Chemical Composition Of Enamel Research Articles

Changes in the chemical composition of mineralised teeth in children after antineoplastic treatment.

IntroductionChemotherapy, neoplasms, and their complications linked to malabsorption, malnutrition, and metabolic disorders may lead to improper tooth development and frequent severe caries in patients during/after antineoplastic treatment and to a more frequent improper tooth development in patients undergoing chemotherapy during odontogenesis. However, the causes of these abnormalities remain unknown; there are no studies on the impact of antineoplastic treatment and its complications on the chemical composition of mineralised teeth.Aim of the studyTo compare the chemical composition of mineralised teeth extracted due to complicated caries in children after chemotherapy, and of teeth extracted due to orthodontic treatment in generally healthy children.Material and methodsThe treatment group included five teeth extracted due to complicated caries in children after antineoplastic treatment. The control group included five teeth extracted due to orthodontic treatment in generally healthy children. The chemical composition of enamel, dentine, cementum, interior of the canal, and enamel abnormalities in teeth extracted from patients after chemotherapy and in generally healthy patients were assessed with energy-dispersive X-ray spectroscopy. Results were analysed statistically.ResultsThe magnesium (Mg) and zinc (Zn) mass contents in the enamel of patients after chemotherapy increased and so did the calcium (Ca) to phosphorus (P) ratio when compared to controls. Areas with abnormal enamel in patients after chemotherapy had lower concentrations of Ca and P, and higher concentrations of trace elements (Mg, Cl, and Na). The levels of the assessed elements in dentine, cementum, and inside the canal were similar in both groups of teeth.

Radiotherapy effect on nano-mechanical properties and chemical composition of enamel and dentine

ObjectiveTo understand radiotherapy-induced dental lesions characterized by enamel loss or delamination near the dentine–enamel junction (DEJ), this study evaluated enamel and dentine nano-mechanical properties and chemical composition before and after simulated oral cancer radiotherapy. DesignSections from seven non-carious third molars were exposed to 2Gy fractions, 5 days/week for 7 weeks for a total of 70Gy. Nanoindentation was used to evaluate Young's modulus, while Raman microspectroscopy was used to measure protein/mineral ratios, carbonate/phosphate ratios, and phosphate peak width. All measures were completed prior to and following radiation at the same four buccal and lingual sites 500 and 30μm from the DEJ in enamel and dentine (E-500, E-30, D-30 and D-500). ResultsThe elastic modulus of enamel and dentine was significantly increased (P≤0.05) following radiation. Based on Raman spectroscopic analysis, there was a significant decrease in the protein to mineral ratio (2931/430cm−1) following radiation at all sites tested except at D-500, while the carbonate to phosphate ratio (1070/960cm−1) increased at E-30 and decreased at D-500. Finally, phosphate peak width as measured by FWHM at 960cm−1 significantly decreased at both D-30 and D-500 following radiation. ConclusionsSimulated radiotherapy produced an increase in the stiffness of enamel and dentine near the DEJ. Increased stiffness is speculated to be the result of the radiation-induced decrease in the protein content, with the percent reduction much greater in the enamel sites. Such changes in mechanical properties and chemical composition could potentially contribute to DEJ biomechanical failure leading to enamel delamination that occurs post-radiotherapy. However, other analyses are required for a better understanding of radiotherapy-induced effects on tooth structure to improve preventive and restorative treatments for oral cancer patients.

Effect of water content on the nanomechanical properties and microtribological behaviour of human tooth enamel

Human tooth enamel exhibits excellent wear-resistance in mouth. It consists of 92–96% inorganic substances, 1–2% organic materials, and 3–4% water by weight. The contribution of water content to its wear mechanism has not been fully understood yet. In this paper, nano-indentation and scratch tests were performed on human tooth enamel after different drying time to study the effect of water content on the nanomechanical properties and microtribological behaviour. The recovery of enamel's tribological properties in water was also investigated by immersing the dried enamel specimens in deionized water. Results showed that the water content within enamel had a significant influence on its nanomechanical properties and microtribological performance. The nanoindentation hardness of enamel increased with the increase of drying time, but its elastic modulus decreased. The friction coefficient and wear loss of enamel also increased. Moreover, an increasing fluctuation occurred to the friction coefficient of enamel as the drying time increased. Microscopic examinations showed that a few micro-voids appeared on the worn surface of dried enamel, and the voids became more and more obvious with the increase of drying time. Additionally, both the friction coefficient and wear loss of the dried enamel specimen were found to significantly decrease after being immersed in water. These results indicated that the water content within human tooth enamel could reduce the value and fluctuation of friction force on the surface and protect the surface from wear damage. The anti-wear properties of enamel decreased with the decrease of its water content. The results would be helpful to extend an understanding of the relationship between the enamel chemical composition and its tribological properties and then develop new dental materials.

