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Results for “Dentin Permeability”

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PubMed2003

Factors contributing to the incompatibility between simplified-step adhesives and chemically-cured or dual-cured composites. Part III. Effect of acidic resin monomers.

PURPOSE: This study examined the polymerization kinetics of acid-contaminated light- and chemically-cured resins with the use of differential scanning calorimetry. MATERIALS AND METHODS: Light-cured and chemically-cured versions of an experimental bis-GMA/TEG-DMA resin at the ratio (w:w) of 62:38 were prepared. Four acidic resin monomers with either carboxylic (DSDM and MAA) or phosphoric functional groups (MP and 2MP) were added at a 10 wt% concentration to these resins to simulate the intermixing of resin composites and unpolymerized acidic monomers along the adhesive-composite interface of simplified-step dentin adhesives. Different concentrations of the most acidic monomer 2MP (10 to 50 wt% for the light-cured resin, and 2 to 4 wt% for the chemically-cured resin) were also added to examine their contribution to reducing the extent and rate of polymerization of these resin mixtures. The effect of sodium benzene sulphinate on the polymerization of the chemically-cured resin that was contaminated with 10 wt% 2MP was also investigated. RESULTS: At 10 wt% concentration, all acidic monomers had a limited effect on the polymerization of the light-cured resin. The rate and extent of polymerization in the chemically-cured resin was substantially reduced by the carboxylic acid monomers DSDM and MAA, while polymerization was completely inhibited in the presence of the organophosphate monomers MP and 2MP. Substantial reductions in the rate and extent of polymerization of the light-cured resin occurred only in the presence of high concentrations (30 to 50 wt%) of 2MP. More acute polymerization inhibition was observed when the chemically-cured resin was contaminated with 2 to 3 wt% 2MP, with polymerization completely inhibited at 4 wt%. Addition of sodium benzene sulphinate to 2MP-contaminated chemically-cured resin revived the previously uncured resins, but their rate and extent of polymerization were still inferior to that of uncontaminated chemically-cured resin. CONCLUSION: When the influence of adhesive permeability was excluded with the use of neat, water-free resins, deactivation of the tertiary amine utilized in the chemically-cured resin by even very low concentrations of acidic resin monomers accounts for the reported incompatibility between simplified-step dentin adhesives and chemically-cured composites. The polymerization of light-cured resin is only affected by much higher concentrations of acidic resin monomers.

Acids↗
PubMedDate not supplied

The influence of drying on quantitative laser fluorescence and optical pathlengths in incipient natural caries lesions.

Drying effects in 14 natural lesions were studied with quantitative light-induced fluorescence and optical pathlength spectroscopy. Results were compared with clinical judgments of the lesion surface and microradiographical characterizations of the lesions. Relative fluorescence and average pathlength decreased as a function of drying time with a decay time ranging from 35.5 to <1 min. Depth and mineral loss correlated with average pathlength total changes (r = -0.79/-0.60, respectively) and poorly with total fluorescence changes (r approximately = 0.3). The decay time of the drying process for the relative fluorescence correlated well with a theoretical model based on water diffusion in lesion and surface layer, but only for large decay times. Clinical judgments could not be related to the surface layer properties or the changes in the average pathlength, but were weakly related to the changes in the relative fluorescence. We conclude that (i) fluorescence effects are mostly due to the screening by the lesion of the fluorescence from the dentin and enamel-dentin junction; (ii) water evaporation in lesions conforms to the diffusion laws only in large lesions with low surface layer penetrability; (iii) the evaporation process is controlled by the surface layer only for small surface penetrabilities (approximately 0.1 vol% microm(-1)).

Algorithms↗
PubMed2006

A new technique for assessing hybrid layer interfacial micromorphology and integrity: two-photon laser microscopy.

PURPOSE: This study describes a two-photon laser fluorescence microscopy technique developed to evaluate the interfacial micromorphology of the hybrid layer in bonded restorations. MATERIALS AND METHODS: Micropermeability of the hybrid layer was characterized by means of simultaneously contrasting a dye-containing adhesive with a differently colored dye placed into the pulp chamber and allowed to diffuse toward the different-colored hybrid layer. A fluorescent red dye (rhodamine B) was incorporated into a commercial dentin bonding agent. Class I preparations (margins in enamel) were made on extracted human third molars. The teeth were restored using conventional methods: bonding agent, composite, finishing, and polishing. An aqueous solution of a yellow/green dye (fluorescein) was then placed into the pulp chamber for 3 h, allowing time to diffuse toward the different-colored bonded interface. The teeth were then embedded, sectioned, and microscopically analyzed using two-photon laser microscopy at 40X magnification. RESULTS: Subsurface fluorescent imaging using this technique enabled interfacial micromorphology to be characterized at submicrometer resolution and provided high-contrast images. The quality of surrounding structures and potential presence of gaps were also precisely assessed. CONCLUSION: Two-photon laser microscopy provided high quality, high-resolution images of the bonded interface and surrounding areas, allowing accurate qualitative and quantitative analysis of the structure and integrity of the hybrid layer.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1992

Demineralization and remineralization evaluation techniques.

