[APROPOS OF THE DISCUSSION OF THE VITAL PROPERTIES OF DENTAL ENAMEL].
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Dental Enamel↗
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Structural changes of dental enamel in both dentitions of cleft lip and palate patients.
The aim of this study was to register the incidence, the location and the character of structural changes in dental morphology in cleft lip and palate patients and to examine the connection between defects of dental enamel and the development of clefts. Twenty-two children and adolescents from a cross-section study carried out in 1987/89 with cleft lip and palate patients could be covered in a second study (longitudinal study). The frequency, the extent and the location of changes of dental hard tissues in both dentitions were assessed in the form of a static and a dynamic examination. Dental enamel anomalies were found in all patients, with opacities of cleft-adjacent incisors being the dominating form of classified defects in both dentitions. In 20 of the 22 examined patients, dental enamel dysplasia was found both in the primary and in the secondary dentition. The intraindividual comparison of the maxillary teeth in both dentitions showed that 19 patients had at least 1 permanent tooth retaining the structural changes in the dental enamel. The location of the defect and the fact that both dentitions were involved reflect the moment of effectiveness of pathogenetic stimuli. Consequently this can be interpreted as the outcome of corresponding pathomechanisms both for disorders of the dental structure and for the development of the primary palate.
Adolescent↗
Scanning electron microscope observations of CO2 laser effects on dental enamel.
Studies of the effects of carbon dioxide (CO2) lasers on dental enamel have demonstrated that surface changes can be produced at low fluences (< 10 J/cm2) if wavelengths are used which are efficiently absorbed by the hard tissues. In this study, scanning electron microscopy (SEM) was used to characterize the wavelength dependence of surface changes in dental enamel after exposure to an extensive range of CO2 laser conditions. Bovine and human enamel were irradiated by a tunable, pulsed CO2 laser (9.3, 9.6, 10.3, 10.6 microns), with 5, 25, or 100 pulses, at absorbed fluences of 2, 5, 10, or 20 J/cm2, and pulse widths of 50, 100, 200, 500 microseconds. SEM micrographs revealed evidence of melting, crystal fusion, and exfoliation in a wavelength-dependent manner. Crystal fusion occurred at absorbed fluences as low as 5 J/cm2 per pulse at 9.3, 9.6, and 10.3 microns, in contrast to no crystal fusion at 10.6 microns (< or = 20 J/cm2). Longer pulses at constant fluence conditions decreased the extent of surface melting and crystal fusion. The total number of laser pulses delivered to the tissue did not significantly affect surface changes as long as a minimum of 5 to 10 pulses was used. Within the four easily accessible wavelengths of the CO2 laser, there are dramatic differences in the observed surface changes of dental hard tissue.
Animals↗
Oral aphthous ulcers and dental enamel defects in children with coeliac disease.
AIM: Coeliac disease is characterized by oral manifestations, such as dental enamel defects and recurrent oral aphthae. In this study we compared the prevalence of enamel defects and recurrent aphthous stomatitis (RAS) between patients diagnosed with coeliac disease and healthy controls. METHODS: A total of 72 patients with coeliac disease were studied together with 162 normal healthy subjects as controls to individualize the prevalence of enamel defects and recurrent aphthous stomatitis (RAS) in this disease. RESULTS: Dental enamel defects were found in 14/70 (20%) coeliac patients and in 9/159 (5.6%) controls. In particular, 13/53 (24.5%) coeliac patients with mixed or permanent dentition and 1/17 (5.8%) coeliac children with deciduous dentition had enamel defects. Altogether, 9/145 (6.2%) control subjects with mixed or permanent dentition had dental enamel defects. None of the controls with deciduous dentition had enamel defects. Thus, the enamel defects occurred more frequently in coeliac patients (p < 0.001). Regarding RAS, 24/72 (33.3%) coeliac patients and 38/162 (23.4%) control subjects had aphthous ulcers. Statistically significant differences were not observed between the two groups (p > 0.05). One in three coeliac subjects suffering from RAS received benefit from a gluten-free diet. CONCLUSION: In the present study, the prevalence of enamel defects was found to be greater in coeliac patients than healthy controls. Even though the prevalence of RAS in coeliac subjects varied from healthy controls, the difference was not statistically significant. However, more than 1/3 coeliac subjects suffering from RAS benefited from a gluten-free diet.