Tooth Bleaching Increases Dentinal Protease Activity

Hydrogen peroxide is an oxidative agent commonly used for dental bleaching procedures. The structural and biochemical responses of enamel, dentin, and pulp tissues to the in vivo bleaching of human (n = 20) premolars were investigated in this study. Atomic force microscopy (AFM) was used to observe enamel nanostructure. The chemical composition of enamel and dentin was analyzed by infrared spectroscopy (FTIR). The enzymatic activities of dental cathepsin B and matrix metalloproteinases (MMPs) were monitored with fluorogenic substrates. The amount of collagen in dentin was measured by emission of collagen autofluorescence with confocal fluorescence microscopy. The presence of Reactive Oxygen Species (ROS) in the pulp was evaluated with a fluorogenic 2′,7′-dichlorodihydrofluorescein diacetate (DCFDA) probe. Vital bleaching of teeth significantly altered all tested parameters: AFM images revealed a corrosion of surface enamel nanostructure; FTIR analysis showed a loss of carbonate and proteins from enamel and dentin, along with an increase in the proteolytic activity of cathepsin-B and MMPs; and there was a reduction in the autofluorescence of collagen and an increase in both cathepsin-B activity and ROS in pulp tissues. Together, these results indicate that 35% hydrogen peroxide used in clinical bleaching protocols dramatically alters the structural and biochemical properties of dental hard and soft pulp tissue.

Regulation of enamel hardness by its crystallographic dimensions

Enamel is a composite biomaterial comprising a minor organic matrix (∼2%) and a hierarchically organized inorganic ultrastructure (∼96–98%). Surprisingly, to date there is no available information in the literature regarding the possible role of the enamel ultrastructure on the nanoscale level in tooth macroscopic properties. Understanding this relationship is of especial interest for restorative purposes in dentistry. Accordingly, this study was designed to investigate how enamel nanocrystals regulate its hardness. We performed microindentation analysis on 100 extracted human teeth. The tooth enamel hardness was quantified and correlated with changes in enamel chemical composition and crystallographic dimensions obtained from Fourier transform infrared spectroscopy and X-ray diffraction, respectively. Enamel hardness was not related to the variability in organic content, but was associated with the size of apatite crystals along the c-axis. This association followed the Hall–Petch model for polycrystalline materials, indicating that the optimal size of apatite nanocrystals (larger than the critical size) provides enamel with the greatest hardness, which enables teeth to survive the heavy wear over a human lifetime.

The role of enamel crystallography on tooth shade

Objectives: Tooth shade is influenced by a combination of extrinsic-stains that are adsorbed to the enamel surface and by its intrinsic-shade resulting from the interaction of light with tooth structures. This study was designed to investigate how the variations in enamel ultrastructure may affect tooth optical properties. Methods: One-hundred extracted teeth were collected from adult patients attending McGill-Undergraduate Dental Clinics. Shade-spectrophotometry, FTIR and XRD were used to assess tooth shade, enamel chemical composition and crystallography. The data obtained was analysed for Pearson correlation analysis and multiple linear regression analysis. The statistical significance was set at P<0.05. Results: Tooth shade parameters varied dramatically within the studied population. Pearson correlation analysis demonstrated that tooth hue was associated with enamel hydroxyapatite (HA) crystal size (R=−0.358; B=−0.866; P=0.007), tooth chroma was associated with enamel HA carbonization (R=−0.419; B=−99.06; P=0.005), and tooth lightness was associated with both enamel HA crystal size (R=−0.313; B=−1.052; P=0.019) and the degree of HA carbonization (R=−0.265; B=−57.95; P=0.033). Multiple linear regression analysis demonstrated that the size of enamel HA crystals and the relative content of mineral carbonate were the most important predictors for tooth shade lightness (P=0.018) and chroma (P=0.008), respectively. In contrast, enamel organic content had no correlation with tooth shade. Conclusions: In the present study we have revealed that the tooth shade is regulated by the size of their HA enamel crystals. On the other hand, variation in the degree of enamel HA carbonization can also affect the tooth shade. These findings are of great relevance in dentistry since it provides better understanding of tooth aesthetics.

