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PubMedDate not supplied

Microscopic evaluation of the interface between glass-ionomer cements and tooth structures prepared using conventional instruments and the atraumatic restorative treatment (ART) technique.

OBJECTIVE: The purpose of this study was to evaluate the effect of cavity preparation using hand instruments and conventional rotary instruments on the bonding of glass-ionomer cements to formerly carious teeth. METHOD AND MATERIALS: In 2 experimental groups (12 teeth each with primary caries) caries was removed and cavities prepared using hand instruments according to the atraumatic restorative treatment (ART) technique or conventional rotary instruments. In the control group (12 caries-free teeth) Class 1 cavities were prepared using conventional instrumentation. Cavities in all teeth were restored with 1 of the commercial glass-ionomer cements designed for use with the ART technique, either Fuji IX (GC) or Ketac Molar (3M Espe). After 21 days of storage in physiologic saline at 37 degrees C, 3 400-microm-thick slices from each tooth were stained using the Mallory method and evaluated using a light transmitting microscope. RESULTS: In all samples, a region of interaction was observed between the cement and dentin and enamel. However, the interface in teeth from which caries had been removed was different from that in the control group. All were stained using Mallory staining, but only teeth which had been carious showed coloration. No differences were found in intensity of color or appearance between the cavity preparation techniques. CONCLUSION: The occurrence of caries in a tooth alters the bonding behavior of glass ionomers to that tooth. The method of caries removal (ART or conventional preparation) does not influence the quality of the interface between a glass ionomer and either dentin or enamel.

Acids↗
PubMed1997

[Ionized calcium in the saliva of children with multiple caries].

Ionized calcium and total content of all Ca fractions were measured in mixed saliva and blood serum of children aged 4 to 12 with solitary carious lesions or multiple caries. The level of ionized Ca was much higher in multiple caries than in individual lesions, and the content of bound Ca (protein-bound and in complex with other compounds) was decreased. The authors propose that recharging of salivary proteins caused by acidification of the saliva and dental deposit due to production of lactate and other organic acids is mainly responsible for redistribution of Ca fractions in mixed saliva. Ca release which results from demineralization of teeth, changed rate of salivary secretion and permeability of the blood-saliva barrier, and other factors may also contribute to redistribution of Ca fractions in the saliva, which plays an important role in the pathogenesis of caries.

Calcium↗
PubMed2002

The mammary gland and its origin during synapsid evolution.

Lactation appears to be an ancient reproductive trait that predates the origin of mammals. The synapsid branch of the amniote tree that separated from other taxa in the Pennsylvanian (>310 million years ago) evolved a glandular rather than scaled integument. Repeated radiations of synapsids produced a gradual accrual of mammalian features. The mammary gland apparently derives from an ancestral apocrine-like gland that was associated with hair follicles. This association is retained by monotreme mammary glands and is evident as vestigial mammary hair during early ontogenetic development of marsupials. The dense cluster of mammo-pilo-sebaceous units that open onto a nipple-less mammary patch in monotremes may reflect a structure that evolved to provide moisture and other constituents to permeable eggs. Mammary patch secretions were coopted to provide nutrients to hatchlings, but some constituents including lactose may have been secreted by ancestral apocrine-like glands in early synapsids. Advanced Triassic therapsids, such as cynodonts, almost certainly secreted complex, nutrient-rich milk, allowing a progressive decline in egg size and an increasingly altricial state of the young at hatching. This is indicated by the very small body size, presence of epipubic bones, and limited tooth replacement in advanced cynodonts and early mammaliaforms. Nipples that arose from the mammary patch rendered mammary hairs obsolete, while placental structures have allowed lactation to be truncated in living eutherians.

Animals↗
PubMed1999

Clinical effectiveness of a Class V flowable composite resin system.

This clinical study evaluated a Class V flowable composite resin restoration system and its ability to reduce dentin sensitivity. Twenty-one patients required Class V restorations because of erosion, abrasion, or decay at the cervical area. Each patient exhibited moderate or severe sensitivity and required replacement of tooth structure. The degree of sensitivity was determined by either tactile scraping of the tip of an explorer over the surface of the tooth or by an air blast from a syringe for 5 seconds. A total of 52 restorations were performed. According to phone conversations and questionnaires, 1 patient experienced continued sensitivity on 1 treated tooth for a duration of 1 week, but this sensitivity was gone at 1-month, 3-month, 6-month, and 1-year recalls. None of the other patients exhibited sensitivity at any phone checks or during recall visits.

