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PubMed1988

Examination of new bone growth on aluminium oxide implant contact surfaces after oral administration of ossein-hydroxyapatite compound to rats.

In view of the many disadvantages of transplantation of autologous bone tissue, factors must be found which locally and systemically will adjust the balance between bone resorption and deposition in favour of new bone growth. The present study was undertaken, therefore, to examine whether oral administration of ossein-hydroxyapatite compound (OHC) could stimulate new bone growth on aluminium oxide implant surfaces and, if so, whether it was the mineral or organic part of the compound which was responsible. Whilst under anaesthesia, adult male Wistar rats each had 2 holes drilled into the femur and 2 precisely fitting aluminium oxide implants inserted. The animals were divided into 5 groups each of 5 rats and the groups received oral daily doses of 20 mg OHC, 100 mg OHC, 10 mg hydroxyapatite, 50 mg hydroxyapatite or no supplement (controls), respectively. After 20 days, each implant was evaluated by 5 cuts through the marrow area and the thickness of the newly grown layer of bone measured by a morphometric procedure. The results showed a significant increase in new bone growth for the 100 mg OHC group in comparison to the control group, and in comparison to the hydroxyapatite group. Because both supplemented groups received equivalent dosages of calcium and phosphate, the additional stimulation of new bone growth must have been due to the organic part of OHC (ossein). It is suggested that these results should stimulate in particular the clinical use of OHC in the critical initial phase of implant healing and delayed fracture healing.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMed1989

[Application of synthetic hydroxyapatite to periodontal therapy].

The purpose of the present study was to evaluate the effectiveness of granular hydroxyapatite as an alloplastic bone implant material in infrabony periodontal defects. Thirty-five infrabony defects in 28 subjects with marginal periodontitis were used. The patients were instructed in oral hygiene and received several sessions of scaling and root planing. Granular hydroxyapatite was implanted into test sites with infrabony defects following application of internally beveled full thickness flaps, root planing, and defect debridement. Pocket depth and attachment level were recorded before and 3 and 6 months after surgery. Gingival recession, mobility of the tooth, plaque index, and gingival index were also recorded before and 1 and 2 weeks, and 1, 3 and 6 months after surgery. Redness and swelling of the gingiva and increase in tooth mobility appeared transiently after surgery, however, they disappeared in a short time. A significant reduction of mean pocket depth of 3.4 mm and a significant increase in the mean attachment level of 2.5 mm were observed at 6 months after surgery. The mean gingival recession during the experimental period was only 0.9 mm. The amount of hydroxyapatite remaining implanted in the infrabony defect was 73% 6 months after surgery. The data and clinical impression suggest that hydroxyapatite has a potential as an alloplastic implant with clinically apparent acceptance by soft and hard tissue.

Bone Resorption↗
PubMed1978

Surface adsorption of fluoride and ionic exchange reactions on hydroxyapatite.

The experiments showed that a part of the fluoride which was taken up by hydroxyapatite or teeth at low concentrations of fluoride at neutral pH was soluble in alkali (IN KOH, 24 h) and was thus not fluoroapatite. Calcium fluoride could not form under the present conditions because the solubility of this compound was not exceeded. It is suggested that the alkali soluble fluoride is adsorbed to calcium ions bound as counterions in the hydration layer of the hydroxyapatite or the enamel. This is consistent with previous findings in this laboratory, showing that fluoride displaced acidic proteins adsorbed to calcium receptors on the hydroxyapatite surface in the same way as other anions displace proteins. It could also be shown that polyanions and polycations adsorbed to hydroxyapatite surfaces by ionic exchange, displacing phosphate or phosphate and calcium respectively in the process. A model is suggested which differs slightly from that proposed by Bernardi.

Adsorption↗
PubMed2002

Supplementation of autogenous bone graft with coralline hydroxyapatite in posterior spine fusion for idiopathic adolescent scoliosis.

