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PubMed1980

The caries resistance of human teeth is determined by the spatial arrangement of hydroxyapatite microcrystals in the enamel.

Teeth from different people differ in their susceptibility to caries. The beginning and the development of tooth decay depend on the presence of bacterial plaque and on the structure of the tooth enamel. But it has not been established whether the organic or the inorganic component of the enamel (which is comprised principally of hydroxyapatite microcrystals organized in a firm matrix), is responsible for most of the resistance of teeth to caries. We report here that the electron spin resonance (ESR) lines of the (CO3)3 defect of samples of enamel prepared from caries-resistant teeth differ significantly from the corresponding spectra of the caries-sensitive samples. We have traced these differences to the hydroxyapatite microcrystalline alignment in the tooth enamel, and found that this alignment is specific to individuals and is therefore probably nutritionally or genetically determined.

Crystallography↗
PubMed1991

[A case report of supernumerary deciduous teeth with the permanent successor in the maxillary region].

We found pure primary supernumerary teeth in the maxillary right deciduous incisor region of a 3 year 11 month old girl. We reported the results of her oral and X-ray analysis results. We would like to report our findings on the results of her oral and X-ray analysis. 1) Two of the primary supernumerary teeth were found between the incisor and canine teeth in the right side of the primary dental arch, and their color, form and size were very similar to normal primary lateral incisor teeth. 2) We also found pure secondary supernumerary teeth by means of X-ray analysis. 3) We suggest that the permeability of the X-ray is important for the ascertainment of both primary and secondary supernumerary teeth by mean of X-ray analysis.

Child, Preschool↗
PubMed2002

Update on materials used in intracoronal bleaching.

Intracoronal bleaching has emerged as a popular technique to bleach discoloured, endodontically treated anterior teeth. Although hydrogen peroxide and sodium perborate have traditionally been used in intracoronal bleaching, some concern has been expressed regarding the use of hydrogen peroxide, mainly because of the suspected "cause and effect" relationship between hydrogen peroxide and invasive cervical root resorption. Other complications associated with use of hydrogen peroxide alone or in combination with sodium perborate include increased dentine permeability, alteration in the chemical structure of dentine, and general weakening of physical properties of dental hard tissues. This has prompted researchers to look for alternative bleaching agents as effective as the traditional bleaching agents but unassociated with such complications. Some of these alternatives have been shown to be as effective as sodium perborate in lightening tooth colour under in vitro conditions and may represent a useful alternative to the traditional materials that are currently in use.

Borates↗
PubMed2005

Severe neuropathy with leaky connexin32 hemichannels.

X-linked Charcot-Marie-Tooth disease is one of a set of diseases caused by mutations in gap junction proteins called connexins. We identified a connexin32 missense mutation (F235C) in a girl with unusually severe neuropathy. The localization and trafficking of the mutant protein in cell culture was normal, but electrophysiological studies showed that the mutation caused abnormal hemichannel opening, with excessive permeability of the plasma membrane and decreased cell survival. Abnormal leakiness of connexin hemichannels is likely a mechanism of cellular toxicity in this and perhaps other diseases caused by connexin mutations.

Adolescent↗
PubMed1997

The effects of immunoglobulins on the convective permeability of human dentine in vitro.

Immunoglobulin molecules are localized in the dentinal tubules of non-carious and carious teeth, but their possible role in caries invasion is not understood. This study sought to examine the effects of immunoglobulin molecules on dentine permeability using a fluid-filtration method. Crown segments cut from impacted human third molars were treated by filtration with 100 micrograms/ml IgG, 100 micrograms/ml IgA or 30 micrograms/ml IgM under a constant pressure. Flow rates were recorded and percent changes in flow rate analysed over time. Filtrates collected at various times were tested for changes in immunoglobulin concentrations by an enzyme-linked immunosorbent assay, and the percent retention of immunoglobulins to dentine was calculated. There was a decreasing non-linear exponential relation between the percent changes in flow rate and filtration time for all three immunoglobulins. The percentage of retained immunoglobulins was significantly related to the filtration time for all three classes of immunoglobulins. Immunoglobulin retention contributed to significant changes in flow rate with time. These in vitro results indicate the potential mechanism of immunoglobulins in decreasing tabular permeability.

Dental Caries↗
PubMed1992

An improved intra-oral enamel demineralization test model for the study of dental caries.