This paper compares the experimental techniques utilized to assess the de- or remineralization of enamel or dentin in intra-oral studies. In in situ studies, it is important for one to know how much mineral has been lost or gained, and where the loss or gain occurred. The main emphasis in this paper is on techniques suitable for direct or indirect mineral quantification. The measuring techniques considered are microradiography, iodine absorptiometry, various microhardness tests, polarized light, light-scattering, iodide permeability, and wet chemical analysis. The various techniques are compared concerning suitability for the determination of mineral content in vol% (or wt%), mineral changes in vol% micron (or kg.m-2), and mineral distributions. Furthermore, sample preparation, the importance of protein penetration, nominal mineral loss range, the estimated mineral loss threshold, and the applicability to dentin are compared and considered. It is concluded that, although more than ten techniques are available for the measurement of changes after de- or remineralization in situ, transverse microradiography is the most practical technique for the direct and quantitative measurement of mineral content, mineral changes, and mineral distributions. Cross-sectional microhardness testing and light-scattering are also practical indirect techniques for quantitative mineral loss (or gain) determination in intra-oral studies.

Dental Enamel↗
PubMed1992

Pulpal vascular changes in inflammation.

Changes in pulpal vessels in experimentally induced acute and chronic pulpitis in dog tooth were investigated using corrosive resin casts and scanning electron microscopic examination. Following a cavity preparation without water spray, increased permeability of blood vessels occurred in the primary stage of acute pulpitis. This was evidenced by the extravasation of resin from the vessel. This phenomenon was found initially in the venular network as well as in the capillary network located under the dentin. The morphological change was minimal in the vascular network underneath the cavity. This is in contrast to an expanded and tortuous vascular network representing an ulceration which was found around an abscess in chronic pulpitis. Furthermore, formation of vascular loops and AVAlc close to the inflamed region may represent a protective change in the pulp against inflammation.

Acute Disease↗
PubMed2004

Osmotic blistering in enamel bonded with one-step self-etch adhesives.

One-step self-etch adhesives behave as permeable membranes after polymerization, permitting water to move through the cured adhesives. We hypothesize that osmotic blistering occurs in bonded enamel when these adhesives are used without composite coupling. Tooth surfaces from extracted human premolars were bonded with 5 one-step self-etch adhesives. They were immersed in distilled water or 4.8 M CaCl(2), and examined by stereomicroscopy, field-emission/environmental SEM, and TEM. Water blisters were observed in bonded enamel but not in bonded dentin when specimens were immersed in water. They collapsed when water was subsequently replaced with CaCl(2). Blisters were absent from enamel in specimens that were immersed in CaCl(2) only. Water trees were identified from adhesive-enamel interfaces. Osmotic blistering in enamel is probably caused by the low water permeability of enamel. This creates an osmotic gradient between the bonded enamel and the external environment, causing water sorption into the interface.

Acid Etching, Dental↗
PubMed2002

Two modes of nanoleakage expression in single-step adhesives.

Self-etch adhesives that etch, prime, and bond simultaneously should not exhibit incomplete resin infiltration within hybrid layers. We hypothesized that nanoleakage patterns in these systems are artifacts caused by mineral dissolution in mildly acidic silver nitrate. Resin-dentin interfaces bonded with four single-step, self-etch adhesives were examined for nanoleakage by conventional (pH 4.2) and basic ammoniacal (pH 9.5) silver nitrate and prepared for transmission electron microscopy. All adhesives exhibited a reticular mode of nanoleakage within hybrid layers when conventional silver nitrate was used. With ammoniacal silver nitrate, an additional spotted pattern of nanoleakage was observed within adhesive and hybrid layers. The reticular mode of nanoleakage in self-etch adhesives probably represents sites of incomplete water removal that leads to regional suboptimal polymerization. The spotted pattern identified with the use of ammoniacal silver nitrate probably represents potentially permeable regions in the adhesive and hybrid layers that result from the interaction of the basic diamine silver ions with acidic/hydrophilic resin components.

Acid Etching, Dental↗
PubMed1994

Prevention of tooth hypersensitivity caused by the hydrodynamic action of zinc phosphate and composite resin luting cements (SEM) study.

This study was done to determine the role of cement liner as a reducing factor to the fluid movement in order to prevent tooth hypersensitivity according to the hydrodynamic theory during cementation of crowns. A total of fourty freshly extracted intact lower molar were selected for this study. After conventional tooth preparation the teeth were sub-divided into four equal groups to identify the role of cement liner in preventing the penetration of used cement into the dentinal tubules. Scanning electron microscopic study proved the efficiency of glass ionomer liner on preventing cement penetration into the dentinal tubules.

Composite Resins↗
PubMed1986

Clinical and experimental observations on resinifying therapy.

