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PubMed1991

The response of porous hydroxyapatite to contiguous tissue infection.

Two patients are presented in whom severe clinical infection developed in tissue adjacent to and contiguous with previously implanted blocks of porous hydroxyapatite. Both infections resolved with appropriate antibiotics, debridement, and drainage of infected tissues. Hydroxyapatite blocks were left in situ. This unusually favorable response of an alloplast to infection is attributable to the abundant vascular supply of this porous implant. Although reliable dogma can hardly be concluded from two clinical examples, these experiences suggest that once ingrown, porous hydroxyapatite does not behave in a fashion that is typical of foreign bodies in the midst of infection. For the first time, clinical evidence has been offered to support the experimental data that vascularized hydroxyapatite has the ability to resist infection.

Adolescent↗
PubMed1992

Hydroxyapatite coatings in implant dentistry.

Hydroxyapatite coatings have shown promise due to the enhanced integration of osseous tissues to coated implant surfaces. When compared with healing around commercially pure or titanium alloy implant surfaces, hydroxyapatite-coated implants appear to be superior in sites which are compromised in either quantity or quality of bone. In spite of these encouraging findings, the long-term stability of the hydroxyapatite/bone interface has been challenged. Microbiologically, the hydroxyapatite-coated implant surface may be at an increased risk to bacterial plaque. However, after 8 years of clinical utilization, the hydroxyapatite-coated implant surface has not been shown to be predisposed to increased long-term failure. Available research as it pertains to this controversial area of implant dentistry is reviewed.

Animals↗
PubMed1992

Detoxification of endotoxin-contaminated titanium and hydroxyapatite-coated surfaces utilizing various chemotherapeutic and mechanical modalities.

The surgical repair of the ailing implant may be complicated by the surface effects of pathogenic bacteria and their products. This study evaluated the ability of various chemotherapeutic modalities to detoxify endotoxin-contaminated titanium alloy and hydroxyapatite-coated test strips. Grit-blasted titanium alloy and hydroxyapatite-coated test strips were contaminated with purified outer membranes of Escherichia coli labeled with radioactive 14C. The titanium alloy strips were treated with citric acid, stannous fluoride, tetracycline HCl, chlorhexidine gluconate, hydrogen peroxide, chloramine T, sterile water, a plastic sonic scaler tip, and an air-powder abrasive unit. Hydroxyapatite-coated strips were treated with chloramine T, citric acid, or burnished with sterile water on cotton pellets. Residual lipopolysaccharide levels were measured by liquid scintillation spectrometry. The air-powder abrasive unit removed significantly greater amounts of lipopolysaccharide than all other treatment modalities on titanium samples (P < 0.05). A 60-second burnish with sterile water was able to remove significant amounts of lipopolysaccharide when compared with untreated controls (P < 0.05). Citric acid was superior in the removal of lipopolysaccharide from hydroxyapatite-coated surfaces when compared with the controls or chloramine T (P < 0.01). Detoxification of an implant infected surface may be beneficial when surgical repair of the ailing implant is indicated.

Air Pressure↗
PubMed2003

Augmentation of the craniomaxillofacial region using porous hydroxyapatite granules.

Augmentation of the craniomaxillofacial region is required for many aesthetic and reconstructive procedures. A variety of different materials and techniques have been used. Coralline hydroxyapatite has proved to have biocompatible properties as a bone graft substitute. This study further analyzes the use of porous coral-derived hydroxyapatite granules in craniomaxillofacial augmentation for cosmetic and reconstructive purposes and evaluates the long-term clinical result. This retrospective study reviewed the use of porous coral-derived hydroxyapatite granules over a 20-year period, between 1981 and 2001, in 180 patients, in whom 393 procedures were performed. The surgical technique is described and discussed. Statistical significance was evaluated by descriptive statistics and the correlation bivariate Spearman's test (p > 0.05). For 61.6 percent of the procedures, the surgical indication was reconstructive and in 38.4 percent, cosmetic. The maxilla was the most common site of surgery (44.3 percent), followed by the mandible (21.6 percent) and zygoma (15.4 percent). The complication rate was 5.6 percent (n = 22 of 393), with contour irregularities being responsible for 59 percent (n = 13 of 22). Both infection and granule extrusion were responsible for 1.3 percent of the complications. Good results were achieved in 96.4 percent of the procedures. Porous coral-derived hydroxyapatite granules have shown considerable efficacy and versatility in craniofacial contour refinement and augmentation. They are stable, biocompatible, and safe. A sterile technique is advised, with care taken not to tear the periosteum in the pocket design and with subperiosteal placement of the granules, compaction of the granules at the site, overcorrection of 15 percent of the required total volume, watertight closure, and postoperative taping to prevent mobilization. The correct surgical indications and adherence to the principles stated above will result in a very satisfactory long-term outcome.

