Enamel Surface Of Human Teeth Research Articles

Antimicrobial Effects of Gum Arabic-Silver Nanoparticles against Oral Pathogens.

Dental caries is considered one of the most prevalent oral diseases worldwide, with a high rate of morbidity among populations. It is a chronic infectious disease with a multifactorial etiology that leads to the destruction of the dental tissues. Due to their antimicrobial, anti-inflammatory, antifungal, and antioxidant properties; silver nanoparticles (AgNPs) are incorporated in dental products to help prevent infectious oral diseases. In this study, the antimicrobial effects of AgNPs synthesized using Gum Arabic extracts (GAE) were examined. The GA-AgNPs were synthesized and characterized using ultraviolet-visible (UV-Vis) spectrophotometer, dynamic light scattering (DLS), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The antimicrobial activity of the GA-AgNPs was evaluated on Streptococcus sanguinis (S. sanguinis), Streptococcus mutans (S. mutans), Lactobacillus acidophilus (L. acidophilus), and Candida albicans (C. albicans) using agar disc diffusion and microdilution assays. The antibiofilm of GA-AgNPs was evaluated on the surface of human tooth enamel that had been exposed to S. mutans with and without the GA-AgNPs using scanning electron microscopy (SEM). GA-AgNPs were spherical in shape with a particle size distribution between 4 and 26 nm. The GA-AgNPs exhibited antimicrobial activity against all the tested oral microbes, with GA-AgNPs_0.4g having higher antimicrobial activity. The GA-AgNPs_0.4g inhibited S. mutans adhesion and biofilm formation on the surface of the tooth enamel. Therefore, this study supports the prospective implementation of the plant extract-mediated AgNPs in dental healthcare.

Nanoscale effects of beverages on enamel surface of human teeth: An atomic force microscopy study

Dental erosion has become a prevalence disease and attracted increasing attention worldwide. In this research, we quantitatively evaluate the mechanical and morphological changes in the very early stages of softening and weakening of human enamel surfaces induced by soft drinks using atomic force microscopy (AFM). With an increase of the immersion time in soft drinks, we found a significant increase of surface roughness (Rq) of the enamel surface. The prismatic structure of enamel was clearly observed after a 1-h immersion in Coca-Cola®, which shows its strong erosion effect. According to the elastic modulus mapping images obtained by AFM, a considerable decrease of elastic modulus (E) of enamel surface has been found as the enamel surface structures are etched away by soft drinks. A high surface roughness of enamel will result in a high chance of cavities due to easier bacterial adhesion on rougher surface, while a drastic deterioration of the mechanical properties of the enamel will weaken its protection property. Our findings show the serious influence of acidic drinks on enamel surface at the very beginning stage of etching process, which is quite meaningful for people to prevent dental erosion and keep dental health.

Acid resistance enhancement of human tooth enamel surface by Nd:YAG laser and incorporating silver nanoparticles: in vitro study

This work was devoted to assess the use of Nd:YAG laser with and without nanosilver particles to enhance tooth resistance of dental enamel against carries. Forty-eight tooth samples were randomly divided into three main groups and received different treatments. Samples of group 1 were illuminated by a single pulse at different laser fluences, while those of group 2 received different number of laser pulses at fixed laser fluence, and finally the samples of group 3 received laser and colloidal silver nanoparticle treatments at different conditions. The samples were subjected to Vickers microhardness test, atomic force microscopy analysis, scanning electron microscopy observation, energy dispersive spectroscopy investigation, and demineralization and re-mineralization tests. Due to fast laser heating and quenching, a significant microhardness increase in the treated dental enamel samples was seen. This resulted in an improvement in the enamel resistance against acids because of the decrease in hydroxyapatite lattice stress and the reduction in enamel solubility. The addition of silver nanoparticles to the laser-treated enamel surface helped stabilize the granules of the enamel surface tissue under the effect of laser irradiation. The demineralization of laser-treated samples showed higher Ca/P ratios than control group, indicating a higher resistance against acids. The combined laser illumination and the addition of silver nanoparticles lowered the tooth abrasion degree and increased tooth resistance to decay. The demineralized samples of all laser-treated samples had higher Ca/P ratios compared to the demineralized control sample. Laser energy has modified the Ca/P mineral ratio and forms steadier and lesser acid soluble compositions.