Composite Resins↗
PubMed1993

Evidence for endothelial junctions acting as a fluid flux pathway in tensioned periodontal ligament.

A continuous tension load of 1.0 N applied to the rat maxillary first molar for 30 min led to a significant increase (p < 0.05) in the mean number of junctions/microns of endothelial perimeter. The mean number of junctions/microns was compared with the mean number of tissue channels/microns 2 as previously reported by fitting linear and quadratic equations. An increase in the mean number of junctions/microns was associated with an increase in mean number of tissue channels/microns 2 (p < 0.01) in control and experimental periodontal ligament. Significant increases in the mean number of junctions/microns occurred in the middle-third zone for venous capillaries (p < 0.01) and in the tooth-third zone for postcapillary-sized venules (p < 0.001). It is concluded that the endothelial junctions of venous capillaries and postcapillary-sized venules provide significant pathways for fluid transport across the tensioned walls of the microvascular bed of the periodontal ligament.

Animals↗
PubMed1992

An evaluation of smear layer with various desensitizing agents after tooth preparation.

According to hydrodynamics, any agent blocking the dentinal tubules reduces the flow of fluids and diminishes hypersensitivity. The properties of the desensitizing agents that sponsor tubular occlusion and the barrier efficiency resulting from the interaction of the smear layer with test materials were examined with the scanning electron microscope and energy-dispersive x-ray microanalysis. Selected dentinal desensitizing was accomplished with burnishing procedures, cavity varnish, calcium hydroxide, and topical fluoride. Subjective evaluations were also recorded clinically after tooth preparation. This investigation indicated that the smear layer did not protect against zinc phosphate cement, and that cavity varnish prevented the formation of the smear plugs. The smear layer and plugs were basically composed of calcium and phosphorus, the major ingredients of dentin.

Adult↗
PubMed2004

Mineral acquisition rates in developing enamel on maxillary and mandibular incisors of rats and mice: implications to extracellular acid loading as apatite crystals mature.

UNLABELLED: The formation rates of mineral in developing enamel were determined by microweighing of incisors of mice and rats. Computations indicated that a large excess of hydrogen ions would result from creating apatite at the calculated rates. Enamel organ cells (ameloblasts), therefore, likely excrete bicarbonate ions to prevent pH in fluid bathing enamel from becoming too acidic. INTRODUCTION: Protons (H+) are generated whenever calcium and phosphate ions combine directly from aqueous solutions to form hydroxyapatite. Enamel is susceptible to potential acid loading during development because the amount of fluid bathing this tissue is small and its buffering capacity is low. The epithelial cells covering this tissue are also believed to form permeability barriers at times during the maturation stage when crystals grow at their fastest rates. The goal of this study was to measure the bulk weight of mineral present in rodent enamel at specific times in development and estimate the amount of acid potentially formed as the apatite crystals mature. MATERIALS AND METHODS: Upper and lower jaws of mice and rats were freeze-dried, and the enamel layers on the incisors were partitioned into a series of 0.5 mm (mouse) or 1.0 mm (rat) strips along the length of each tooth. The strips were weighed on a microbalance, ashed at 575 degrees C for 18-24 h to remove organic material, and reweighed to determine the actual mineral weight for each strip. RESULTS AND CONCLUSIONS: The data indicated that, despite differences in gross sizes and shapes of maxillary and mandibular incisors in rats and mice, the overall pattern and rates of mineral acquisition were remarkably similar. This included sharply increasing rates of mineral acquisition between the secretory and maturation stages, with peak levels approaching 40 microg/mm tooth length. Computer modeling indicated that quantities of H+ ions potentially generated as apatite crystals grew during the maturation stage greatly exceeded local buffering capacity of enamel fluid and matrix proteins. In other systems, bicarbonate ions are excreted to neutralize highly acidic materials generated extracellularly. Data from this study indicate that ameloblasts, and perhaps cells in other apatite-based hard tissues, use similar bicarbonate release mechanisms to control excess acid arising from mineral formation.

