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PubMed2003

Assessment of the effects on growth of porous hydroxyapatite granule cranioplasty in the immature guinea pig craniofacial skeleton.

The immature guinea pig was used to study the effects on growth of porous granular hydroxyapatite used as an onlay cranioplasty and inlay cranioplasty to reconstruct full-thickness cranial defects in a growing craniofacial skeleton. Forty Hartley guinea pigs, 20 immature animals and 20 mature animals, were divided into four groups each containing five mature and five immature animals. The mature animals served as controls. Group I underwent elevation and replacement of the parietal periosteum. Group II underwent placement of hydroxyapatite between periosteum and parietal bone. Group III underwent elevation and replacement of autogenous bone flap after the formation of a 1 x 1-cm craniectomy defect in the parietal skull. Group IV underwent elevation of a 1 x 1-cm parietal craniectomy and reconstruction of the defect with hydroxyapatite granules placed between the dura and periosteum. Immature animals were killed at maturity at 3.5 months and mature animals were killed 2.5 months postoperatively. Macroscopic examination of the operative field, transverse and longitudinal cephalometric measurements, and histological sections encompassing the operative sites were compared. Macroscopically, all reconstructed operative sites were fully incorporated into the cranium. Histological staining of the sectioned operative site revealed no hydroxyapatite migration through the cranial bone or dura. No inflammatory or foreign body reaction was evident in the subcutaneous tissue, periosteum, or dura. No statistically significant cephalometric intergroup or intragroup differences were found at the conclusion of the study. The results of this study indicate that a granular porous form of hydroxyapatite may be used as an onlay or inlay cranioplasty in the immature guinea pig craniofacial skeleton without evidence of dural inflammation, granule migration, or growth restriction or retardation.

Age Factors↗
PubMed1995

Efficacy of XeCl-308 excimer laser in fusing hydroxyapatite to seal the root apex.

Sealing the root apex during apical surgery is important for a successful outcome. The effect of XeCl-308 nm excimer laser irradiation on the fusion and seal of hydroxyapatite to the root apex was tested in extracted human teeth. Twenty-four roots of intact single-rooted premolars were instrumented to size 30 K-file at the apex leaving a patent apical foramen. The apex of each tooth was covered with a freshly prepared paste of hydroxyapatite powder mixed with saline. The samples were then divided into two groups. In 12 teeth, the apical area was irridiated with XeCl-308 nm excimer laser at a fluence of 0.7 J/cm2 for 5 s with pulse repetition rate of 25 Hz and a spot size of 0.13 cm2 immediately after the hydroxyapatite application. In the other 12 teeth, no laser treatment was performed after the hydroxyapatite application. The roots were mounted on a model for the detection of radicular leakage of hydrogen peroxide. The hydrogen peroxide leakage of each sample was measured and the difference between the test groups compared. The ability of the hydroxyapatite plug to prevent hydrogen peroxide leakage at the apex was also tested by applying compressed air from the triple syringe on the coronal access preparation for 2 min. Apical leakage was found in four teeth in the lased group and in eight teeth in the non-plased group. However, the difference between the groups was not statistically significant. Compressed air applied to the coronal access caused hydrogen peroxide leakage in all the teeth.(ABSTRACT TRUNCATED AT 250 WORDS)

Chi-Square Distribution↗
PubMed2005

Hydroxyapatite promotes superior keratocyte adhesion and proliferation in comparison with current keratoprosthesis skirt materials.