Adolescent↗
Quantitative microradiography for studying dental enamel demineralization and remineralization.
A method for quantitative determination of mineral density changes in dental enamel has been developed. It utilizes the quantitative microscopy capabilities of image analysis or photometer systems. Characteristic demineralization of bovine enamel in acetate buffers containing calcium and phosphate has been used to demonstrate the results. The method together with chemical kinetic data obtained from spectrophotometric and ion-selective electrode measurements of the bulk solution for calcium, phosphate, and fluoride permit important basic studies to be conducted on demineralization and remineralization of dental enamel.
Animals↗
Reconstructing impairment of secretory ameloblast function in porcine teeth by analysis of morphological alterations in dental enamel.
We studied the relationship between the macroscopic appearance of hypoplastic defects in the dental enamel of wild boar and domestic pigs, and microstructural enamel changes, at both the light and the scanning electron microscopic levels. Deviations from normal enamel microstructure were used to reconstruct the functional and related morphological changes of the secretory ameloblasts caused by the action of stress factors during amelogenesis. The deduced reaction pattern of the secretory ameloblasts can be grouped in a sequence of increasingly severe impairments of cell function. The reactions ranged from a slight enhancement of the periodicity of enamel matrix secretion, over a temporary reduction in the amount of secreted enamel matrix, with reduction of the distal portion of the Tomes' process, to either a temporary or a definite cessation of matrix formation. The results demonstrate that analysis of structural changes in dental enamel allows a detailed reconstruction of the reaction of secretory ameloblasts to stress events, enabling an assessment of duration and intensity of these events. Analysing the deviations from normal enamel microstructure provides a deeper insight into the cellular changes underlying the formation of hypoplastic enamel defects than can be achieved by mere inspection of tooth surface characteristics alone.
Ameloblasts↗
Structural changes in human dental enamel after subablative erbium laser irradiation and its potential use for caries prevention.
Numerous studies have confirmed the potential of erbium laser irradiation for increasing the acid resistance of dental enamel. The objective of the present paper was to investigate the effect of subablative erbium laser irradiation on the structure and acid resistance of dental enamel by means of confocal laser scanning microscopy (CLSM). To this end, 12 samples of human dental enamel were irradiated with subablative energy densities (Phi) of an Er:YAG (lambda = 2.94 microm, Phi = 6 J/cm(2)) and an Er:YSGG laser (lambda = 2.79 microm, Phi = 8 J/cm(2)). The enamel surfaces of 6 samples were polished prior to irradiation. The remaining 6 samples were left intact (without polishing procedures) and, in the further course of the study, they were subjected to 1-week in situ demineralisation. All irradiated test surfaces were assigned a control surface on the same sample. The changes following laser irradiation and the in situ wearing time were assessed qualitatively using a confocal laser scanning microscope. The irradiation of dental enamel with subablative erbium laser irradiation produces fine cracks in the enamel surface. These cracks act as starting points for acid attack and favour deep demineralisation. These changes reduce or eliminate the positive effect of subablative erbium laser irradiation observed in connection with caries-preventive use. The clinical use of subablative erbium laser irradiation to prevent caries would appear not to make sense under the conditions studied.
Dental Caries↗
Some observations on the trace element concentrations in human dental enamel.
The concentration of trace elements has been measured for dental enamel from 86 healthy human teeth using particle-induced X-ray emission (PIXE). The majority of the teeth (n = 70) were collected from dentists in the county of Oxfordshire in the United Kingdom, although a smaller group (n = 16) were collected from Cornwall. The elements K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Sr, Pb, and Hg have been detected and statistically analyzed by grouping according to sex, age, and geographical location. The concentrations of Fe and Cu were found to be lower in the teeth from female donors (P < 5%) and are believed to result from the continued burden of blood loss during menstruation. Strong positive correlations (P < 0.1%) were found between Ca, Co, Ni, and Zn for all groups; these elements were also found to exhibit a negative correlation (P < 1%) with age for teeth from female donors. This is believed to be related to decalcification during the menopause. Pb was found to exhibit a positive correlation (P < 5%) with age for both sexes, and is believed to substitute for Ca in the Ca hydroxy apatite (HAP) within the dental enamel.