Chemical Analysis of Enamel and Dentin Following the Application of Three Different At-home Bleaching Systems

To determine the change in the chemical composition of enamel and dentin as well as to evaluate the differences in surface texture of the same dental hard tissues following three at-home bleaching systems in vitro. Sixty extracted intact human anterior teeth were used in this study. Thirty teeth were used as samples for enamel, and the buccal surfaces of the remaining 30 teeth were abraded and used as dentin samples. Prior to bleaching treatments, calcium (Ca), phosphorus (P), potassium (K), sodium (Na), magnesium (Mg), fluoride (F), and oxygen (O) levels of each sample were measured using an energy dispersive spectrometer. The teeth were then randomly allocated into three groups according to the bleaching system used, as follows: GI, 10% carbamide peroxide (CP); GII, 20% CP; GIII, and 35% CP. Following the bleaching treatments, Ca, P, K, Na, Mg, F, and O measurements were repeated. The surface configurations were examined using scanning electron microscopy (SEM). The data were analyzed using Wilcoxon signed rank and Kruskal-Wallis tests followed by the Dunn test. All three bleaching systems tested caused similar changes in the chemical composition of enamel and dentin. Bleaching systems decreased Ca and K, while F and O levels increased in enamel. In dentin, Ca, P, and K levels decreased; however, Na, F, and O levels increased. SEM observations revealed no deleterious effect on enamel and dentin. The use of home bleaching agents could affect the chemical composition of dental hard tissues, whereas the change in the chemical composition of enamel and dentin was not affected by the CP concentration of the bleaching systems used.

Three-dimensional Orientation Analysis of Human Enamel Crystallites Using X-ray Diffraction

Tooth enamel is composed of nano-scale, needle-like biological apatite crystallites. These crystallites constitute the enamel prisms. The generally accepted Meckel's model of arrangement of crystallites in enamel prism might be slightly revised according to the variations in tooth enamel chemical composition and structures. An x-ray diffraction method was proposed to survey the three-dimensional crystallite orientation instead of electron microscopy. Preliminary results showed clear difference in the convergence and broadening of enamel crystallite orientations of human tooth enamel. This method has high potential in analyzing partial deviation in crystallite orientation as well as easy sample preparation and operation.

Chemical composition of enamel and dentine in modern reptile teeth

AbstractElemental distribution maps by wavelength-dispersive electron microprobe of enamel and dentine in modern crocodile teeth illustrate variations in both minor and major elements. Mg has the largest difference between the enamel and dentine, being enriched in the dentine. Mg, Ca and P are not homogeneously distributed in the dentine, but their distribution reflects changes during growth of the teeth. These variations in compositional differences of teeth from modern samples potentially can assist in establishing growth rates in fossil teeth samples, and thereby provide information on the physiology of extant species.

Chemical composition of enamel and dentine in primary teeth in children from Thailand exposed to lead

Enamel and dentine in teeth of children with high blood levels of lead were analyzed by means of secondary ion mass spectrometry (SIMS) and X-ray micro-analyses (XRMA) and compare with teeth from children with low blood levels of lead. The SIMS analysis revealed detectable levels of Pb in dentine close to the pulp. The XRMA analyses could not detect any lead. There were no differences found in lead level in enamel of high lead level exposed teeth from low level exposed. The results confirm that children with high blood levels of lead have an uptake of lead in dentine close to the pulp.