The intra-oral enamel demineralization test (IEDT) was introduced by Brudevold et al. (1984). This caries model involves human subjects wearing palatal appliances each holding eight bovine enamel blocks covered by a bacterial cell layer prepared by the harvesting of cultures of Streptococcus mutants (test plaque). The original model used the iodide permeability test for assessment of the extent of demineralization of bovine enamel blocks resulting from acid production by the test plaque after dietary substrate challenge. The IEDT model has been expanded and improved by us in the following ways: (1) Based on encouraging findings from an in vitro study (Zero et al., 1990), the surface microhardness test has been adopted to measure the extent of demineralization occurring at three sites on the enamel blocks corresponding to an area over which the effective plaque thickness is 0.5, 1.5, and 2.5 mm; (2) intra-oral pH of the test plaque is measured by means of a Beetrode miniature pH electrode at baseline, then at five, 10, 15, 30, and 45 min after the start of a test; (3) plaque samples are collected at the end of a test and analyzed for organic acid content by means of HPLC; (4) the bacterial test challenge has been expanded to include different cariogenic bacteria which are grown under various growth conditions. The improved model has the capability of studying fundamental aspects of the caries process, namely, the relationships among dietary substrate challenge, plaque pH change, plaque organic acid profiles, microbial virulence properties, and enamel demineralization. Furthermore, the model has the potential for use in more applied research on caries-preventive agents such as fluoride.

Adult↗
PubMed2006

In vitro FT-IR study of the effects of hydrogen peroxide on superficial tooth enamel.

OBJECTIVES: The aim of the present study was to determine the alteration in human enamel after hydrogen peroxide treatment using FT-IR spectroscopy. It is hypothesized that infrared spectroscopy is capable of showing alterations in human enamel after peroxide treatment and the alteration in enamel is proportional to peroxide concentration. METHODS: The effects of 10, 20 and 30% hydrogen peroxide solutions on human enamel were tested. Thirty non-carious human teeth, extracted for periodontal reasons, were used in this study. They were divided into 3 groups of 10, according to the peroxide concentration, sectioned, and the specimens were embedded in resin for infrared spectroscopic analysis. The total treatment time was 120 min. Spectra of the specimens were taken before treatment and 30, 60 and 120 min after it. Another spectrum was taken in a week. RESULTS: Infrared spectroscopic analysis showed two distinct bands (biological PO(4)nu1 and nu2) that were capable of describing the alterations in enamel structure. On comparing the infrared spectra of non-treated and treated specimens, structural changes were detected in the superficial enamel. The alteration in enamel was proportional to treatment time and hydrogen peroxide concentration. Higher concentration and longer treatment time resulted in more severe alterations. The numerical analysis of the spectra revealed that on using concentrated hydrogen peroxide solutions the alterations of the IR spectra were more pronounced. The spectra taken in 1 week after treatment did not show spontaneous reversibility in enamel structure. CONCLUSION: At-home and in-office peroxide-containing bleaching agents are capable of causing alteration in enamel at low and high concentrations as well. According to the results of this study it is recommended to perform tooth whitening using low concentration of hydrogen and/or carbamide peroxide, and shorten treatment time to reduce the possible destruction but reach the required change in color.

Dental Enamel↗
PubMed1988

Micro-analysis of mineral saturation within enamel during lactic acid demineralization.

In this study, the physicochemical factors responsible for caries-like lesion propagation were investigated by means of a micro-analytical system used to study the fluid within a lesion during a simulation of the decay process. Four 500-microns-thick serial sections prepared from a single human molar were mounted between glass plates with only the natural surface of the tooth exposed. Microwells were then drilled into sound and pre-existing carious regions of the section through one of the plates. These microwells were then filled with fluid under mineral oil, and after a week of equilibration, the natural surface of the section was exposed to a lesion-producing fluid. The concentrations of calcium, phosphate, and hydrogen ions of the fluid in the wells were then followed as a function of time as the lesion advanced. The results of this study, in which lactic acid was used to demineralize enamel, were consistent with those previously reported (Vogel et al., 1987a): The solution within the lesion remained saturated during the acid attack. Differences in initial mobilities of the calcium and phosphate and other ions, a result of the permselectivity of the enamel, increased the concentrations within the lesion and permanently changed the ratio of these ions in the lesion solution. Based on these results, we suggest that the ionic permselectivity of tooth enamel can have a profound effect on the transport of mineral from a caries lesion.

Calcium↗
PubMed1997

The dentin substrate: structure and properties related to bonding.

