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Why is glass ionomer cement so popular?

Glass ionomer cements are popular today because they satisfy many of the characteristics of an ideal cement. They can be mixed easily by hand or triturator. They bond to teeth moderately, have optimum flow properties allowing easy seating, are cariostatic and are relatively inexpensive. On the downside, however, they are not easy to use properly, can cause significant postoperative tooth sensitivity, are moderately soluble in mouth fluids and have slightly less than optimum strength characteristics. Resin modifications of glass ionomer cements, to be introduced soon, may overcome many of the negatives associated with current glass ionomer cement. There will be further discussion of these as soon as they are available.

Adhesiveness↗

Adhesive bonding of various materials to hard tooth tissues: XXIII. Isotonic monomer formulations.

With regard to adhesion to dentin by chemical mechanisms, the vitality of odontoblasts and contiguous pulpal cells might require that materials influencing the dentinal tubules be maintained within certain limits of osmotic pressure. Resins for use in adhesive formulations can be made isotonic with vital tissues by adjusting the proportions of hydrophilic monomers and the water contents of the formulations.

Acrylates↗

Biological basis for clinical success: pulp protection and the tooth-restoration interface.

This article provides biological and technological information that strengthens clinicians' understanding of cohesive hybridization and pulp therapy in order to support their routine use of bonding and resin systems. Utilizing cohesive systems, clinicians should experience several advantages over traditional water-soluble base and liner systems. When properly applied, cohesive hybridization of vital dentin prevents immediate postoperative hypersensitivity under all restorations and completely seals the entire tooth-restoration interface, which provides a reduction in recurrent caries.

Animals↗

Ultrastructural study of apatite crystal dissolution in human dentine and bone.

The width and thickness of normal apatite monocrystals were determined in human dentine and alveolar bone on non-decalcified thin sections made perpendicular to the c axis. A mean width (L) of 364.50 A +/- 14.50 A and 562.10 A +/- 19 A was respectively found for dentine and bone monocrystals, whereas their mean thickness (E) was respectively 103.30 A +/- 2.70 A and 79.10 A +/- 3.10 A. The study of the ratio L.E.-1 for dentine and bone monocrystals showed a plate-like configuration which was more accentuated in bone crystals. Apatite crystal dissolution was studied during the carious process in dentine and bone resorption during advanced periodontal lesions. It could be shown that, in both conditions, one or several central core lesions developed along the c axis of the crystals. These central core lesions, extending laterally along (100) planes, progressively fused together, leading to the splitting up of the monocrystals into two thin plates by a complete destruction of the central part of the monocrystal.

Adolescent↗

The current state of dentine bonding systems: a review of materials and techniques.

The acid-etch technique for bonding composite resin to enamel is a well-established clinical procedure. Although bonding composite resin to dentine has proved to be a difficult challenge, it has become an indispensable link in aesthetic dentistry. The purpose of this article is to provide a brief history of dentinal bonding as well as an overview of clinical indications and available products for the bonding of composites and/or amalgam.

Acid Etching, Dental↗

[Evaluation methods of nightguard teeth bleaching with opalescence (ultradent) based on clinical and experimental tests].

In March 1989 Haywood and Heymann presented a new method for bleaching teeth called by them "nightguard vital bleaching". This procedure requires that the patient wears for 6 to 8 hours an individually designed guard filled with a viscous solution of carbamide peroxide. The aim of the present study was to determine the efficiency of the guard bleaching method and to address frequently asked questions concerning local complications and the influence of the preparation on the enamel surface. The scanning electron microscope was used in the experimental part to reveal changes in microhardness and on the surface of the bleached human enamel. The purpose of the clinical part was to determine the efficiency of bleaching, to estimate the frequency of pain and other symptoms and to check the influence of bleaching guard on accumulation of dental plaque and gingival status as reflected by the Plaque Index (Pl.I.) and the Gingival Index (G.I.). It was found that bleaching with 10, 20 or 35% carbamide peroxide reduced the microhardness and modified the morphology of enamel surface proportionally to the concentration of the bleaching agent. It was ascertained that 10% carbamide peroxide effectively bleached teeth and considerably improved the hygiene of the oral cavity and gingival status (Pl.I, G.I.). During bleaching, over half of the patients suffered from local complications--thermal hypersensitivity of teeth and irritation of gums. Some deterioration of the bleaching effect was observed after 12 months in females only. Almost 100% of the patients were satisfied with the results of bleaching and would recommend this procedure to family members.

Acid Etching, Dental↗

The solubilization of bone and dentin collagens by pepsin. Effect of cross-linkages and non-collagen components.

