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At least 109 records · Page 6Linked to original sources
PubMed2006

Effect of an iron mouthrinse on enamel and dentine erosion subjected or not to abrasion: an in situ/ex vivo study.

OBJECTIVES: This in situ/ex vivo study evaluated whether a rinse with an iron solution could reduce wear and the percentage of microhardness change of human enamel and dentine submitted to erosion followed by brushing after 1 or 30min. DESIGN: During 2 experimental 5-day crossover phases (wash-out period of 10 days), 10 volunteers wore intraoral palatal devices, with 12 specimens (6 of enamel and 6 of dentine) arranged in 3 horizontal rows (4 specimens each). In one phase, the volunteers immersed the device for 5min in 150mL of cola drink, 4 times a day. Immediately after immersion, no treatment was performed in one row. The other row was brushed after 1min using a fluoride dentifrice and the device was replaced into mouth. After 30min, the remaining row was brushed. In the other phase, the procedures were repeated, but after immersion the volunteers rinsed for 1min with 10mL of a 10mM ferrous sulphate solution. Changes in surface microhardness (%SMH) and wear (profilometry) of enamel and dentine were measured. Data were tested using ANOVA and Tukey's tests (p<0.05). RESULTS: The enamel presented more wear than dentine, under all experimental conditions. The iron solution caused a significant reduction on the %SMH in enamel, and a significant reduction on the wear in dentine, regardless the other conditions. CONCLUSIONS: Rinsing with an iron solution after an erosive attack, followed or not by an abrasive episode, may be a viable alternative to reduce the loss of dental structure.

Adult↗
PubMed1976

The identity of a cyanogen bromide fragment of bovine dentin collagen containing the site of an intermolecular cross-link.

A peptide fraction isolated from a cyanogen bromide digest of bovine dentin collagen had a molecular weight of 46000. Its size and amino acid composition indicated that it could not consist of peptides derived from the cleavage of a single alpha chain. On reduction with tritiated sodium borohydride, radioactivity was incorporated primarily into 5, 5'-dihydroxylysinonorleucine without degradation at the peptide backbone. Periodate cleavage of the reduced or nonreduced peptide fraction generated one fragment of molecular weight 28000 and one of 18000 completely accounting for the size of the parent peptide. On amino acid analysis the constituent single-chain peptides were determined to be alpha2CB4 and alpha1CB6. Both peptides isolated after periodate oxidation of the tritiated borohydride reduced cross-link peptide were found to contain (3H)hydroxynorvaline. These data show that some hydroxylysine of alpha2CB4, a helical region peptide, was present in aldehyde form and could act as the aldehyde donor icross-link, Schiff's base formation. The only cross-linkage of this alpha2CB4 acting as an aldehyde donor peptide to alpha1CB6 would be a helical region to helical region bond, perhaps accounting for the unusual stability and low solubility of dentin collagen.

Amino Acids↗
PubMed1993

Postmortem estimation of age at death based on aspartic acid racemization in dentin: its applicability for root dentin.

The extent of aspartic acid racemization in total dentin and in dentin protein fractions from the roots of third molars was determined. In several cases coronal dentin was also investigated. The results of other authors, according to which the racemization of aspartic acid in root dentin apparently proceeds differently than in coronal dentin, could be confirmed. Consequently, the data published so far on age determination based on the extent of aspartic acid racemization in coronal dentin and the "entire dentin of longitudinal sections" cannot be applied to root dentin. In total root dentin and the acid soluble protein of root dentin, a close relationship was observed between the extent of aspartic acid racemization and age. Accordingly, estimation of age at death based on aspartic acid racemization in dentin is also possible for root dentin, apparently with good results. This is important particularly in those cases where a large portion of the coronal dentin is absent, for instance following dental treatment. In the investigation of root dentin, regression equations specific for root dentin must be employed in the estimation of age at death. Corresponding equations for third molars were calculated.

