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PubMed2004

Reconstruction of post-traumatic frontal-bone depression using hydroxyapatite cement.

The safety and efficacy of hydroxyapatite cement (Bone Source, Howmedica, Leibinger, Inc. Dallas, TX) use for the augmentation of post-traumatic frontal-bone depression was evaluated in a study of 20 consecutive oriental patients between June 1998 and July 2000 inclusively. The size of the depressed frontal bone ranged from 5 x 5 cm to 8 x 5 cm. The cement was placed in contact with the frontal sinus for 12 patients, none of whom revealed a history of paranasal sinus mucoperiosteal disease. Follow-up averaged 28 months for all 20 patients. Postimplantation evaluations included serial photographs, repeated physical examination, and 3-dimensional computed tomography for all patients. The cement paste allowed for precise and easy contouring of the bony depression's restoration. Meticulous hemostasis is essential to ensure a dry surgical field and successful application of the cement. No infection of the surgical site or extrusion of the cement was noted for any of our patients, and the contour of the reconstructed frontal bone was acceptable esthetically without any secondary depression noted during the follow-up period. Three-dimensional computed tomographic scans taken 2 years subsequent to implantation revealed good preservation of the cement restoration material. Small areas of cement loss due to cement absorption into the ambient fluid were noted for 2 patients, but such resorption did not appear to esthetically influence the final results. The results from this clinical study indicated that hydroxyapatite cement is a biocompatible, alloplastic material useful for augmentation of post-traumatic frontal-bone depression with stable volume maintenance over time. Judicious use of the hydroxyapatite cement offers an alternative to autogenous bone grafts or the use of methyl methacrylate for augmentation of the craniofacial skeleton among oriental patients.

Bone Cements↗
PubMed1984

The conditioning role of saliva in streptococcal attachment to hydroxyapatite surfaces.

The solution properties of saliva and its role in conditioning both the substrate and the bacterial surface have been investigated with regard to the attachment of oral streptococci to hydroxyapatite surfaces. Saliva from eight subjects was used and the attachment of three organisms, Streptococcus mutans strains FA-1 (serotype b) and KPSK2 (serotype c) and S. sanguis T175-1, was studied. An adsorbed salivary layer on a hydroxyapatite surface substantially reduced the affinity of the organisms for the surface. Adsorbed saliva on the bacterial surfaces, however, tended to increase the organisms' affinity for saliva-coated apatite. The source of saliva was important in determining the extent of inhibition of attachment. The data indicated that the negatively charged and hydrophilic nature of salivary conditioning films was important in controlling bacterial adsorption to hydroxyapatite. The results also suggested that hydrophobic salivas could promote binding of the more hydrophobic bacteria known to be early colonizers of the teeth.

Adsorption↗
PubMed1978

Characterization of hydroxyapatite powders and compacts at room temperature and after sintering at 1200 degrees C.

Synthetic HAP made in the laboratory as 'synthetic bone' may be a possible replacement or repair material, since the mineral phase of dental hard tissue and bone is essentially hydroxyapatite in form. Hydroxyapatite or modified compositions of HAP appear to offer possibilities as a substitute for the original material provided by nature. A high surface area (70.4 m2/g) commercially available hydroxyapatite (HAP) of poor crystallinity was converted to a highly crystalline HAP through sintering at 1200 degrees C in an atmosphere of steam and nitrogen. Compacts were made of the powdered HAP from 500 to 25,000 psi and sintered under the same conditions. The changes in the resulting pore volumes, pore sizes, pore size distributions, densities, and surface areas of the sintered compacts were determined by mercury porosimetry. A 20-fold reduction in open pore volume for sintered compacts was observed. For compacts made at pressures above 5000 psi, the reduction in open pore volume was compensated for by the formation of closed pore volume. The sintering mechanism was attributed mainly to neck formation, growth between particles, diffusion, and plastic deformation.

Chemical Phenomena↗
PubMed1979

Affinity of hydroxyapatite for furfural and a brown pigment formed by furfural and glycine.

The affinity of hydroxyapatite for furfural and a brown pigment formed by furfural and glycine was studied. A series of mixtures containing 1 M furfural and 0.25-2.0 M glycine were incubated at 37 degrees C and aliquots of hydroxyapatite added. The apatite showed a strong affinity for the brown pigment formed, and an excess of glycine in the mixtures appeared to enhance the binding. The adsorption of furfural to hydroxyapatite was estimated by a spectrophotometric method. The data revealed that pretreatment with CaCl2 and glycine significantly increased the adsorption of furfural.

