibrin monomers in blood coagulation or extracellular proteins in extracellular matrix formation. In early stages of bone healing migration and proliferation of endothelial cells lead to formation of new vessels. The aim of this study was to investigate the angiogenetic activity of plasma factor XIII in bone defects filled with nanoparticulate hydroxyapatite paste. A critical size defect was created in the tibial head of rats which was not filled in group I. In group II the defect was filled with hydroxyapatite paste, and in group III with hydroxyapatite paste enriched with factor XIII. Ten days after surgery angiogenesis in the defects was assessed using immunohistochemistry and confocal laser scanning microscopy. Ac16 antibody was used to detect activation of factor XIII into factor XIIIA. In defects without biomaterial (group I) vessel-rich connective tissue and diffuse distribution of capillaries was observed. In defects filled with pure hydroxyapatite (group II) formation of capillaries was limited to the host bone-hydroxyapatite interface. In contrast, addition of plasma factor XIII to hydroxyapatite (group III) stimulated formation of vessels within the biomaterial. The current study reveals that factor XIII can improve angiogenesis in hydroxyapatite.

Absorbable Implants↗