Adult↗
PubMed1992

Physical examination of caffeine's effects on the enamel surface of first molar in new-born rats.

Samples of the first molars of offspring whose dams were fed a diet supplemented with caffeine were examined by scanning electron microscopy, X-ray diffractometry and electron microprobe analysis. Scanning microscopy of the enamel surface of the caffeine group revealed a consistently rougher surface than in the non-caffeine controls, both before and after acid exposure. X-ray diffraction analysis of the pulverized whole tooth in the caffeine group showed broader diffraction peaks for the lattice plane reflections (202) and (300), indicating smaller crystallites. Pure enamel samples of the caffeine group examined with a Gandolfi X-ray camera also revealed more diffuse diffraction lines than in the non-caffeine controls, further indicating smaller crystallites in the enamel. The calcium and phosphorus contents of the acid-exposed samples in both control and caffeine groups were lower than the non-acid exposed control and caffeine groups by electron microprobe analysis. After exposure to acid, the calcium and phosphorus contents of the outer surface of the enamel in the caffeine group were greatly reduced as compared to that of the non-caffeine controls. Thus various methods consistently indicate that caffeine ingestion during early growth affects the enamel surface of the first molars, resulting in impaired mineralization. Caffeine intake may therefore have a negative effect on amelogenesis and possibly increases susceptibility to dental caries.

Animals↗
PubMed1981

Non-collagenous proteins of rat dentin. Evidence that phosphoprotein is not covalently bound to collagen.

The non-collagenous proteins of rat dentin that remain firmly bound to the matrix after demineralization were studied in order to ascertain if they are covalently linked to insoluble dentin collagen. After solubilization with CNBr or with bacterial collagenase, unusually small amounts of dentin phosphoprotein were detected in the matrix. The phosphoprotein obtained by CNBr digestion of the matrix was separated from collagen peptides using two chromatographic steps. Thus even this small quantity of phosphoprotein found in decalcified rat dentin matrix was not covalently bound to collagen.

Amino Acids↗
PubMed1979

Fluoride treatment and microhardness of dentin.

Effects of various fluoride treatments on the microhardness of human dentin were determined. Treatment with acidulated phosphate-fluoride at pH 3.0 induced a significant (p less than .05) softening when compared to treatment with water. APF at pH 4.0 did not bring about a significant change. Response to treatment with 0.4% SnF2 did not differ significantly from water treatment. Sequential treatment with APF (pH 4.0) followed by SnF2 produced significant (p less than .05) hardening of dentin. This hardening with APF-SnF2 differed at a high level of significance (p less than .001) from the softening produced by the pH 3.0 APF. A similarly significant difference was found between this single APF treatment and the single SnF2 treatment. When hardening of exposed dentin surfaces is desired, the sequential treatment method should be employed.

Acidulated Phosphate Fluoride↗
PubMed1989

The possible role of pH changes during EDTA demineralization of teeth.

Demineralization of dentin is a dynamic process. The pH of EDTA solutions inside pulp cavities decreases as demineralization occurs. Increasing EDTA concentration from 0.1 mol/L to 0.5 mol/L causes a faster acid accumulation and a higher demineralization rate. The efficiency of EDTA solutions decreases as time goes on, probably because of the acid released from EDTAHNa3 (the predominating species under the neutral conditions). Not all the available EDTA reacts after a few hours. The so-called autolimitation might be due to this acidification of the EDTA solution.

Acids↗
PubMed2005

Age-related transparent root dentin: mineral concentration, crystallite size, and mechanical properties.

