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Scanning electron microscopic and X-ray microdiffractometeric studies on sialolith-crystals in human submandibular glands.

The crystalline structures of 18 submandibular gland calculi were studied by radiomicrography , scanning electron microscope, and X-ray microdiffractometeric techniques. The following observations were made by SEM: Granular or globular structure was seen on the surface of all cases and pyramidal crystal in one case. In the inside, all showed lamellar pattern with amorphous nucleus in the center, and granular, plate-like and rhombohedral structures were also observed. X-ray microdiffractometeric analyses: Apatite was frequently observed in both outside and inside of the calculi. Whitlockite was next frequently detected and was seen more often in the inside. Brushite and weddellite were noted in the outside of calculi in one case each. Thus, it is suggested that brushite and weddellite were present in the front portion of calculus formation and then transformed into the more stable form e.g. apatite.

Apatites↗

Bone response adjacent to calcium phosphate electrostatic spray deposition coated implants: an experimental study in goats.

BACKGROUND: A new technique to deposit calcium phosphate (CaP) coatings onto titanium substrates has been developed recently. This electrostatic spray deposition (ESD) technique seems to be very promising. It appears to have clinical advantages such as an inexpensive and simple set-up, high deposition efficiency and the possibility to synthesize layers with a defined surface morphology. OBJECTIVE: The aim of this study was to examine biological properties and osteoconductivity of ESD CaP coatings when inserted into the femoral condyle of a goat. MATERIAL AND METHODS: Twenty-four implants with two gaps, i.e. 1 or 2 mm, were inserted into the femoral condyles of six goats. The implants were coated on one side with either a commercially available plasma-sprayed hydroxyapatite (HAPS) coating or an ESD carbonate apatite (CAESD) coating. The other side of the implant was always left uncoated (Ti). Twelve weeks after implantation the animals were sacrificed and the characteristics of bone ingrowth and bone contact were evaluated. RESULTS: At 3 months, histological and quantitative histomorphometrical measurements demonstrated more bone ingrowth and bone contact for coated sites as compared with uncoated sites. Statistical testing revealed that for both the 1 and 2 mm gaps HAPS (plasma-sprayed hydroxyapatite) as well as CAESD (ESD carbonate apatite) -coated surfaces always had a significantly higher (P<0.05) amount of bone contact than uncoated Ti surfaces. On HAPS surfaces always significantly more bone was present than on CAESD surfaces. Further statistical testing revealed a significant difference in bone ingrowth between the HAPS as well as CAESD and Ti 1+2 mm gap specimens (P<0.05). Further, HAPS 1 mm gaps showed more bone ingrowth than CAESD 1 mm gaps. No significant difference existed between HAPS and CAESD 2 mm gaps. CONCLUSION: On the basis of our observations, we conclude that the used ESD technique is a promising new method to deposit CaP coatings onto titanium substrates. On the other hand, plasma-spray HA-coated implants have a still more favourable effect on the bone response.

Animals↗

Uptake of KOH-soluble and KOH-insoluble fluoride in sound human enamel after topical application of a fluoride varnish (Duraphat) or a neutral 2% NaF solution in vitro.

The uptake of alkali-soluble fluoride (calcium fluoride-like material and adsorbed fluoride) and alkali-insoluble fluoride (apatitically bound fluoride) on sound human enamel from treatment with Duraphat or a neutral 2% NaF solution was investigated in vitro. Blocks from impacted third molars were used. More fluoride was deposited on the enamel from the neutral 2% NaF solution than from the Duraphat treatment. All the fluoride could be dissolved in alkali. Globules of calcium fluoride-like material were demonstrated by scanning electron microscopy. Chemical analysis showed no measurable increase in the apatitically bound fluoride (alkali-insoluble fluoride) after brief exposures. Duraphat-treated samples submerged in water after the exposure lost only about 50% of the deposited fluoride, whereas samples treated with 2% NaF are known to lose all their fluoride under similar circumstances, a condition which may be related to the favorable clinical effect of Duraphat.

Acid Etching, Dental↗

On the formation of amelogenin microribbons.