Bone and dentin collagen are less susceptible to solubilization by pepsin digestion then is skin collagen. Digestion at 4 degrees C for 72 h solubilized only 35.3% of bovine cortical bone and 5.6% of bovine dentin compared with nearly 100% dissolution of bovine skin. Sodium dodecyl sulfate-acrylamide gel electrophoresis and molecular sieve chromatography showed that, for bone and dentin, intact alpha chains and cross-linked aggregates of beta, gamma and higher weight remained intact after pepsin solubilization but lower molecular weight fragments also were prevalent indicating chain scission in helical regions. Electron microscopic examination of segment long spacing precipitates of the soluble collagens confirmed the presence of solubilized polymerized collagen. The principal reducible cross-link in both bone and dentin was the precursor of dihydroxylsinonorleucine and this cross-link was also present in the solubilized collagens. Small amounts of non-collagenous proteins and glycosaminoglycans of different compositions in dentin and bone resisted extraction before pepsin digestion. However, the differences in solubilization of the collagens have been related to differences in cross-linkage placement.

Amino Acids↗

Water sorption/solubility of dental adhesive resins.

OBJECTIVES: This study evaluated the water sorption, solubility and kinetics of water diffusion in commercial and experimental resins that are formulated to be used as dentin and enamel bonding agents. METHODS: Four commercial adhesives were selected along with their solvent-monomer combination: the bonding resins were of Adper Scotchbond Multi-Purpose (MP) and Clearfil SE Bond (SE) systems, and the "one-bottle" systems, Adper Single Bond (SB) and Excite (EX). Five experimental methacrylate-based resins of known hydrophilicities (R1, R2, R3, R4 and R5) were used as reference materials. Specimen disks were prepared by dispensing the uncured resin into a mould (5.8mm x 0.8mm). After desiccation, the cured specimens were weighed and then stored in distilled water for evaluation of the water diffusion kinetics over a 28-day period. RESULTS: Resin composition and hydrophilicity (ranked by their Hoy's solubility parameters) influenced water sorption, solubility and water diffusion in both commercial and experimental dental resins. The most hydrophilic experimental resin, R5, showed the highest water sorption, solubility and water diffusion coefficient. Among the commercial adhesives, the solvated systems, SB and EX, showed water sorption, solubility and water diffusion coefficients significantly greater than those observed for the non-solvated systems, MP and SE (p<0.05). In general, the extent and rate of water sorption increased with the hydrophilicity of the resin blends. SIGNIFICANCE: The extensive amount of water sorption in the current hydrophilic dental resins is a cause of concern. This may affect the mechanical stability of these resins and favor the rapid and catastrophic degradation of resin-dentin bonds.

Absorption↗

The relationship between surface free-energy and kinetics in the mineralization and demineralization of dental hard tissue.

The interfacial free-energy is an important factor in the regulation of mineralization and dissolution at the surfaces of dental hard tissues. However, few thermodynamic studies have been aimed at the elucidation of the interfacial terms. Contact angle measurements (sessile drop and thin layer wicking) and kinetic dissolution and growth techniques have been used to study the interfacial properties of root dentin (D), human enamel (E), and hydroxyapatite (HAP). The interfacial tensions between water (w) and each of these phases were calculated from contact angle data according to surface tension components theory. The values gamma wD = 4.5 x 10(-3) J m-2, gamma wE = 8.8 x 10(-3) J m-2, and gamma w,HAP = 10.4 x 10(-3) J m-2 were of the same order of magnitude as those obtained from dissolution kinetic data (pH = 4.5): gamma wD = 1.4 x 10(-3) J m-2, gamma wE = 3.2 x 10(-3) J m-2, and gamma wHAP = 9.3 x 10(-3) J m-2. Kinetics studies of the crystallization of HAP on HAP, dentin, and enamel yielded the interfacial free-energy values, gamma wHAP = 17.1 x 10(-3) J m-2, 17.7 x 10(-3) J m-2, and 9.4 x 10(-3) J m-2, respectively, probably reflecting the interfacial energies of the deposited phases rather than those of the dental hard-tissue substrata. The lower interfacial tension values are consistent with the higher solubilities of these solid phases: logKSO = -52.0, -55 approximately 57, and -58 approximately 59, for root dentin, enamel, and HAP, respectively, expressed as an equivalent HAP ionic product. The higher interfacial free-energy is also consistent with the slower mineralization of HAP on dentin and enamel surfaces.

Crystallization↗

Age estimation using the racemization of amino acid in human dentin.

This study was made to improve the validity of age estimation from teeth using amino acid racemization. The correlation between actual age and the D/L ratio of aspartic acid was investigated by analyzing not only the total amino acid but also its fractionated substances, insoluble collagen and soluble peptide. The coefficient values of correlation between the D/L ratio and actual age in adult lower central incisors were 0.996 (sigma = +/- 1.0 year) for the total amino acid, 0.988 (sigma = +/- 1.8 years) for insoluble collagen, and 0.997 (sigma = +/- 0.9 years) for soluble peptide. The corresponding figures in adult first premolars were 0.991 (sigma = +/- 1.6 years), 0.988 (sigma = +/- 1.9 years), and 0.994 (sigma = +/- 1.4 years), respectively. The reactive velocity of aspartic acid racemization was highest for soluble peptide in both the lower central incisors and first premolars and approximately three times as rapid as that for total amino acid. As a result, age estimated from the analysis of soluble peptide was most accurate. The velocity for insoluble collagen was slightly lower than that for total amino acid. Age estimation was attempted from the teeth of an unknown body. These results suggest that the analyses, not only of total amino acid in dentin but also of its fractionated and extracted substances, can lead to higher reliability in age estimation. Soluble peptide, in particular, has been found to be most effective.