Adolescent↗
PubMed2005

A comparison of resistance to fracture among four commercially available forms of hydroxyapatite cement.

Hydroxyapatite cement is a relatively new biomaterial that has found widespread use in craniomaxillofacial surgery. Despite its common usage, complication rates as high as 32% have been reported. When failed implants are removed, implant fracture has been cited as a potential cause of failure. The purpose of this study was to evaluate resistance to fracture among 4 commercially available hydroxyapatite cement formulations. The materials tested included Norian Craniofacial Repair System (carbonated apatite cement) (AO North America, Devon, PA), Norian CRS Fast Set Putty (carbonated apatite cement) (AO North America), BoneSource (hydroxyapatite cement) (Stryker Leibinger, Portage, MI), and Mimix (hydroxyapatite cement) (Walter Lorenz Surgical, Inc, Jacksonville, FL). To ensure consistency, all materials were embedded in acrylic wells. Each material was placed into a well 2.54 cm in diameter and 0.953 cm in thickness. The materials were prepared per manufacturer specifications. All materials were incubated at 37.0 degrees C, in 6% CO2, 100% humidity for 36 hours. Using the Bionix MTS Test System, a 12-mm-diameter probe applied incremental force to the center of the disk at a rate of 0.1 mm per second. The transmitted force was measured using a Bionix MTS Axial-Torsional Load Transducer for each disk. The force which resulted in fracture was recorded for each material. Ten disks of each material were processed by this method, for a total of 40 disks. The significance of resistance to fracture for the 4 compounds was analyzed using 1-way analysis of variance with post hoc Scheffe method. Mean fracture force with related P values was plotted for direct comparison of group outcomes. Material type contributed significantly to variance in fracture force for the biomaterials studied. Norian CRS required the greatest mean fracture force (1385 N, SD+/-292 N), followed by Norian CRS Fast Set Putty (1143 N, SD+/-193 N). Mimix required a mean fracture force of 740 N, SD+/-79 N. BoneSource required a mean fracture force of 558 N, SD+/-150 N. Mimix and BoneSource required significantly less force for fracture when compared with Norian CRS and Fast Set Putty (P<0.01). Comparisons of fracture load resistance between 4 commonly used bone substitute materials have not been previously reported. Increasing biomaterial strength may reduce complications resulting from reinjury to cranioplasty sites. In this model, Norian CRS and Norian CRS Fast Set Putty demonstrated a significantly greater resistance to fracture when compared with BoneSource and Mimix.

Analysis of Variance↗
PubMed1983

Adsorption of glucosyltransferase to saliva coated hydroxyapatite. Possible mechanism for sucrose dependent bacterial colonization of teeth.

Glucosyltransferase (GTF) adsorbed to hydroxyapatite and to saliva coated hydroxyapatite in vitro. Several proteins which are known to be present in the "pellicle" which forms on hydroxyapatite when this mineral is exposed to whole saliva were shown to stimulate or inhibit GTF. It is suggested that these proteins may interact with GTF and cause binding of the enzyme to saliva coated hydroxyapatite. A model is suggested where GTF adsorbed to tooth surfaces may induce binding of microorganisms to tooth surfaces.

Adhesiveness↗
PubMed1979

Effects of dextranases on attachment of Streptococcus mutans to hydroxyapatite.

A Fusarium dextranase and a Penicillium dextranase were compared for their relative ability to quantitatively reduce the adsorption of (3)H-labeled Steptococcus mutans cells onto hydroxyapatite. Fusarium dextranase-treated hydroxyapatite disks caused a statistically significant decrease in the hydroxyapatite adsorption of both the OMZ 176 and NCTC 10449 strains of S. mutans relative to untreated control disks. The extent of initial bacterial adsorption was not promoted by sucrose-dependent glucan synthesis. Since the Fusarium dextranase has a much greater affinity for hydroxyapatite than the Penicillium dextranase, it could represent an enzyme with improved decay-preventive therapeutic properties. This was concluded because the Fusarium dextranase may interfere with both the initial attachment and later glucan-dependent accumulation of dental plaque microorganisms.