Effect of calcium ions on the adsorption and lubrication behavior of salivary proteins on human tooth enamel surface

The aim of this study is to investigate the effect of calcium ions on the adsorption and lubrication behavior of salivary proteins on human tooth enamel. Human whole saliva was collected from healthy donors. Three testing groups were calcium ion-enhanced saliva samples with an increased ion concentration of 1 mmol/L, 5 mmol/L, and 10 mmol/L, respectively. Normal saliva was used as a control. The adsorption behavior was tested using quartz crystal microbalance with dissipation (QCM-D), while the mechanical properties and lubricating behavior of salivary pellicle were examined by nano-indentation/scratch technique. Results show that the increased calcium ion concentration in the saliva weakens the electrostatic interaction between the salivary proteins and enamel surface, but causes increases in the thickness and viscoelasticity of the salivary pellicle formed on enamel surface. Therefore, the load-bearing and anti-shear capacity of the pellicle is improved, and then the anti-wear and friction-reducing effect of the pellicle is enhanced. In sum, the addition of calcium ion in saliva can contribute to the formation of the salivary pellicle with enhanced lubrication performance and help to alleviate the excessive tooth wear of xerostomia patients.

Effect of saliva flow rate on the adsorption kinetics and lubrication of salivary pellicle on human tooth enamel surface

The adsorption and lubrication of salivary pellicle is closely associated with saliva secretion, while the relationship between saliva flow rate and salivary pellicle lubrication is still unclear. In this study, the adsorption kinetics and lubrication behavior of salivary pellicle on human tooth enamel surface has been investigated in vitro at different salivary flow rates using quartz crystal microbalance with dissipation (QCM-D) and nano-indentation/scratch technique. Human whole saliva was collected from healthy donors. Regardless of flow rates, salivary protein adsorption on the enamel surface experiences initially rapid saturated adsorption to form a stable multi-layer structure of salivary pellicle and then slow oversaturated adsorption of some proteins with weak bonding. With the flow rate increasing, the saturated adsorption process is expedited, but the oversaturated adsorption is decelerated. Hence, the pellicle has decreased roughness, thickness, viscoelasticity, and normal load-bearing capability at high flow rates than at low flow rates. Its anti-wear properties are slightly weakened but its friction-reducing properties are enhanced. In sum, there exists a coupling effect of flow rate and adsorption time on the adsorption of salivary proteins. Saliva lubrication mainly depends on the saturated adsorption of salivary proteins on enamel surface.

Remineralization Potential of Lacto se- free and Plant based milk on Enamel surface of Human teeth subjected to Energy Drinks

Objective: Multiple etiological factors contribute to the process of erosion and destructionof enamel. Among which, carbonated soft beverages and energy drinks are the most aggressiveextrinsic causes. The consumption of milk whether bovine or plant based highly contributes to theremineralization process.Design: Thirty five freshly extracted sound human maxillary first premolars were used andrandomly divided into the following groups; Group I (Control group): included 5 teeth immersedin distilled water. Group II (Power Horse group): 15 teeth were immersed in 330ml of the drink.Group III (Cornelius group): 15 teeth were immersed in 330ml of the energy drink. After 10 days,the teeth were further randomly divided as follows (5 teeth each); Group IV (Power Horse +Lactosefree milk), Group V (Power Horse +Almond milk), Group VI (Cornelius +Lactose free milk) andGroup VII (Cornelius +Almond milk). Teeth of groups IV-VII were placed in both types of milk for5 days where the milk was changed every 2 hrs. The remaining teeth from groups II and III (5 teetheach) were kept in distilled water. At the end of the experimental period, the teeth were prepared forSEM examination, EDX and statistical analyses.Results: SEM examination showed that surface erosion was more aggressive in Power Horsegroup (II) when compared to Cornelius group (III). Furthermore, the results revealed betterremineralizing effect in groups IV and VI (lactose free treated) rather than those treated withalmond milk (groups V and VII ). EDX results presented statistically significant decrease in Caand P wt % in group II compared to group III . Statistically significant increase in Ca and P wt % ingroup IV in relation to group V and similarly, significant increase in group VI compared to groupVII were also detected.Conclusion: Energy drinks produce erosive defects of varying intensity on the enamel surfaceof human teeth. The intake of remineralizing agents; such as milk, immediately following everymeal containing acidic diet is mandatory to reverse the demineralization process.

