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The linear coefficient of expansion of enamel, dentin as well as selected dental working materials is estimated by means of holographic-interferometric measurements. A good correlation was found between hard dental texture and a phosphate glass envisaged for use with lasers. The possible effects of the greatly increased coefficient of expansion of tested composites is discussed.
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In the study in question, tests were made to determine whether a dental salt, with or without the addition of fluoride, can improve the remineralization effect of the saliva. The experiments were performed in vitro by applying a method in which the dental enamel was softened and rehardened several times within a short period. The Knoop hardness of the enamel surface was used to determine the degree of de- and remineralization. The results clearly confirm the remineralization-promoting effect of the fluoride added to the dental salt.
Etching of dental enamel using pulsed carbon dioxide (CO2) laser radiation has been shown to give acceptable bond strengths when hydrophobic enamel bonding resins are used between the lased surface and composite resin. There have been dramatic changes in the composition of bonding agents in recent years. The present laboratory study examined the influence of the bonding agent on the shear bond strength to laser- and acid-etched enamel. Two current generation bonding systems were used (Scotchbond Multipurpose and Optibond). Shear bond strengths in the order of 10 MPa were consistently obtained using laser etching at "optimal" parameters, in the absence of any other preparation of the natural enamel surface. Although there was a consistent trend for shear bond strengths to be greater with Optibond than for Scotchbond MP in both human and porcine test systems, this difference was only statistically significant with acid etching of nonpolished human enamel, and suboptimal laser etching of polished human enamel. Prior surface polishing increased the shear bond strength obtained with maleic acid etching and Scotchbond MP by more than 2-fold, and increased bond strength when Optibond was used following optimal laser etching. These results indicate that both the type of surface preparation and the choice of bonding agent can influence bond strengths to laser-etched and acid-etched enamel.
Cauterized dental enamel was fluoridized with a solution of sodium monofluorophosphate. Using ESCA methods of measurement, it was demonstrated that almost the entire amount of absorbed fluoride was present in the form of fluorphosphate.
Incipient dental caries at the stage of demineralization is reversible, and remineralization can be achieved by the help of locally applied fluorides. In crystalchemical experiments, however by treating natural apatites with lanthanides Ce, La, Pr, Nd, Sm, Eu, Tb...Y, Sc, a more resistant complex could be developed. In this study extracted human molar teeth were kept for 60 days in Cerium (III)-nitrate solution, in order to investigate the incorporation of Ce3+ into human sound and carious enamel by light-microscopic-, and electronmicroprobe methods. Ce3+ was incorporated in sound enamel as well as into the incipient carious lesions, showing the histological characteristics of a remineralizing lesion. The mean values of the microprobe analysis data showed an increase in Ce3+ changing place with the Ca2+, the developing cerium-apatite being more hard an resistant from a mineralo-physical point of view.
Specimens of human dental enamel were topically applied with solutions of sodium fluoride (NaF) or acidulated phosphate fluoride (APF) before and after laser irradiation. APF application after laser irradiation caused a remarkable increase in acid resistance of the enamel, while APF application before laser irradiation showed a lesser effect, similar to either APF treatment alone or laser irradiation alone. These results were consistent with observations made using a scanning electron microscope. APF application after laser irradiation produced a greater fluoride uptake in the enamel than APF application before laser irradiation, as shown by electron probe microanalyzer. NaF application caused lesser acid resistance and lesser fluoride uptake than APF application, even when the enamel was treated with laser irradiation.
Translucency of human dental enamel was determined by total transmittance of wavelengths from 400 to 700 nm. The transmission coefficient at 525 nm was 0.481 mm-1. Total transmission of light through human dental enamel increased with increasing wavelength. Human tooth enamel is more translucent at higher wavelengths. The translucency of wet human enamel and enamel after dehydration was also measured by total transmittance. The transmission coefficient at 525 nm decreased from 0.482 to 0.313 mm-1 after dehydration and was reversed on rehydration. The decrease in translucency occurred as a result of the replacement of water around the enamel prisms by air during dehydration.
Spectra of human dental enamel was recorded in the 200-400 nm UV region. It showed the weak band at 280 nm which were present in enamel protein. Excimer laser are gas lasers which emit light with photochemical decomposition. The wavelength depends on the 248 nm with krypton-fluoride. The enamel surfaces of extracted human teeth were exposed to KrF excimer laser by an energy density range from 29.6 to 3200 J/cm2. The purpose of this study was to investigate the changes with photo chemical reaction in enamel by light microscopy, SEM and X ray diffraction method. Results of analyses suggested that the observed changes of enamel exposed to this laser were the alpha and beta-tricalcium phosphate (TCP) phase in small amounts. No histological changes were observed in grain boundaries of cross sectioned lased enamel under light microscopy. The SEM examination revealed a roughened surface with bubble formation at 800-3200 J/cm2. SEM of etched enamel surface with 0.1 N HCl after laser irradiation at 400-800 J/cm2 showed the extension along the length of the rods. At 1600-3200 J/cm2, there appeared to be a melting of prism structures, because of conversion of photon energy into thermal energy. These results showed the KrF excimer laser irradiation to dental enamel might be a new type of treatment modality and diagnosis in preventive dentistry.
