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PubMedDate not supplied

Differences in solubility of two types of heterogeneous fluoridated hydroxyapatites.

Two types of heterogeneous fluoridated apatites, H-F and F-H, were synthesized by supplying fluoride over the whole range of the degree of fluoridation (X = 0-1.0) during the initial or final half of the experimental period. Although X-ray diffraction patterns and scanning electron microscopy (SEM) photographs of both H-F and F-H type apatites were not significantly different, high-resolution transmission electron microscopy (HR-TEM) showed quite different features; H-F type apatites were elongated hexagons with electron beam damage in the core, while F-H type apatites were rather wider hexagons and approached the typical hexagon of fluorapatite. These results supported the previous speculations on the two different types of heterogeneous fluoridated hydroxyapatites synthesized with fluoride concentration stoichiometrically equivalent to that of fluorapatite: hydroxyapatite covered with fluorapatite and fluorapatite covered with hydroxyapatite. The apparent solubility of H-F type apatites decreased with increases in degree of fluoridation, while that of F-H type apatites decreased markedly and then remained almost constant.

Apatites↗

PubMed1992

Influence of coralline hydroxyapatite used as an ocular implant on the dose distribution of external beam photon radiation therapy.

Coralline hydroxyapatite spheres are used as buried integrated ocular implants after enucleation or evisceration surgery. Because such implants are used after surgery for intraocular malignancy and because some patients may require postoperative radiation therapy for orbital tumor recurrence, the radiation attenuation characteristics of the implant are of interest. The authors evaluated the attenuation and scattering properties of coralline hydroxyapatite implants using a 4 MV photon beam and film dosimetry. Optical density analyses indicate that coralline hydroxyapatite implants have no significant influence on the attenuation or scattering properties of the photon beam. As such, there is no basis for concern that such implants might adversely affect external beam photon irradiation.

Absorptiometry, Photon↗

PubMed1993

Uncemented acetabular components. Histologic analysis of retrieved hydroxyapatite-coated and porous implants.

Histologic sections of five hydroxyapatite-coated acetabular components retrieved at autopsy (2 dual geometry and 3 threaded cup designs) were analyzed, and the extent and pattern of bone apposition were compared with that of an uncoated, porous (beaded) dual geometry acetabular cup that had been removed for repeated dislocations. The results show hydroxyapatite and bone apposition most prominent in areas of likely load transmission, primarily around the peripheral rim of the dual-geometry cups and at the peaks of the threads of the screw cups. Hydroxyapatite and bone may have been removed by remodeling from the grooves between the threads. Although no significant wear debris was identified, the screw holes were incompletely covered by bone. The dual-geometry designs generally showed somewhat more bone apposition than the threaded cups, but all implants demonstrated less bone than might have been predicted from radiographs.

Adult↗

PubMed1989

Human tissue response to porous hydroxyapatite implants. A case report.

Histological examination of 2 porous hydroxyapatite implants removed from a patient showed a pattern of ossification similar to that reported in a previous animal study. New bone was laid down on the surface of the hydroxyapatite but did not progress to occupy all the pores. Although porous hydroxyapatite blocks are biocompatible and well tolerated by the tissues, they are not recommended for augmentation of the resorbed alveolar ridge where the overlying mucosa is thin and atrophic, because of the risk of mucosal dehiscence and implant exposure. They are suitable in situations where they are deeply buried in the tissues and not subjected to direct trauma.

Alveolar Ridge Augmentation↗

PubMed2003

Hydroxyapatite cement (BoneSource) for repair of critical sized calvarian defects--an experimental study.