Effect of cinnamon extract solution on human tooth enamel surface roughness

Cinnamon is known to have antimicrobial, antifungal, and anti-inflammatory effects on toothache and can aid in fighting bad breath. Cinnamon extract solution has an acidic pH that can affect enamel surface roughness. This study aimed to determine the effect of cinnamon extract solution exposure on human enamel surface roughness. A laboratory experiment was performed using 12 specimens of human premolar teeth that were divided into two treatment groups for immersion in cinnamon extract solutions of concentrations 4% with pH 5.38 (n = 6) and 12.5% with pH 5.45 (n = 6). Each group was immersed for 60, 120, and 180 min. Surface roughness was measured using a surface roughness tester (SurfTest SJ-301, Mitutoyo, Japan). Results analyzed with repeated measures analysis of variance showed that teeth immersed in the 4% cinnamon extract solution for 60, 120, and 180 min showed no significant changes in surface roughness (p > 0.05), while teeth immersed in the 12.5% solution for 120 and 180 min showed a significant reduction in surface roughness (p < 0.05). It is found that pH, concentration, and duration of exposure to cinnamon extract solution can cause changes in enamel surface roughness.

Novel methodology for determining the effect of adsorbates on human enamel acid dissolution

ObjectiveThe effect of various interventions on enamel demineralisation can be determined by chemically measuring mineral ions dissolved by the attacking acid. Results are usually expressed as mineral loss per surface area of enamel exposed. Acid resistant varnish or adhesive tape are typically used to delineate an area of enamel. However, enamel surface curvature, rugosity and porosity reduce the reliability of simple area measurements made at the macro scale. Our aim was to develop a simple method for investigating the effect of adsorbates on enamel demineralisation that does not rely on knowing the area of enamel exposed. As an exemplar we have used salivary proteins as a model adsorbate. DesignNatural human tooth enamel surfaces were subjected to five sequential acid challenges and then incubated in adsorbate (whole clarified saliva) followed by a further 15 acid challenges. Demineralisation was determined by measuring the phosphate released into the acid during each exposure by a spectrophotometric assay. The initial five challenges established a mean baseline mineral loss for each tooth against which the effect of subsequently adsorbed proteins could be compared. ResultsSalivary proteins significantly reduced the acid demineralisation of human enamel by 43% (p<0.01). Loss of proteins during each challenge corresponded to a gradual reduction in the degree of protection afforded. ConclusionsThe methodology provides a simple and flexible means to investigate the effect of any adsorbate on enamel acid dissolution. Knowledge of the area of exposed enamel is irrelevant as each tooth acts as its own negative control.

Effect of alcohol stimulation on salivary pellicle formation on human tooth enamel surface and its lubricating performance

This study was to investigate the salivary pellicle formation on the surface of human tooth enamel and its lubricating behavior under alcohol stimulation. Normal saliva and alcohol-stimulated saliva were collected from a young male volunteer after rinsing mouth with deionized water and different-concentration alcohol aqueous solution, respectively. Saliva-adsorption treatment was conducted in vitro on enamel surface to obtain salivary pellicle. Microscopic examinations and lubrication testing of salivary pellicle were performed by nanoscratch technology. Given that the pellicle lubricating properties are closely associated with its adhesion strength to substrates, the adhesion force between salivary pellicle and enamel was measured using an Atomic Force Microscopy. Compared with normal salivary pellicle, the salivary pellicle obtained from alcohol-stimulated saliva was not uniform anymore and even without any orderly multi-layer structure. Although alcohol stimulation improved the pellicle bonding to enamel surface, it caused the pellicle lubrication worse. In sum, the lubricating performance of salivary pellicle was more dependent on its orderly multi-layer structure from salivary protein self-assembly than its adhesion strength to enamel.