Adhesiveness↗
PubMed1981

Role of surface fimbriae (fibrils) in the adsorption of Actinomyces species to saliva-treated hydroxyapatite surfaces.

We studied the adsorption, morphological, and serological characteristics of selected Actinomyces and related species. Evaluation of uranyl acetate-stained cells by electron microscopy revealed wide variations among strains in the frequency of surface fimbriae. These variations did not always correlate with the percent adsorption to saliva-treated hydroxyapatite of the various Actinomyces strains. However, two strains of Rothia dentocariosa possessing no surface fimbriae and five strains of A. israelii possessing very few surface fimbriae exhibited feeble adsorption to saliva-treated hydroxyapatite. Although the calculated number of adsorption sites on saliva-treated hydroxypatite did not vary widely among the strains tested, significant differences were observed in the affinities calculated for some species or serotypes. The mean affinities for strains of A. viscosus serotype 2 and A. naeslundii serotype 3 were similar, and these strains adsorbed well to saliva-treated hydroxyapatite. The mean adsorption and affinity for the A. naeslundii strain serotype 1 and all strains of A. israelii tested were significantly less than those determined for the A. viscosus serotype 2 or A. naeslundii serotype 3 strains. Adsorption inhibition activity of antiserum to strain T14V, previously shown to be solely related to antibodies in immune serum directed against the VA1 fimbria (fibril) antigen, was removed by preadsorption of the antiserum with most A. viscosus and A. naelundii strains, but not with A. israelii strains. This suggests some cross-reactivity among strains of A. viscosus and A. naeslundii but not A. israelii. Adsorption to saliva-treated hydroxyapatite of all A. viscosus and A. naeslundii strains tested was strongly inhibited by fimbriae isolated from A. viscosus strain T14V. Collectively, these data suggest that the adsorption of certain A. viscosus and A. naeslundii strains is mediated by surface fimbriae, many of which appear serologically cross-reactive with strain T14V fimbriae.

Actinomyces↗
PubMed1983

Effect of adsorbed protein on hydroxyapatite zeta potential and Streptococcus mutans adherence.

The adherence of Streptococcus mutans PK1 to hydroxyapatite disks pretreated with various acidic and basic proteins in imidazole buffer was studied. Adsorption of a basic protein onto an hydroxyapatite disk enhanced or had no effect on bacterial adherence, whereas adsorption of an acidic protein reduced adherence. The effect of adsorbed protein on bacterial adherence was of both short and long range. The long-range effect of the acidic proteins in reducing the number of bacteria adhering to hydroxyapatite was related to protein adsorption causing an increase in surface net negative charge, as shown by zeta potential measurement. Basic protein produced a net positive surface charge which facilitated adherence. Within the acidic protein group, the acidic residue percentage of the adsorbed protein was negatively correlated with the number of bacteria adhering, whereas the nonpolar residue percentage was positively correlated with bacterial adherence. Within the basic protein group, the basic residue percentage was correlated with the number of cells adhering. These results indicate the involvement of short-range hydrophobic and ionic interactions in bacterial adherence to protein-coated hydroxyapatite.

Adhesiveness↗
PubMed1984

Specific inhibition of adsorption of Actinomyces viscosus T14V to saliva-treated hydroxyapatite by antibody against type 1 fimbriae.

Specific antibodies and their Fab fragments were used to study adsorption of Antinomyces viscosus T14V to saliva-treated hydroxyapatite. Antibody against A. viscosus T14V blocked adsorption of the strain to saliva-treated hydroxyapatite, and this activity was removed after preincubation of the immune immunoglobulin G (IgG) with purified type 1 fimbriae in amounts near equivalence but not after preincubation with type 2 fimbriae in antigen excess. Specific IgG or Fab fragments against type 1 fimbriae inhibited adsorption of strain T14V to saliva-treated hydroxyapatite and promoted desorption of cells already attached to the apatite surface. Anti-type 2 IgG or Fab fragments did not possess these activities. These data demonstrate that type 1 but not type 2 fimbriae mediate adsorption of strain T14V to the saliva-treated hydroxyapatite surface.

Actinomyces↗
PubMed1984

Adherence of Streptococcus sanguis to saliva-coated hydroxyapatite: evidence for two binding sites.