AIM: In an experimental study the hydroxyapatite cement BoneSource was tested for the ability in relation to the defect size and for its resorption properties. MATERIAL AND METHODS: In an animal study, BoneSource was applied to repair bicortical defects of different sizes in frontal bones of six Goettingen minipigs. The area was evaluated radiographically and histologically 12, 18 and 40 weeks postoperatively. RESULTS: After 40 weeks approximately 90% of the hydroxyapatite cement had been resorbed and replaced with bone. After 12 weeks, approximately 30% had been degraded, and 40% after 18 weeks. In small bone defects, the mucosa of the frontal sinus lined the bone substitute (BoneSource). In the reconstruction of large areas, a membrane was used to stabilize the material. Despite this membranous support, BoneSource material prolapsed into the frontal sinus. DISCUSSION: Hydroxyapatite cement is for the repair of bone defects. It can be moulded to shape the reconstruction. Its use is limited by the defect size and the need for a dry bed. CONCLUSION: BoneSource is well suited to repair small defects with proven high biocompatibility. However, in large defects, the material is not sufficiently stable.

Animals↗

PubMed2005

Synthesis of hydroxyapatite crystals using amino acid-capped gold nanoparticles as a scaffold.

Inorganic composites are of special interest for biomedical applications such as in dental and bone implants wherein the ability to modulate the morphology and size of the inorganic crystals is important. One interesting possibility to control the size of inorganic crystals is to grow them on nanoparticles. We report here the use of surface-modified gold nanoparticles as templates for the growth of hydroxyapatite crystals. Crystal growth is promoted by a monolayer of aspartic acid bound to the surface of the gold nanoparticles; the carboxylate ions in aspartic acid are excellent binging sites for Ca(2+) ions. Isothermal titration calorimetry studies of Ca(2+) ion binding with aspartic acid-capped gold nanoparticles indicates that the process is entropically driven and that screening of the negative charge by the metal ions leads to their aggregation. The aggregates of gold nanoparticles are believed to be responsible for assembly of the platelike hydroxyapatite crystals into quasi-spherical superstructures. Control experiments using uncapped gold nanoparticles and pure aspartic acid indicate that the amino acid bound to the nanogold surface plays a key role in inducing and directing hydroxyapatite crystal growth.

Amino Acids↗

PubMed1996

The hydroxyapatite orbital implant: a prospective study.

The hydroxyapatite orbital implant was first released for use as an orbital implant in humans in August 1989. It has been shown to be well tolerated, providing good motility of the artificial eye with a low complication rate when used as a primary implant. This prospective study evaluated the hydroxyapatite orbital implant used as both a primary and a secondary implant. Sixty patients were implanted between October 1992 and November 1994, 28 being implanted as a primary procedure at the time of enucleation or evisceration, and 32 as a secondary procedure. Seven patients underwent second-stage drilling and pegging of the implant. The mean follow-up time was 13 months (range 2-26 months). A standardised operative and post-operative protocol was followed. The patients were evaluated post-operatively for the amount of enophthalmos, degree of upper lid sulcus deformity, motility of the prosthesis, location of the implant in the socket, socket status and the presence or absence of discharge, position of the drill hole and coverage of the implant. Complications and their management were documented. Both patient and surgeon made a subjective assessment of cosmesis and the patient's satisfaction with the overall result was noted. The results of this study show the hydroxyapatite orbital implant to provide excellent motility of the artificial eye and good cosmesis with a low rate of complications when used both as a primary and as a secondary implant.

Adolescent↗

PubMed1998

The controlled release of antibiotic by hydroxyapatite: anionic collagen composites.

Major problems with the treatment of osteomyelitis are associated with poor antibiotic distribution at the site of infection due to limited blood circulation to the skeletal tissue. Improved treatment procedures have been used in drug delivery systems that include bioceramics and natural and synthetic polymers. This work reports the development of anionic collagen:hydroxyapatite composite paste for sustained antibiotic release. Antibiotic release by the composite was characterized by two steps. In the first, 15.0+/-4.9% was released in the first 5 h (n = 53) by a normal Fick diffusion mechanism. In the second step, only 16.8+/-2.2% was released after 7 days. In conclusion, hydroxyapatite:anionic collagen composite can be an efficient support for sustained antibiotic release in the treatment of osteomyelitis because most of the antibiotic release may be associated with composite bioresorption, thus permitting antibiotic release throughout the healing process. Hydroxyapatite:anionic collagen paste showed good biocompatibility associated with bone tissue growth with material still being observed after 60 days from the time of implants.

