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At least 19 recordsLinked to original sources

Neonatal hamster molar tooth development: extraction and characterization of amelogenins, enamelins, and soluble dentin proteins.

Amelogenins, enamelins, and soluble dentin proteins were sequentially separated under dissociative conditions from morphologically characterized molar tooth germs of 4-, 6-, and 7-day-old hamsters. Polyacrylamide gel electrophoretic, gel filtration chromatographic, and amino acid compositional data of neonatal hamster amelogenin extracts were in general agreement with those obtained from fetal bovine enamel under similar extraction conditions. As development progressed (e.g., 4 vs. 7 days of life), changes in amelogenin proteins were manifested by altered values of all biochemical parameters measured. A high molecular weight (approximately 160,000-200,000 daltons) Stains-All-positive protein band was observed for all hamster enamelin extracts on SDS gels. Amino acid compositional data from this "enamel crystal protein," partially purified by dissociative gel-filtration chromatography, are presented. The hamster dentin phosphoprotein was partially purified by ion-exchange chromatography in 7M urea. The molecular weight (75,000-80,000 daltons) and amino acid composition of this protein were similar to those of rat incisor dentin phosphoprotein, but different from those of the fetal bovine phosphoprotein.

Amelogenin↗

Biochemical characterization of guanidinium chloride-soluble dentine collagen from lathyritic-rat incisors.

alpha- and beta-Chains were isolated by sequential ion-exchange and gel-filtration chromatography of guanidinium chloride-soluble dentine collagen obtained from Tris/NaCl-extracted EDTA-demineralized lathyritic-rat incisors. The alpha-chains were identified as alpha 1 I and alpha 2 by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and amino acid analysis of the intact chains and their CNBr peptides. The dentine alpha-chains exhibited higher lysine hydroxylation and phosphate content, but lower hydroxylysine glycosylation, than alpha-chains from skin. Increased lysine hydroxylation was observed in the helical sequences. The alpha 1 I/alpha 2 ratio was approx. 3:1, and was presumably due to the presence of (alpha 1 I)3 molecules along with (alpha 1 I)2 alpha 2 molecules as shown recently for neutral-salt-soluble dentine collagen [Wohllebe & Carmichael (1978) Eur. J. Biochem. 92, 183--188]. In the borohydride-reduced beta 11- and beta 12-chains from guanidinium chloride-soluble dentine collagen, the reduced cross-links hydroxylysinohydroxynorleucine and hydroxylysinonorleucine were present. A higher proportion of hydroxylysinonorleucine in the reduced beta 12-chain probably reflects differences in extent of hydroxylation of specific lysine residues of the alpha 1 I- and alpha 2-chains.

Amino Acids↗

Estimating age through the amino acid racemization of acid-soluble dentinal peptides.

We studied the possibility of estimating age through the amino acid racemization of acid-soluble dentinal peptide (SP). The correlation of the D/L ratio of aspartic acid and the actual age was the highest in the SP extracted with 1 M HCl (r = 0.996, sigma = +/- 0.8), followed by the total amino acids (TAA:r = 0.995, sigma = +/- 1.0), and the SP extracted with 2 M HCl (r = 0.980, sigma = +/- 1.9) and then SP extracted with 5 M HCl (r = 0.951, sigma = +/- 2.7). The rate of the racemization reaction decreased in the order of SP extracted with 1 M HCl, 2 M HCl, 5 M HCl and the total amino acids (TAA). Consequently, an extraction with 1 M HCl seemed best for estimating the age from SP to serve actual cases.

Age Determination by Teeth↗

Water sorption and solubility of dentin bonding agents light-cured with different light sources.

OBJECTIVE: The aim of this study was to compare water sorption (WS) and solubility (WSB) of different dentin bonding agents (DBA) as regards classification and light-activation system. The null hypotheses were: (1) there is no difference among DBA with respect to water sorption and solubility; (2) there is no effect of light-curing source on water sorption and solubility of DBA. METHODS: The tested materials were: three-step etch-and-rinse (ScotchBond multi-purpose and Heliobond-control groups), two-step etch-and-rinse (Excite, Adper Single Bond, Adper Single Bond 2), self-etching (Adhse) and all-in-one (Xeno III) systems. For each material, six specimens were prepared (0.8mmx5.5mm) for each light-activation device: halogen lamp (control) or light-emitting diodes (LED). They were transferred to desiccators until a constant mass was obtained (m(1)), subsequently immersed in deionized water until no alteration was obtained (m(2)). Following, the specimens were reconditioned to constant mass in desiccators (m(3)). The volume (V) of each specimen was calculated (mm(3)). WS and WSB were determined using the equations (m(2)-m(3)/V) and (m(3)-m(1)/V), respectively. Data were subjected to one-way analysis of variance and Tukey test (p<0.05). The influence of photo-activation units was analyzed by t-test. RESULTS: Higher values of WS and WSB were observed for the two-step etch-and-rinse and all-in-one systems. The employed light-activation unit also affected the tested characteristics. Thus, the anticipated null hypotheses were rejected. CONCLUSIONS: Simplified systems were more susceptible to water adverse and they may become more prone to degradation over time regardless of the type of light-activation source.

