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At least 1,063 records · Page 59Linked to original sources
PubMed1999

[Regulation of adherence to serum-coated hydroxyapatite by Streptococcus sanguis].

OBJECTIVE: To investigate the effects of pH and calcium iron on adhesion of Streptococcus sanguis to serum-coated hydroxyapatite. METHODS: The adhesion model in vitro established by Clark W. B. in 1977 was used to quantify adsorptive cells through [3H] thymidine labelling. RESULTS: The cpm values between different pH groups showed significant differences. Also, there were significant differences of cpm values between calcium groups and control group. CONCLUSION: Either pH or calcium iron has obvious effect on adherence of Stroptococcus sanguis to serum-coated hydroxyapatite. The findings suggest that regulating pH and concentration of calcium iron can help to change colonization on teeth surfaces by Streptococcus sanguis in periodontal circumstance.

Animals↗
PubMed1976

[Dissolution kinetics of synthetic hydroxyapatite and human enamel crystals].

A comparative study of the dissolution of synthetic hydroxyapatite and human enamel crystals has been realized in a buffered (sodium citrate - citric acid) solution in presence of variable quantities of sodium fluoride. The pH of the solutions used was 3.7 and 5.6. The dissolution curves of the synthetic hydroxyapatite and the human enamel crystals were similar. In all cases, the dissolution mechanism was characterized by a first step with a rapid kinetic corresponding to the formation of a central cavity extending parallel to the c axis of the apatite crystal and observed with the electron microscope. In a second stage, the dissolution kinetic was much slower corresponding to a saturation of the buffered solution and an extension of the crystal destruction towards its lateral external surfaces. The dissolution kinetic was faster in a more acidic solution and the total dissolution at a given moment varied inversely to the fluoride amount.

Chemical Phenomena↗
PubMed1998

[Study on bone-repairing biomaterial ytterbium oxide-hydroxyapatite].

Hydroxyapatite was extensively used to repair osteoshortage recently. To improve its bondibility and X-ray obstructibility, we added ytterbium oxide of different proportions in the synthetic process of hydroxyapatite. Ytterbium oxide is characterized by high activity and X-ray obstructibility. A cheap biomaterial with good biocompatibility and high X-ray obstructibility has been got in this way.

Animals↗
PubMed1998

[Experimental study on the biocompatibility and toxicology of interface between hydroxyapatite coating and bone].

According to "The standards for biological evaluation of bio-materials and bio-products abbreviated to STANDARDS" newly set by the Ministry of Health, PRC, 5 observation indexes were selected to evaluate systematically the biocompatibility and toxicology of China-made hydroxyapatite, which is clinicall used. The results revealed no effects of allergy, mutation and hemoclasis reaction except mild cytotoxicity. These indicate that the China-made hydroxyapatite meets the demand of STANDADS and thus may be clinically with safety.

Coated Materials, Biocompatible↗
PubMed2002

[Preparation of thin hydroxyapatite layers on cp titanium through anodic oxidation followed with hydrothermal treatment].

To study the method of anodic oxidation followed by hydrothermal treatment for cp titanium and to know bone response to thin hydroxyapatite layers in vivo, commercially pure titanium plates were anodized at 200 V-400 V with direct electric current density no more than 50 mA/cm2 for 15 minutes in the electrolytic trough. beta-glycerophosphate sodium(0.03-0.04 M) and calcium acetate(0.2-0.3 M) were used as electrolytes. Then, titanium plates were hydrothermal treated in the autoclave for 2 hours at 280 degrees C-300 degrees C. Polishing and grit-blasting surface was used as control to learn bone response to thin layers. Twelve rabbits were evenly divided into 3 groups, each group was implanted with 12 implants into the rabbits femoral bone. After 4, 8 and 16 weeks, implants were taken out and collected respectively and were made grinding slices. The bone-implant interface was observed with light microscope. And the bone-implant interface of polishing and layered implants after 8 weeks implantation was observed with scanning electron microscope. The element contents at the interface of polishing and layered implants before and after 8 weeks implantation were detected with EDAX. Results showed that there was hydroxyapatite(HA) precipitated on the titanium surfaceamellae bone in 8 weeks for thin HA coatings, and no HA debris were found at the interfacial zone. In addition, Ca and P content on the hydrothermal treated implant surface increased much more after implantation than that of polished implants. It was concluded that anodic oxidation followed by hydrothermal treatment could precipitate thin hydroxyapatie layer on the surface of cp titanium, which could improve early formation of woven bone and accelerate woven bone transferring to lamellae bone at the implanted site.