We recently reported the remarkable spontaneous self-assembly and hierarchical organization of amelogenin 'microribbons' and their ability to facilitate oriented growth of apatite crystals in vitro. In a letter of correction we communicated the finding that the X-ray diffraction pattern reported in our original report was that of cellulose contaminant and not amelogenin microribbon. We have re-evaluated our data and confirmed the protein nature of the microribbons using Fourier transform infrared and Raman microspectroscopy. Some microribbons were remarkably similar in their morphology to that of cellulose fibers. The size distribution of amelogenin microribbons was wider, particularly in width and length, and generally smaller than those originally reported. Here we present additional detailed information on the formation of a series of intermediate hierarchical structures of amelogenin assemblies prior to the formation of microribbon. The most significant finding was that full-length amelogenin nanospheres had a tendency to assemble into collinear arrays whose function is assumed to be critical at the initial stage of enamel mineral deposition. The present data gives an insight into the step-by-step assembly process of amelogenin from nanometer scale molecules to micrometer scale organized structures that can be used as templates for controlled and oriented growth of apatite mineralization in vitro.

Amelogenesis↗

Atherosclerotic plaque: x-ray diffraction investigation.

Human atherosclerotic plaque material continuotusly maintained in an aqueous environment has been subjected to examination by x-ray diffraction. The first diffraction pattern from single crystals of human biological apatite was obtained from the plaque material of a freshly excised plaque when it was equilibrated with its aqueous environment. As the plaque material dried, the discrete spots characteristic of single crystal diffraction disappeared, leaving only the powder pattern of apatite.

Apatites↗

Crystal deposition in hypophosphatasia: a reappraisal.

Six subjects (three female, three male; age range 38-85 years) with adult onset hypophosphatasia are described. Three presented atypically with calcific periarthritis (due to apatite) in the absence of osteopenia; two had classical presentation with osteopenic fracture; and one was the asymptomatic father of one of the patients with calcific periarthritis. All three subjects over age 70 had isolated polyarticular chondrocalcinosis due to calcium pyrophosphate dihydrate crystal deposition; four of the six had spinal hyperostosis, extensive in two (Forestier's disease). The apparent paradoxical association of hypophosphatasia with calcific periarthritis and spinal hyperostosis is discussed in relation to the known effects of inorganic pyrophosphate on apatite crystal nucleation and growth.

Adult↗

Effects of a 'common sense diet' on urinary composition and supersaturation in patients with idiopathic calcium urolithiasis.

OBJECTIVES: To test whether dietary advice as the only treatment is able to reduce urinary supersaturation in patients with idiopathic calcium urolithiasis. METHODS: By means of EQUIL 2, we calculated relative supersaturations of calcium oxalate (RS(CaOx)), brushite (RS(Brushite)), apatite (RS(Apatite)) and uric acid (RS(UA)) of 24-hour urine samples of 68 healthy male controls as well as of 47 male idiopathic calcium stone formers (ICSF) before and after individualized dietary advice (DA). Main goals of DA were (1) to keep urine volume > 2,000 ml/day, and (2) to reduce meat protein intake to 1 g/kg body weight per day. Compliance was judged from changes in urine volume and U(Urea)xV. RESULTS: In the whole group of ICSF, DA did not alter supersaturations. Only in those 9 ICSF (19%) with good compliance (increase in volume and decrease in U(Urea)xV), RS(CaOx) and RS(UA) fell by 26 and 49%, respectively. Besides poor compliance, these findings can be explained by positive correlations between changes in volume and U(Urea)xV in ICSF (r = 0. 319, p = 0.037) or U(Na)xV (r = 0.342, p = 0.019). For instance, ICSF with volumes >/= 2,000 ml/day had evidence of elevated protein and salt intake; thus, DA mainly focused on protein and salt intake, but not on volume. This resulted in decreases in U(Urea)xV and U(Na)xV, but also in volume; thus, RS(CaOx) remained unaltered. CONCLUSIONS: DA is able to significantly lower RS(CaOx); however, because intakes of fluid and protein are directly and positively linked to each other, this only can be achieved if high fluid and lower meat protein intake are equally stressed in all ICSF.

Adult↗

Partial defluoridation of drinking water using fluorapatite precipitation.