Cartographic method of surface characteristics analysis

A wide range of investigations is based on analysis of experimental data, which are represented as a function of two variables (height of the relief h(x, y), microhardness, color, etc.). In the studying of process or phenomenon change of these functions after the experiment is of great interest. On numerous occasions the main problem in comparative analysis of the data sets is the absence of a natural reference level (such as sea level), respect to which changes of the surface characteristics can be determined. We suggest the possible algorithm of determining of the reference level. Also there is its comparison with the standard methods in this paper. This method was used for AFM data processing in the study of effects of natural and artificial factors on the surface of human tooth enamel. The paper presents the main results of this research and shows the necessity of additional data processing using the developed method.

Hydroxyapatite-anchored dendrimer for in situ remineralization of human tooth enamel

In situ remineralization of hydroxyapatite (HA) on human tooth enamel surface induced by organic matrices is of great interest in the fields of material science and stomatology. In order to mimic the organic matrices induced biomineralization process in developing enamel and enhance the binding strength at the remineralization interface, carboxyl-terminated poly(amido amine) (PAMAM–COOH)—alendronate (ALN) conjugate (ALN–PAMAM–COOH) was synthesized and characterized. PAMAM–COOH has a highly ordered architecture and is capable of promoting the HA crystallization process. ALN is conjugated on PAMAM–COOH due to its specific adsorption on HA (the main component of tooth enamel), resulting in increased binding strength which is tight enough to resist phosphate buffered saline (PBS) rinsing as compared with that of PAMAM–COOH alone. While incubated in artificial saliva, ALN–PAMAM–COOH could induce in situ remineralization of HA on acid-etched enamel, and the regenerated HA has the nanorod-like crystal structure similar to that of human tooth enamel. The hardness of acid-etched enamel samples treated by ALN–PAMAM–COOH can recover up to 95.5% of the original value with strong adhesion force. In vivo experiment also demonstrates that ALN–PAMAM–COOH is effective in repairing acid-etched enamel in the oral cavity. Overall, these results suggest that ALN–PAMAM–COOH is highly promising as a restorative biomaterial for in situ remineralization of human tooth enamel.

A New Model for Nanoscale Enamel Dissolution

The dissolution kinetics of human tooth enamel surfaces was investigated using nanomolar-sensitive constant composition (CC) and in situ atomic force microscopy (AFM) under simulated caries formation conditions (relative undersaturation with respect to hydroxyapatite = 0.902, pH = 4.5). Scanning electron microscopic (SEM) examination of the resulting etched enamel surfaces showed that deminerzalization, initiated at core/wall interfaces of rods, developed anisotropically along the c-axes. After an initial rapid removal of surface polishing artifacts, the dissolution rate decreased as the reaction proceeded in accordance with our recently proposed crystal dissolution model, resulting in hollow enamel cores and nanosized remaining crystallites, resistant to further dissolution. Generally, dissolution of minerals is regarded as a spontaneous reaction in which all the solid phase can be dissolved in undersaturated solutions. However, the dissolution of some biominerals may be suppressed when the crystallites approach nanometer size. This study shows that CC demineralization of enamel in acidic medium follows this new model that can be used to mimic carious lesion formation. In dissolution studies, nanosized enamel crystallites exhibit a remarkable degree of self-preservation in the fluctuating physiological milieu.