The composition and dental properties of eight different soft drinks, representing some of the most popular types used in the U.K., were examined. Demineralisation experiments were conducted on hydroxylapatite, the basic component of dental enamel, determining calcium dissolving by atomic absorption spectroscopy and phosphorus by UV/vis spectrophotometry. The titratable acid content of the drinks was found to give a better guide than their pH to their potential dental erosiveness. The sugars content, in their ready-to-drink form, varied from zero in a low-calorie product up to almost 14% in a black-currant drink, but using a technique with a relatively long contact time, and in the absence of intact dental plaque, the demineralising action on hydroxylapatite of the acids already in the drinks eclipsed the effects of the acid generated by oral micro-organisms from the sugars in the drinks. The pure citrus juices showed potentially the worst dental properties, followed by the orange and blackcurrant concentrates after dilution to their ready-to-drink form, with least demineralisation from the carbonated drinks, and a cola drink giving especially low figures.
Removal of gingival calculus was performed with two different scalers on teeth that had been extracted previously. Using scanning electron microscopic prints and the Hommel tester, it was demonstrated that the dental surface had obtained a clearly visible roughness. This is determined by the dental surface, the compressive strength and the characteristics of the various scalers. The use of a Tompkin reamer to smooth the surface produced even deeper criss-cross grooves than the scaler, and not a satisfactory smooth surface.
Previous studies using bovine dental enamel as a model have shown that surface and subsurface dissolution of enamel may be governed by micro-environmental solution conditions. We have now investigated the demineralization phenomenon more rigorously with the primary objective of developing a method for deducing solution species concentration profiles as a function of time from appropriate experimental data. More specifically, in this report, a model-independent method is described for determination of the pore solution fluoride gradients in bovine enamel during subsurface demineralization. Microradiography was used to determine the mineral density profiles, and an electron microprobe technique to determine total fluoride (F) profiles associated with the enamel. In each case, matched sections of bovine enamel were exposed to partially saturated acetate buffers at pH = 4.5 containing 0.5 ppm F for various periods of time (from six to 24 hours). The treated enamel was found to have an intact surface layer and subsurface demineralization. The extent of the demineralization and the depths of the lesions increased with time in all cases. The data were first used to calculate (a) the total F gradients in the enamel at various times, and (b) the local uptake rate of F as a function of time and position. Then, by manipulation of the equations describing the uptake and transport of F, we calculated the pore diffusion rate of F and the micro-environmental solution F concentration in the aqueous pores as a function of time and of distance from the enamel surface. It was also possible to calculate an intrinsic F diffusion coefficient in the pores, which was about 1.0 X 10(-5) cm2/sec, in good agreement with reported values. 14C-sucrose uptake and release experiments with identically prepared demineralized enamel sections were also conducted to provide an independent check on the assumed dependence of porosity on mineral density. The results of this investigation, especially the outcomes relative to this new method for determination of pore solution F gradients during acid attack of the dental enamel, should be valuable in future studies of the mechanism(s) of the action of F in inhibiting dental enamel demineralization.
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Dental enamel hypoplasia (DEH), as an indicator of nonspecific stress during development, provides an assessment of the relative morbidity of past human populations. An investigation of 669 Neandertal dental crowns yielded an overall DEH frequency of 36.0% by tooth (41.9% for permanent teeth; 3.9% for deciduous teeth) and about 75% by individual. These incidences place the Neandertals at the top of recent human ranges of variation in DEH frequencies, indicating high levels of stress during development. The paucity of deciduous tooth DEH and M1 DEH, combined with generally increasing levels of DEH through later calcifying teeth, suggests that the stress was primarily nutritional, beginning at weaning and continuing through adolescence. This supports paleontological and archeological interpretations implying significantly lower effectiveness for Neandertal foraging compared to that of modern humans.
The biomineralization of the dental enamel matrix with a carbonated hydroxyapatite mineral generates one of the most remarkable examples of a vertebrate mineralized tissue. Recent advances in the molecular biology of ameloblast gene products have now revealed the primary structures of the principal proteins involved in this extracellular mineralizing system, amelogenins, tuftelins, ameloblastins, enamelins, and proteinases, but details of their secondary, tertiary, and quaternary structures, their interactions with other matrix and or cell surface proteins, and their functional role in dental enamel matrix mineralization are still largely unknown. This paper reviews our current knowledge of these molecules, the probable molecular structure of the enamel matrix, and the functional role of these extracellular matrix proteins. Recent studies on the major structural role played by the amelogenin proteins are discussed, and some new data on synthetic amelogenin matrices are reviewed.
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The permeability of dental enamel can be estimated by means of diffusion measurements with radio-isotopes. Because of the low intrinsic permeability of enamel membranes, determination via this route may take two weeks. A much faster electrochemical method is presented, in which the real and imaginary part of the membrane impedance are measured at discrete intervals in the frequency-range 1 Hz-1 MHz. Using the principles of network-analysis, a phenomenological interpretation of these electrochemical data in terms of a 6-parameter model is given. The model contains R0, the intrinsic membrane resistance, R infinity, the residual membrane resistance and the four parameters, necessary to describe the postulated enamel diffusion impedance, which bears strong resemblance to the Warburg impedance. Starting from this model, optimal estimates (with standard-errors) of a membrane's R0 and vmax (the log of the frequency where the imaginary part of the membrane impedance is maximal) were derived. These parameters were predictors of the permeability of enamel.