Twenty-seven consecutive patients with adolescent idiopathic scoliosis underwent posterior spinal fusion with pediatric Texas Scottish Rite Hospital instrumentation. Coralline hydroxyapatite (Interpore, Irvine, Calif) was mixed with limited autograft from posterior iliac crest (an approximate 70/30 ratio of coralline hydroxyapatite to autograft). Patient evaluation was based on clinical and radiographic findings. On initial radiographic evaluation, a "snowstorm" appearance consistent with the exoskeleton of the coralline hydroxyapatite was observed. After two years, the fusion mass had a "marble-like" appearance with distinct decreased visibility of the disk spaces in the fusion mass. This latter stage of "marbilization correlated with solid fusion clinically. All patients achieved solid fusion at an average follow-up of 27 months. Coralline hydroxyapatite is safe, biocompatible, and effective in augmenting autogenous bone graft in the treatment of idiopathic adolescent scoliosis with posterior spinal fusion. In addition to decreased donor site morbidity, this may be invaluable in cases where there is insufficient autograft available.

Adolescent↗
PubMed1989

[Histological investigation of improvement of jaw-bone structure 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 jaw-bone with atrophic structure. The lower P3, P4 and the mesial root of M1 of 6 mongrel dogs were extracted. At 4 months, the trabeculae were taken out and porous hydroxyapatite granules were filled in the vacant spongiosa. At 8 months, hydroxyapatite dental implants were placed into this area. After 1 week and after 2 months, specimens were taken out and fixed by 10% formalin alcohol. They were embedded in polyester resin and undecalcified thin sections were prepared. The sections were stained with toluidine blue and observed under light microscopy. RESULTS: 1) A larger amount of bone compared with that of the peripheral spongiosa was observed among the granules. 2) One week after implantation, differentiation around the implant was rather slow in the area of the granules. But in the area of the granules next to the spongiosa, differentiation was normal. 3) Two months after implantation, a new bone was observed, which filled the implantation space and united the implant to the bone among the granules. But on some implant surface, a fibrous connective tissue was seen. These results suggest that this method is able to improve the jaw-bone structure sufficiently to apply the hydroxyapatite dental implant.

Animals↗
PubMed1993

Rationale and clinical application of hydroxyapatite coatings in pressfit total hip arthroplasty.

Although the long-term clinical results of cemented total hip arthroplasty are quite good, there is a significant problem with failure after approximately 10 years, especially with younger patients. Uncemented total hip arthroplasty has been developed in response to prosthesis loosening due to cement fragmentation and osteolysis. Porous-coated hip stems have been used, with generally promising results. However, clinical studies of porous-coated prostheses have revealed findings of concern such as thigh pain, subsidence of the femoral prosthesis, and radiographic lucencies at the bone-prosthesis interface. Hydroxyapatite coatings were developed to improve the fixation of uncemented prostheses. This article discusses the chemical, mechanical, and biological properties of hydroxyapatite coatings, and reviews the biologic behavior of experimental hydroxyapatite-coated implants. The clinical and radiographic results of a 4-year prospective trial are presented. The authors conclude that the reported experimental evidence, as well as the early clinical experience of this series and others, support the continued clinical evaluation of hydroxyapatite-coated titanium for total hip arthroplasty in younger, active patients.

Acetabulum↗
PubMed1991

Clinical and roentgenographic evaluation of hydroxyapatite-coated and uncoated porous total hip arthroplasty: a preliminary report.