The principles, indications, and techniques of resinifying therapy and the composition of a resinifying agent are described in this article. The permeability and bacteriostasis of the agent and the volume change of the agent after treatment were observed, and 14C-labeled phenoaldehyde showed that the agent not only filled the main canals and accessory canals but also infiltrated into dentinal tubules with a depth one fourth to one third the total length of the tubules. The antimicrobial activity of the agent after polymerization for 2 to 6 months was determined. Even 9 months after treatment, no change in volume of the agent was found in vivo, and sealing of canals was maintained. Seventy-eight teeth in 69 patients with pulpoperiapical diseases were subjected to resinifying therapy and followed up for 6 to 12 months; the success rate was 82.05%. The histologic study indicated that, of the specimens experimentally treated for 6 to 12 months, 85.7% showed mild or no inflammation while 53.6% showed complete healing or an obvious healing tendency. Furthermore, the mechanisms and advantages of this therapy are discussed.

Animals↗
PubMed1979

Biological testing of dental restorative materials in vitro--a review.

In vitro methods for the biological evaluation of dental restorative materials are discussed, with particular reference to the type of cells used, the physical state of the test material, the method of establishing cell-material contact, and the criteria of cytotoxicity. It is postulated that in vitro methods should provide a reliable assessment of the toxicity of dental restorative materials, but since the current in vitro methods do not mimic in vivo conditions sufficiently closely, the correlation between in vitro and in vivo results is at present poor. The development of in vitro methods more closely simulating in vivo circumstances is advocated.

Biocompatible Materials↗
PubMedDate not supplied

Shear bond strength of 4th & 5th generation dentin bonding agents in the presence and absence of moisture. An in vitro study.

Extracated human molars were used for the study, flat dentinal surfaces were prepared on the occlusal surfaces, and then 4th and 5th generation dentin bonding agents were used in dry and moist conditions to bond composite resin onto the flat dentin surfaces. Shear Bond Strength was measured using Instron Universal Testing machine. Failures were recorded as adhesive, cohesive and mixed. Bond strength was highest in moist condition, because the moist surface permits more porous collagen network and hence greater infiltration of adhesive monomers, than do surfaces that are air dried. Moreover, those dentin bonding agents whose primers are based on acetone show improved bond strength, because acetone aggressively pursues and displaces water in the substrate, resulting in the primer resin being carried into tissue channels and porosities. When the dentin is air dried, the water that is supporting the collagen network evaporates causing the collagen network to collapse network is greatly reduced, which in turn decreases the premeability of intertubular dentin to adhesive resin and as a result causes decrease in bond strength. 5th generation dentin bonding agent showed significant improvement in the moist dentin bond strength.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1975

Sealing properties of intermediary bases and effect on rat molar pulp.

Five "cream-like" intermediary bases (Hypocal¿, Dycal¿, Reocap¿, Cavitec¿ and Dropsin¿) were studied using ZnO-eugenol (ZOE) and phosphate cement for comparison. The in vitro experiments, which were designed to reveal the penetration of a dye and an etching liquid, showed that Dropsin and Hyypocal were permeable to dye and that Dropsin was permeable to acid as well. The in vivo experiments revealed no definite differences between the different cream-like base materials, nor were there differences between those and the conventional cements. The overall mildness of the dentin-pulp reactions and the suitability of the rat molar for this kind of research are discussed.

Animals↗
PubMed1977

A method for the in vitro toxicity testing of dental restorative materials.

An vitro method of toxicity testing of dental restorative materials is described in which their clinical usage is closely simulated. The test material was separated from the cells by either a synthetic filter or dentine slice. Toxic effects were quantiated by determining changes in enzyme activity by scanning and integrating microdensitometry.

Acid Phosphatase↗
PubMedDate not supplied

Tissue-engineered hybrid tooth and bone.

Tooth loss accompanied by alveolar bone resorption presents a significant clinical problem. We have investigated the utility of a tissue-engineering approach to provide corrective therapies for tooth-bone loss. Hybrid tooth-bone tissues were bioengineered as follows. Tooth implants were generated from pig third molar tooth bud cells seeded onto polyglycolide (PGA) and polyglycolide-colactide (PLGA) scaffolds, and grown for 4 weeks in the omenta of adult rat hosts. Bone implants were generated from osteoblasts induced from bone marrow progenitor cells obtained from the same pig, seeded onto PLGA fused wafer scaffolds, and grown for 10 days in a rotational oxygen-permeable bioreactor system. The tooth and bone implants were harvested, sutured together, reimplanted, and grown in the omenta for an additional 8 weeks. Histological and immunohistochemical analyses of the excised hybrid tooth-bone constructs revealed the presence of tooth tissues, including primary and reparative dentin and enamel in the tooth portion of hybrid tooth-bone implants, and osteocalcin and bone sialoprotein-positive bone in the bone portion of hybrid tooth-bone constructs. Collagen type III-positive connective tissue resembling periodontal ligament and tooth root structures were present at the interface of bioengineered tooth and bone tissues. These results demonstrate the utility of a hybrid tooth-bone tissue-engineering approach for the eventual clinical treatment of tooth loss accompanied by alveolar bone resorption.

Animals↗