Adolescent↗
[Viability of dental enamel and the biological theories on dental caries].
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Dental Caries↗
[Concentration of fluorides in dental enamel and resistance of teeth to dental caries].
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Dental Caries↗
Erosion of dental enamel among competitive swimmers at a gas-chlorinated swimming pool.
In September 1982, two Charlottesville, Virginia, residents were found by their dentists to have general erosion of dental enamel consistent with exposure to acid. Both patients were competitive swimmers at the same private club pool. No other common exposure could be determined. An epidemiologic survey was made of 747 club members. Symptoms compatible with dental enamel erosion were reported by 3% of nonswimmers (9/295), 12% of swimmers who were not members of the swim team (46/393), and 39% of swim team members (23/59). All four swimmers with clinically verified dental enamel erosion had trained regularly in the pool for competitive swimming meets, compared with one of eight matched swimmers without enamel erosion. Examination of the implicated swimming pool revealed a gas-chlorinated pool with corrosion of metal fixtures and etching of cement exposed to the pool water. A pool water sample had a pH of 2.7, i.e., an acid concentration approximately 100,000 times that recommended for swimming pools (pH 7.2-8.0). A review of pool management practices revealed inadequate monitoring of pool water pH. Acid erosion of dental enamel--"swimmer's erosion"--is a painful, costly, irreversible condition which can be caused by inadequately maintained gas-chlorinated swimming pools.
Adolescent↗
Ultrastructure of dental enamel afflicted with hypoplasia: an atomic force microscopic study.
The ultrastructure of the human tooth enamel from a patient diagnosed with hypoplasia (HYP) was investigated using atomic force microscopy (AFM) and compared with the surface of normal human tooth enamel. Hypoplasia is a hereditary defect of dental enamel in which the enamel is deficient in either quality or quantity. AFM results presented for the HYP tooth enamel clearly demonstrate that the apatite crystal morphology in hypoplasia tooth enamel is perturbed in the diseased state which could result from a defective synthesis of the extracellular matrix proteins, e.g., amelogenin, by the ameloblasts. HYP enamel consisting of loosely packed, very small grains does not present a tendency for association, as in the case of the normal healthy tooth. Indeed, the enamel surface affected by HYP is porous and is made of much smaller grains. In some samples, the HYP part of enamel surface appeared in the form of a point-defect, which we believe may be associated with the early stages of the HYP deformation.
Apatites↗
[The mechanism of topical applied ion supplemented acidulated phosphate fluoride gel effects on dental enamel demineralization: an in vitro study].
The present study was carried out on dental enamel to describe surface changes in the scanning electron microscope and crystallites changes in the high-resolution transmitted electron microscope as related to treatments of topical applied ion supplemented acidulated phosphate fluoride (APFI) gel and artificial caries agent demineralization in vitro, which imitated in vivo with pH- cycling condition. Our data suggest that topical application of APFI gel produce some CaF2 spheres on the surface of enamel and some fluoride-containing apatites in dental enamel. The latter are considered as result of F- and CaHPO4 or hydroxyapatites. The essence of chemical reactions are discussed. The results confirm that enamel treated with APFI gel becomes more resistant to artificial caries agent and electron radiation damage.
Acidulated Phosphate Fluoride↗
Determination of mineral concentration in dental enamel from X-ray attenuation measurements.
The mineral content of dental enamel is commonly measured by X-ray attenuation experiments. Most studies have used contact microradiography in which intensities are measured with photographic film which is convenient and gives high spatial resolution. However photon counting intensity measurements are to be preferred in many experiments (longitudinal and scanning microradiography, and microtomography), as illustrated here, because they have a larger dynamic range and greater sensitivity to small intensity changes. Additionally, the detector and specimen are well separated which allows the pseudo-continuous study of de- and remineralization. The mineral content is often quoted as 95 wt% or 87 vol% hydroxyapatite for permanent human enamel. This determination from attenuation experiments requires accurate values of elemental mass attenuation coefficients and a number of assumptions. The effects of possible choices of these are considered and it is shown that the most important is the density of enamel mineral used in conversion of wt% to vol%. If the density is taken as 2.99 g cm(-3), as recently suggested (J.C. Elliott, Dental Enamel, Ciba Foundation Symposium 205, Wiley, Chichester, pp. 54-72, 1997), instead of 3.15 g cm(-3) as for hydroxyapatite, the calculated vol% is approximately 93 instead of approximately 87.