Animals↗

PubMed1999

Augmentation of distal radius fracture fixation with coralline hydroxyapatite bone graft substitute.

We implanted coralline hydroxyapatite bone graft as a substitute for autogenous bone graft to support the reduced articular surface of 21 consecutive patients with distal radius fractures treated with external fixation and K-wires. The purpose of this single-cohort retrospective study was to report the outcomes of treatment with this material, complications associated with its use, and its efficacy in supporting the articular surface reduction. Eighteen patients were available for independent evaluation of motion, subjective outcome analysis, and final radiographic analysis at an average of 35 months after surgery. Wrist motion averaged 90% of the uninjured wrist and grip strength measured 75% of the uninjured side. Results in 17 of the 18 cases were rated as good or excellent by the criteria of Gartland and Werley; 12 by the criteria of Green and O'Brien. Seventeen had good or excellent radiographic results by the modified Lidstrom radiographic scoring system. The average DASH functional/symptom score was 90.3 (maximum, 100). Radiographic parameters were restored to an average of 12 mm radial length, 4 degrees volar tilt, 23 degrees radial inclination, and 0.6 mm positive ulnar variance. Articular reduction was maintained in all patients. A complication related to the use of coral was a 0.5 mm prominence of coralline hydroxyapatite beyond the subchondral line at the radiocarpal joint in 1 patient, which was not present on final radiographs. Coralline hydroxyapatite was effective at maintaining articular surface reduction when used in combination with external fixation and K-wires and had a safety profile comparable to other forms of treatment.

Bone Substitutes↗

PubMedDate not supplied

[Short-term results (2-5 years) of type Furlong hydroxyapatite-coated hip endoprosthesis].

The short term clinical and radiological results of a hydroxyapatite-coated hip prosthesis with bonding osteogenesis on the hydroxyapatite ceramic and bony tissue reaction had to be studied. 233 patients who had hip replacement were followed up for two to five years and assessed radiologically and by the Merle D'Aubigné rating. Primary total hip arthroplasty as well as revision arthroplasty show sufficient clinical results. Tight pain and aseptic loosening of the stem did not occur. Hydroxyapatite-coating and contour for the Furlong hip prosthesis show a reliable short term anchorage.

Adult↗

PubMed1993

Nucleation of hydroxyapatite by bone sialoprotein.

Bone sialoprotein (BSP) and osteopontin, the major phosphorylated proteins of mammalian bone, have been proposed to function in the initiation of mineralization. To test this hypothesis, the effects of BSP and osteopontin on hydroxyapatite crystal formation were determined by using a steady-state agarose gel system. At low calcium phosphate concentrations, no accumulation of calcium and phosphate occurred in control gels or gels containing osteopontin. Gels containing BSP at 1-5 micrograms/ml, however, exhibited a visible precipitation band and significantly elevated Ca + PO4 contents. By powder x-ray diffraction, the precipitate formed in the presence of BSP was shown to be hydroxyapatite. These findings suggest that bone sialoprotein may be involved in the nucleation of hydroxyapatite at the mineralization front of bone.

Animals↗

PubMed1982

Inhibition of lectin-binding to saliva-treated hydroxyapatite, to buccal epithelial cells, and to erythrocytes by salivary components.