Ameloblasts↗
PubMed1991

Influence of posteruptive age of enamel on its susceptibility to artificial caries.

Epidemiologic studies and caries experiments with animals have suggested that caries susceptibility of teeth decreases with age. Observations on the changes in the dental tissues and their environment with age have pointed out that a process commonly referred to as 'posteruptive maturation' of the dental enamel may be responsible. To test this assumption 10 unerupted third molars and 56 erupted human premolar teeth of various posteruptive ages were subjected for 130 days to an acid gel for caries-like lesion formation in vitro. Sections of the teeth were examined with polarized light and 'contour maps' were drawn with the approximate porosity of the lesions. The results were: unerupted = 833 microns (+/- 261); erupted of posteruptive age 0-3 years = 561 microns (+/- 150), 4-10 years = 470 microns (+/- 136), 11-30 years = 459 microns (+/- 192) and over 30 years = 297 microns (+/- 89). These findings show a decrease in the susceptibility of enamel to artificial caries with increasing age, which was especially marked at and shortly after eruption. This may be explained by a completion of mineralization of the outer enamel at about eruption, by a maturation process of the outer enamel posteruptively and by a reduction in the permeability of enamel occurring through to old age. The fluoride content of the mid-coronal buccal surface enamel under study was found to decrease posteruptively with age, therefore not accounting for the decreasing caries susceptibility.

Adolescent↗
PubMed1976

Characterization and modification of permselective properties of apatite membranes.

Compressed apatite disks were used as models for tooth enamel. Their permselective properties were studied as functions of the pH of the gradient solutions, the composition of the apatites, and the pretreatments with anionic phosphate compounds and cationic proteins. The results are discussed in relation to the caries mechanisms.

Apatites↗
PubMed1992

Changes in pulpal blood flow and in fluid flow through dentine produced by autonomic and sensory nerve stimulation in the cat.

We have recorded the flow of fluid through exposed dentine in cat canines. The effects on this flow of electrical stimulation of the cervical sympathetic trunk (CST) and of the inferior alveolar nerve (IAN) were investigated. In some preparations, pulpal blood flow was also monitored with a laser Doppler flow meter and the compound action potentials evoked by IAN stimulation were recorded from the tooth. CST stimulation (0.5-5/s) resulted in a significant decrease in the rate of outward flow of fluid through the dentine or, with the higher frequencies tested, a reversal of the flow. CST stimulation also produced vasoconstriction. IAN stimulation caused a significant increase in the rate of outward flow of fluid from the dentine. This effect required the recruitment of A delta fibres: A beta fibres alone had no effect. Pulpal vasodilatation occurred with the same threshold. Mechanical stimulation of dentine in an acutely denervated tooth also caused vasodilatation, indicating that pulpal afferents were involved. The results show that the rate of fluid flow through dentine, and hence the rate of inward diffusion of chemicals from the oral cavity, can be influenced by changes in the state of the pulpal microvasculature.

Action Potentials↗
PubMedDate not supplied

Influence of the substrate and load application method on the shear bond strength of two adhesive systems.

The difficulty with comparing data obtained from different research centers calls for the standardization of laboratory procedures. This in vitro study compared the shear bond strength (SBS) of two adhesive systems--a self-etching system, Etch&Prime 3.0 and a one-bottle total-etch system, Single Bond--using two methods of load application (orthodontic edge wire loop and knife-edge blade). The hypothesis of substrate influence on the results obtained for both tests was also investigated. Twenty-four recently extracted human teeth were embedded in PVC tubes using acrylic resin and divided into two groups (n=12). A proximal surface of each tooth was wet-ground flat to expose dentin. Etch&Prime 3.0 and Single Bond adhesive systems were applied according to the manufacturers' instructions, and cone-shaped restorations were then built using Z100 resin composite. After storage in distilled water at 37 degrees C for 24 hours, the specimens were submitted to SBS testing using an orthodontic edge wire loop. The same teeth were again embedded in PVC tubes using acrylic resin and the other proximal surface was wet-ground flat to expose dentin. The specimens were prepared as explained above, and after storage in distilled water under the same previous conditions, they were submitted to SBS testing using a knife-edge blade. Two-way ANOVA and Tukey's tests were performed to determine any statistically significant differences among testing conditions. Results indicated that SBS values obtained for Etch&Prime 3.0 were significantly lower than Single Bond for both methods of load application (p<0.001). Regarding the load application method, statistically significant higher values (p<0.01) were obtained for Etch&Prime 3.0 when the knife-edge blade was used, whereas, no significant difference was observed between the two methods for Single Bond. There was a significant correlation between the bond strength values obtained on the same tooth (p<0.05). SEM examination found that Etch&Prime 3.0 demonstrated narrower tags than Single Bond. Moreover, the peritubular dentin was not adequately decalcified when Etch&Prime 3.0 was used.