AIM: Published clinical series suggest the osteoodontokeratoprosthesis (OOKP) may have a lower extrusion rate than current synthetic keratoprostheses. The OOKP is anchored in the eye wall by autologous tooth. The authors' aim was to compare adhesion, proliferation, and morphology for telomerase transformed keratocytes seeded on calcium hydroxyapatite (the principal mineral constituent of tooth) and materials used in the anchoring elements of commercially available synthetic keratoprostheses. METHODS: Test materials were hydroxyapatite, polytetrafluoroethylene (PTFE), polyhydroxyethyl methacrylate (HEMA), and glass (control). Cell adhesion and viability were quantified at 4 hours, 24 hours, and 1 week using a calcein-AM/EthD-1 viability/cytotoxicity assay. Focal contact expression and cytoskeletal organisation were studied at 24 hours by confocal microscopy with immunoflourescent labelling. Further studies of cell morphology were performed using light and scanning electron microscopy. RESULTS: Live cell counts were significantly greater on hydroxyapatite surfaces at each time point (p<0.04). Dead cell counts were significantly higher for PTFE at 7 days (p<0.002). ss(1) integrin expression was highest on hydroxyapatite. Adhesion structures were well expressed in flat, spread out keratocytes on both HA and glass. Keratocytes tended to be thinner and spindle shaped on PTFE. The relatively few keratocytes visible on HEMA test surfaces were rounded and poorly adherent. CONCLUSIONS: Keratocyte adhesion, spreading, and viability on hydroxyapatite test surfaces is superior to that seen on PTFE and HEMA. Improving the initial cell adhesion environment in the skirt element of keratoprostheses may enhance tissue integration and reduce device failure rates.

Biocompatible Materials↗
PubMed2001

Adhesion to and decalcification of hydroxyapatite by carboxylic acids.

Fundamental to the processes of decalcification of or adhesion to mineralized tissues is the molecular interaction of acids with hydroxyapatite. This study was undertaken to chemically analyze the interaction of 1 mono-, 2 di-, 1 tri-, and 2 polycarboxylic acids with hydroxyapatite in an attempt to elucidate the underlying mechanism. Maleic, citric, and lactic acid decalcified hydroxyapatite, in contrast to oxalic acid and the two polycarboxylic acids that were chemically bonded to hydroxyapatite. Solubility tests showed that the calcium salts of the former were very soluble, whereas those of the latter could hardly be dissolved in the respective acid solutions. Based on these data, an adhesion/decalcification concept was advanced that predicts that carboxylic acids, regardless of concentration/pH, either adhere to or decalcify hydroxyapatite, depending on the dissolution rate of the respective calcium salts in the acid solution. This contrasting behavior of organic acids most likely results from their differential structural conformations.

Acrylic Resins↗
PubMedDate not supplied

Two-stage procedure for management of large exposure defects of hydroxyapatite orbital implant.

PURPOSE: To report the results of a newly devised two-stage surgical technique for management of large hydroxyapatite exposure defects. METHODS: Eight patients with exposed hydroxyapatite orbital implant were treated in two stages. The exposed hydroxyapatite anterior surface was burred down and the defect was directly closed 3 to 13 months after the primary procedure. Then a mucous membrane or dermis-fat graft was added for socket reconstruction. RESULTS: Trauma was the primary cause of enucleation in all patients. Hydroxyapatite exposures occurred 1 to 2 weeks after implantation. Mean defect size was 15 mm in the greatest dimension (range 10-21 mm). Socket reconstruction was done in seven patients with mucous membrane graft and in one patient with dermis fat graft 3 to 13 months after direct repair of the defects. All eight patients maintained closure of the defects during a mean follow-up of 13 months (range 9-19 months). CONCLUSIONS: Management of hydroxyapatite exposures, especially those with large defects, can be difficult. Based on our experience, optimal results can be obtained after direct closure of the defect under minimal tension at the expense of foreshortening the fornices after which the socket can be reconstructed with a mucous membrane or dermis fat graft as a secondary procedure.

Adipose Tissue↗
PubMed2005

A six-year study of hydroxyapatite-coated root-form dental implants.

BACKGROUND: The effect of hydroxyapatite coating of dental implants is controversial. The long-term fate of hydroxyapatite-coated implants has been the subject of some criticism. PURPOSE: The aim of this retrospective study was to assess the clinical outcome of hydroxyapatite-coated cylindrical root-form endosseous Impladent dental implants (LASAK Ltd, Prague, Czech Republic) during a six-year course. METHODS: Three-hundred and ninety-one consecutively placed implants were used in 169 patients and followed for four to six years. Interval and cumulative success of implants and prostheses survival was tabulated. Marginal bone loss was measured RESULTS: Of the total number of implants, 98.5% achieved initial osseointegration. The cumulative success was 98.3% after one year, 97.0% after three years, 92.8% after five years and 90.4% after six years. The prostheses survival at the end of the study was 100% for fixed bridges totally supported by implants, 96.5% for fixed bridges with combined implant and tooth support, 94.2% for single crowns, 90.9% for mandibular overdentures and 81.3% for maxillary overdentures. Marginal bone loss averaged 2.4 +/- 0.8 mm at the end of five years. CONCLUSION: The success rate of the investigated hydroxyapatite-coated implants was comparable with the data presented in the literature and with the results of the similar implants without hydroxyapatite-coating. However, the marginal bone loss was of interest. Longer monitoring of the implants is necessary.

