Ultrasonic measurement of dental enamel demineralization

The DONAR (digital ultrasonic system) has been used to continuously measure the displacement, due to etching by hydrochloric acid, of the surface of bovine enamel and to monitor the development of a demineralized layer. Conventional pulse echoes are used to measure displacements of the order of micrometres with an uncertainty no greater than 0.1 μm. The demineralized zone in one instance attained a maximum thickness of 5 μm and was much less in other experiments.     

Architectonics and optical properties of dentin and dental enamel

The optical polarization method is used to study the distribution of tubules in human dentin. Horizontal sections of molars display circular local regions 1 mm in diameter and inclined with respect to the section surface, which are continuations of the pulp horns towards the crown cusps. They exhibit specific optical effects resembling conoscopic patterns, revealing the highly hierarchical structure of the crown dentin.     

AFM analysis of bleaching effects on dental enamel microtopography

The purpose of this in vitro study was to test a new methodology to evaluate the effects of 35% hydrogen peroxide agent on the microtopography of sound enamel using an atomic force microscope (AFM). The buccal sound surfaces of three extracted human lower incisors were used, without polishing the surfaces to maintain them with natural morphology. These unpolished surfaces were subjected to bleaching procedure with 35% hydrogen peroxide that consisted of 4 applications of the bleaching agent on enamel surfaces for 10 min each application. Surface images were obtained in a 15 μm × 15 μm area using an AFM. The roughness (Ra and RMS) and the power spectral density (PSD) were obtained before and after the bleaching treatment. As results we could inquire that the PSD analyses were very suitable to identifying the morphological changes on the surfaces, while the Ra and RMS parameters were insufficient to represent the morphological alterations promoted by bleaching procedure on enamel. The morphological wavelength in the range of visible light spectrum (380-750 nm) was analyzed, showing a considerable increase of the PSD with the bleaching treatment.     

Fluorine absorption in dental enamel assisted by UV irradiation

Summary A new method of dental fluorine prophylaxis based on the chemical reaction induced by UV irradiation in dental enamel has been presented. Fluorine ions from a gel topic can be retained to the dental apatite in the lamp-irradiated samples at about 70% and in the laser-irradiated samples at about 80% of the maximum deposited value. The¹⁹F(p,α)¹⁶O nuclear reaction was used to measure the fluorine concentrations in the first 3 μm of the enamel of healthy teeth before and after the gel topic applications with and without UV irradiation. This method of dental prefenction resolves the problem of the traditional fluorine prophylaxis which brings fluorine in the enamel without binding the apatite. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Calculation of anisotropic properties of dental enamel from synchrotron data

Obtaining information about the intrinsic structure of polycrystalline materials is of prime importance owing to the anisotropic behaviour of individual crystallites. Grain orientation and its statistical distribution, i.e. the texture, have an important influence on the material properties. Crystallographic orientations play an important role in all kinds of polycrystalline materials such as metallic, geological and biological. Using synchrotron diffraction techniques the texture can be measured with high local and angular resolving power. Here methods are presented which allow the spatial orientation of the crystallites to be determined and information about the anisotropy of mechanical properties, such as elastic modulus or thermal expansion, to obtained. The methods are adapted to all crystal and several sample symmetries as well as to different phases, for example with overlapping diffraction peaks. To demonstrate the abilities of the methods, human dental enamel has been chosen, showing even overlapping diffraction peaks. Likewise it is of special interest to learn more about the orientation and anisotropic properties of dental enamel, since only basic information is available up to now. The texture of enamel has been found to be a tilted fibre texture of high strength (up to 12.5×). The calculated elastic modulus is up to 155 GPa and the thermal expansion up to 22.3 × 10^?6 °C^?1.     

FT‐Raman investigation of human dental enamel surfaces

FT‐Raman spectra of human enamel surfaces from sound, affected (with 1 cavity) and highly affected (with at least 3 cavities) tooth samples were analyzed by principal component analysis (PCA). Major differences between the unaffected and affected tooth samples seem to arise from the structural changes along the c‐axis of hydroxyapatite, the chief crystalline component of human dental enamel. Based on Fisher index calculations, the most discriminative value was obtained for the intensity of the only Raman active ν₂PO₄³⁻ (E₁) symmetric deformation mode at 428 cm⁻¹. Moreover, these changes can be observed through the whole tooth enamel surface, establishing a predisposition to caries correlated to chemical and structural composition of tooth enamel. No spectral changes regarding the CO₃²⁻ substitution were detected by both nondestructive FT‐Raman and FTIR (Fourier transform infrared) spectroscopy of the powdered teeth samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Absorption and thermal study of dental enamel when irradiated with Nd:YAG laser with the aim of caries prevention