Sixty osteoarthritic patients undergoing primary uncemented total hip arthroplasty were matched for age and weight and randomized into one of four groups with respect to implant coating and postoperative protected weight-bearing status: group 1, hydroxyapatite, 12 weeks; group 2, uncoated, 12 weeks; group 3, hydroxyapatite, 6 weeks; group 4, uncoated, 6 weeks. Tantalum spheres were implanted periprosthetically into the femur at the time of arthroplasty, thus providing constant references for stereoscopic radiographs. Patients were then evaluated over a 1-year period with clinical examination, plain radiography, and roentgen stereophotogrammetric analysis (RSA). Clinical evaluation using Charnley scoring showed no significant preoperative or postoperative intergroup differences, whereas visual analog testing noted less thigh pain with hydroxyapatite-coated stems at 12 weeks and 6 months follow-up. Plain radiographic analysis produced no significant differences, with no instability detected and bony ingrowth noted uniformly in all groups. The preliminary stereographic evaluation showed migration in all groups, but there were no significant differences between coated and uncoated stems or 6-week and 12-week partial weightbearing protocols. The Charnley, plain radiographic, and preliminary stereogrammetric evaluations all suggest that migration is unaltered by enhanced surfaces and that early unprotected weightbearing does not jeopardize implant fixation regardless of coating design. The lower incidence of visual analog thigh pain with the hydroxyapatite-coated stems, however, may be a reflection of bony ingrowth and as such add some validity to the theoretical advantages of enhanced surface prostheses.

Aged↗
PubMed2001

[Cytotoxicity of the strontium-substituted hydroxyapatite evaluated by MTT colorimetry].

This study was conducted to evaluate the cytotoxicity of strontium-substituted hydroxyapatite by methyl thiazolyl tetrazolium (MTT) colorimetry. We used the MTT method to assay the cytotoxicity of the strontium-substituted hydroxyapatite containing different strontium concentrations (1%, 5%, 10%, 100% Sr2+) and the pure hydroxyapatite. The results showed that the cytotoxicity scores of the different materials were grade 0 or grade 1. These led us to the conclusion that strontium-substituted hydroxyapatite has good biocompatibility.

Animals↗
PubMed2001

[Optimizing the synthesis of hydroxyapatite as a method for the defluoridation of drinking water].

As the cheaper raw materials for the synthesis of hydroxyapatite as a defluoridator, calcium hydroxide and phosphoric acid are used. Hydroxyapatite is made by a hydro-synthesis method, and optimum conditions are determined by batch test for defluoridation with respect to the consumption of phosphoric acid, reaction time and acid-washed product. The results showed that the defluoridation capacity of the synthetic hydroxyapatite for break through (F- 1.0 mg/L is considered as the break through point) was F- 5.6 mg/g in column test, and F- 10.7 mg/g for saturation in column test. After optimization of the synthesis method, the defluoridation capacity of hydroxyapatite is much higher than activated alumina and bone charcoal, which are used currently.

Fluorides↗
PubMed1991

Six-year histology of an avulsed molar reimplanted in a hydroxyapatite augmented socket: a case report.

This case report deals with the histologic examination of an avulsed tooth that was reimplanted in a socket where a distal root defect was augmented with hydroxyapatite. The 6-year results showed a "repair" type of connective tissue attachment. There were areas of ankylosis present on the distal root above an area of prior cystic debridement. The hydroxyapatite particles present demonstrated biocompatibility and encapsulation by new bone growth. There was a longer junctional epithelium present on the distal root than on its mesial counterpart. Histology of the distal root demonstrated fibrous repair, ankylosis, and osseous formation around the hydroxyapatite particles. This type of result was not apparent on the mesial root, devoid of hydroxyapatite, where a "splicing" type of healing occurred in the periodontal ligament.

Adult↗
PubMed1991

A study on the surface strain distribution on the hydroxyapatite-implanted canine tibia: a preliminary report.

It has been said by many investigators that hydroxyapatite ceramics may be prospective bone substitute materials. Its mechanical brittleness and strength has been the most serious consideration. In the present article a study has been done using animal experiments, the changes of surface strain at the hydroxyapatite implantation site of long-bone when the compressive stress is applied in the direction of long axis, in order to clarify the mechanical behaviors of hydroxyapatite living bone complex. The nonimplanted side was used as the control. Results revealed that the hydroxyapatite living bone complex has been proven to have sufficient flexibility such that it shows no hysteresis in stress versus strain relation up to 200 kg of applied load. The strain distribution pattern on the HA-implanted bone is quite similar to that of the nonimplanted one. This characteristic also suggests that it has normal skeletal function.

Animals↗
PubMed1991

Hydroxyapatite-coated femoral stems. Histological analysis of components retrieved at autopsy.

