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PubMed1985

[Histological study of the biocompatibility of hydroxyapatite crystals in periodontal surgery].

The purpose of this investigation was to analyse, after 6 years of clinical trials, the findings obtained from biopsies of infrabony defects in man treated by grafts of hydroxyapatite. Filled extraction sockets in miniature swine treated in a similar manner with apatite were also studied. Light microscope analysis showed bone neoformation around and in the neighbourhood of grafted apatite fragments with the presence of osteocytes, osteoblasts and a normal peripheral connective tissue without inflammatory reaction. These results demonstrate the biocompatibility of the implanted apatites accompanied by a normal fibrogenesis and a seeming osteogenesis.

Adult↗

PubMed1977

[Infrared spectroscopy in the quantitative determination of urinary calculi constituents (author's transl)].

Infrared spectroscopy of urinary calculi can be used for the quantitative determination of the major constituents in mixed stones; the method is simple and consists in area-measurements of specific absorption peaks of the spectrum of each compound. In the area-measurement method the average error is +/- 2,5% in calcium-oxalate-apatite and +/- 2% in ammonium magnesium phosphate-carboapatite mixtures; within these limits the calculus matrix do not affect significantly the value of areas. An investigation of 64 mixed renal stones shows that in 57% of the samples, apatite is present in the nucleus; uric acid and calcium-oxalate are the most frequent superficial compounds, while the external layer of ammonium magnesium phosphate and the mixture uric acid-calcium phosphate are rare events. In calcium-oxalate-apatite and ammonium magnesium phosphate-carboapatite calculi the quantitative composition of the nucleus and the external layer differ significantly. The proposed method of analysis of internal and external structures in renal calculi can be useful for the study of etiology, for the prevention and the treatment of urolithiasis.

Humans↗

PubMed1984

Transmission electron microscopic studies on articular calcium crystals and associated protein coatings.

Calcium pyrophosphate (CPPD) and apatite crystals are associated with several types of arthritis. Using transmission electron microscopy both the tiny apatite-like crystals and larger CPPD can be seen to be associated with granular materials. With the ferritin bridge technique immunoglobulins and complement are seen in the material with the apatite but not the CPPD. Immunoprotein is seen both intracellularly and extracellularly. Further study of these coatings is needed to ascertain if they have consistent patterns on all crystals and how they affect the ability of the crystals to induce inflammation.

Calcinosis↗

PubMed1983

In vitro formation of dicalcium phosphate dihydrate, CaHPO4 . 2H2O (DCPD).

Dicalcium phosphate dihydrate, CaHPO4 . 2H2O (DCPD) crystals were grown in solutions and in different types of gels (silica, agar, collagen) at different pH's, in the presence of other ions, and on different Ca-bearing substrates (enamel, dentine, bone, calcite). Hydrolysis of DCPD to other calcium phosphates and calcium oxalates were made in solutions containing different ions at 37 degrees C, 24h. Results showed that the type of media (solution or gel), type of gel, pH, presence of other ions affect the morphology (size/shape) and growth of DCPD. In systems of changing pH, the more basic calcium phosphate (e.g., apatite, OCP) formed in the first zone, DCPD in the last zone, regardless of the initial Ca/P of the system. Growth of DCPD was suppressed in the presence of F-(which favored growth of apatite), of Cd2+, Pb2+ (which favored OCP). Hydrolysis of DCPD to apatite was promoted in solutions containing Ca2+, F-, CO3=, and inhibited by Mg2+, P2O74-. Hydrolysis of DCPD to calcium oxalate occurs in presence of C2O4=. Results indicate that the variation in morphology of DCPD occurring in various human tissue calcinosis and the co-existence of DCPD with other calcium phosphates and oxalates in urinary and dental calculi are due to variations in pH, and presence of different ions in the media.

Acid Phosphatase↗

PubMed1981

Mineral and collagen-binding proteins of fetal calf bone.

Subperiosteal fetal calf bone is subjected to sequential dissociative extraction in the presence of protease inhibitors first with guanidine HCl and then with guanidine HCl/EDTA. Over two-thirds of the total noncollagenous protein is recovered in the second extraction step, which operationally solubilizes proteins associated with the apatite of mineralized bone lamellae. Three new proteins, comprising over 40% of the fetal bone noncollagenous protein, are purified from the second extract by gel filtration in 4 M guanidine HCl and ion exchange in 7 M urea. These are two glycoproteins both containing organic phosphate at apparent molecular sizes of 32,000 and 62,000 daltons and a protein of 24,000 daltons containing both hydroxyproline and organic phosphate. Of these three proteins, the Mr = 32,000 species binds to apatite and collagen with the greatest affinity. It comprises 25% of the fetal calf bone noncollagenous protein and is selectively adsorbed both by apatite crystals in 4 M guanidine HCl and on gelatin affinity columns at physiological pH and ionic strength.