Dental Enamel↗
[Dental enamel pitting in tuberous sclerosis complex].
We studied pitting of the dental enamel in cases of tuberous sclerosis complex (TSC), by staining defect sites. Many pits were found in the enamel of the TSC patients, especially on the labial surface of the incisors. Although the pathogenesis is unclear, pits of this type have been reported in TSC patients, but in the author's experience, have never been observed in cases of other diseases. On the basis of the results in this study and those previously published, we conclude that dental enamel pitting is a finding which suggests the diagnosis of TSC.
Adult↗
Physical model for non-steady-state dissolution of dental enamel.
The purpose of this study was to provide a rigorous theoretical understanding of the dissolution behavior of dental enamel over the entire time-course of demineralization and to simulate by computer an erosion-type caries lesion according to the physical "hydroxyapatite model". The appropriate diffusion equations which account for simultaneous diffusion and equilibrium of all species in enamel pores, boundary layer, and bulk solution, and which also take into consideration surface reaction kinetics, were employed to allow for calculation of the micro-environmental solution concentration and changes in the mineral density as a function of time and distance within the enamel. This comprehensive physical model for non-steady-state enamel dissolution also explicitly takes into account changes in the diffusivity and the dissolution rate constant as a function of mineral density. Demineralization experiments were conducted in 0.1 mol/L sink acetate buffer (pH = 4.50, mu = 0.50), with ground bovine dental enamel blocks of known surface area mounted (with beeswax) in a rotating disk apparatus. Mineral density profiles were quantified by means of contact x-ray microradiography. The physical model was used to predict mineral density profiles for given demineralization treatments. The experimental profiles agreed quite well with the predicted profiles, when the effective diffusivity of the enamel was assumed to be a function of porosity and when changes in surface area of the crystallites were taken into consideration.
Animals↗
Subsurface demineralization in dental enamel and other permeable solids during acid dissolution.
Subsurface demineralization of dental enamel during acid dissolution has been reported many times, but its cause remains obscure. At first, the phenomenon was thought to result from the physical structure of enamel. More recent studies have shown that subsurface demineralization occurs in other permeable solids, indicating that there must be more fundamental factors involved in this curious effect. In order for this phenomenon to be investigated, dissolution experiments were carried out by means of real-time scanning microradiography in various systems, including enamel, or aggregates of hydroxyapatite (calcium, strontium, or barium), or hydroxides (calcium or magnesium). These were chosen to discriminate between effects of structure and composition. It was found that it was not possible for the demineralization observed in these systems to be attributed to a common feature. From this, it is concluded that subsurface demineralization in enamel and other mineralized tissues should not be ascribed to a single cause.
Acetates↗
Enhanced permeability of acid-etched or ground dental enamel.
STATEMENT OF PROBLEM: Acid etching creates retentive microcraters on enamel surfaces. Designing of a partial denture often involves reshaping the supporting and retentive teeth by grinding the enamel. Unfortunately, both these procedures damage the enamel surface. In vivo such surface damage takes several months to recover. PURPOSE: This study evaluated the effect of 1-minute etching, prolonged etching, and grinding on the permeability of dental enamel for water-soluble molecules. MATERIAL AND METHODS: With the electron paramagnetic resonance and a two-chamber diffusion cell, the influence of etching and grinding on the diffusion of spin label molecules through the enamel was studied quantitatively. The enamel permeability was measured in 30 sound enamel samples, of which 10 samples were exposed to 1-minute etching with 37% phosphoric acid, 10 samples were etched for 5 minutes, and 10 samples were ground with a diamond bur. RESULTS AND CONCLUSIONS: All procedures significantly increased the permeability of dental enamel. These results demonstrate that in vivo the acid-etched and ground dental enamel surfaces are less protected and consequently, unless the tooth is properly protected, are more susceptible to carious lesions. Therefore ground or accidentally etched enamel should be protected.
Acid Etching, Dental↗