Animals↗
PubMed2002

[Study on the regeneration methods of the synthetic hydroxyapatite as a material for defluoridation of drinking water].

The regeneration efficiencies of the synthetic hydroxyapatite saturated by fluoride using either sodium hydroxide method or surface coating method are studied and compared. Both static and dynamic conditions for surface coating regeneration method are also tested. The results showed that the regeneration efficiency of the synthetic hydroxyapatite saturated by fluoride treated by surface coating method is 46%-64%, more than two times of that of it treated by the traditional sodium hydroxide regeneration method.

Fluoridation↗
PubMed1992

A histomorphometric study of unthreaded hydroxyapatite-coated and titanium-coated implants in rabbit bone.

Hydroxyapatite-coated and titanium-coated IMZ dental implants were investigated in an animal study. The implants were placed in the distal femurs of rabbits. Six months after placement, histomorphometric evaluation of the bone-to-implant contact was conducted. The hydroxyapatite-coated specimens demonstrated significantly more direct bone contact compared to the titanium-coated controls.

Alveolar Process↗
PubMed1992

Long-term retrospective studies on hydroxyapatite coated endosteal and subperiosteal implants.

This article reports a long-term retrospective study on hydroxyapatite-coated implants, which covers more than 6 years of clinical use. The authors discuss not only cylinder implants, but blade and subperiosteal implants as well. This study reveals that, for the time covered, a definite clinical advantage exists to coating implants with hydroxyapatite.

Dental Implantation, Endosseous↗
PubMed1992

Reconstruction of a segmental clavicular defect with a Marlex mesh-enveloped composite graft consisting of a hydroxyapatite prosthesis and autogenous bone: a case report.

The present study reports a case of a 38-year-old man with a malignant lymphoma of the right clavicle who underwent reconstruction after a segmental resection of the clavicle. A hydroxyapatite prosthesis in the shape of the clavicle was placed across the defect in conjunction with Marlex mesh which entirely enveloped the prosthesis and iliac crest autogenous bone. The mesh also acted as a stabilizer to the segments. The postoperative management was not a burden to the patient. Postoperative radiographs indicated bony union to have been completed within six months of the operation. The patient returned to work as a driver eight months after surgery. The range of motion of the shoulder joint was not limited. The patient had no trouble in carrying out his daily life without pain. The appearance of the area operated was excellent. At the postoperative 39 months follow-up visit, a radiograph reconfirmed the stable reconstruction with a composite graft and bone bridging at the gap left in the prosthesis to have been maintained with little bone absorption. The results indicate a reconstruction using a Marlex mesh-enveloped composite graft consisting of a hydroxyapatite prosthesis and autogenous bone to be a useful alternative to other types of reconstruction for segmental clavicular defects.

Adult↗
PubMed1992

Interaction of bile salts with calcium hydroxyapatite: inhibitors of apatite formation exhibit high-affinity premicellar binding.

Of the major human bile salts, only the glycine-conjugated dihydroxy species prevent the transformation of amorphous calcium phosphate to calcium hydroxyapatite, a component of gallstones; we have proposed that this inhibition occurs by competition between the bile salt and HPO4(2-) anions for binding site on the apatite crystal embryo. Now we show that the binding affinity of bile salts to fully mature hydroxyapatite has the following order: glycine-conjugated dihydroxy salts > taurine-conjugated dihydroxy salts > glycocholate approximately taurocholate. Glycine-conjugated dihydroxy bile salts bound with high affinity as "premicellar" aggregates, but the remaining species appeared to bind as a wider range of aggregate sizes. Glycochenodeoxycholate binding was decreased as the pH increased from 6.6 to 9.8 and the apatite surface charge reversed from net positive to net negative. Binding was competitively inhibited by HPO4(2-), but not by H2PO4-. Ca2+ promoted the binding of glycochenodeoxycholate, taurochenodeoxycholate and glycocholate, and for the latter two bile salts the increase was associated with enhanced "premicellar" binding. The binding of taurocholate was not influenced by Ca2+. When either glycocholate or taurocholate was mixed with glycochenodeoxycholate, mixed aggregates were formed that had a lower affinity for apatite than had pure glycochenodeoxycholate aggregates. Because only glycine-conjugated dihydroxy bile salts inhibit apatite formation, these results suggest that inhibition depends on high-affinity "premicellar" bile salt-apatite binding.

Anions↗
PubMed1992

Histologic case reports of coralline hydroxyapatite grafts placed in human intraosseous lesions: results 6 to 36 months postimplantation.