Many fractures occur in teeth that have been altered, for example restored or endodontically repaired. It is therefore essential to evaluate the structure and mechanical properties of these altered dentins. One such altered form of dentin is transparent (sometimes called sclerotic) dentin, which forms gradually with aging. The present study focuses on differences in the structure and mechanical properties of normal versus transparent dentin. The mineral concentration, as measured by X-ray computed microtomography, was significantly higher in transparent dentin, the elevated concentration being consistent with the closure of the tubule lumens. Crystallite size, as measured by small angle X-ray scattering, was slightly smaller in transparent dentin, although the importance of this finding requires further study. The elastic properties were unchanged by transparency; however, transparent dentin, unlike normal dentin, exhibited almost no yielding before failure. In addition, the fracture toughness was lowered by roughly 20% while the fatigue lifetime was deleteriously affected at high stress levels. These results are discussed in terms of the altered microstructure of transparent dentin.

Aged↗
PubMed2004

Effects of solvents on the early stage stiffening rate of demineralized dentin matrix.

OBJECTIVES: To monitor the stiffening rate of demineralized dentin matrix at the early stages after exposure to different neat solvents. METHODS: Dentin beams approximately 0.8x0.7x8.0 mm were obtained from human third molars. After covering their ends with resin composite, the middle exposed length of 4.0mm (gauge-length) was demineralized in 0.5 M EDTA (pH 7.0) for 7 days. The specimens were gripped by a testing machine, pre-loaded to 10 g and cyclically stressed in tension to 5% strain, for 30 repeated cycles (total 20 min) at 0.6 mm/min while immersed in water (control). Then, water was replaced by either 100% acetone, methanol, ethanol, propanol, HEMA or air and the specimens subjected to the same cyclic protocol. The maximum apparent modulus of elasticity (E(Max)) was calculated for every cycle, plotted as a function of time and subjected to regression analysis. Stiffening rate was calculated as changes in E (min). Regression analysis examined the relationship between E and time for each solvent. Data were analyzed by one-way ANOVA and Student-Newman-Keuls test at alpha=0.05. RESULTS: Regression analysis showed that E increased significantly with time in all water-free solvents (R2=0.8-0.99). Stiffening rate was higher for acetone (0.9 MPa/min) and ethanol (0.8 MPa/min), intermediate for air (0.7 MPa/min), methanol (0.6 MPa/min) and propanol (0.5 MPa/min), lower for HEMA (0.2 MPa/min) and practically none for water (0.07 MPa/min) with p<0.05. CONCLUSIONS: The solvent-induced stiffening rate of demineralized dentin matrix is both time and solvent-dependent. The ability of solvents to promptly stiffen the demineralized dentin matrix may be important in maintaining the resin-infiltrated matrix expanded during the solvent evaporation stage of resin bonding.

1-Propanol↗
PubMed2005

Development of an in situ root caries model B. In situ investigations.

OBJECTIVES: The aims of this pilot study were to assess the suitability of an in situ model for root caries studies, and to investigate the effect of sub-surface lesion mineral content and ultrastructural organisation on remineralisation. METHODS: Subjects were selected by criteria generally used for coronal caries models. Plaque pH responses and salivary flow rates were determined by standard methods. The chosen substrate was human dentine with artificially induced caries-like demineralisation and sterilised by gamma-irradiation (4100 Gy). Two levels of baseline demineralisation were induced by exposure to an acid buffer for 2 or 5 days. Mineral content was measured by computer-controlled quantitative microradiography. RESULTS: Remineralisation in situ was greater in smaller lesions with lower surface mineral content than in larger lesions in which the surface mineral content was high. CONCLUSIONS: The model is suitable for further development for investigating dentinal caries. More work is needed to validate the model by means of a fluoride dose-response study.

Adult↗
PubMed2005

Development of an in situ root caries model. A. In vitro investigations.