It is widely recognized that Nd:YAG can increase enamel resistance to demineralization; however, the safe parameters and conditions that enable the application of Nd:YAG laser irradiation in vivo are still unknown. The aim of this study was to determine a dye as a photoabsorber for Nd:YAG laser and to verify in vitro a safe condition of Nd:YAG irradiation for caries prevention. Fifty-eight human teeth were selected. In a first morphological study, four dyes (waterproof India ink., iron oxide, caries indicator and coal paste) were tested before Nd:YAG laser irradiation, under two different irradiation conditions: 60 mJ/pulse and 10 Hz (84.9 J/cm²); 80 mJ/pulse and 10 Hz (113.1 J/cm²). In a second study, the enamel surface and pulp chamber temperatures were evaluated during laser irradiations. All dyes produced enamel surface melting, with the exception of the caries indicator, and coal paste was the only dye that could be completely removed. All irradiation conditions produced temperature increases of up to 615.08°C on the enamel surface. Nd:YAG laser irradiation at 60 mJ/pulse, 10 Hz and 84.9 J/cm² promoted no harmful temperature increase in the pulp chamber (ANOVA, p < 0.05). Among all dyes tested, the coal paste was an efficient photoabsorber for Nd:YAG irradiation, considered feasible for clinical practice. Nd:YAG laser at 84.9 J/cm² can be indicated as a safe parameter for use in caries prevention.     

Phase-resolved photoacoustic spectroscopy to monitor dental plaque on tooth enamel

Dental plaque is a biofilm on the enamel surface of the teeth, formed by colonizing bacteria. It is essential to monitor the biofilm presence on the surface of the enamel of the teeth, since plaque is a reason for periodontal disease and dental caries. This paper proposes applying photoacoustic spectroscopy to monitor and the phase-resolved photoacoustic method to analyze the biofilm plaque on samples of human dental enamel facets. The biofilm growth occurred in the oral cavity environment at deposition time of 48 and 72?h. Photoacoustic ex vivo monitoring found that: (1) Photoacoustic spectroscopy is a helpful tool to identify the bactericidal effect on dental plaque; (2) the biofilm deposition provides an optical absorption of the Soret band at 410?nm and increase of hydroxyl absorption band; (3) the biofilm thickness by phase-resolved photoacoustic method is in agreement with the literature in situ measurements. These new knowledges may help in development of a greater practicality and safety equipment able to identify and quantify dental biofilm, which may be achieved with low-cost Soret-band light emitting diode as light excitation.     

3D scanning electron microscopy applied to surface characterization of fluorosed dental enamel

The enamel surfaces of fluorotic teeth were studied by scanning electron stereomicroscopy. Different whitening treatments were applied to 25 pieces to remove stains caused by fluorosis and their surfaces were characterized by stereomicroscopy in order to obtain functional and amplitude parameters. The topographic features resulting for each treatment were determined through these parameters. The results obtained show that the 3D reconstruction achieved from the SEM stereo pairs is a valuable potential alternative for the surface characterization of this kind of samples.     

Identification of oxygen in dental enamel following tooth bleaching using confocal micro Raman spectroscopy

Oxygen is a polymerization inhibitor of 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloxypropoxy) phenyl]propane (Bis‐GMA) and triethylene glycol dimethacrylate, a basic constituent of most dental adhesive materials. Some hypothesis that oxygen remains in tooth mineralized tissues following some dental treatments and thus reducing adhesive forces and compromising the restorative treatments, have been advanced, but no experimental demonstration has been conducted. We used for the first time a confocal micro Raman technique to successfully identify the presence of oxygen generated by tooth bleaching products in tooth enamel surface, hence, helping to provide confirmation for this theory. This new data result from a multidisciplinary research approach between physics and dentistry is pioneering and could in the future support dental treatment protocol changes, increasing productivity and patient's benefits. Copyright © 2012 John Wiley & Sons, Ltd.     