The characteristics of bacterial adherence to saliva-coated hydroxyapatite were examined for a salivary aggregating strain of Streptococcus sanguis, strain 12, and for its nonaggregating variant, strain 12na. Both strains were found to adhere in similar numbers to saliva-coated hydroxyapatite that had been preincubated at 4 degrees C overnight. Preincubation of saliva-coated hydroxyapatite overnight at 37 degrees C reduced subsequent adherence of S. sanguis 12 by approximately 10%, whereas adherence of S. sanguis 12na was reduced by over 80%. Preincubation at 37 degrees C in the presence of neuraminidase reduced adherence of S. sanguis 12 by over 90% and caused some additional reduction in adherence of S. sanguis 12na. The data were analyzed with Langmuir isotherms, Scatchard plots, and Hill plots. Some evidence of cooperativity was seen. A peak in the Scatchard plot for S. sanguis 12 binding to saliva-coated hydroxyapatite preincubated at 4 degrees C disappeared after preincubation at 37 degrees C, suggesting the loss of a salivary receptor. Many more organisms were found to bind when adherence was measured by assays counting the number of organisms remaining in suspension after the beads had settled. These weakly binding organisms, which were removed by washing, demonstrated adherence characteristics similar to those of the firmly bound organisms. Both strains were strongly hydrophobic. It is proposed that the binding of S. sanguis 12 and 12na involves two types of receptor on the salivary pellicle. One type of receptor is stable at 37 degrees C, but sensitive to neuraminidase; the second type is inactivated by prolonged incubation at 37 degrees C. S. sanguis 12 may bind to both types of receptor, whereas S. sanguis 12na binds only to the second type. The neuraminidase-sensitive receptor might be involved in saliva-mediated aggregation.

Adhesiveness↗
PubMed1985

A morphological study of macrophage and synovial cell interactions with hydroxyapatite crystals.

Hydroxyapatite crystals have been found in synovial fluids and periarticular spaces in association with osteoarthritis. This study examined the morphology of the interaction of macrophages and synovial cells with hydroxyapatite in order to determine the fate of hydroxyapatite over an extended culture period. Mouse peritoneal macrophages and bovine synovial cells were grown as monolayers. The morphology of the interaction between hydroxyapatite crystals (HAC) and these cells was studied by light microscopy, transmission and scanning electron microscopy for up to 14 days. Phagocytosis of HAC, phagosome formation, and concentration of crystal aggregates around the cells began within four minutes of their addition to the cultures. Phagocytosis and cellular aggregation continued after this time. HAC caused minimal cellular disruption despite the uptake of large amounts of crystalline material and significant cellular enlargement. HAC remained within cells for the duration of the study without any apparent dissolution by the cells. Whether macrophages are stimulated to produce interleukin I as a result of HAC uptake is currently under investigation.

Animals↗
PubMed1989

Synovial fluid hydroxyapatite crystals: detection thresholds of two methods.

A method of synovial fluid preparation giving optimal hydroxyapatite detection as well as definitions of the threshold masses of hydroxyapatite in viscous synovial fluid detectable by x ray diffraction and scanning electron microscopy with energy dispersive analysis is reported. Use of an equal volume of 100% hydrazine with the synovial fluid optimised detection of hydroxyapatite. By x ray diffraction the threshold mass of hydroxyapatite was 500 micrograms and by scanning electron microscopy with associated energy dispersive analysis 5 micrograms.

Centrifugation↗
PubMedDate not supplied

Effect of trace elements on dissolution of hydroxyapatite by cariogenic streptococci.

The effect of low levels of strontium, boron, lithium, molybdenum, and fluorine, alone and in combination, on hydroxyapatite solubility, bacterial growth, and acid production in five antigenic types of Streptococcus mutans was investigated. Pour plates containing synthetic hydroxyapatite were used to compare dissolution of hydroxyapatite. The colonies of the five antigenic types of S mutans produced zones of dissolution that were measured. Acid production and growth were studied in broth culture media. The results show that low levels of strontium and fluorine can significantly reduce demineralization of synthetic hydroxyapatite by S mutans in vitro.

Animals↗
PubMedDate not supplied

Kinetics and mechanism of hydroxyapatite crystal dissolution in weak acid buffers using the rotating disk method.