Amino Acids↗

PubMed1995

The nature and functional significance of dentin extracellular matrix proteins.

Odontoblasts are responsible for formation of predentin, which is transformed to dentin when apatite crystals are formed and the fibrillar matrix becomes mineralized. Odontoblasts are specialized cells that synthesize and secrete a unique set of non-collagenous proteins (NCPs), as well as the collagenous matrix largely comprised of type I collagen. The NCPs consist of dentin specific and mineralized tissue specific proteins, as well as other proteins that are found in a variety of tissues. Three dentin specific proteins have been recognized to date: dentin phosphoprotein (DPP), also called phosphophoryn, AG1 (dentin matrix protein 1, Dmp1) and dentin sialoprotein (DSP). DPP appears to be made by odontoblasts and appears at the mineralization front within a short time. It may be secreted via odontoblastic processes. DPP binds to collagen and potentially initiates formation of apatite crystals. A second DPP function appears to be to bind to the 100 face of growing apatite crystals and to inhibit or slow their growth; thus, DPP may play a dual role by initiating mineralization and then affecting the crystal growth and perhaps the habit of the crystals. Although no function has been ascribed to AG1 or DSP, they should prove to be important markers for the odontoblast phenotype. A recent unique finding is that two separate genes appear to code for more than one DSP mRNA; other transcripts may result from differential splicing. Examples of mineralized tissue specific proteins expressed by osteoblasts as well as odontoblasts are bone sialoprotein (BSP) and osteocalcin. Some NCPs expressed by osteoblasts, odontoblasts and several other tissues include osteopontin (OPN) and the chondroitin sulfate containing proteoglycans, decorin and biglycan. We propose that characterization of odontoblasts in tissues and cultures should rely upon utilization of sets of markers for the above NCPs and their mRNAs. Similar approaches are commonly used in investigations on osteoblasts. Finally, dentin (like bone) contains other molecules such as growth factors, and serum derived proteins, found within the matrix; no functional significance has yet been placed upon this finding. Future experiments should focus upon the elucidation of the three dimensional structures of the collagenous fibrillar network and of the NCPs to determine the relationships to mineralization. The role played by odontoblasts in controlling extracellular events, such as by selective secretory routes, will require careful exploration.

Amino Acid Sequence↗

PubMed1994

Intramedullary deposits of hydroxyapatite crystals in a patient with rheumatoid arthritis.

A 63-year-old women with a 12-year history of rheumatoid arthritis (RA) had calcific deposits in the periarticular soft tissues with subsequent involvement of the medullary canals of adjacent bones. Except for the RA, there was no evidence of other abnormalities of the bones or mineral homeostasis. Chemical analyses of the deposits identified the crystalline material as apatite. Although the deposition of apatite in the soft tissues of RA is known to occur rarely, this is the first known case of intraosseous apatite deposition.

Arthritis, Rheumatoid↗

PubMed1976

Urease. The primary cause of infection-induced urinary stones.

Previous reports have suggested that urease-producing bacteria play a prominent role in the formation of infection-induced urinary stones. We have carried out crystalization experiments in vitro which show that bacterial urease alkalinizes urine, thereby causing: (i) supersaturation with respect to struvite and calcium phosphate; and (ii) formation of struvite and apatite crystals. Growth of Proteus in urea-free urine or in urine which contained a urease inhibitor did not cause alkalinization, supersaturation, or crystallization of struvite and apatite. Growth of Klebsiella, Escherichia coli, or Pseudomonas was not associated with significant alkalinization, supersaturation, or crystallization. Struvite and apatite crystals dissolved in Proteus-infected urine in which undersaturation was maintained by urease inhibition. Similar results in all experiments were obtained using human urine and a synthetic urine which was devoid of matrix, pyrophosphate, or other undefined solutes. Urease-induced supersaturation appears to be the primary cause of infection-induced urinary stones.

Bacteria↗

PubMed1997

Two-dimensional electrophoretic analyses of urinary proteins in Chinese male urinary stone patients.