Adult↗

Recent advances in stannous fluoride technology: antibacterial efficacy and mechanism of action towards hypersensitivity.

Stannous fluoride (SnF2) is highly susceptible to oxidation and hydrolysis but both anhydrous and aqueous preparations can be well established by proper formulation. When stability in aqueous preparations is achieved by the use of certain strong complexing agents, reduced antibacterial activity is observed which may be attributed to reduced bioavailability of the stannous ion. In contrast, an anhydrous SnF2 preparation maintains stannous ion in a stable but, uncomplexed form. This preparation displays antibacterial activity in saliva and delivers stannous ion which is absorbed onto surfaces making them less susceptible to plaque formation for an extended period of time (hours). When this anhydrous preparation is brushed onto dentine in vitro or in situ, one observes a nearly complete coverage of the dentine surface and occlusion of tubules by a tin-rich surface deposit. This finding indicates that the observed clinical efficacy of this preparation at relieving hypersensitivity is due to occlusion of tubules by a mixture of low solubility complexes of tin. A water-based SnF2 preparation containing strongly complexed stannous ions does not form a surface coating on dentine in vitro suggesting that this preparation may not be optimal for treating hypersensitivity. Overall, the findings indicate that the stannous ions in a SnF2 preparation must be maintained in a stable, bioavailable form for optimal efficacy against plaque and hypersensitivity to be obtained. The results suggest that these properties are provided by stable anhydrous preparations but are difficult to achieve simultaneously in aqueous preparations. When properly formulated, stannous fluoride preparations can provide multiple oral therapeutic benefits.

Bacteria↗

Calcium-induced associations of the caseins: a thermodynamic linkage approach to precipitation and resolubilization.

Calcium-induced changes in protein solubility play a role in a variety of important biological processes including the deposition of bone and dentin and the secretion of milk. The phenomena of salt-induced (calcium) precipitation of proteins (salting-out), and the resolubilization of these proteins at higher salt concentrations (salting-in) have been studied and quantitated using an approach based on the concepts of Wyman's thermodynamic linkage. Salting-out has been described by a salt-binding constant, k1, the number of moles of salt bound per mole of protein, n, and S1, the fraction soluble at saturation of n; salting-in has been described by corresponding constants k2, m, and S2. Analysis of salt-induced solubility profiles was performed using nonlinear regression analysis. Results of calcium-induced solubility profiles of two genetic variants of alpha s1-casein (alpha s1-A), (alpha s1-B), and beta-casein C (beta-C) at 37 degrees C, where hydrophobic interactions are maximized, showed no salting-in behavior and for salting-out, yielded k1 values of 157, 186, and 156 liters.mol-1 and n values of 8, 8, and 4, respectively. The values of k1 can be correlated with the apparent association constant for calcium binding to casein, while the values of n can be correlated with the number of calcium binding sites of the respective caseins. At 1 degree C, where hydrophobic interactions are minimized, nominally only hydrophilic and electrostatic interactions can be linked to the salt-induced solubility profiles; here beta-C is totally soluble at all calcium concentrations and alpha s1-B and alpha s1-A were now found to have salting-in parameters, k2 and m, of 2.5 liters.mol-1 and 4, and 11 liters.mol-1 and 8, respectively. alpha s1-A is more readily salted-in and studies on the variation of S1 with added KCl for this protein at 1 degree C indicated that salting-in is also mainly electrostatic in nature and may result from competition between K+ and Ca2+ for binding sites rather than from solute-solvent interactions as previously proposed. Comparison of k1 and k2 values between the two genetic variants, coupled with the known sequence differences (the A variant is a linear deletion of 13 amino acids) suggest the existence of a hydrophobically stabilized ion pair in alpha s1-B which is deleted in alpha s1-A; it is speculated that such bonds may play a role in other calcium-induced changes in protein solubility.

Calcium↗

Serine phosphate, threonine phosphate and gamma-carboxyglutamic acid in normal and experimentally induced, pathologically calcified rat skin (topical cutaneous calciphylaxis).

The amount of non-collagenous proteins is increased greatly during the pathological calcification of rat skin experimentally induced by dihydrotachysterol (DHT) and Ovalbumin (topical cutaneous calciphylaxis). This is accompanied by an increase in the total amount and concentrations of protein-bound serine phosphate [Ser(P)], threonine phosphate [Thr(P)] and gamma-carboxyglutamic acid (Gla), almost all of which can be extracted from the tissue and can be dissociated from collagen in 0.5M EDTA. The EDTA-soluble, non-collagenous proteins are rich in aspartic and glutamic acids, similar to the non-collagenous, EDTA-soluble proteins of bone, cementum and calcified cartilage, and quite distinct from those of dentin and enamel.

1-Carboxyglutamic Acid↗