OBJECTIVES: The paper describes preliminary in vitro investigations, the objectives of which were to examine the influence of certain experimental parameters on artificial carious lesion formation in root hard tissues, and their remineralisation. These experiments formed part of a wider study that aimed to develop an in situ model of root caries, based on the existing coronal caries model used in Liverpool. The present studies examined the effects (a) of the anatomical origin of the dentine, the presence or absence of cementum, the exposure time and the type of demineralising system, on lesion development, and (b) of baseline lesion size on the extent and location of mineral re-precipitation. METHODS: Mineral content parameters in plano-parallel sections taken from dentine lesions were determined by computer-controlled transverse microradiography. RESULTS: The importance of the anatomical origin of the dentine on lesion formation was investigated by comparing in vitro lesion formation in premolar and molar dentine, and in dentine from apical, middle and coronal thirds of the root: no difference was observed between these sites. Lesions formed more rapidly in acid buffer solutions than in acid gel systems, and were more reliably produced when cementum was removed. The effect of baseline lesion size on subsequent in vitro remineralisation demonstrated that a small baseline mineral content was associated with a larger percentage mineral gain. The location of mineral deposition throughout the lesion was also influenced by baseline mineral content parameters. CONCLUSIONS: The results form a basis for the further development of an in situ dentinal caries model, providing data to suggest that manipulation of parameters involved in the preparation of artificial carious lesions has a significant effect on the behaviour of the lesion, particularly the phenomenon of remineralisation. Further work is needed to investigate the behaviour of the model in situ.

Bicuspid↗
PubMed2005

Effect of sodium hypochlorite on primary dentin--a scanning electron microscopy (SEM) evaluation.

OBJECTIVE: The aim of this study was to evaluate the alterations of etched deciduous dentin when submitted to different time and concentrations of sodium hypochlorite (NaOCl), using scanning electron microscopy (SEM). MATERIAL AND METHODS: Forty deciduous anterior teeth were selected, cleaned and ground until expose a flat dentin area on the buccal surface. The specimens were randomly distributed into eight groups (n=5), according to dentin surface treatment (35% phosphoric acid etching for 7s--AE and/or NaOCl application), NaOCl solution concentration (5% or 10%), and time of application (0, 30, 60, and 120 s), as follows: G1: control (without AE and NaOCl); G2: only AE; G3, G4, and G5: AE+5% NaOCl for 30, 60, and 120 s, respectively; G6, G7, and G8: AE+10% NaOCl for 30, 60, and 120 s, respectively. All specimens were prepared for SEM analysis and the photomicrographs (three for each specimen) were classified according to a score as follow: 0: presence of smear layer (SL); 1: absence of SL+non-altered collagen fibrils; 2: absence of SL+collagen fibrils slightly altered; 3: absence of SL+collagen fibrils severely altered; and 4: absence of SL and absence of collagen fibrils. Data were submitted to Kruskal-Wallis and Mann-Whitney tests (p<0.05). RESULTS: All groups treated with NaOCl solution were significant different from G1 and G2, and showed alterations on the collagen fibrils network. Collagen complete removal was only observed when a 5% NaOCl solution was applied for 120 s and 10% NaOCl solution for 30, 60, and 120 s. CONCLUSIONS: The NaOCl action produced significant changes in the etched deciduous dentin. The higher NaOCl concentration, the lower the time required to completely removing the collagen fibrils network in deciduous dentin.

Acid Etching, Dental↗
PubMed2002

Characterization of sound human dentin particles of sub-millimeter size.

OBJECTIVES: To obtain small dentin particles to provide material for the characterization of dentin. To study the interaction of etchants with dentin not covered by a smear layer and bonding agents. METHODS: Sound human dentin particles of sub-millimeter sizes were obtained by room temperature high-pressure fragmentation. Smear-layer free particles of three different average sizes were obtained by sieving. Surface areas were measured by the BET method. Simultaneous thermogravimetric and differential thermal analysis was carried out on all specimens and etched samples. Densities were measured by helium pycnometry. RESULTS: On average, the water, organic and mineral contents show the expected proportions. The more dense particles tend to be in the smaller sized fractions. Thus dentin particles of average size 100 microm have a density of 2.482(0.002) g/ml which is statistically different from the 300 microm average sized particles with 2.306(0.002) g/ml. However, the respective measured specific surface areas of 2.54(0.01) and 2.50(0.02) m(2)/g are not found to be statistically different. The specific surface areas of dentin particles increase upon etching, the increase being related to acid strength. Thermal analysis of acid-etched 200 microm diameter particles shows up to 75% loss of carbonate and only 30% loss of phosphate. SIGNIFICANCE: Smear-layer free dentin particles which have not been exposed to heat by grinding can be obtained by room temperature high-pressure fragmentation. Such sub-millimeter sized dentin particles can be acid-etched to significantly increase their specific surface area. Thermogravimetry used to analyze carbonate and phosphate contents gives new insight to the buffering action of human dentin.