Alveolar Bone Loss↗
PubMed2003

Hydroxyapatite coating of external fixation pins to decrease axial deformity during tibial lengthening for short stature.

BACKGROUND: Tibial valgus, a known complication of leg lengthening with external fixation techniques, has been related to the stability of the bone-fixator system and, in particular, to pin loosening. A hydroxyapatite coating has been reported to enhance the quality of the bone-pin interface. The aim of this study was to compare the prevalence of axial deformity after tibial lengthening with hydroxyapatite-coated external fixation pins with the prevalence after tibial lengthening with uncoated pins. METHODS: We conducted a prospective study of thirty-four symmetrical tibial lengthening procedures in seventeen pathologically short patients. One limb of each patient was lengthened with use of hydroxyapatite-coated pins and the other, with standard uncoated pins; the sides of the operations were randomly selected. The bone angle in the frontal plane was measured before the operation and at the end of the fixation period, and the difference between these measurements was compared between the lengthening procedures performed with coated pins and those performed with uncoated pins. RESULTS: The mean valgus deviation of the tibia was 6.5 degrees in the group treated with hydroxyapatite-coated pins and 12.5 degrees in the group treated with uncoated pins (p = 0.023). With the numbers available, other factors previously related to the development of valgus deformity did not differ significantly between the two groups. CONCLUSION: Tibiae that are lengthened with the use of hydroxyapatite-coated external fixation pins are less prone to axial deviation in the frontal plane than are those treated with uncoated pins. LEVEL OF EVIDENCE: Therapeutic study, Level I-1a (randomized controlled trial [significant difference]). See Instructions to Authors for a complete description of levels of evidence.

Adolescent↗
PubMed2005

Advantages of TOF-SIMS analysis of hydroxyapatite and fluorapatite in comparison with XRD, HR-TEM and FT-IR.

The chemical analysis of hydroxyapatite and fluorapatite was carried out using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Hydroxyapatite and fluorapatite were synthesized at 80 +/- 1 degrees C and pH 7.4 +/- 0.2. Fluorapatite was better crystallized, with its (300) reflection shifted to a slightly higher angle. High-resolution transmission electron microscopy clearly revealed a typical, regular hexagonal cross section perpendicular to the c-axis for fluorapatite and a flattened hexagonal cross section for hydroxyapatite. FT-IR spectra of fluorapatite confirmed the absence of OH absorption peak--which was seen in hydroxyapatite at about 3570 cm(-1). TOF-SIMS mass spectra showed a peak at 40 amu due to calcium. In addition, a peak at 19 amu due to fluorine could be clearly seen, although the intensities of PO, PO2, and PO3 were very low. It was confirmed that TOF-SIMS clearly showed the differences between positive and negative mass spectra of hydroxyapatite and fluorapatite, especially for F-. We concluded that TOF-SIMS exhibited distinct advantages compared with other methods of analysis.

Apatites↗
PubMed2000

Effects of geometry of hydroxyapatite as a cell substratum in BMP-induced ectopic bone formation.

Three different types of porous hydroxyapatite with pore sizes of 100-200 micrometer in diameter-porous particles of hydroxyapatite (PPHAP), porous blocks of hydroxyapatite (PBHAP), and honeycomb-shaped hydroxyapatite (HCHAP)-were compared in terms of their abilities to induce osteogenesis when implanted subcutaneously with recombinant human BMP-2 into rats and extracted at 1, 2, 3, and 4 weeks. Histologically, direct bone formation occurred in PPHAP and PBHAP while only endochondral ossification took place in HCHAP. Interestingly, cartilage in the central zones and bone in the orifice zones of the tunnels of the HCHAP were observed at 2 weeks. After 3 weeks, the cartilage disappeared and bone formation occurred throughout the inner surface of the tunnels of the HCHAP, always leaving space for capillaries within the tunnels. Alkaline phosphatase activity and osteocalcin content were the highest in HCHAP among the three hydroxyapatite implants. These results clearly indicate that BMP-induced bone formation is highly dependent on the geometry of the carrier, which provides feasible structural factors for vascularization.