The influence of human saliva on the binding of several lectins to saliva-treated hydroxyapatite surfaces which mimic the teeth, to buccal epithelial cells, and to erythrocytes was determined. Clarified whole saliva inhibited binding of 3H-labeled concanavalin A, wheat germ, soy bean, Ulex europaeus, and peanut agglutinins to saliva-treated hydroxyapatite by 75 to 95%, depending on lectin concentration used. Different fractions of saliva-inhibited binding of different lectins. For example, salivary mucins reduced the binding of wheat germ agglutinin to saliva-treated hydroxyapatite, but they did not significantly affect binding of other lectins studied. Components of saliva also inhibited lectin-mediated hemagglutination. Using an indirect enzyme-linked immunoassay, wheat germ and peanut agglutinins were found to bind in a specific manner to human buccal epithelial cells, and this was also greatly reduced by saliva. The data suggest that one of the major functions of salivary and other alimentary secretions may be to reduce the extent of interaction of dietary lectins with mucosal surfaces.

Arachis↗

PubMed1992

Comparison of inorganic bovine bone mineral particles with porous hydroxyapatite granules and cranial bone dust in the reconstruction of full-thickness skull defect.

Twenty adult rabbits were used to evaluate the biocompatibility and osteoconductivity of Bio-Oss, an inorganic bovine bone mineral, in the reconstruction of full-thickness skull defects. Skull defects were treated with either autogenous bone dust, porous hydroxyapatite granules, Bio-Oss particles, or were left untreated as controls. Histological examination of decalcified sections showed incorporation of Bio-Oss into the host tissue without a significant inflammatory reaction. Measurement of the profile area occupied by the bone revealed that Bio-Oss, hydroxyapatite, and the control had the same amount of bone ingrowth, whereas autogenous bone dust produced a greater amount of bone (p < 0.01). We conclude that Bio-Oss, like porous hydroxyapatite, has sufficient osteoconductive properties and can also be used as a bone substitute material.

Animals↗

PubMed1997

A method for repairing zygomatic arch fractures using a hydroxyapatite cement paste (BoneSource).

A new method has been developed for the closed reduction of minimally displaced, noncomminuted zygomatic arch fractures that is minimally invasive and precludes the use of nonresorbable materials such as plates and wires in the repair. Twenty rats received simple, minimally displaced right-sided zygomatic arch fractures under general anesthesia. In 10 animals these fractures were treated with closed reduction through a temporal approach (Gillies method) to reapproximate the fractured segments. In the second group of 10, immediately after the closed fracture reduction, 1 ml of hydroxyapatite cement paste (BoneSource, Leibinger Corp., Dallas, TX) was injected through a 14-gauge needle into and around the fracture site. This paste, which is remodeled into bone over time, hardens into a plaster-like substance within 20 minutes of mixing. The majority of the paste was placed on the medial aspect of the fracture to act as a buttress between the fractured zygoma and the temporalis muscle lying on the greater wing of the sphenoid. This served to support the fracture by "casting" the bone and preventing it from collapsing medially. Nine of the 10 fractures treated with the hydroxyapatite paste healed completely without evidence of zygomatic displacement or malunion. One fracture had mild displacement of the fractured segment but good bone healing between the fractured sides. No adverse effects were noted in the temporalis muscle of these animals, and mastication was normal. Five of the 10 treated with closed reduction alone also had a good result. Of the remaining 5 fractures 2 had a mild to moderate bony deformity as a result of improper alignment during fracture healing. The other 3 did not heal and, therefore, formed a fibrous nonunion at the fracture site. We concluded that closed reduction of simple zygomatic fractures can be performed if the fracture site is held in place with a stabilizing material such as a hydroxyapatite cement paste.

Animals↗

PubMed1997

Hydroxyapatite cement paste cranioplasty for the treatment of temporal hollowing after cranial vault remodeling in a growing child.