Analysis of Variance↗
PubMed2001

Synthetic hammerhead ribozymes as tools in gene expression.

The assessment of genetic controls for sequential developmental processes such as tooth formation and biomineralization is often difficult in transgenic "knockout" models, where phenotypes reflect only the permanent eradication of a gene, and reveal little about the dynamic range of expression for the gene(s) involved. One promising strategy to overcome this problem is through the use of ribozymes, a class of metalloenzymes made entirely of ribonucleic acid (RNA), that are capable of cleaving other RNA molecules in a catalytic fashion. Their activity can be targeted against specific mRNAs by selection of unique sequences flanking a conserved catalytic motif. In synthetic ribozymes, specificity, stability, and cell permeability can be dramatically improved by the incorporation of chemically modified ribonucleotides. This review focuses on the design and application of hammerhead ribozymes, the best-known and most widely used class of RNA-based enzymes. So far, except for a few conserved structures at the catalytic core, no one particular model or superior ribozyme design has been identified. It may well be that each cell, tissue, and organism has different requirements for the uptake, activity, and stability of hammerhead ribozymes. However, designed ribozymes can be highly effective agents for timed and localized elimination of gene products. As the 3D structures of active hammerhead molecules are revealed, more effective ribozymes will be developed. Today, developments in ribozyme-mediated sequence-specific blocking of gene expression hold great promise for active RNA enzymes as tools in biomolecular research and for eliminating unwanted gene expression in human diseases.

Animals↗
PubMedDate not supplied

Microporous dentin zone beneath resin-impregnated layer.

The purpose of this study was to investigate marginal microleakage by examining the resin/dentin interface using a cryo-SEM and a silver ion penetration method. Class 5 cervical cavities were restored using an adhesive resin system following treatment with 37% phosphoric acid gel. The cavity wall adaptation was observed using cryo-SEM to avoid specimen damage. This observation showed excellent marginal adaptation of material to cavity walls and no gap formation. However, silver ions had penetrated beneath the resin-impregnated layer when observed with conventional SEM images, which showed the leakage of silver ions between the resin and decalcified tooth structure without gap formation. This study suggests that the bonding monomers of Clearfil Photo Bond were not fully able to penetrate into the demineralized dentin after phosphoric acid etching, thus leaving a porous zone as a microleakage pathway beneath the resin-impregnated layer.

Acid Etching, Dental↗
PubMed1982

The pocket epithelium: a light- and electronmicroscopic study.

The POCKET epithelium is important for the pathogenesis of gingivitis and periodontitis. However, this epithelial variant has never been adequately described. The bioptic material with supraalveolar pockets originated from previous studies in which cotton floss ligatures were placed around the crowns of premolars in eight dogs. After periods of 4 to 21 days or up to 5 months, block biopsies comprising dental and gingival tissues were taken on the buccal side. The tissues were processed for light- and electron microscopic examination. The observations revealed that the pocket epithelium (1) does not attach to the tooth, (2) forms irregular ridges and, over connective tissue papillae, thin coverings which occasionally ulcerate, (3) consists of cells only some of which show a tendency to differentiate, (4) presents a basal lamina complex with discontinuities and multiplications, and (5) is infiltrated mainly by lymphocytes, T- and B-blasts and plasma cells, and is transmigrated by neutrophilic granulocytes. It is concluded that the mosaic-like structure of the pocket epithelium reflects the heterogeneity of the adjacent plaque, that this structure together with the absence of membrane coating granules is the basis for an extremely high permeability, and that epithelial ridges may conduct and collect foreign substances which thereby become more easily recognizable for leukocytes.

Animals↗
PubMed2006

HEMA diffusion from dentin bonding agents through various dentin thicknesses in primary molars.