Plasma-sprayed coating of hydroxyapatite are biocompatible and, because of their osteoconductive properties, may contribute to the early fixation of total joint prostheses. To evaluate this interface, we histologically analyzed five hydroxyapatite-coated femoral stems which, along with the surrounding bone, were retrieved from three humans at autopsy. The five femoral components had been in situ for a mean duration of twelve months (range, almost five to twenty-five months) and had been inserted for osteonecrosis (two), osteoarthrosis (two), and as an uncermented revision for failure of a cemented stem. The three patients had had a good or excellent clinical result and had died of causes unrelated to the joint arthroplasty. A coating of hydroxyapatite was identified on each stem. There was a variable amount of apposition of bone (32 to 78 per cent of available surface per section). The deposition of bone was most prominent on the surface of the prosthesis that was close to the endosteal surface of the bone, especially in areas that are predicted by Wolff's law (anterior and medial aspects of the implant, and at lateral-oblique corners). There were occasional foci of bone-remodeling around the implant, including osteoclast-mediated removal of the coating of hydroxyapatite along with adjacent bone. Occasional particles of ceramic were present within macrophages in the adjacent bone marrow. Other areas showed formation of new bone with a few areas of bone directly against the metal substrate. The over-all histological features suggest mechanically stable implants with bone-remodeling at the surface of the bone-implant interface.

Adult↗
PubMed1990

A comparison of the effects of urate, hydroxyapatite and diamond crystals on polymorphonuclear cells: relationship of mediator release to the surface area and adsorptive capacity of different particles.

The ability of monosodium urate monohydrate (MSUM), hydroxyapatite and diamond crystals to stimulate phagocytosis, degranulation and secretion of cell movement factors (CMF) from polymorphonuclear leukocytes (PMN) was determined. The ability of each crystal to adsorb PMN derived enzymes and CMF was also compared. MSUM crystals stimulated greater enzyme release and generation of CMF than hydroxyapatite; in contrast, hydroxyapatite crystals exhibited greater adsorption of PMN products. This was partly due to the greater surface area (at a given concentration) of hydroxyapatite crystals. Diamond crystals clearly interacted with PMN, but they did not stimulate degranulation or CMF production.

Adsorption↗
PubMed1990

Experimental study of osteogenic activity of sintered hydroxyapatite--on the relationship of sintering temperature and pore size.

In order to determine the most appropriate properties for hydroxyapatite, four kinds of sintered hydroxyapatite (50-250 microns & 900 degrees C, 50-250 microns & 1,100 degrees C, 300-600 microns & 1,100 degrees C, and dense & 1,100 degrees C, pore size and sintering temperature, respectively) were implanted in the animals and studied histologically. In addition, the responses at different implantation sites were compared. The results are 1) hydroxyapatite sintered at 900 degrees C temperature showed higher osteogenic activity than that sintered at 1,100 degrees C in the early period. However, this difference disappeared with time, and at 26 weeks, there was no significant difference between the two groups. 2) hydroxyapatite with a 300-600 microns pore size demonstrated osteogenic activity superior to that with a 50-250 microns pore size. 3) implantation at the epiphysis produced higher osteogenic activity in the early period, compared to implantations at the metaphysis or diaphysis. This difference in bone ingrowth had disappeared at the 26-week.

Animals↗
PubMed1987

Reconstruction of the ossicular chain with hydroxyapatite prostheses.

To achieve a lasting result in reconstruction of the ossicular chain, strict material and surgical criteria must be combined. The best biomaterial, apart from bone, is hydroxyapatite, the mineral matrix of living bone tissue. For the reconstruction, the assembly technique is used instead of a columella. Direct contact with the drum membrane is not reliable if a columella is used, and extrusion or lateralization may influence postoperative results. In the case of a missing incus, an assembly prosthesis of dense hydroxyapatite is placed on top of the stapes head and the handle of the malleus, in a pocket between drum membrane and the neck of the malleus. Long postoperative follow-up of 120 patients showed an air-bone gap closure within 20 dB for 83.3% of the patients, no extrusion was observed, and the hearing gain stayed constant. Reconstruction of a tympanic membrane perforation and posterior canal wall was performed in the same stage in sixty patients. In the case of a missing incus and stapes superstructure, an incus/stapes prosthesis of dense hydroxyapatite, as assembly between footplate and handle of the malleus, was used. Long postoperative follow-up of twenty-five patients showed an air-bone gap closure within 20 dB for 68% of the patients. Reconstruction of a tympanic membrane perforation and posterior canal wall was performed in sixteen patients. No extrusion was observed and the hearing gain stayed constant. Hydroxyapatite prostheses have proven to be a good alternative for autologous and homologous ossicles.