The chemical compositions of dentine and enamel from recent reptile and mammal teeth—variability in the diagenetic changes of fossil teeth

Principal component analyses, based on microprobe data and coupled with microstructural observations, have been applied to investigate the differences between teeth of recent and fossil mammals and reptiles, and their fossil counterparts. In recent samples, enamel is compositionally distinct from dentine, and differences also exist between mammal and reptile teeth. During fossilization, both the physical structure and chemical composition of enamel and dentine can be altered, the degree and extent of which varies from site to site, depending on the nature of the burial environment. The higher porosity of the dentine structure allows for a more open pathway for fluids within the burial environment to permeate more efficiently. Subsequently, dentine is often considered to be more susceptible to diagenesis than enamel. However, enamel from one fossil site has undergone significant diagenetic alteration. Because of the variable and unpredictable effects of diagenesis, the chemical composition of fossil teeth is not a reliable indicator of the lifetime (i.e.in vivo) composition. Thus, interpretation of the lifestyle or environment of individuals that is based on compositional parameters, such as palaeodiet, needs to take into account the degree and extent of diagenetic alteration associated with individual fossil sites. Additional factors that can affect post-mortem alteration of teeth, are the mechanical and chemical modifications that result from predation and digestion.

Morphological appearance and chemical composition of enamel in primary teeth from patients with 22q11 deletion syndrome

Patients with 22q11 deletion syndrome have many and complex medical problems, including hypocalcemia and/or hypoparathyroidism. Odontological findings include enamel aberrations in both dentitions. In order to describe enamel morphology, chemical composition in primary teeth, and to investigate the relationship between medical history and morphological appearance, dental enamel was investigated in 38 exfoliated primary teeth from 15 children and adolescents. Morphology was studied by the use of a polarized light microscope, microradiography, scanning electron microscopy, X-ray microanalysis, and secondary ion mass spectrometry. The morphological findings were compared with medical history. The teeth showed, in principle, a normal morphological appearance with regard to prism structure. A high frequency of aberrations, such as hypomineralization, hypoplasia and extra incremental lines, were found. The majority of the aberrations were found around the neonatal line. There was a relationship between high numbers of medical problems in the patients and enamel deviations. The result supports the hypothesis of under-reporting of both hypocalcemia and hypoparathyroidism in patients with 22q11 deletion syndrome.

Factors affecting the differential dissolution of human enamel in acid and EDTA. A scanning electron microscope study

Surfaces of sound, human permanent teeth, either natural surfaces or surfaces cut in various planes, were etched with a variety of agents. In general, acids preferentially removed prism centres and ethylene diamine tetra-acetic acid (EDTA), at neutral pH, preferentially removed prism peripheries. A relationship between time and concentration was suggested by the observations that application of very dilute EDTA solutions resulted in the formation of narrow clefts at prism junctions which progressed to destroy the prism peripheries. Short exposures to dilute acids produced similar clefts as well as shallow concavities within the body of the prism; these concavities deepened with length of exposure leaving the prism cortex relatively unaffected. Etching with organic acids at neutral pH, where they might be expected to manifest some chelating activity, and etching with EDTA at acid pH, produced variable results with features typical of both acid and neutral EDTA attack. When the ionization of acids was inhibited by preparation in non-aqueous solvents, prism junctions appeared to be preferentially attacked. The role of crystal orientation and regional differences in chemical composition of enamel are discussed as possible explanations for the findings. It is suggested that the major factor which determines the differential etching by different agents is the greater permeability of prism junctions, which admits the large EDTA molecule and acid anions more readily than the bodies of the prisms. The pattern of tissue destruction seen in enamel caries could be explained on the basis of acid dissolution alone, or by a mixture of acid dissolution and calcium complexation.

INFLUENCE OF CHEMICAL COMPOSITION OF ENAMEL ON A FEW OF ITS PROPERTIES

AbstractTo enlarge the knowledge and data of the relation between the chemical composition of enamel and its properties, many enamels were melted and their acid resistance, viscosity, and opacity were measured. The results have been assembled in graphs representing measurements of these properties in relation to the systematic change of the composition. On the basis of the results, a revision of information is offered relating to the acid resistance of glass and enamel.

The Chemical Composition of Enamel and Dentin in High and Low Caries Areas in South Africa

The Chemical Composition of Enamel and Dentin in High and Low Caries Areas in South Africa