Alkaline Phosphatase↗
PubMed2001

Hydroxyapatite-coated total hip replacements in patients 65 years of age and over.

Prospective review examined 69 patients aged over 65 years (mean: 73 years; range: 65 to 85 years) who underwent 72 primary hydroxyapatite-coated total hip replacements by one surgeon. The femoral component used was titanium alloy coated by hydroxyapatite on the proximal third and the acetabular component was spherical and unthreaded, coated with hydroxyapatite. All patients were evaluated clinically by Harris Hip Score and radiologically using Engh's criteria with a mean follow-up of 86 months (range: 29 months to 10 years). Preoperative radiologic evaluation for osteoporotic bone using the Singh index was performed. Average Harris Hip Score increased from 45 before surgery to 89 at last follow-up. Two femoral and one-acetabular components were shown to probably be loose, but none was definitely loose or unstable by Engh's criteria. There was no correlation between clinical and radiologic results with respect to age, sex, and preoperative diagnosis. In contrast, significant statistical correlation was demonstrated between Charnley groups A or B, and group C, with regard to the Harris Hip Score (p = 0.047). There was no correlation between Charnley groups and radiological results. There was no statistical difference between patients with osteoporotic bone (Singh 1-3) and non-osteoporotic bone (Singh 4-6) with respect to clinical and radiologic evaluation. These early clinical and radiologic results compare favorably with those of hydroxyapatite-coated total hip replacements for younger patients and cemented total hip replacements in older patients. We recommended that hydroxyapatite-coated total hip replacements should not be reserved for younger patients. They can be used safely in patients over 65 years of age, promising minimal postoperative thigh pain and satisfactory clinical and radiologic results.

Aged↗
PubMed2000

[Evaluation of cariogenic potential of Streptococcus mutans isolated from caries-free and -active persons: adherence properties to saliva-coated hydroxyapatite].

OBJECTIVE: In this study, authors used saliva-coated hydroxyapatite to simulate tooth surface in oral cavity to evaluate adherence of different Streptococcus mutans isolated from caries-free and -active persons to saliva-coated hydroxyapatite. METHODS: Streptococcus mutans isolated from people with different carious experiences were divided into two groups: the caried-free group (DMFS = 0) including 19 persons and the caries-active group (DMFS > or = 6) including 40 persons. Totally 105 genotype Streptococcus mutans strains were obtains, including 22 strains from the caries-free group, and 83 strains from the caries-active group. The adhering properties of Streptococcus mutans (serotype c) strains were investigated, and different adhering properties were compared between the caries-free group and the caries-active group in order to find the correlationship between carious experiences and adhering properties of Streptococcus mutans. Saliva-coated hydroxyapatite was used to simulated tooth surface in oral cavity. Streptococci mutans were cultured in TPY liquid medium containing 3H-TDR in the same radioactive concentration. After being cultured in an anaerobic incubator for 18 hours, Streptococci mutans were radiolabelled by 3H-TDR. Saliva-coated hydroxyapatite and bacterial liquid(BSA = 0.52) were mixed for 90 minutes. Samples were assayed by using liquid scintillation counter, and binding abilities of strains were evaluated by the count per minute(cpm). RESULTS: Binding abilities of strains were significantly different in two groups, Caries-active people harbored more Streptococci mutans with high binding abilities(cpm > 2000) than caries-free people did(P < 0.05). The binding abilities to saliva-coated hydroxyapatite were different between strains of differing genotypes isolated from the same person. Each person always harbored one or two strains with high binding abilities(cpm > 2000) in the caries-active group. CONCLUSION: 1. Different genotypes have different adhering properties. 2. In caries-active group, different genotype strains have synergic effects, and adhesion of high binding ability strains cause caries susceptibility. 3. The differences in binding properties of isolates might relate to differences in carious experiences.

