Effect of drying and heating on the solubility of powdered dental enamel.
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Dental Enamel↗
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Results for “DENTAL ENAMEL”
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The effect of penicillin- and tetracycline-containing medicaments on the microhardness of human dental enamel. An in vitro study.
While the sugar content of various medicaments has been accepted as a hazard to dental health, the possible detrimental effect of the medicaments per se has been largely overlooked. In the present study the microhardness of dental enamel was examined before and after the exposure to various salts of penicillin, to tetracycline chloride, and to human saliva. The Vickers hardness index was found to 1. remain stable or increase slightly in enamel exposed to saliva, nonaqueous penicillin suspensions and certain watery solutions of phenoxymethylpenicillin calcium. 2. decrease to a moderate degree in most aqueous penicillin solutions, and 3. decrease drastically in tetracycline solutions and in phenoxymethylpenicillin calcium solutions containing citrate. The results indicate that a direct reaction may take place between the dental enamel and the medicament and/or its degradation products when antibiotic compounds are taken per os.
Dental Enamel↗
Microhardness evaluation of in situ vital bleaching on human dental enamel using a novel study design.
OBJECTIVES: The aim of this 'in situ' study was to evaluate the microhardness of dental enamel following treatment with an in-office and an at-home vital bleaching agent through a novel approach using samples temporarily bonded 'in vivo'. METHODS: Human dental enamel slabs (n=88) were subjected to sequential polishing and initial Knoop microhardness tests were performed. The slabs were fixed to the facial surfaces of the maxillary first molars of 44 human volunteers. They were divided into four groups (n=11) according to the treatment group: G1- in-office-CP37+ at-home-CP10; G2- in-office-CP37+ at-home-PLA; G3- in-office-PLA and at-home-CP10; G4- in-office and at-home-PLA. After 3 weeks of treatment, final microhardness measurements were performed. RESULTS AND SIGNIFICANCE: ANOVA and Tukey's HSD hoc analysis (alpha=0.05) revealed no differences among initial or final microhardness values (p>0.05); however, significant differences occurred between initial and final values for each group (p<0.01), The evaluation of microhardness revealed a reduction of 6.8% for G1, 4.1% for G2, 3.4% for G3 and 3.5% for G4. In-office bleaching with 37% carbamide peroxide, an at-home bleaching with 10% carbamide peroxide, and a combination of both resulted in lower enamel microhardness when measured immediately post-treatment. However, long-term effects of these treatments are not known, and are believed to be clinically insignificant due to the relatively small reductions observed in enamel microhardness. Interestingly, the carrier, Cabopol 934P, also resulted in similar reduction in enamel microhardness even when administrated alone as a placebo.
Acrylates↗
The effect of X-ray irradiation on the demineralization of bovine dental enamel. A constant composition study.
In this study the effect of X-ray irradiation on demineralization of bovine dental enamel in vitro was investigated. Enamel specimens were irradiated with 72 Gy and subsequently demineralized (140 h) under reproducible constant composition conditions at pH = 5 in the presence of methylhydroxydiphosphonate (MHDP). Microhardness measurements after demineralization without MHDP showed significant differences (p less than 0.001) between irradiated and nonirradiated enamel specimens; no significant differences were found in the presence of MHDP. Quantitative microradiography showed that both mineral loss and lesion depth were significantly lower (p less than 0.001) for the irradiated enamel specimens compared with the nonirradiated ones. Surface layer formation was observed in irradiated enamel demineralized in a solution without MHDP. It was shown that X-ray irradiation decreased the enamel acid solubility in vitro.
Animals↗
[DISCUSSION OF THE VIABILITY OF DENTAL ENAMEL].
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Dental Enamel↗
[Use of Electronic Spin Resonance in the study of dental enamel caries. Preliminary results].
BACKGROUND: By means of the Electron Spin Resonance technique (EPR) it is possible to detect carbonate-related paramagnetic centers in human tooth enamel. Several arguments indicate that the radicals formed after X-ray irradiation (CO2- and CO3(3-)) are ascribed to carbonate which is the most important constituent of hydroxyapatite. There is experimental evidence that the distribution of the orientation of these centers is related to microcrystal alignment in dental enamel, which might be responsible for caries susceptibility. The results reported in the literature, however, should be interpreted very carefully. METHODS: In our own preliminary research we studied twenty-seven samples of dental enamel taken from the buccal face of upper molars. Fifteen were carious and the other ones were sound. We used the R-parameter and the S-parameter to convert our experimental results into numerical values. The R-parameters, as introduced by Cevc et al. (1976-1980) is the ratio of the amplitude for the high field and the low component of the EPR signal. The S-parameter is the ratio of the amplitude of the A2 component and the low one. RESULTS: No significant difference was found between the R and S-value of carious and sound dental enamel samples. The degree of microcrystal alignment in enamel of clinically sound upper molar from their buccal site is very high. However, this result is not sufficient to evaluate the caries susceptibility or the caries resistance of tooth enamel. CONCLUSIONS: Therefore, we can conclude that it is not sufficient to ascribe the caries susceptibility to the R-value, because other factors (such as etiological factors and the structure of the teeth) should be considered.