Optically stimulated luminescence (OSL) of dental enamel for retrospective assessment of radiation exposure

This paper briefly reviews the optically stimulated luminescence (OSL) properties of dental enamel and discusses the potential and challenges of OSL for filling the technology gap in biodosimetry required for medical triage following a radiological/nuclear accident or terrorist event. The OSL technique uses light to stimulate a radiation-induced luminescence signal from materials previously exposed to ionizing radiation. This luminescence originates from radiation-induced defects in insulating crystals and is proportional to the absorbed dose of ionizing radiation. In our research conducted to date, we focused on fundamental investigations of the OSL properties of dental enamel using extracted teeth and tabletop OSL readers. The objective was to obtain information to support the development of the necessary instrumentation for retrospective dosimetry using dental enamel in laboratory, or for in situ and non-invasive accident dosimetry using dental enamel in emergency triage. An OSL signal from human dental enamel was detected using blue, green, or IR stimulation. Blue/green stimulation associated with UV emission detection seems to be the most appropriate combination in the sense that there is no signal from un-irradiated samples and the shape of the OSL decay is clear. Improvements in the minimum detection level were achieved by incorporating an ellipsoidal mirror in the OSL system to maximize light collection. Other possibilities to improve the sensitivity and research steps necessary to establish the feasibility of the technique for retrospective assessment of radiation exposure are also discussed.     

Signal processing for radiation dosimetry using EPR in dental enamel: comparison of three methods

We are reporting an alternative method of extracting useful dose information from complex EPR spectra of dental enamel. Digital differentiation of the initial first derivative spectrum followed by filtering is used to clearly distinguish the radiation-induced signal from the native background signal. The peak-to-peak height of the resulting second derivative of the signal is then measured as an indication of absorbed dose. This method does not require preliminary elimination of the native background signal, and is not effected by any uncertainty in the determination of the background signal or by errors resulting from the subtraction of two signals of comparable magnitude. Ten enamel samples were irradiated with known doses in the range of 250–10⁵ mGy. There was agreement for all the samples, within the typical experimental error of ±10% for EPR dosimetry in dental enamel, between the doses determined by two common techniques using native signal subtraction and the doses determined by the new second derivative method proposed here.     

A study of bremsstrahlung spectra and absorbed dose of beta in teeth enamel and dentin

The beta‐induced bremsstrahlung spectra produced by 113 pure beta nuclides in teeth enamel and dentin are computed. The computed spectral distributions are presented. The spectral shapes are primarily responsible for variations in the shapes of depth‐dose distributions. They are intended to provide a quick and convenient reference for spectral shapes and to give an indication of the wide variation in these shapes. The computed bremsstrahlung spectrum is used in the evaluation of bremsstrahlung dose in teeth enamel and dentin. The evaluated Beta bremsstrahlung dose as a function distance for the studied nuclides is also presented. The beta bremsstrahlung dose decreases with the increase of distance. Copyright © 2013 John Wiley & Sons, Ltd.     

Multi-frequency EPR study of radiation-induced radicals in tooth enamel

Human tooth enamel powders, unheated as well as heated prior to X -irradiation at room temperature, have been investigated by means of Q - and W -band Electron Paramagnetic Resonance (EPR). Upon irradiation of enamel, carbonate-derived radicals are generated. The simplest acquired EPR spectra in this study consist mainly of a group of three different \hbox{CO}_3^{3-} signals, with a very weak \hbox{CO}_2^{-} contribution. The characterisation of the paramagnetic species in enamel is quite important for the reliability of EPR applications ( e.g. , EPR retrospective dosimetry). The spectra from the heated samples reveal a striking resemblance with spectra from certain irradiated synthetic apatite powders. The spin Hamiltonian parameters obtained from the computer simulations of the Q - and W -band spectra are compared with those reported in the literature.     

A study to determine whether cavitation occurs around dental ultrasonic scaling instruments

The aim of this investigation was to determine if cavitation occurred around dental ultrasonic scalers and to estimate the amount of cavitation occurring. Three styles of tip (3 x TFI-10, 3 x TFI-3, 3 x TFI-1) were used, in conjunction with a Cavitron SPS ultrasonic generator (Dentsply, USA), to insonate terephthalic acid solution. The hydroxyl radical, [*OH], concentration, produced due to cavitation from the scaler tips, was monitored by fluorescence spectroscopy. Cavitational activity was enhanced at higher power settings and at longer operating times. The tip dimensions and geometry as well as the generator power setting are both important factors that affect the production of cavitation.     