Adsorption↗
PubMed1990

Effect of silicone oil on protein adsorption to hydroxyapatite in vitro and on pellicle formation in vivo.

Silicone oil has been introduced in a dentifrice for smokers because of its effect as a polishing agent. Silicone oils are hydrophobic in character and have low surface tensions and good wetting properties. Due to the low surface tension, silicone oils may spread readily on solid surfaces and cover them with a thin, water-repellent film. Introduced via dentifrices silicone oil may thus well be able to adsorb to enamel surfaces and to interfere with surface characteristics such as protein adsorption. The aim of the present study was to examine the effect of silicone oil on protein adsorption to hydroxyapatite (HA) in vitro and on pellicle formation in vivo. The effect on protein adsorption to HA in vitro was studied by adsorption of albumin to either untreated or silicone oil treated HA powders. Ion exchange chromatography was also used with either untreated or silicone oil treated HA as bed materials. The effect on pellicle formation in vivo was studied using enamel fragments carried in the mouth to acquire pellicle material. The chemical composition of the acquired pellicle was studied by collection and chemical analysis of pellicle material formed on enamel surfaces in vivo. The study showed that silicone oil treated HA took up less protein and that the adsorbed protein was bound to hydroxyapatite by a different mechanism as compared to untreated controls. The results indicated that hydrophobic interactions could be involved in binding of proteins to silicone oil treated hydroxyapatite. Silicone oil treated enamel fragments carried in the mouth showed a slower rate of pellicle formation as compared to untreated fragments. The amino acid composition of the acquired pellicle collected in vivo from silicone oil treated enamel surfaces was also different from pellicle material collected from untreated enamel.

Adsorption↗
PubMed1980

Fibril-mediated adherence of Actinomyces viscosus to saliva-treated hydroxyapatite.

Fibril-mediated adherence of Actinomyces viscosus strain T14V cells to saliva-treated hydroxyapatite was studied. Fibrils were purified by ammonium sulfate precipitation and differential centrifugation from the crude supernatant of whole cells that were sheared by one passage through a French pressure cell. Purified fibrils and crude supernatant inhibited strain T14V adherence to saliva-treated hydroxyapatite to similar extents. However, anti-strain T14V serum and antifibril specific antibody completely abolished strain T14V adherence. The blocking immunoglobulin could be adsorbed from anti-T14V serum by strain T14V whole cells, by purified fibrils, and, to a lesser extent, by cell walls. It was concluded that fibrils mediate adherence of strain T14V cells to saliva-treated hydroxyapatite. In addition, fibril preparations were shown to contain more than 95% protein and to be antigenically homogeneous by immunodiffusion and Laurell rocket immunoelectrophoresis. Purified fibril preparations showed serological identity with the virulence-associated 1 antigen of Lancefield-extracted T14V cells, whereas crude supernatants contained both virulence-associated 1 and virulence-associated 2 antigens, as shown by rocket immunoelectrophoresis.

Actinomyces↗
PubMed1981

Effect of bacterial aggregation on the adherence of oral streptococci to hydroxyapatite.

Several in vitro assay systems to measure the adherence of human dental plaque bacteria to solid surfaces such as teeth, glass, and hydroxyapatite have been published. In many studies a variety of macromolecular solutes have been used to study the adherence process. Often these solutes are able to aggregate the test bacterial and thus may alter the outcome of adherence experiments. In this study, the effects of the aggregation of Streptococcus sanguis on adherence to spheroidal hydroxyapatite is described. Adherence of preformed aggregates and of bacteria which were aggregating during the adherence reaction was examined. Bacteria were aggregated with whole saliva, concanavalin A, and wheat germ lectin. Further effects of the coaggregation of S. mitis and Actinomyces viscosus to saliva-coated spheroidal hydroxyapatite are presented. These studies suggest that formation of large aggregates resulted in a decrease in the numbers of organisms which adhered. In contrast, the formation of small aggregates actually increased the numbers of bacteria that adhered. All increases in adherent bacteria occurred at low concentrations of aggregating substance in which visible bacterial aggregation was not evident. The data indicate that adequate dose-response experiments must be performed to ensure that solutes used as probes to study adherence mechanisms do not affect the adherence simply as a result of aggregation of the test microorganisms.

Actinomyces↗
PubMed1983

Concentration-dependent multiple binding sites on saliva-treated hydroxyapatite for Streptococcus sanguis.