Four intrabony lesions from four patients were studied. Presurgical measurements included clinical attachment level, degree of recession, probing pocket depth, Plaque Index, Gingival Index, and Sulcular Bleeding Index. These measurements were also taken at 6-month intervals after surgery. Surgery involved exposing the intrabony defects by a papillary preservation technique, planing, and placing blocks of coralline hydroxyapatite. Three biopsy specimens and one block section were removed from the treated lesions at various periods ranging from 6 to 36 months. Clinical and histologic observation provided evidence of osteogenesis around and through the coralline hydroxyapatite.

Adult↗
PubMed1992

Chemical characterization of a potassium hydroxyapatite prepared by soaking in potassium chloride and carbonate solutions.

A potassium-doped synthetic apatite was prepared by soaking hydroxyapatite in potassium carbonate and potassium chloride solutions. The hydroxyapatite was prepared by firing slip cast ceramic bodies in vacuum at 1100 degrees C. The conical ceramic samples and a crushed material of this were soaked in carbonate and chloride solutions for 2, 4, 6, and 8 weeks. Potassium, calcium, and phosphate were determined by direct current plasma emission spectroscopy. The carbonate content was determined by thermogravimetric analysis and chloride titrimetrically. After 2 weeks, one potassium ion substituted one calcium ion when soaked in a carbonate solution. When soaked in the chloride solution substitution occurred to the same extent. At phosphate sites the substitution of phosphate for carbonate occurred at one sixth of the sites after 2 weeks. Chloride incorporated one half of the OH-sites after 2 weeks. After 4 weeks about one chloride ion was found in the apatite, and after 6 weeks one and a half of the OH-sites were occupied by chloride ions.

Carbonates↗
PubMed2004

Chromosome aberration test for hydroxyapatite in sheep.

The present study is aimed at finding the mutagenicity and cytotoxicity of dense form of synthetic hydroxyapatite (Source: School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia) in the blood of sheep. The biomaterial was implanted in the tibia of Malin, an indigenous sheep breed of Malaysia. Blood was collected from the sheep before implantation of the biomaterial, cultured and a karyological study was made. Six weeks after implantation, blood was collected from the same animal, cultured and screened for chromosome aberrations. The mitotic indices and karyological analysis indicated that the implantation of synthetic hydroxyapatite (dense form) did not produce any cytotoxicity or chromosome aberrations in the blood of sheep.

Animals↗
PubMed2004

DNA damage evaluation of hydroxyapatite on fibroblast cell L929 using the single cell gel electrophoresis assay.

Hydroxyapatite is the main component of the bone which is a potential biomaterial substance that can be applied in orthopaedics. In this study, the biocompatibility of this biomaterial was assessed using an in vitro technique. The cytotoxicity and genotoxicity effect of HA2 and HA3 against L929 fibroblast cell was evaluated using the MTT Assay and Alkaline Comet Assay respectively. Both HA2 and HA3 compound showed low cytotoxicity effect as determined using MTT Assay. Cells viability following 72 hours incubation at maximum concentration of both HA2 and HA3 (200 mg/ml) were 75.3 +/- 8.8% and 86.7 +/- 13.1% respectively. However, the cytotoxicity effect of ZnSO4.7H2O as a positive control showed an IC50 values of 46 mg/ml (160 microM). On the other hand, both HA2 and HA3 compound showed a slight genotoxicity effect as determined using the Alkaline Comet Assay following incubation at the concentration 200 mg/ml for 72 hours. This assay has been widely used in genetic toxicology to detect DNA strand breaks and alkali-labile site. The percentage of the cells with DNA damage for both substance was 27.7 +/- 1.3% and 15.6 +/- 1.0% for HA2 and HA3 respectively. Incubation of the cells for 24 hours with 38 microg/ml (IC25) of positive control showed an increase in percentage of cells with DNA damage (67.5 +/- 0.7%). In conclusion, our study indicated that both hydroxyapatite compounds showed a good biocompatibility in fibroblast cells.

Animals↗
PubMed2005

The use of hydroxyapatite cement and a pericranial/deep temporal fascia graft for cranioplastic reconstruction of translabyrinthine craniectomy defects.