Dental Caries↗
[Dental enamel hardness tests in diabetics].
The authors studied by in vivo methods (Fosse et al. 1986) the microhardness of dental enamel in diabetic patients compared to healthy persons. No differences of enamel microhardness values between diabetics and healthy persons, neither by longer diabetes duration nor by worse diabetes attitude have been found.
Adolescent↗
["Scanning" electron microscopic studies of the fluoride treated dental enamel].
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Dental Enamel↗
Study of dental enamel and synthetic hydroxyapatite irradiated by EPR at K-band.
In this preliminary work the EPR spectra of a small dental enamel block and a synthetic B-type hydroxyapatite in powder form, both irradiated with gamma rays, were analyzed in K-band. The spectra of the dental enamel block allow the analysis of independent components with different angular orientations, while the study of the dosimetric properties of the synthetic hydroxyapatites showed good performance of this spectrometer. K-band spectra show better resolution when compared to X-band, while using significantly less sample material.
Body Burden↗
X-ray study and microhardness data of some dental enamel species.
X-ray analysis and microhardness of dental enamel of some human and animal species were investigated. Human enamel is composed mainly of hydroxyapatite and fluorapatite together with traces of delta calcium metaphosphate. Prominant apatite phases with a small amount of basic calcium carbonate are also present in the enamel of dog canine teeth. Calcite forms the main crystalline components of rat enamel with some hydroxyapatite. A relatively higher hardness value was detected for enamels of human incisors than for that of rats; the dog enamel was, however, apparently harder than that of the human variety. The hardness values generally decreased with increasing the applied load. The correlation between the phase analysis of the enamel materials and their microhardness values and the dependence of this property on the load applied are discussed.
Adult↗
The absorption and scattering of light in bovine and human dental enamel.
The reflectance and transmission of thin slabs of dental enamel has been measured at all wavelenghts between 220 and 700 nm by means of an integrating sphere. From the results the true scattering and absorption coefficients have been computed. The theoretical model used is an extended two-flux model, which is presented and discussed. The absorption spectrum of the dissolved organic component of enemel was also determined. An absorption peak at 270 nm is common to all the spectra. This peak in the bovine enamel spectrum is about three times as high as in the spectrum of human enamel. The peak of the dissolved material is about as high as the peak of the corresponding enamel. Hence it is concluded that the organic component, presumably aromatic amino acids, is responsible for most or all of the observed optical absorption.
Absorption↗
[Micromechanical characteristics of restoration stomatological materials and human dental enamel and dentin].
Polished sections of human teeth and 11 Russian and foreign restoration materials (silver amalgam, cements, and polymer-based materials) were studied with an MTI-3M microhardness meter. Microhardness immediately under loaded diamond indentor of the device, elastic and plastic deformations were evaluated. Dental enamel is characterized by the greatest microhardness. Inorganic filler essentially (3-fold) increases the microhardness of polymer-based material. Microhardness of dental tissues and restoration materials notably decreased as the strength of indentor loading, i.e. the depth of its submerging in material, increased. Dental enamel is characterized by the most elastic deformation; dentin approximates the enamel by this parameter, as well as some restoration materials (prodigy, degufil-H, degufil-SC) when exposed to the saliva.
Compressive Strength↗
The effect on the ultrastructure of dental enamel of excimer-dye, argon-ion and CO2 lasers.
This study aimed to investigate the ultrastructural changes that occur in dental enamel irradiated with pulsed excimer-dye, continuous-wave (CW) argon-ion and CW CO2 lasers. The pulsed excimer-dye laser produced deep craters, rough damaged surfaces with underlying porosity and amorphous vitrified material. The vitrification of the enamel indicated that the temperature in these areas must have been at least in the range 1280 to 1600 degrees C. The CW argon-ion laser irradiation produced a changed non-cratered surface with inter-crystalline porosity and a mixture of small and some large irregularly packed recrystallized enamel crystals. The CW CO2 laser produced shallow craters, surface crazing and lifting off the removal of the surface layer to expose the underlying roughened enamel. The ultrastructure revealed inter- and intra-crystalline porosity, a mixture of small but variable size irregularly packed recrystallized enamel crystals and also well packed large crystals which indicated further grain growth. The porosity in lased enamel was overall very similar to that seen in enamel heated in an electric furnace to a temperature of 600 degrees C. The presence of recrystallized enamel crystals indicated a temperature rise of approximately 1000 degrees C and the grain growth indicated that a temperature > or = 1000 degrees C existed for some time after the laser irradiation. In general the excimer-dye laser produced most surface destruction because of its higher power density and shorter interaction time and the argon-ion laser produced least damage. These results indicated that the lasers used in this study require much more refinement before they can find therapeutic application to dental enamel, and this may well be the case for other lasers being investigated for clinical dental practise.