OBJECTIVES: Dentin is a vital, hydrated composite material with structural components and properties that vary with location. These variations are reviewed along with alterations by physiological and pathological changes that allow classification into various forms of dentin. Structural characteristics and mechanical properties are reviewed and the limitations of our understanding of structure-property relationships for normal and modified forms of dentin are discussed with respect to their impact on dentin bonding. Recent progress in methods available to study dentin and its demineralization are emphasized with their promise to increase our understanding of dentin properties and structure. DATA SOURCES: Recent microstructural studies, focusing on scanning electron microscopy, atomic force microscopy and X-ray tomographic microscopy are included. A review of fundamental studies with emphasis on microstructurally sensitive methods, and prior reviews of basic mechanical properties are included with discussion of their correlation to composition and structure. STUDY SELECTION AND CONCLUSIONS: Emphasis in this work was placed on the major structural components of the tissue, including the collagen based organic matrix and its mineral reinforcement, the distribution of these components and their microstructural organization as related to mechanical properties and response to demineralization. Little information is included on biochemical and developmental studies or on non-collagenous proteins and other organic components for which limited understanding is available with respect to their role in structure-property relations and influence on bonding. In spite of the fact that the complexity of dentin precluded a comprehensive review, it is clear that local structural variations influence properties and impact nearly all preventive and restorative dental treatments. Much more work is needed in order to understand differences between vital and non-vital dentin, and dentin from extracted teeth. Although our knowledge is rudimentary in certain areas, increasingly sophisticated methods of studying dentin should provide the necessary information to model structure-property relations, optimize dentin bonding, and improve many aspects of preventive and restorative dentistry.

Apatites↗
PubMed2006

Effects of smear layer and surface moisture on dentin bond strength of a waterless all-in-one adhesive.

The purpose of this study was to evaluate the microtensile bond strength (MTBS) of a waterless all-in-one adhesive system, Absolute, to dentin. Eighteen human molars were either ground with 600-grit SiC paper or cut with a diamond bur. The following dentin bonding procedures were then performed: dentin surface was kept moist; dentin surface was dried; or dentin surface was dried but equivalent amount of water was added to the adhesive (1:1 by volume). After adhesive curing, a resin composite was incrementally built up. After the specimens were kept in water for one day, MTBSs were measured at a cross-head speed of 1 mm/min. Two-way ANOVA (p = 0.05) indicated that the MTBS of the adhesive system was not influenced by surface texture, but enhanced by the presence of water on tooth surface. It was concluded that water is essential to obtaining good dentin bonding for this adhesive system.

Analysis of Variance↗
PubMedDate not supplied

Effect of new generation surface sealants on the marginal permeability of Class V resin composite restorations.

This study evaluated, in vitro, the effectiveness of 5 surface sealants (Biscover, Optiguard, Seal-n-Shine, PermaSeal and DuraFinish); 1 pit and fissure sealant (Helioseal) and 1 dentin bonding agent (Adper Scotchbond MultiPurpose Adhesive) on the marginal sealing ability of Class V hybrid resin composite (Esthet.X) restorations. Ninety-six non-carious human molars were randomly assigned to 8 groups (n=12). Class V cavities were prepared on either the facial or lingual surfaces, with coronal margins in enamel and apical margins in cementum (dentin), and restored following manufacturers' instructions. Following finishing and polishing procedures, the covering agents were applied to each restoration and adjacent tooth surface, except for the control group restorations, which were not sealed. The teeth were thermocycled, immersed in a 1% methylene blue dye solution, sectioned and analyzed for dye penetration (leakage) using a 20x binocular microscope. Microleakage was evaluated at the coronal and apical margins using an 0-3 ordinal grading scale. Non-parametric data was analyzed at a p< or =0.05 level of significance. The Kruskal-Wallis test showed a significant difference was exhibited among groups at the coronal margins, with Helioseal pit/fissure sealant and DuraFinish surface sealant exhibiting significantly less leakage than the control and Adper Scotchbond MultiPurpose adhesive. At the apical margins, DuraFinish surface sealant showed significantly less leakage than the Biscover, Seal-n-Shine and PermaSeal surface sealants or Helioseal pit/fissure sealant, Adper Scotchbond MultiPurpose adhesive and the control group. According to the Wicoxon signed-rank test, significantly greater leakage was revealed at the apical margins compared to the enamel margins of the material groups.

Acrylates↗
PubMed1996

Methods of assessing erosion and erosive potential.