Most translabyrinthine temporal bone defects are reconstructed with free abdominal fat grafts, with or without the use of hydroxyapatite cement. However, these procedures are associated with considerable morbidity at the graft donor site, with a 6 to 15% incidence of cerebrospinal fluid (CSF) leaks, and with postoperative headaches. We have developed a new technique for reconstructive cranioplasty that involves the use of hydroxyapatite cement and a pericranial/deep temporal fascia graft. This technique obviates the need for an abdominal fat graft and therefore circumvents the morbidity associated with it; it may also significantly reduce the incidence of CSF leaks and postoperative headaches. We describe the results of our use of this technique in a series of 10 patients. Based on our early findings, we believe that this technique holds great promise for reconstructive cranioplasty following translabyrinthine craniectomy.

Adult↗
PubMed2005

[Cervical posterior laminoplasty operation using coralline hydroxyapatite].

OBJECTIVE: To study the results of using coralline hydroxyapatite (CHA) in cervical posterior laminoplasty operation. METHODS: Two hundred and fifty-six patients underwent cervical spinous process-splitting laminoplasty using CHA. All patients had been followed up over 3 months. One hundred and forty-two patients were followed up at least 2 years. All patients had spinal stenosis at least at 3 levels or OPLL. The average follow up time was 34.6 months. RESULTS: The CHA grafts were stable between the split spinous processes. The union rate of CHA was 83.5%. After operation, the spinal cord moved dorsally, and the anteroposterior compression ratio had been improved from 0.19 to 0.42. No apparent kyphosis occurred. The JOA score improvement rate was 58.3%. There were 24 patients (17%) with axial symptom. CONCLUSION: Cervical posterior laminoplasty operation using coralline hydroxyapatite may achieve good results.

Adult↗
PubMed2005

Backfill for iliac-crest donor sites: a prospective, randomized study of coralline hydroxyapatite.

We report on a prospective randomized study of coralline hydroxyapatite (CH) used as backfill for iliac-crest donor sites. Autogenous iliac-crest bone graft is routinely harvested for spinal fusion. Donor-site morbidity is underappreciated; the presumption is that donor sites regenerate. In this study, we assessed the biological viability of the backfill CH (Pro OsteonTM Implant 500 Hydroxyapatite Bone Void Filler; Interpore, Irvine, Calif) and compared donor-site morbidity after harvest. Twelve patients (11 men, 1 woman) were enrolled: 5 in the backfill group and 7 in the no-backfill group. As part of routine evaluations done preoperatively and 6 weeks, 3 months, 6 months, and 1 year postoperatively, plain radiographs and computed tomography (CT) scans were used to assess bone ingrowth, and technetium bone scans were used to assess biological activity. Postoperative pain analysis was also done. Ten patients (9 men, 1 woman) completed the study. Of the 4 completers in the backfill group, 3 (75%) showed bony ingrowth on plain radiographs and CT scans at 1 year; the fourth patient showed bony ingrowth only on plain radiographs. All 4 patients showed biological activity on bone scans and reported mild pain to no pain. Of the 6 completers in the no-backfill group, 1 (17%) showed bony ingrowth on plain radiographs and CT scans. No patient showed biological activity on bone scans at 1 year. CH aids in iliac-crest healing after bone-graft harvesting by acting as a biological osteoconductive matrix. Postoperative pain at the bone-graft site is potentially reduced. More studies of larger numbers of patients are needed to assess the true long-term benefits of this material in a clinical setting.

Adult↗
PubMed2006

[Repair of canine segmental mandibular defects using autogenous bone marrow stromal cells and coralline hydroxyapatite].

OBJECTIVE: To repair segmental mandibular defects with autogenous bone marrow stromal cells (BMSCs) and coralline hydroxyapatite. METHODS: Isolated BMSCs were in vitro expanded and osteogenically induced. In 11 canines, a 3 cm segmental mandibular defect in right mandible was created. Five canine's defects were repaired with cell-scaffold constructs made from induced BMSCs and coralline hydroxyapatite (CHA); Others were repaired with CHA as control. The engineered bone was evaluated by X-ray, CT, gross and histological examination, biomechanical test 12, 26, 32 weeks post-operation respectively. RESULTS: BMSCs grew well on the CHA. X-ray and CT images showed better callus formation at connection sites in experimental group over time while worse formation at connection sites eventually in control group. At 32 weeks post-operation in experimental group, the defects were well repaired grossly. Histologically, there were bony healing and lamellar bone formation, in experimental group fibrous healing and woven bone formation in control group. Biomechanical test revealed no significant difference between experimental group and normal control group. CONCLUSIONS: Canine segmental mandibular defects can be ultimately repaired with the tissue-engineered bone generated by autogenous osteogenic BMSCs and CHA scaffold.

Animals↗