Argon↗
Etiological factors influencing the prevalence of developmental defects of dental enamel in nine-year-old New Zealand children participating in a health and development study.
Over 1000 children, participating in a longitudinal study of health and development, possess documented medical histories based on birth records and regular assessments starting at age 3. A dental examination at age 5 of 923 participants recorded their exposure to fluoride and evidence of trauma to the deciduous teeth. The prevalence of developmental defects of dental enamel in 696 of the children when aged 9 was reported as 56% (Suckling et al., 1985). For the present study, a number of illnesses, accidents, and other experiences were selected from the recorded information as possible etiological factors for any defect, demarcated and diffuse opacities, and hypoplasia. Despite extensive statistical testing, positive and strong associations were few. The prevalence of hypoplasia, seen in 15% of the sample, was higher in those children who had chicken pox before age 3 and, as reported previously, in those children with a history of trauma to their deciduous incisors. This study illustrates the difficulty of establishing the etiology of enamel defects, even when medical and dental histories are available.
Asthma↗
Coeliac-type dental enamel defects in patients with dermatitis herpetiformis.
The teeth of 30 adult patients with dermatitis herpetiformis and 66 sex- and age-matched healthy controls were examined for dental enamel defects. Sixteen of the patients (53%) with dermatitis herpetiformis, opposed to only one (2%) of the healthy controls (p less than 0.001), were found to have coeliactype permanent-tooth enamel defects. The grades of these defects were milder than those described for severe coeliac disease. There was no correlation between the degree of enamel defects and jejunal villous atrophy. The present finding of frequent coeliactype dental enamel defects in adults with dermatitis herpetiformis suggests that these patients were already suffering from subclinical gluteninduced enteropathy in early childhood, at the time when the crowns of permanent teeth develop.
Adult↗
In vitro techniques for erosive lesion formation and examination in dental enamel.
An in vitro experimental model has been developed for erosive lesion formation in dental enamel which can mimic in vivo conditions at the tooth surface. The features of this model provide a very reproducible method of producing erosive lesions in several teeth under identical conditions which can be varied to allow examination of a number of different parameters. A replica impression technique has also been developed for subsequent non-destructive microscopic examination of the lesions and comparison with in vivo lesions.
Acrylic Resins↗
[The effect of the light from a helium-neon laser on normal dental enamel solubility and in caries].
Effects of He-Ne laser radiation at a wavelength 0.63 micron for 90 sec on dental enamel mineral metabolism were studied from Ca, P levels and Ca/P ratio in 67 children aged 3 to 7. Ca and P solubility in surface enamel layers was found reduced after He-Ne laser irradiation in both healthy children and those with caries. Laser was found to normalize the oral fluid mineral composition.
Biopsy↗
Influence of the pulse duration of an Er:YAG laser system on the ablation threshold of dental enamel.
The present study examines the dependence of the ablation threshold on the duration of the applied laser pulses in the dental enamel of human wisdom teeth. To this end, 600 treatments with the Er:YAG laser (lambda=2940 nm) were carried out on a total of 50 extracted teeth. The laser light was coupled into a fluoride glass light guide for this purpose, in order to ensure almost gaussian distribution of the light in a radially symmetrical beam. The beam diameter on the specimen was 610 micro m. The radiant exposure on the tooth surface was varied between 2 and 20 J/cm(2), while the duration of the pulses applied was changed in four steps from 100 micro s to 700 micro s. The irradiated tooth surfaces were examined for visible signs of ablation under a reflected-light microscope. The experiments revealed that, when pulses of shorter duration are used, the limit at which ablation sets in is reduced by up to approx. 3 J/cm(2). This expands the ablation threshold range of Er:YAG laser radiation to between 6 and 10 J/cm(2). In this context, both the pulse duration and the radiant exposure have a statistically significant influence on the ablation threshold (logistic regression, p<0.0001). Although the ablation threshold of the dental enamel can be changed by varying the pulse duration of the Er:YAG laser, no clinical consequences can be expected, as the shift is only slight.
Dental Enamel↗