PURPOSE: To evaluate in vitro HEMA diffusion amounts from three dentin-bonding systems in primary molars with various remaining dentin thicknesses. METHODS: Occlusal cavities were prepared with remaining dentin thickness of 0.5, 1 and 2 mm respectively. Chambers that contain 1 ml of distilled water were attached to each tooth. The groups were treated with Total Etch + Syntac Single Component, Syntac Single Component and Clearfil SE Bond. Water eluates were removed after 72 hours for analyses by HPLC. RESULTS: The cumulative HEMA release amounts were significantly different between all groups (P< 0.05). Decreasing dentin thickness and acid-etching significantly increased pulpward diffusion of HEMA.

Acid Etching, Dental↗
PubMedDate not supplied

Effect of collagen removal on microleakage of resin composite restorations.

This study evaluated the effects of collagen removal on the microleakage of two single-bottle adhesive systems. Forty human third molars were selected and each received two root preparations. The roots were randomly assigned for restoration using Prime & Bond 2.1 (Dentsply Ltda, Petrópolis, RJ 90915, Brazil) or Single Bond (3M Dental Products, St Paul, MN 55144, USA). One root in each tooth was treated with 36% H3PO4 for 15 seconds and the other received an additional treatment with 10% NaOCl for 60 seconds to remove the collagen layer before adhesive was applied. All preparations were restored with Z100 restorative resin (3M Dental Products). The specimens were submitted to 5,000 thermal cycles (5-55 degrees C) and stored in 37 degrees C distilled water for one year. The specimens were then coated with a varnish except for 1 mm of tooth structure surrounding the restoration and immersed in 2% buffered methylene blue for four hours. After rinsing, the restorations were sectioned and two independent observers scored the microleakage at the interface between the restorative material and the tooth using an optical microscope at x45 magnification. The scores were submitted to Fisher's Exact Test and the results showed that collagen removal significantly reduced microleakage for Prime & Bond 2.1 and had no effect on microleakage for Single Bond.

Acetone↗
PubMed1997

Treatment of hypersensitive teeth using neodymium:yttrium-aluminum-garnet lasers: a comparison of the use of various settings in an in vivo study.

The spectrum of the methods available to treat hypersensitive teeth is very great. The chances for success in the use of these different therapies are equally variable. Faced with the already successful effort of the Nd:YAG laser in the treatment of exposed tooth necks, the effectiveness of the use of different settings of the Nd:YAG laser on exposed dentine was examined in this clinical study. In the case of comparison of the therapy success of the laser settings amongst one another, no significant difference could be found. This leads us to a conclusion, that laser irradiation is therapeutically effective at very low settings.

Adult↗
PubMed1995

Lipoteichoic acid inhibits remineralization of artificial subsurface lesions and surface-softened enamel.

Dental plaque produces not only acids by which underlying enamel is demineralized but also compounds which may inhibit repair of the lesions. The aim of this study was to determine how lipoteichoic acid, a bacterial compound that is abundant in dental plaque and inhibits calcium phosphate precipitation in vitro, affects the remineralization of incipient enamel lesions. Subsurface and surface-softened lesions were made in thin sections of bovine enamel, incubated with various amounts of lipoteichoic acid (isolated from Lactobacillus casei), and remineralized in 1.5 mmol/L CaCl2, 0.9 mmol/L KH2PO4, 130 mmol/L KCl, and 20 mmol/L Hepes, pH 7.0. Remineralization was followed during several weeks by repeated microradiography of the sections, and characterized by the changes in the integrated mineral loss of the lesions and the differential mineral profiles. The results showed that: (1) the effects of lipoteichoic acid on lesion remineralization were dose-dependent; (2) in subsurface lesions only the highest dose of lipoteichoic acid affected remineralization, which was delayed throughout the lesions; and (3) in surface-softened enamel, lipoteichoic acid did not affect the remineralization of the deeper parts, but remineralization of a surface zone of from 25 to 30 microns was increasingly inhibited with increasing doses. These effects were explained by different permeabilities of the surfaces of both types of lesions for the inhibitor: In subsurface lesions, lipoteichoic acid may have mainly clogged the porosities in the surface layer, whereas it could penetrate substantially into surface-softened enamel.

Animals↗