Maxillary dental arch form related to voice classification: A pilot study

This pilot study evaluated maxillary dental arch form dimensions and volume to determine if these parameters could be predictors for or related to voice classification. Nine white female professional singers ranging in age from 26 years to 53 years were studied. A maxillary dental impression and stone dental casts were made using standard dental procedures. Measurements were made from 10 points on each cast to determine the depth of the palate measured from first molar (depth A) and from first bicuspid (depth B), the width measured from cuspid-to-cuspid (width A) and from second molar to second molar (width B), and the length of the palate. An impression of the palatal arch of each cast was made to determine the volume of the palate using fluid displacement methods. Audio recordings were made for each subject, and based on speaking fundamental frequency, spectral analysis, voice profile, and tessitura confirmation, the actual voice classification of each subject in soprano, mezzo, and alto was achieved. Correlation and discriminant analysis tests were performed on the data. The discriminant analysis revealed that no single measurement is a predictor for voice classification. However, the discriminant analysis applied to the predictors depth A, depth B, and volume gives optimal results, ie, each subject was classified in her true group.     

Changes in dental enamel oven heated or irradiated with Er,Cr:YSGG laser. Analysis by FTIR

This study evaluated the change that occurs in dental enamel under action of oven heating or Er,Cr:YSGG laser irradiation aiming to obtain a structure more resistant to demineralization. Enamel powder was obtained from bovine teeth. Samples were subjected to oven heating at temperatures of 200, 400, 600, 800, and 1000°C or during laser irradiation with energy densities of 7.53, 10.95, and 13.74 J/cm². The infrared thermography was used to measure the surface temperature generated in the solid samples of enamel during lasers irradiation. The samples were analyzed by Fourier transform infrared spectroscopy (FTIR), which shows changes on enamel oven heated or laser irradiated, due to treatments, related to carbonates, adsorbed water and hydroxyl content. These compositional effects were more evident in lased samples. These changes may alter the material properties such as its solubility, and decrese of demineralization that is important for caries prevention.     

Elemental and chemical compounds study of enamel and dentine of porcine primary molar teeth

For the enamel and dentin of porcine primary molar teeth, the spatial variability of the elements and chemical groups was studied with the aim of identifying the chemistry of porcine teeth, and it was then compared with results for human primary teeth. Porcine teeth were taken from specially bred animals. An electron microprobe was applied for the elemental analyses and a Raman microscope for the determination of chemical groups. The distribution of the main elements (Ca, P) was similar for both porcine and human teeth, whereas major differences were found in the distributions of minor elements (Mg, Sr, Cl, C). Carbonates were present in porcine dentin mainly as A-substituted species, whereas the B-substituted ones prevailed in enamel. The mechanism of asymmetric enrichment of Ca and P was quantitatively calculated as a consequence of Mg release. The layer close to the surface of the enamel with air had a unique composition. Cl involvement in enamel close to the boundary with air is a complex process, coupled with the involvement of Sr and release of Mg. The discoveries shed light on the role of elements in apatites, especially the role of carbonates and magnesium in porcine teeth, and put in doubt the potential use of pig apatite as a substitute for human apatite in filling materials.     

Broad‐beam PIXE and µ‐PIXE analysis of normal and in vitro demineralized dental enamel

Dental enamel has been widely studied by particle‐induced x‐ray emission (PIXE), but less attention was paid to its demineralization, which leads to caries formation. Using broad‐beam PIXE and µ‐PIXE, we investigated normal enamel and the in vitro formation of pre‐carious lesion in lactic acid solution, aiming also to evaluate intercusp differences within the same tooth. Broad‐beam PIXE was performed using 3.0 MeV protons, and µ‐PIXE maps of Ca, Fe and Zn were collected with 3.1 MeV protons at ～4 µm resolution. In normal enamel a differentiated Ca‐rich surface layer was observed, where Fe and Zn reached their highest levels. In deeper layers, Fe and Zn evidenced quasiperiodic patterns of maxima, possibly due to coupled diffusion‐reaction catalytic processes involved in the enamel growth. Both Fe and Zn appeared to be located in a few distinct types of pools. Near the surface, demineralization induced an increase of Fe, Cu, Zn, Sr and Pb with respect to Ca, attributed to partial hydroxyapatite dissolution and/or to chelate extraction and concentration of trace metals. Ca maps revealed limited changes in the surface layer and a massive loss in the inner enamel; here, Fe was almost depleted and Zn partially removed. The maps of Ca, Fe and Zn demonstrated major intercusp variations in both normal and altered enamel. Thus, broad‐beam PIXE and µ‐PIXE, which do not require (semi)thin sectioning of the tooth as the conventional methods, provide compositional and structural insight of normal dental enamel, of its intercusp variability and of the alterations produced by in vitro demineralization, largely not accessible to the current techniques, and highly relevant for understanding the incipient caries formation. Copyright © 2008 John Wiley & Sons, Ltd.