Methods for use in vitro are reviewed first, classified under the examination of extracted teeth, chemical and physical methods, digital image analysis, scanning electron microscopy and other potentially useful techniques. Methods for recording erosion in laboratory animals are dealt with next, including techniques that can also be used in vitro, Restarski's system and various modifications of it, and digital image analysis. Thirdly the main systems and indices that have been designed for clinical use are arranged under case histories and clinical examination, scales of severity and indices of diagnosis of varying complexity. Finally, some of the main advantages and limitations of the techniques are summarized.

Acids↗
PubMed2000

The chemistry of enamel caries.

The chemical changes which occur during the process of carious destruction of enamel are complex due to a number of factors. First, substituted hydroxyapatite, the main component of dental enamel, can behave in a very complex manner during dissolution. This is due not only to its ability to accept substituent ions but also to the wide range of calcium phosphate species which can form following dissolution. In addition, the composition, i.e., the extent of substitution, changes throughout enamel in the direction of carious attack, i.e., from surface to interior. Both surface and positively birefringent zones of the lesion clearly illustrate that carious destruction is not simple dissolution. Selective dissolution of soluble minerals occurs, and there is the probability of reprecipitation. The role of fluoride here is crucial in that not only does it protect enamel per se but also its presence in solution means that rather insoluble fluoridated species can form very easily, encouraging redeposition. The role of organic material clearly needs further investigation, but there is the real possibility of both inhibition of repair and facilitation of redeposition. For the future, delivering fluoride deep into the lesion would appear to offer the prospect of improved repair. This would entail a delivery vehicle which solved the problem of fluoride uptake by apatite at the tooth surface. Elucidation of the role of organic material may also reveal putative mechanisms for encouraging repair and/or protecting the enamel mineral.

Animals↗
PubMedDate not supplied

Quantitative microleakage evaluation around amalgam restorations with different treatments on cavity walls.

The purpose of this in vitro study was to evaluate the dye penetration around amalgam restorations in dentin cavities by a quantitative test. Standardized circular cavities were prepared on the facial surface of 75 extracted human single-rooted teeth, and restored with dental amalgam. Different bonding/sealing treatments were used on the cavity walls before the restorations were placed. The specimens were thermo-cycled between 5 +/- 2 degrees C and 55 +/- 2 degrees C for 500 cycles with 1-minute dwell times, followed by immersion in a 2% methylene blue solution for 12 hours at 37 degrees C. The quantitative microleakage was evaluated by spectrophotometry and was expressed by microgram dye per tooth structure. The results showed that the use of bonded amalgam restorations was more effective in reducing microleakage.

Dental Amalgam↗
PubMed1992

Effect of trichloracetic acid on the microhardness and surface morphology of human dentin and enamel.

Trichloracetic acid is recommended for the treatment of external cervical root resorption. The present study examined the effect of 90% trichloracetic acid on the microhardness and surface morphology of human dentin and enamel. Intact extracted human teeth were sectioned and embedded in acrylic resin. Each tooth was grinded and highly polished exposing a flat surface of dentin and enamel. The teeth were treated with 90% trichloracetic acid for 30, 60 and 90 s. Vicker's microhardness of the dentin and enamel was assessed for each tooth before and after each treatment. In addition the surface morphology of a trichloracetic acid treated tooth was examined via SEM. The results showed that 90% trichloracetic acid caused a second order type reduction of the microhardness, as well as structural changes in both dentin and enamel.

Acid Etching, Dental↗
PubMedDate not supplied

Marginal permeability of self-etch and total-etch adhesive systems.