The influence of bacterial cell concentration on estimates of the number of binding sites and the affinity for the adsorption of a strain of Streptococcus sanguis to saliva-treated hydroxyapatite was determined, and the possible presence of multiple binding sites for this organism was tested. The range of concentrations of available bacteria varied from 4.7 x 10(6) to 5,960 x 10(6) cells per ml. The numbers of adsorbed bacteria increased over the entire range tested, but a suggestion of a break in an otherwise smooth adsorption isotherm was evident. Values for the number of binding sites and the affinity varied considerably depending upon the range of available bacterial concentrations used to estimate them; high correlation coefficients were obtained in all cases. The use of low bacterial cell concentrations yielded lower values for the number of sites and much higher values for the affinity constant than did the use of high bacterial cell concentrations. When data covering the entire range of bacterial concentrations were employed, values for the number of sites and the affinity were similar to those obtained by using only high bacterial cell concentrations. The simplest explanation for these results is that there are multiple binding sites for S. sanguis on saliva-treated hydroxyapatite surfaces. When present in low concentration, the streptococci evidently attach to more specific high-affinity sites which become saturated when higher bacterial concentrations are employed. The possibility of multiple binding sites was substantiated by comparing estimates of the adsorption parameters from a computer-simulated isotherm with those derived from the experimentally generated isotherm. A mathematical model describing bacterial adsorption to binary binding sites was further evidence for the existence of at least two classes of binding sites for S. sanguis. Far fewer streptococci adsorbed to experimental pellicles prepared from saliva depleted of bacterial aggregating activity when low numbers of streptococci were used, but the magnitude of this difference was considerably less when high streptococcal concentrations were employed. This suggests an association between salivary components which possess bacterial-aggregating activity and bacterial adsorption to high-affinity specific binding sites on saliva-treated hydroxyapatite surfaces.

Adsorption↗
PubMed1984

Optimization of an hydroxyapatite adhesion assay for Streptococcus sanguis.

Previous studies have compared the adhesion of [3H]thymidine-labeled Streptococcus sanguis to saliva-coated hydroxyapatite (SHA) and buffer-coated hydroxyapatite (HA) beads. Although the hypotonic buffer used in these assays was adjusted to simulate saliva, it does not necessarily provide the optimal parameters for the quantitative estimate of adhesion under in vitro conditions. Optimization is necessary to provide the maximum sensitivity of the assay for detecting the effects of various salivas as well as for quantitating the effect of environmental growth conditions on the adhesion of S. sanguis to SHA and HA. A major distinction between the adhesion of S. sanguis to SHA and HA was observed when the bacterial concentration was varied. At high cell concentrations, the number of cells adhering to SHA was twice the number adhering to HA. Such differences were not detected at low cell concentrations. The optimal pH for the adsorption to both SHA and HA was 6. Changes in the ionic strength or addition of mono- or divalent cations found in saliva had little effect on adhesion to HA. In contrast, high concentrations of monovalent cations inhibited adhesion to SHA. Anions such as carbonate, chloride, and sulfate did not have specific effects on adhesion, whereas acetate inhibited adhesion to both SHA and HA. Fluoride inhibited adhesion to both SHA and HA, suggesting an interaction between fluoride and hydroxyapatite. These results indicated that 2 mM phosphate buffer at a pH of 6 containing 5 mM KCl and 1 mM CaCl2 was the optimal buffer for studying the in vitro adhesion of S. sanguis to SHA.

Durapatite↗
PubMed1973

Hydroxyapatite chromatography and formamide denaturation of adenovirus DNA.

Denatured adenovirus DNA was retained by hydroxyapatite columns under conditions generally used for selective retention of double-stranded DNA, probably due to several partially complementary sequences within single-stranded DNA. It was found that addition of formamide reduced the fraction of sonically treated, denatured adenovirus DNA bound to hydroxyapatite from about 30% to less than 1%. This led to a study of the effect of formamide on the melting temperature (T(m)) of double-stranded DNA in solution or bound to hydroxyapatite. The T(m) of DNA decreases 0.56 C/1% formamide, a value determined in buffered solutions with purified formamide.

Adenoviridae↗
PubMed1990

Calcium hydroxyapatite deposition disease.

Calcium hydroxyapatite crystal deposition disease is characterized by the presence of basic calcium phosphate crystals--predominantly hydroxyapatite--in the periarticular soft tissues, especially the tendons. The entity is best recognized as "calcific tendinitis" at its most frequent site about the shoulder, but the disease involves numerous other sites and may be more appropriately termed calcific periarthritis. This article illustrates typical and atypical radiographic features of hydroxyapatite deposition, as well as some unusual manifestations of the disease. A brief review of various theories on the pathogenesis of the disease and a section on differential diagnosis is included.