Ion adsorption and ion exchange are two methods commonly used in small home units to treat drinking water to bring the fluoride concentration to within acceptable limits. However, the necessary flowthrough system is often difficult to arrange where there is no piped supply and gradual exhaustion of the active agent is not easily detected. In an attempt to overcome these problems a defluoridation method based on the precipitation of a sparingly soluble fluoride salt, fluorapatite, has been studied. Samples of simulated high-fluoride drinking waters, approximately 10 ppm F, were saturated with brushite, resulting in a state of supersaturation with respect to fluorapatite. Subsequent seeding with hydroxyapatite caused a lowering of the calcium, phosphate, and fluoride concentrations in solution, indicative of fluorapatite precipitation. Repeating the process had an additive effect. Bone char was a less effective seed than hydroxyapatite with water containing fluoride only, but was a more effective seed with simulated Kenyan borehole water containing additional salts. Sixty-minute brushite saturation and apatite seeding steps were generally more effective than 10-min steps. The results suggest that apatite coprecipitation may be a convenient low-technology way to defluoridate drinking water, although prior testing might be useful to ensure adequate removal of fluoride.

Apatites↗

The effect of mineral-derived zinc ions on in vitro glucose metabolism of Streptococcus mutans NCTC 10449.

Mouthrinses containing zinc ions inhibit plaque acidogenicity, but the effect is transient. Zinc-containing apatite or zinc phosphate precipitated within dental plaque might serve as a reservoir for zinc ions, thus providing prolonged inhibition of acid formation. Zinc-containing fluorhydroxyapatite was prepared from solutions containing CaCl2, KH2PO4, NaF and increasing amounts of ZnCl2 (0.0, 0.005, 0.02, 0.1, 0.2 or 1 mM; minerals No. 1-6, respectively) by raising the pH with ammonia. Zinc phosphate tetrahydrate (mineral No. 7) was prepared in a similar manner from a solution containing ZnCl2 and KH2PO4 only. Dense cell suspensions of Streptococcus mutans NCTC 10449 were incubated with 14C-glucose and one of the test minerals (No. 1-7). Glycolysis was allowed to proceed, with or without pH control, in a pH-stat. Samples were withdrawn at 1, 2, and 3 min, and extracellular glycolytic metabolites were identified by HPLC. Mineral No. 7 inhibited glycolysis and any pH fall almost completely. With the pH fixed at 5.5, reduction of glucose consumption and lactate formation was 83 and 93%, respectively, compared to the no-zinc control mineral (No. 1). No changes in glucose consumption or lactate formation were evident in the presence of minerals No. 2-6. All apatitic minerals had a buffering effect and, in the absence of pH control, glycolysis was increased due to the higher pH. Detectable levels of fluoride were not released by any mineral into the incubation mixture, and zinc only by minerals No. 6 and 7 in greater than trace amounts.(ABSTRACT TRUNCATED AT 250 WORDS)

Acids↗

Transformation of hydroxyapatite to fluorapatite by irradiation with high-energy CO2 laser.

High-energy laser irradiation has been shown to cause crystalline transformations in apatites, which may lead to the formation of tricalcium phosphates with a resulting decrease in acid resistance. Depending on the nature and energy density of laser irradiation used, however, an increase of acid resistance of dental enamel has also been reported after laser irradiation. The aim of the present study was to investigate the phase transformation of hydroxyapatite (HA) to fluorapatite (FA) in a model system that incorporates sodium fluoride (NaF) into apatite structure by using laser irradiation. A CO2 laser was used at energy densities ranging from 21 to 500 J/cm2. Synthetic HA mixed with NaF (10:1) was the target of laser irradiation. The crystalline structures were then investigated using X-ray diffraction analysis. The results showed that a phase transformation of HA to FA could be realized, and that the threshold energy density needed was 38 J/cm2. Not only is the finding crystallographically important, but it also opens new perspectives for future research regarding the development of laser technology for clinical purposes.

Apatites↗

Wet powder processing of sol-gel derived mesoporous silica-hydroxyapatite hybrid powders.

This paper describes a method by which a porous silica coating layer can be obtained on different apatite particles through a simple sol-gel synthesis route. Sol-gel derived powders of hydroxyapatite (HAP) and beta tricalciumphosphate (beta-TCP) were coated with a mesoporous silica using C16TAB (hexadecyltrimethylammonium bromide) as a template in order to induce mesophase formation. Further calcination of the material removes the template from the mesophase and leaves a highly ordered hexagonal arranged mesoporous silica structure with a core of HAP/beta-TCP. The phase purity of the SiO2/apatite composites has been thoroughly investigated by the means of FT-IR, XRD, and solid state 31P MAS NMR. The phase purity of these materials is shown to be dependent on the solubility properties of the used apatites. The hybrid materials are suitable as a multifunctional biomaterial where osteoconductive properties can be combined with drug delivery.