Acid Etching, Dental↗
PubMed2003

Tissue-dissolution capacity and dentin-disinfecting potential of calcium hydroxide mixed with irrigating solutions.

OBJECTIVE: The goal of this study was to compare the tissue-dissolution potential and antibacterial effectiveness of a conventional Ca(OH)(2)/saline paste with equivalent Ca(OH)(2)/NaOCl and Ca(OH)(2)/chlorhexidine digluconate medications. STUDY DESIGN: Tissue specimens were obtained from freshly dissected pig palates. Tissue pieces of similar form and weight were incubated in air-tight containers with Ca(OH)(2) pastes or solutions proper for up to 7 days. Antimicrobial testing was performed in dentin blocks infected with Enterococcus faecalis. Medicated, sealed dentin specimens were incubated for 1 and 5 days, and bacterial growth was tested at different dentin depths. RESULTS: Up to day 4, the Ca(OH)(2)/irrigating solution mixtures dissolved tissue more effectively than the conventional Ca(OH)(2)/saline paste. After 7 days, however, no statistically significant differences were found between the saline and hypochlorite mixtures, but the Ca(OH)(2)/chlorhexidine medication was significantly less effective. Dentin block disinfection was quicker and more thorough with the Ca(OH)(2)/chlorhexidine or the Ca(OH)(2)/NaOCl than with the Ca(OH)(2)/saline paste. CONCLUSION: Ca(OH)(2)/irrigant mixtures under investigation appear more advantageous than the conventional Ca(OH)(2)/saline mixture, and merit further investigation in a clinical study.

Analysis of Variance↗
PubMed1980

A major intermolecular cross-linking site in bovine dentine collagen involving the alpha 2 chain and stabilizing the 4D overlap.

Approximately 20% of the radioactivity incorporated into the dentine collagen of unerupted bovine molars after reduction with tritiated sodium borohydride was recovered in a cyanogen bromide peptide fraction of Mr 61 000 following chromatography on agarose A5m. After rechromatography on agarose A1.5m, this fraction was resolved into ten components by gel isoelectric focusing. Of these components, nine (the most acidic) were tritiated and contained the reduced cross-links dihydroxylysinonorleucine and hydroxylysinonorleucine. The amino acid compositions were consistent with the identification of each of these components as alpha 2CB3,5 linked to one or two small peptides. By limited Edman degradation, with and without prior digestion with pyroglutamate aminopeptidase (EC 3.4.11.8), these small peptides were identified as alpha 1CB0,1 and alpha 2CB1, occurring in a ratio of approximately 2:1. Specific cleavage with cathepsin D revealed that all the cross-link was associated with the C-terminal one-third of the alpha 2 chain, thus fixing the displacement of the participating molecules at 4D. The content of the known reducible cross-links present in these peptides, calculated from the specific activity of the reductant, was sufficient to account for only 10--20% of the cross-linking actually found, suggesting that stabilization is mainly through nonreducible cross-links of as yet undetermined structure. By quantitative analysis of homoserine content and semiquantitative amino-terminal analyses, it was determined that virtually all of the alpha 2 chain of bovine dentine collagen is cross-linked in this manner. One cross-link per molecule in this location could made a major contribution to the mechanical stability of the insoluble collagen fibrils in this tissue.

Amino Acids↗