Arthrography↗
PubMedDate not supplied

Reconstruction of the ossicular chain with hydroxyapatite implants.

This paper describes the clinical results of the application of dense hydroxyapatite assembly prostheses. A study of 60 patients with hydroxyapatite incus prostheses revealed an air-bone gap closure within 20 dB in 86.6% of the cases, and an air-bone gap closure of less than 10 dB in 60.6%. No improvement was seen in 5% of the patients. The follow-up period varied from 1 to 4 years with an average of 2 years, and the hearing gain remained constant during this period. Hydroxyapatite may be considered a useful material for reconstructive middle ear surgery.

Adolescent↗
PubMedDate not supplied

Chromatographic properties of denatured skin and bone collagens on hydroxyapatite.

Denatured collagen samples extracted from the skin and bone of lathyritic rats with guanidine hydrochloride were chromatographed on hydroxyapatite columns. A major fraction of the bone extract that was rich in alpha chain showed a stronger binding to hydroxyapatite when compared to the corresponding fraction from skin. Thus, bone collagen shows a special affinity for hydroxyapatite after isolation and denaturation.

Amino Acids↗
PubMed1985

Photo-oxidation of tetracycline adsorbed on hydroxyapatite in relation to the light-induced staining of teeth.

In an attempt to understand the chemistry of the light-induced staining of children's teeth by tetracycline, we studied the photo-chemical behavior of tetracycline adsorbed on hydroxyapatite, as a simple model of enamel. Tetracycline was strongly bound by hydroxyapatite to give a pale yellow material which, under ultraviolet light, showed a bright yellow fluorescence (lambda max 525 nm). On exposure of this material to the radiation from a medium-pressure mercury lamp, the fluorescence gradually disappeared, and a red-purple product was formed. Photo-acoustic spectroscopy was employed to follow the disappearance of tetracycline and the concomitant formation of the red-purple product, the spectrum of which (lambda max 530 nm) led to the conclusion that it was 4 alpha, 12 alpha-anhydro-4-oxo-4-dedimethylaminotetracycline (AODTC). This assignment was supported by the observation that 1 mole of oxygen was absorbed per mole of adsorbed tetracycline converted to the red-purple product. It is suggested that the formation of AODTC on hydroxyapatite probably takes place by a mechanism of photo-oxidation similar to that already proposed for solutions of tetracycline, and that the formation of AODTC in children's teeth is responsible for the light-induced staining caused by tetracycline.

Child↗
PubMed1991

Bonding of hydroxyapatite-coated femoral prostheses. Histopathology of specimens from four cases.

We examined specimens of hydroxyapatite-coated femoral prostheses from four patients who had died within nine months of implantation for fractured neck of femur. Histology showed newly formed immature bone overlying the hydroxyapatite coating with new trabeculae bridging to the endosteal bone layer. In the diaphysis, where there had been contact between the hydroxyapatite and the cortex, there was dense, firmly anchored bone with an haversian architecture. In other places the newly formed bone had a trabecular structure, containing bone marrow tissue with normal cellularity. It appeared that biological osseointegration had taken place.

Aged↗
PubMed1991

Fixation of hip prostheses by hydroxyapatite ceramic coatings.

We report the histological findings in post-mortem specimens obtained ten days, 17 days and seven weeks after implantation of hydroxyapatite-coated femoral components of hip arthroplasties. There was early deposition of woven bone on the hydroxyapatite ceramic, identical to that deposited on surviving cancellous trabeculae. The space between these deposits became bridged from both sides by new trabeculae, and there was no evidence of an inflammatory reaction or of fibrous tissue formation. The use of an hydroxyapatite coating seems to allow early, sound, secondary fixation of implants.

Biocompatible Materials↗
PubMed1992

Hydroxyapatite coating on carbon composite hip implants in dogs.

In 33 dogs we implanted femoral stems made either of carbon composite, some coated with hydroxyapatite, or of titanium alloy with a porous coating. Osseointegration was greater in the hydroxyapatite-coated than in the un-coated stems (p less than 0.001). Push-out tests, at an average of 7.2 months after implantation, showed a six-fold increase in interface shear strength and a twelve-fold increase in shear stiffness in the hydroxyapatite-coated group compared with noncoated implants. The highest shear-strength values were found in the porous-coated titanium alloy stems, around which there was also the most resorptive bone remodelling.

Animals↗