Apatites↗

A study of vertebral bone powder from patients with chronic renal failure.

Bone powder from patients dying with chronic renal failure of more than 1 yr duration was shown to release less calcium and more phosphate when equilibrated with a buffer solution. pH 7.4 at 4 degrees C. This change persisted after removal of the organic component and was associated with a reduction in the bone carbonate content. Crystal size and surface area showed no consistent changes from the controls and it was concluded that an alteration in the apatite crystal composition had occurred in long-standing uremia with carbonate-phosphate interchange. Support for this was provided by synthesis of apatites which were carbonate deficient and behaved in a similar manner to the uremic bones.

Adult↗

Tooth enamel: current state of the art.

Important progress has been made relative to the growth, structure and function of enamel. Better understanding of the epithelial mesenchymal interactions during odontogenesis has been gained through tissue culture, and the predominant role of the dental papilla has been established. Differences between rodent and human amelogenesis have been demonstrated. With radioautography and cytochemistry, a significant amount of new information has been obtained on the metabolism of the ameloblasts, concerning the synthesis of proteins, glycoproteins and proteoglycans, as well as calcium transport. Numerous biochemical investigations have been devoted to developing and mature enamel matrix. The organic components of human adult enamel are mainly constituted of lipids and proteins, but further investigations are still needed to elucidate their precise nature. The so-called key-hole configuration of adult enamel can be questioned when amelogenesis is considered since the tissue does not develop in a prismatic head-tail fashion. The most important results have probably been obtained in the field of individual enamel apatite crystals shape and ultrastructure as well as in the description of the precise patterns of their carious dissolution which bears great similarities to the dissolution of synthetic apatites in acids.

Amelogenesis↗

The crystalline components of dental calculi: human vs. dog.

Dental calculus from the dog was found to consist principally of the calcite form of calcium carbonate mixed with small amounts of apatite; other calcium phosphates, consistently present in human calculus, were not present in dog calculus. Precipitable calcium salts from human saliva were mainly apatite; for the dog the principal precipitated salt was calcium carbonate (calcite form).

Animals↗

Orientations of carbonate ions in human tooth enamel studied with use of the CO3-3 radical ions as probes.

With the use of CO3-3 radical ions as probes, it is concluded that the carbonate ions substitute in the apatite lattice of human tooth enamel in two different ways. Most of the carbonate ions in the apatite lattice are aligned with their symmetry axis parallel to the c axis, whereas the remaining carbonate ions are aligned with their symmetry axis perpendicular to the c axis.

Apatites↗

Comparison of calcification between Bacterionema matruchotii and Actinomyces naeslundii.

The purpose of this research was to examine the requirements for proteolipid initiation of calcification in culture. Proteolipid from a calcifiable microorganism, Bacterionema matruchotii, was compared with proteolipid isolated from a non-calcifiable microorganism, Actinomyces naeslundii. Although A. naeslundii does not calcify in culture, lyophilized cells and proteolipid-containing extracts do initiate apatite formation. A. naeslundii proteolipid (ANN) differs from B. matruchotii (BMN) in concentration, apoprotein polarity, and phospholipid composition. These differences may alter the ability of ANN to nucleate apatite in the intact cell.

Actinomyces↗

Synthesis of osteoconductive organic inorganic nanohybrids through modification of chitin with alkoxysilane and calcium chloride.

The so-called bioactive ceramics have been attractive because they spontaneously bond to living bone. Organic-inorganic hybrids consisting of organic polymers and the essential constituents of the bioactive ceramics, i.e., silanol (Si-OH) group and calcium ions (Ca(2+)), are useful as novel bone substitutes, owing to bioactivity and high flexibility. In the present study, organic-inorganic hybrids are synthesized from chitin by modification with glycidoxypropyltrimethoxysilane (GPS) and calcium chloride (CaCl(2)). Their apatite-forming ability is examined in a simulated body fluid (SBF). The prepared hybrids form apatite on their surfaces in SBF within 7 days.

Apatites↗