Adolescent↗
PubMed1987

Is hydroxyapatite ceramic an adequate biomaterial in ossicular chain reconstruction?

The suitability of high-density hydroxyapatite ceramic without macropores for ossicular chain reconstruction was examined in animal experiments. The material was implanted both mobilely and immobilely, in compact cylinders and as granules at different locations. Biocompatibility was studied by the sawing and grinding technique without decalcification. If high-density hydroxyapatite was not in direct and stable contact with living bone, resorption and osteoneogenesis could not be observed. In cases of mobile contact with living bone there was a jointlike connection. Osteoneogenesis was seen only if the hydroxyapatite was in primary stable contact with living bone. We concluded that high-density hydroxyapatite ceramic, positioned as an ossicular replacement prosthesis, is an adequate biomaterial in ossicular chain reconstruction.

Animals↗
PubMed1988

Porous hydroxyapatite and tricalcium phosphate cylinders with two different pore size ranges implanted in the cancellous bone of rabbits. A comparative histomorphometric and histologic study of bony ingrowth and implant substitution.

To investigate the histophysiology of implant degradation, hydroxyapatite and tricalcium phosphate cylinders with a diameter of 3 mm were implanted in the cancellous bone of the distal femur and the proximal tibia of 15 New Zealand White rabbits for up to six months. All implants had a homogeneous pore distribution and a porosity of 60%. Ceramics with a pore size range of 50-100 micron and 200-400 micron were compared. Morphometric analysis showed that up to 85.4% of the originally implanted tricalcium phosphate was degraded after six months, whereas the volume reduction of the hydroxyapatite was only 5.4% after the same period. Within the first months bone and tissue ingrowth and implant resorption occurred at a higher rate in the smaller-pored tricalcium phosphate than in the larger-pored material. Hydroxyapatite cylinders with small pores were totally infiltrated by bone or bone marrow after four months, whereas in the larger-pored hydroxyapatite implants tissue did not penetrate all pores after six months and the amount of bone within the implant was small. Scanning electron microscopy of the material before implantation revealed the existence of numerous pore interconnections with diameters of about 20 micron in the smaller-pored ceramics. Such interconnections were rare in the larger-pored implants. The pore interconnections seem to promote vascular and tissue ingrowth and consequently the initial rate of implant resorption. Implant resorption is an active process and involves two different cell types. Acid phosphatase-positive osteoclast-like cells suggesting active resorption adhere directly to the surface, especially in tricalcium phosphate implants. Clusters of macrophages tightly packed with granular material are found in the pores and along the perimeter of all implant cylinders. They may play an active role in the intracellular degradation of small detached ceramic particles.

Animals↗
PubMed1987

High-performance liquid chromatography using novel square tile-shaped hydroxyapatite crystals as adsorbent.

High-performance liquid chromatography using, as adsorbent, novel square tile-shaped hydroxyapatite crystals (with thicknesses of about 2 microns and diameters of 3-7 microns) has been developed. The chromatographic efficiencies of the novel hydroxyapatite packed columns are almost equal to those of the previously developed spherical hydroxyapatite packed columns; high chromatographic resolutions can be obtained by using extremely reduced column lengths of 0.5-3 cm. Since both the square and the spherical hydroxyapatite have roughly the same particle size of some micrometers, the chromatographic efficiency can be deduced to be determined mainly by the particle size rather than the particle shape.

Adsorption↗