Bacterial Adhesion↗
PubMed1993

[Using Metronidazole and Hydroxyapatite for preventing dry socket after extraction of impacted mandibular 3rd molar]

Dry socket is one of the most frequent complications after teeth extraction,especially in impacted mandibular third molars.The etilogy and prevention is not clear.This study id based on principles of clinical epidemiology.Randomized double-blind method was carried out in 549 patients to test the value of the prophylactic use of Hydroxyapatite,to test the value of the prophylactic use of Hydroxyapatite and Metronidazole,placed in the sockets of extracted impacted mandibular third molars.The results of the incidence of DS was 7.1% of Metronidazole treated sockets,and 2.1% of Hydroxyapatite treated sockets,It is concluded that Hydroxyapatite is an effective preventive factor for dry socket,The possible mechanism of Hydroxyapatite and the dry socket etiology were discussed.

Journal Article↗
PubMed2004

[Cytocompatibility of nanophase hydroxyapatite ceramics].

OBJECTIVE: To evaluate the cytocompatibility of nanophase hydroxyapatite ceramics in vitro. METHODS: Hydroxyapatite (HA) was prepared via wet method. The grain size of the hydroxyapatite in the study was determined by scanning electron microscope and atomic force microscope with image analysis software. Primary osteoblast culture was established from rat calvaria. Cell adherence and proliferation on nanophase hydroxyapatite ceramics and conventional hydroxyapatite ceramics were examined at 1, 3, 5, 7 days. Morphology of the cells was observed by microscope. RESULTS: The average grain size of the nanophase and conventional HA was 55 nm and 780 nm, respectively. Throughout 7 days period, osteoblast proliferation on the HA was similar to that on tissue culture borosilicate glass controls, osteoblasts could attach, spread and proliferate on HA. However, compared to conventional ceramics, osteoblast proliferation on nanophase HA was significantly better after 1, 3, 5 and 7 days. CONCLUSION: Cytocompatibility of nanophase HA was significantly better than conventional ceramics.

Animals↗
PubMed2005

[Application of elemental microanalysis for estimation of osteoinduction and osteoconduction of hydroxyapatite bone implants].

Hydroxyapatite (HAp) ceramics based on calcium phosphates, chemical compounds being natural constructive element of bones is now regarded to be one of better implantation materials in osseous surgery and stomatology. HAp is poorly soluble and slowly resorbing in tissues material. Easiness of connecting of hydroxyapatite ceramics with other materials creates possibilities to produce new composites of chemical compounds containing calcium and easier resorbing. An important and till now not fully known problem is influence of hydrodroxyapatite grafts on the processes leading to production of calcium and phosphorus ions responsive for mineralization of bone tissue around the graft. Proliferation of osteoblasts and rate of osseous trabeculas production depends, among others, concentration of calcium and phosphorus ions. The main target of this study was the comparative analysis of the bone mineralisation rate after implantation of hydroxyapatite (HAp) and composites hydroxyapatite + beta tricalcium phosphate (HAp + TCP) and hydroxyapatite + calcium hydrosulfate (HAp + gypsum), on the basis of elemental microanalysis. Implantation studies were carried out on 24 rabbits. Sections were carried out 5, 9, 11 and 14 weeks after implantation of the tested materials. The carried out punctual analysis of the occurring elements and their topographic location (mapping) in bones after implantation showed essential differences among the tested grafts. Those differences were most significant after 5 and 14 weeks and depended on the rate of the tested materials resorption. On the basis of conducted macroscopic evaluation and scanning microscope assessment we can stated that the composite of HAp+TCP showed the best osteocunductive properties, while the best osteoinductive influence was shown by the composite HAp + gypsum.

Animals↗
PubMedDate not supplied

[The immunotropic and allergenic activity of hydroxyapatite with an ultrahigh degree of dispersion].