This study was aimed to detect the differences in soluble urinary proteins between normal Chinese male individuals and urinary stone formers by 2-dimensional electrophoresis. Twenty urine samples were obtained from normal male adults and 35 from recurrent male urinary stone formers. The stone compositions included calcium oxalate, uric acid, carbonate apatite, and brushite. Two hundred milliliters of fresh urine was collected for analysis. Each urine sample was concentrated, dialyzed, frozen and lyophilized. The samples of the same stone composition were pooled and subjected to two-dimensional electrophoresis. Comparison of protein profiles between normal individuals and stone formers revealed a number of proteins which are not present in the urine of normal individuals, 5 from calcium oxalate, 2 from uric acid, 3 from carbonate apatite and 2 from brushite. These urinary stone-associated proteins comprise proteins A (37kd), B (30kd), C (26kd), D (25kd), and E (22kd) for calcium oxalate, proteins F (63kd) and G (59kd) for uric acid, protein H (65kd), I (42kd), and J (30kd) for carbonate apatite as well as proteins K (61kd) and L (59kd) for brushite. Among them, the proteins A, I, and J exhibited charge heterogeneity.

Adult↗

PubMed1997

[The possible mechanisms of alkaline phosphatase and alpha-amylase immobilization in dental enamel].

The kinetic method revealed that by the rate of adsorption on apatite, serum alkaline phosphatase (AlP) is homologous and salivary AlP consists of two fractions: "slow" with the constant of adsorption rate approximating that of serum AlP and "fast" with 5-6 times greater constant. A mechanism of phosphatase immobilization on apatite by two-stage sequential reaction is proposed. The constants of rates of both stages for the serum phosphatase and fast salivary fraction are determined. Difference of the products of both stages by the Michaelis constant (KM) is demonstrated for the fast fraction. The KM of the second-stage immobilization product is close to that of AlP immobilized on dental enamel, which confirms the hypothesis about their identity. In contrast to AlP, both serum and salivary alpha-amylase react with apatite at the same rate and, probably, by the same mechanism as the bulk of salivary and serum protein.

Adsorption↗

PubMed1998

[Urinary calculi in small and other animals--a retrospective study of the years 1980-1989].

More than 500 uroliths from dogs, cats, minks, rabbits and 9 further animal species originating from various regions of former East Germany were analysed. The observations were made between 1980 and 1989 using X-ray diffraction and infrared spectroscopy. The urinary stones consisted of struvite, whewellite, weddellite, cystine, ammonium urate, brushite, whitlockite, hydroxyapatite or carbonate-apatite, calcium carbonate, silicon dioxide and organic matrix stones. In dogs, the most frequent types were struvite and apatite concrements, followed by calcium oxalate and cystine uroliths. Among the diseased animals poodles, dachshunds and terriers ranked first. In the analysed material from cats apatite and struvite predominated. With few exceptions, minks formed struvite uroliths only. The analysed calculi from rabbits consisted principally of calcium phosphate or calcium carbonate concrements. The present analysis has been compared with results of former studies, differences are discussed.

Animals↗

PubMed1998

Detoxified glutaraldehyde cross-linked pericardium: tissue preservation and mineralization mitigation in a subcutaneous rat model.

BACKGROUND AND AIM OF THE STUDY: Glutaraldehyde is considered a promoter of calcification by the action of toxic aldehyde group residuals from cross-linking. Post-fixation treatment with homocysteic acid (HA), besides bonding aldehyde groups and neutralizing toxicity, should enhance biocompatibility due to the strongly electronegative sulfonic group. The aim of this investigation was to evaluate HA efficacy on tissue preservation and dystrophic calcification mitigation in glutaraldehyde cross-linked bovine pericardium (BP) using a subcutaneous rat model. METHODS: Four samples of BP, two with glutaraldehyde-HA and two with glutaraldehyde treatment, were implanted in each of 24 male Sprague-Dawley rats. Three rats were killed at 14 days, eight at 28 days, eight at 56 days and five at 84 days. Unimplanted glutaraldehyde-HA- and glutaraldehyde-treated samples served as controls. All samples were studied by gross examination, mammography, light transmission and scanning electron microscopy, and atomic absorption spectroscopy. The nature of mineralization was investigated by coupling techniques of scanning electron microscopy, electron microprobe analysis and X-ray powder diffraction. RESULTS: No histological and ultrastructural differences were found between glutaraldehyde-HA- and glutaraldehyde-treated BP, whether implanted or unimplanted. In both groups, calcification progressed with time, but significantly less after glutaraldehyde-HA treatment than after glutaraldehyde alone and at all time intervals (14.63 +/- 21.34 versus 43.17 +/- 15.99 at 28 days, p = 0.003; 56.42 +/- 40.20 versus 90.59 +/- 32.90 at 56 days, p = 0.008; 91.68 +/- 67.68 versus 156.23 +/- 17.85 at 84 days, p = 0.01). Differences were evident by mammography and histology (von Kossa stain). Electron microprobe analysis in both groups showed the composition of calcified nuclei to be calcium phosphate, stoichiometrically close to apatite (Ca5(PO4)3(OH)). The occurrence of crystallized apatite was supported by X-ray powder diffraction findings, the amount of crystallized apatite being higher in glutaraldehyde-treated samples. CONCLUSIONS: Post-fixation treatment with HA preserves BP structural properties and significantly mitigates mineralization of long-term subcutaneous implants.