Absorption↗

Adhesive bonding of various materials to hard tooth tissues--solubility of dentinal smear layer in dilute acid buffers.

While the acid etch technique has largely solved the problem of bonding restorative materials to enamel, attempts to improve adhesive bonding to dentin have so far had only limited success. One aspect to which insufficient attention has been paid is the presence of a smear layer on cut surfaces and of pellicle on surfaces exposed to saliva, both of which would reduce or prevent durable adhesive bonds. The present study attempts to evaluate the usefulness of various acidic solutions in removing these surface layers while causing minimal damage to the vital contents of the dentinal tubules. A series of twelve 0.16 M buffer solutions were applied to cut dentin surfaces which were then washed, dried and sputter-coated with gold/palladium in preparation for examination by scanning electron microscopy. It is concluded that the smear layer on cut dentin surfaces can be substantially removed in vitro by a 30 second exposure to an isotonic solution of buffered monobasic acids having pKa values between 3.8 and 2.5. Since these solutions did not always remove material from grooves in the prepared surface clinical techniques should aim at producing a smooth cut surface. The response of the vital pulp to this treatment still awaits investigation.

Acid Etching, Dental↗

Adsorption of dentine proteins onto spheroidal calcium phosphate in a neutral and in an acidic environment.

The adsorption of four different dentine protein fractions onto hydroxyapatite (HAP) was investigated in a nearly neutral (pH 6.7) and in an acidic environment (pH 5.0). The soluble dentine proteins were isolated according to their extractability in successively: 4M guanidine-HCl (GuHCl), 0.5M acetic acid pH 3 (after extraction with GuHCl), and 0.01M EDTA pH 7.4 and 0.1M EDTA pH 7.4 (after complete demineralization with acetic acid). The amounts isolated were 1.2, 3.3, 6.1 and 3.7 mg protein per gram dentine, respectively. The GuHCl extractable proteins exhibited the lowest affinity and the acetic acid extractable proteins the highest affinity for HAP. Acetic acid extractable proteins, were significantly less adsorbed than the other protein fractions at pH 5.0. The maximum adsorbed amount of these proteins increased with decreasing pH which indicated that all the soluble dentine proteins, except perhaps those that one GuHCl-extractable have to be considered as potential demineralization inhibitors.

Acids↗

[Ectopic bone induction by human fetal enamel proteins].

Mixture of amelogenin, enamelin and soluble dentin proteins with plaster of Paris and distilled water were implanted in the left thigh-muscle pouch of C57BL/6 T mice, and PLP or BSA/PLP were implanted in the contralateral limbs for controls. The hind limbs were examined by means of microradiographic and histological methods three weeks after the implantation. Implants of PLP, BSA/PLP or E/PLP did not evoke formation of new cartilage or bone. Roentgenography showed highly mineralized tissues in the implantation areas of A/PLP or D/PLP, histological examination confirmed this as induced new bone or cartilage formation. Thus it indicates that amelogenins and soluble dentin proteins have bone induction activity as bone morphogenetic protein, they could induce the differentiation of mesenchymal cell in the muscles into chondrocyte and osteocyte.

Amelogenin↗

Influence of substrate nature and immobilization of implanted dentin matrix components during induction of reparative dentinogenesis.

The biological effects of isolated soluble dentin extracellular matrix components on the induction of reparative dentinogenesis in exposed cavities in ferret canine teeth have been shown to be blocked by immobilizing the extracellular matrix components on nitrocellulose or Millipore membranes during implantation. This contrasts with the picture of induction of odontoblast-like cell differentiation and reparative dentin deposition on existing insoluble dentin matrix of the exposure walls when the extracellular matrix components are implanted in lyophilized form. These data indicate the importance of an existing insoluble dentin matrix in providing a substrate to potentiate the growth factor-like activity of soluble isolated dentin extracellular matrix components in the induction of reparative dentinogenesis.

Animals↗