The model given in this report and the rotating disk method provide a useful combination in the study of dental enamel and hydroxyapatite dissolution kinetics. The present approach is a significant improvement over earlier studies, and both the ionic activity product that governs the dissolution reaction and the apparent surface dissolution reaction rate constant may be simultaneously obtained. Thus, these investigations have established the baseline for the dissolution rate studies under sink conditions. Concurrent studies, under conditions where the acidic buffer mediums are partially saturated with respect to hydroxyapatite have shown another dissolution site for hydroxyapatite that operates at a higher ionic activity product but has a much smaller apparent surface reaction rate constant. This has raised the question of whether the presence of this second site may interfere with the proper theoretical analysis of the experimental results obtained under sink conditions. A preliminary analysis of the two-site model has shown that the dissolution kinetics of hydroxyapatite under sink conditions is almost completely governed by the sink condition site (KHAP = 10(-124.5), k' = 174) established in this report. The difference between the predicted dissolution rate for the one-site model and the two-site model are generally of the order of 4 to 5% where the experiments are conducted under sink conditions and over the range of variables covered in the present study.

Acids↗
PubMed1978

Compounds which affect the adherence of Streptococcus sanguis and Streptococcus mutans to hydroxyapatite.

Several compounds were evaluated in an in vitro assay system for their ability to block the adherence of Streptococcus sanguis to saliva-coated hydroxyapatite and Streptococcus mutans to dextran-coated hydroxyapatitite. Fatty acids, ranging from C-12 to C-20, the enzyme amylase, chlorhexidine, human sera, and several serum proteins blocked S sanguis adherence to saliva-coated hydroxyapatite. Chlorhexidine blocked S mutans adherence to dextran-coated hydroxyapatite, but human sera and serum proteins did not. The effects of these compounds on the adherence of these organisms to hydroxyapatite may help in the development of specific plaque control methods for use in human populations.

Adhesiveness↗
PubMed1993

The effects of titanium and hydroxyapatite on osteoblastic expression and proliferation in rat parietal bone cultures.

Titanium and hydroxyapatite are used for the fabrication of dental and orthopedic implants. The longevity of these implants depends on the amount and rate of bone formation that occurs around their surfaces. In the present study, the effects of titanium, hydroxyapatite, and polystyrene (control) on the proliferation of rat calvarial cells, and on their capacity to express alkaline phosphatase and respond to parathyroid hormone (PTH) stimulation, were studied. The nature of the substrate did not affect the DNA and protein contents of experimental and control cultures throughout the experimental period. Alkaline phosphatase expression and PTH response, as assessed by DNA synthesis and adenylate cyclase activity, were higher in cultures grown on hydroxyapatite and polystyrene than in those grown on titanium. These results indicate that hydroxyapatite was a more favorable substrate than titanium for the growth and differentiation of osteoblast-like cells in vitro.

Alkaline Phosphatase↗
PubMed2006

Coralline hydroxyapatite bone graft substitute in hindfoot surgery.

BACKGROUND: Coralline hydroxyapatite bone graft substitute material is created by the conversion of the calcium carbonate structure of coral into hydroxyapatite. The microstructure of the material resembles cancellous bone and provides an osteoconductive scaffold for bone ingrowth. The use of this material is reported in the orthopedic oncology and trauma literature. Short-term reports in foot procedures have been reported. METHOD: A retrospective review identified 10 patients who had undergone hindfoot arthrodesis with coralline hydroxyapatite bone graft. The charts were reviewed for outcomes, operative complications, and time to union. Nine of the 10 patients were available for additional examination. RESULTS: The average followup was 6 years. There were three complications. One patient had sural nerve numbness with partial resolution which was unrelated to the graft material. A rheumatoid patient on methotrexate and prednisone developed a deep wound infection 9 months after surgery. One patient had a nonunion of the talonavicular joint. Eight of the 10 patients reported good or excellent results. Radiographs continued to demonstrate the presence of the graft material at 6 years. Radiographs showed extrusion of the graft from the joint in all patients. No patient had symptoms from the extruded material. DISCUSSION: Coralline hydroxyapatite bone graft substitute appears to be a clinically effective material for use in foot procedures. No adverse events could be linked to the graft material. The graft material is difficult to contain and extrusion was present in all patients. The slow resorption is a concerning characteristic of the graft material. At 6-year followup, the continued presence of the material has not shown any adverse effect.

Arthrodesis↗