Animals↗

PubMed1996

Recent observations on enamel crystal formation during mammalian amelogenesis.

BACKGROUND: Enamel mineralization taking place during amelogenesis is a unique model to investigate carbonatoapatite formation in vivo. The abundance of proteinaceous crystal growth inhibitors, in particular amelogenins, contributes significantly to the mineralization process. Their putative roles are to prevent random proliferation of crystal nuclei and to regulate the growth kinetics and orientation of the formed enamel crystals. METHODS: The enamel fluid surrounding the forming enamel crystals contains high concentrations of carbonate and magnesium ions, both of which seem to modulate the mineralization process. Particularly, Mg ions can adsorb onto enamel crystal surfaces in a manner to compete with Ca ions. Enamel mineral formed during amelogenesis is featured as calcium-deficient, acid phosphate-rich carbonatoapatites. Currently the most putative stoichiometry model for enamel mineral is (Ca)5-x(HPO4)v(CO3)w(PO4)3-x (OH)1-x. RESULTS: Very significant changes in the morphology, stoichiometry, and solubility of enamel crystals occur during the various stages of amelogenesis. The early enamel mineralization comprises two events: the initial precipitation of the well-documented thin ribbons and the subsequent overgrowth of apatite crystals on those templates. The thin ribbons precipitated in the vicinity of the secretory ameloblasts have the highest contents of acid phosphate, particularly in the form of exchangeable species, whereas both the exchangeable and unexchangeable acid phosphate decrease concomitantly with the progress of the apatite overgrowth and the appearance of elongated hexagonal crystals in the late secretory stages. CONCLUSIONS: Those morphological and compositional features seem to be consistent with the formation of precursors, such as octacalcium phosphate.

Amelogenesis↗

PubMed1997

Bioactive bone cement: comparison of AW-GC filler with hydroxyapatite and beta-TCP fillers on mechanical and biological properties.

Three types of bioactive bone cement (designated AWC, HAC, and TCPC), each consisting of bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin and a bioactive filler of apatite and wollastonite containing glass-ceramic (AW-GC), sintered hydroxyapatite (HA), or beta-tricalcium phosphate (beta-TCP) powder were made in order to evaluate the influence of the bioactive filler on the mechanical and biological properties of bone cement. The proportion of filler added to the cements was 70% w/w. The compressive, bending, and tensile strengths and the fracture toughness of AWC were higher than HAC and TCPC under wet conditions. The cements were evaluated in vivo by packing them into the intramedullary canals of rat tibiae. An affinity index that equalled the length of bone in direct apposition to the cement was calculated for each cement and expressed as a percentage of the total length of the cement surface. Histological examination of rat tibiae up to 8 weeks after implantation revealed that AWC had higher bioactivity than HAC and TCPC. New bone had formed along the AWC surface within 2 weeks, and at 4 weeks newly formed bone surrounded the cement surface almost completely. In HAC- and TCPC-implanted tibiae, immature bone had formed directly toward but not along the cement surface at 2 weeks. Observation of cement-bone interfaces showed that AWC had bonded to the bone via a so-called "Ca-P-rich layer"; the cement-bone interface remained stable, and the width of the CA-P-rich layer became thicker with time. On the other hand, in HAC- and TCPC-implanted tibiae, the cement surface fillers were surrounded by new bone and were absorbed gradually to become bone matrix. The cement-bone interfaces went inside the cement with time. Our results indicate that stronger interstitial bonding between the inorganic filler and the organic matrix resin in AWC lead to higher mechanical properties; results also indicate that the more stable cement-bone interface and higher bioactivity of AWC are due to early and uniform apatite formation on the cement surface.

Animals↗

PubMed1998

Resorbable calcium phosphate bone substitute.