Hydroxyapatite is a well-known biologic material intended for intraosseous implantation which is widely used in practical dentistry. The agent causes no inflammatory reaction at the site of administration and is not characterized by acute or chronic toxicity. The possibility of development of specific contraindications against hydroxyapatite has not yet been studied; such contraindications might be connected with its possible immunotropism and allergenic activity which are to this or that measure present in all materials used for implantation into the bone. Since hydroxyapatite is known as surfactant, we used in our studies its modification characterized by the highest specific surface known at present, and therefore the most biochemically active. "Cold", that is, not exposed to high-temperature treatment ceramics was used in order to prevent reduction of hydroxyapatite reaction capacity. Complex of animal experiments showed that hydroxyapatite cannot possess immunotropic or allergenic characteristics.

Animals↗
PubMed1995

Vicryl-mesh wrap for the implantation of hydroxyapatite orbital implants: an animal model.

OBJECTIVE: To evaluate host fibrovascularization of hydroxyapatite orbital implants wrapped in sclera or in Vicryl (polyglactin 910) mesh in a rabbit model. NUMBERS: Eight adult New Zealand white rabbits that received hydroxyapatite orbital implants wrapped in homologous donor sclera (four animals) or Vicryl mesh (four animals). INTERVENTIONS: The rabbits had one eye enucleated and then received a 12-mm hydroxyapatite implant wrapped in sclera or Vicryl mesh. Magnetic resonance imaging (MRI) and bone scintigraphy were done to assess host fibrovascularization of the implant 4, 8, 12 and 20 weeks after implantation. Two animals (one in each group) were killed at each of these times, and the implant was removed for histopathological examination. MAIN OUTCOME MEASURES: Enhancement on MRI, uptake on bone scintigraphy, fibrovascularization seen on histopathological examination. RESULTS: The degree of fibrovascularization was substantial in all the specimens but appeared greater in the Vicryl-mesh-wrapped implants in the first 12 weeks after implantation on both histopathological and MRI studies. At 20 weeks these findings were similar in the two groups. A granulomatous foreign-body giant-cell reaction to both the Vicryl mesh and the implant itself was present up to 8 weeks after implantation. Bone scans showed only grade 1+ activity in all the implants. CONCLUSIONS: Host fibrovascularization in the rabbit appears to occur to a greater degree in Vicryl-mesh-wrapped hydroxyapatite implants than in those wrapped in donor sclera during the first 12 weeks after implantation. Vicryl mesh appears to be an acceptable alternative wrap for the hydroxyapatite implant, eliminating the need for donor sclera and its potential risks of transmissible diseases.

Animals↗
PubMed1996

A morphological study on obliteration of the temporal dorsal bullae using hydroxyapatite granules.

The present study deals with morphological observations of temporal dorsal bullae obliterated by implantation of hydroxyapatite granules. The specimens were obtained from guinea pigs 1 year after implantation, and undecalcified tissue sections were examined under a light microscope. The temporal dorsal bullae were found to be completely filled with bone tissue including the hydroxyapatite granules in all animals examined. The bone and hydroxyapatite granules interdigitated tightly without any intervening connective tissue or dead space. The newly formed bone displayed incomplete osteon structures with lamellae surrounding a haversian canal. There was no evidence of inflammation, such as lymphocyte infiltration, in the temporal bullae. The bone formation induced by hydroxyapatite implantation appeared to be a physiological reaction. It was concluded that the hydroxyapatite granules are safe and useful for mastoid obliteration during tympanoplasty.

Animals↗
PubMed1997

Human dura mater as a wrapping material for hydroxyapatite implantation in the anophthalmic socket.

Homologous sclera and autologous fascia lata have been accepted as common wrapping materials for hydroxyapatite implantation; however, various problems have been observed, such as the risk of transmittable diseases such as AIDS or hepatitis. This report details the use of cadaver dura mater to wrap hydroxyapatite implants. For 73 eyes of 73 patients with hydroxyapatite implantation, cadaver dura mater was used to wrap the hydroxyapatite after enucleation or secondary implantation. Of the 73 patients, 20 had conjunctival erosion; however, all of the patients but 1 healed spontaneously within an average of 22 days. Only 1 of the 73 patients progressed to implant exposure requiring a dermis graft. The authors suggest that cadaver dura mater is a suitable wrapping material for hydroxyapatite implantation.

Anophthalmos↗