This study evaluated microleakage in vitro of self-etch and multi-step, total-etch adhesive systems. Ninety-six extracted non-carious human molars were randomly assigned to eight groups (n=12) and restored with different adhesive systems: Optibond Solo Plus, iBond, Adper Prompt L-Pop, Xeno III, Simplicity, Nano-Bond, Adper Scotchbond Multi-Purpose and Touch & Bond. Each group was treated following the manufacturer's instructions. Class V cavities were prepared on the facial or lingual surfaces of each tooth with coronal margins in enamel and apical margins in cementum (dentin). The teeth were restored with Z-100 resin composite. After polishing with Sof-Lex disks, the teeth were thermocycled for 1000 cycles and coated with nail varnish to within 1.0 mm of the restoration. The teeth were stained in 1% methylene blue dye for 24 hours and sectioned from the facial to lingual surface. Dye penetration (microleakage) was examined with a 20x binocular microscope. Enamel and dentin margin leakage was scored on a 0 to 3 ordinal scale. Data were analyzed using Kruskal-Wallis Analysis of Variance and Mann-Whitney U tests. Comparison of the adhesive groups at the enamel margin revealed: 1) Adper Scotchbond Multi-Purpose exhibited significantly less leakage than the other adhesive groups (except iBond); 2) among the self-etch adhesive groups, iBond exhibited significantly less leakage than Nano-Bond and 3) the other adhesive groups clustered intermediately. In contrast, there were no significant differences among the adhesive groups when the dentin margin was evaluated. A Wilcoxin signed rank test showed significantly less leakage at the enamel margins compared to the dentin margins of the eight adhesive systems tested. All data were submitted to statistical analysis at p<0.05 level of significance.

Acid Etching, Dental↗
PubMed1993

Inhibitory influence of sympathetic nerves on afferent nerve-induced extravasation in the rat incisor pulp upon direct electrical stimulation of the tooth.

Previous studies have shown that sympathetic nerve stimulation reduces afferent nerve-induced vasodilation by mechanisms unrelated to vasoconstriction in the rat incisor pulp. The present investigation concerned whether similar modulatory mechanisms might also influence neurogenic plasma extravasation in dental pulp. Rat mandibular incisors were electrically stimulated and blood flow reactions in the pulp were recorded by laser Doppler flowmetry. Plasma extravasation in the incisor pulp, gingiva and lip were indirectly assessed by the Evans-blue method. Stimulation of teeth with 50 microA (5 min) did not cause increased dye accumulation in the stimulated pulps whereas stimulation with 100 microA significantly increased the dye content in ipsilateral pulps by 32% as compared to controls; 100 microA stimulation was without effect in unilaterally denervated animals. Tooth stimulation with 50 microA (5 min), in the presence of either the alpha-adrenergic blocker phenoxybenzamine (3 mg/kg), or the alpha 1-adrenergic antagonist prazosin (50 micrograms/kg), as well as in chronically sympathectomized animals, significantly increased the Evans-blue content in the stimulated pulps by 47, 83 and 86%, respectively. Application of short trains of impulses (same number of impulses as for the continuous stimulation but producing minimal vasoconstriction) resulted in some dye accumulation, which was enhanced in the ipsilateral pulps in the presence of prazosin (100 micrograms/kg) or after acute resection of the superior cervical sympathetic ganglion by 70 and 64%, respectively. The Evans-blue content in the lip and gingiva was uninfluenced by the tooth stimulation. The results indicate that activation of sympathetic nerves inhibits the afferent nerve-induced plasma extravasation in rat incisor pulp and this effect is mediated by alpha-adrenoceptors not associated with vasoconstriction.

Animals↗
PubMed2004

Effect of bur type on microtensile bond strengths of self-etching systems to human dentin.

PURPOSE: To compare the microtensile bond strength (microTBS) of five adhesives to human dentin prepared with 600-grit SiC abrasive paper (SiC), a diamond rotary instrument, or a carbide bur. The null hypothesis was that different cavity preparation instruments do not affect adhesion of resin adhesives. MATERIALS AND METHODS: Human molars (n = 45) were randomly divided into three groups according to surface treatment. Each group was bonded using a total-etch adhesive (Single Bond, 3M ESPE), one of three self-etching primer systems (Clearfil SE Bond or ABF, Kuraray; Imperva Fluorobond, Shofu), or a self-etching adhesive (One-Up Bond F, Tokuyama). A 4-mm composite crown was built over the bonded surface. Specimens were stored in water for 24 h at 37 degrees C. They were sectioned into 0.7-mm-thick slabs, trimmed to a cross-sectional area of 1 mm2, and loaded to failure at a crosshead speed of 1 mm/min using a tabletop tester (EZ-Test, Shimadzu). Microtensile bond strength data were analyzed using analysis of variance and Fisher's PLSD test. RESULTS: Surface preparation using a carbide bur generally yielded higher bond strengths than preparation using either a diamond rotary instrument or SiC abrasive paper. SE Bond had the highest mean microTBS of the five adhesives tested. CONCLUSION: Resin-dentin bond strengths can be affected by the type of instrument used to prepare the tooth. Specifically, higher bond strengths might be achieved by using carbide burs rather than diamond cutting instruments.

Acid Etching, Dental↗