The in vitro and in vivo properties of a novel, fully resorbable, apatitic calcium phosphate bone substitute (ABS) are described. The ABS was prepared from calcium phosphate precursors that were hydrated to form an injectable paste that hardens endothermically at 37 degrees C to form a poorly crystalline apatitic calcium phosphate (PCA). The PCA reaction product is stable in vivo as determined by FTIR and XRD analysis of rabbit intramuscular implants of ABS retrieved 4, 7, and 14 days postimplantation. Bone formation and resorption characteristics of the ABS material were characterized in a canine femoral slot defect model. Femoral slot defects in dogs were filled with either autologous bone implants or the ABS material. Sections of femoral bone defect site from animals sacrificed at 3, 4, 12, 26, and 52 weeks demonstrated that new bone formation proceeded similarly in both autograft and ABS filled slots. Defects receiving either material were filled with trabecular bone in the first 3 to 4 weeks after implantation; lamellar or cortical bone formation was well established by week 12. New bone formation in ABS filled defects followed a time course comparable to autologous bone graft filled defects. Histomorphometric evaluation of ABS resorption and new bone formation indicated that the ABS material was greater than 99% resorbed within 26 weeks; residual ABS occupied 0.36+/-0.36% (SEM, n = 4) of the original defect area at 26 weeks. Quantitatively and qualitatively, the autograft and ABS were associated with similar new bone growth and defect filling characteristics.

Animals↗

PubMed2000

Bioactivity and mechanical properties of PDMS-modified CaO-SiO(2)-TiO(2) hybrids prepared by sol-gel process.

Hydrolysis and polycondensation of poly(dimethylsiloxane) (PDMS), tetraethoxysilane (TEOS), tetraisopropyltitanate (TiPT), and calcium nitrate gave essentially pore- and crack-free transparent monolithics of PDMS-modified CaO-SiO(2)-TiO(2) hybrids, when PDMS/(TEOS + TiPT) was larger than 26:74 in weight, under constant ratios of TEOS/TiPT of 9:1 in mol and Ca/(TEOS + TiPT) of 0.15 in mol. Their apatite-forming abilities in a simulated body fluid, which is indicative of bioactivity, increased with decreasing PDMS/(TEOS + TiPT). Their extensibility and Young's modulus decreased and increased, respectively, with decreasing PDMS/(TEOS + TiPT). The hybrids with PDMS/(TEOS + TiPT) of about 30:70 in weight showed fairly high apatite-forming ability, high extensibilities, and Young's moduli almost equal to those of the human cancellous bones. These new kind of bioactive materials with unique mechanical properties may be useful as bone-repairing materials.

Apatites↗

PubMed1989

Is it mandatory to examine synovial fluids promptly after arthrocentesis?

Fifty synovial fluid (SF) samples from patients with various types of arthritis were examined promptly after joint aspiration and after storage at room temperature (22 degrees C) or at refrigerator temperature (4 degrees C) for 1 hour, 2 hours, 3 hours, 6 hours, 1 day, and 3 days, then weekly for 3 weeks and monthly for 2 months. We found that the leukocyte count (white blood cell [WBC] count) decreased within a few hours. In 4 SF samples from patients with mild inflammation (initial range 3,150-6,200 WBC/mm3), the WBC count decreased into a "noninflammatory" range (less than 2,000/mm3) within 5-6 hours. In 3 of 5 SF samples that on the first day were found to be laden with crystals of calcium pyrophosphate dihydrate (CPPD), the crystals were much less abundant and were difficult to recognize by the next day. CPPD crystals dissolved completely in all SF samples by 3-8 weeks of the study. Monosodium urate crystals remained detectable throughout the 8 weeks of study, but they became smaller, less birefringent, and less numerous with time. Clumps of apatite-like crystals persisted for several months. Most SF samples initially negative for apatite-like crystals remained negative over time. New, artifactual crystals, including alizarin red S-positive clumps or star-shaped arrays, plate-like structures, positively birefringent Maltese crosses, and hematoidin crystals, developed with time. Because of these observations, we urge prompt examination of SF specimens to avoid the problems of misdiagnosing borderline inflammatory fluids, missing CPPD crystals that dissolve with time, or over-interpreting the findings because of the new, artifactual crystals.

Apatites↗

PubMed1982

Articular cartilage in the degenerative arthropathy of hemochromatosis.

Iron was readily demonstrated in chondrocytes in 3 of 4 hemochromatosis articular cartilages studied. Either apatite, calcium pyrophosphate dihydrate crystals, or both were found in all cartilages including those of 3 patients who had no radiographic or light microscopic evidence of calcification. These crystals, which may be secondary to degenerative changes or may play a role in cartilage degeneration, were not seen in any consistent morphologic relationship with the iron deposits. In fact, apatite was found in one cartilage in which no iron was identified in the sections studied. If iron, as demonstrated in the chondrocytes, is contributing to the calcium crystal deposition, it would most likely do so indirectly, for example by altering chondrocyte enzymes or connective tissue components.

Aged↗