Postoperative depression of the temporal fossae and calvarial contour deficits are common sequelae following orbital rim advancement and cranial vault remodeling in children. Reconstructive options in the growing child are limited. Autogenous bone graft has a high rate of resorption when placed as an onlay to augment the craniofacial skeleton, and many of the available alloplasts will not remodel to adapt to the growing calvarium. We report a 9-month follow-up of the use of hydroxyapatite cement paste for the reconstruction of postoperative bitemporal hollowing and depressions in cranial contour in a 4.5-year-old boy. This is the first case of which we are aware that reports the use of hydroxyapatite cement paste for craniofacial augmentation in a growing child. Longitudinal follow-up of this patient will help to determine the long-term outcome of hydroxyapatite cement paste in this setting.

Bone Cements↗

PubMed2004

The fate of hydroxyapatite cement used for cranial contouring: histological evaluation of a case.

Craniofacial contouring is a commonly performed procedure applied for traumatic and postsurgical cranial vault or facial skeleton irregularities. Hydroxyapatite cement is an alloplastic material composed of tetracalcium phospate and dicalcium phospate anhydrous that transforms into a paste-like substance when these two compounds placed in an aqueous environment. This mixture, which is a nonceramic microporous calcium phosphate combination, is another alternative for refining the craniofacial contour. There are not enough data regarding bone formation within this material after its use in human beings, however. A case requiring secondary craniofacial contouring after a motor vehicle accident is presented. Hydroxyapatite cement was used for reconstruction, and a second look was carried out for further correction during which secondary contouring of the cement was made and a sample of the previously implanted material was histologically evaluated. It was observed in this case that hydroxyapatite cement is incorporated within the surrounding bony structures and permits secondary contouring procedures. New bone and vessel formation was also detected within the implanted material, but this was limited and thus was not convincing for significant osteoconversion as seen in animal studies.

Accidents, Traffic↗

PubMed2002

A contraindication for the use of hydroxyapatite cement in the pediatric population.

The authors report on their experience with a particular hydroxyapatite cement in the pediatric population and review cases that elucidate potential limitations of its use in this population. In all patients, the implant was used for recontouring and augmenting the cranial vault. Seven of 15 patients had a direct communication between sinus mucosa and the implant at the time of surgery. Three of the seven patients developed late postoperative inflammatory reactions of the surgical site with delamination of the implant. Each patient required an aggressive irrigation and débridement with removal of the delaminated hydroxyapatite. Pathologic findings showed evidence of a foreign body inflammatory reaction in the tissue, and mixed bacterial flora were identified in all specimens. No late problems with the cement were seen in patients without a communication to the sinuses. Our findings suggest that the use of BoneSource, an essentially nonviable, nonvascularized implant, in areas exposed to bacterial contamination is contraindicated in the pediatric population. BoneSource and other similar hydroxyapatite biomaterials do have a role as implants in the craniofacial skeleton. The indications and contraindications of these substances will need to be further defined for wide acceptance to occur.

Adolescent↗

PubMed2004

Use of fast-setting hydroxyapatite cement for secondary craniofacial contouring.

Patients who have previously had surgical correction of major craniofacial deformities will often have residual contour deformities they wish to have improved at a later date. The development of hydroxyapatite cement has simplified these procedures. The setting time is reduced to 5 to 8 minutes by mixing the cement with a phosphate-based solution, increasing the tensile strength, and maintaining the same biocompatibility and osseoconductivity. This study includes 48 patients who presented with a variety of residual contour irregularities secondary to a craniofacial congenital anomaly or a posttraumatic defect. All but one of the patients with congenital craniofacial conditions had their initial surgical correction performed by the senior author (Magee) and had regular follow-up visits. Variable amounts of hydroxyapatite cement were used according to the size of the defect to be corrected. Five patients had a postoperative complication: two infections, one seroma, one persistent swelling, and one drain retention. Patients were followed from 6 months to 3 years (mean, 1 year 5 months). Good results were achieved in 38 patients, acceptable results with minor asymmetries were seen in seven patients, and three other patients required a second intervention to obtain a better contour. Cranioplasty with fast-setting hydroxyapatite cement is a simple and reliable procedure, with a low complication rate. Attention to simple technical and operative principles can provide excellent results.

Adolescent↗