In vitro demineralization/remineralization cycles at human tooth enamel surfaces investigated by AFM and nanoindentation

The early stages of enamel surface dissolution (erosion) are of high scientific relevance; however, little is known about if and to what extent these early stages, which result in the softening of the enamel surface, are reversible. The present study investigated the possible rehardening of surface softened enamel in two separate experiments in vitro, employing physiologically relevant demineralization and remineralization times and remineralizing solutions possessing chemical properties close to those of human saliva. Atomic force microscopy (AFM) based nanoindentation has been used to study the nanomechanical properties and the ultrastructure of polished enamel samples as affected by demineralization/remineralization cycles. In contradiction to previous studies employing microhardness techniques, no enamel rehardening has been observed after remineralization; however, the demineralization schemes used in the present study (short treatments with a citric acid buffer) are not comparable to the ones used in previous studies, making a comparison difficult. A mineral deposition after remineralization on softened enamel samples has been observed by AFM; however, a protective effect of this deposited layer could not be revealed. The exposure of softened enamel samples to either a remineralizing solution or a mineral water led to an improved acid resistance of these samples as shown in a demineralization/remineralization cycle. The present study has demonstrated that AFM based nanoindentation is a useful tool to investigate the demineralization and remineralization of surface softened enamel with high accuracy.

Surface Characterisation of Laser Modified Human Tooth Enamel Using Laser Microprobe Mass Spectrometry and Scanning Electron Microscopy

A technique in preventative dentistry currently under development is the modification of the tooth surface by the fusion of glassy metal oxides into the enamel surface using a CO2 laser. This could provide a protective coating to the tooth which would be applied in the mouth. Such a radical treatment is intended to produce major changes in chemistry at the tooth surface and characterisation of these changes is a necessary part of the development of the technology. LMMS and SEM have been used, as part of a feasibility study, to characterise coatings deposited with laser assisted fusion on the surface of human tooth enamel, in particular the chemical and topographical changes taking place. The results demonstrate that the analytical approach adopted provides useful qualitative information about the physical and chemical changes taking place. They highlight the fact that although deposition of the coating is patchy, areas are present where the coating has apparently fused to the tooth enamel. Changes in the chemistry of the tooth enamel subjected to laser irradiation were identified, both in the absence of coating precursors and with precursor materials present.

In vitro fatigue testing of a dental bonding system on enamel.

The aim of this study was to investigate the in vitro fatigue behavior of a dental bonding system [ScotchBond Multi Purpose (SBMP)] by using a cyclic shear loading test. Cylinders of a light-cured hybrid composite resin (Z100) were formed on, and bonded with SBMP to, the flattened, acid-etched enamel surface of human teeth. Thirty-two samples (eight per group) were used to determine the 1-h, 1-day, 7-day, and 30-day shear bond strengths. For the shear fatigue test, the stress was cycled, at a rate of 1 Hz, between 0 and a present value in the 12-28 MPa range (from -3 SD to +1 SD around the 24-MPa mean bond strength of the 1-h specimens). The applied stress and the number of cycles to failure were recorded for each of the 75 samples tested (15 samples per set-stress). Three stress versus number of cycles curves (low, median, and high S-N curves) were obtained and an approximate endurance limit of 10 MPa was identified for the SBMP bonding system. The data obtained explain, in part, the discrepancy between in vitro and in vivo results and underline the difficulty of predicting the in vivo behavior based on results of in vitro bond strength tests alone. Shear fatigue test data, however, could provide a better insight into the long-term in vivo behavior of a dental bonding system.

Sequential observations followed by acid etching on the enamel surfaces of human teeth under scanning electron microscopy at low vacuum.

A scanning electron microscope equipped with a low vacuum specimen chamber and a Robinson's backscattered electron detector was employed to observe the natural surfaces of human buccal enamel before and after 30 percent phosphoric acid etching sequentially up to 90 sec at the same sites with no coatings. Furthermore, successive etching patterns were compared between deciduous and permanent teeth. On the imbrication lines of young permanent teeth, prism-end pits surrounded with a "prismless" structure occasionally disappeared after acid etching and became a prismless enamel. Sequential etching caused the prismless areas and the areas of a type 1 etching pattern to decrease, and a cone-shaped prism structure and a complex type of the type 1 and type 2 etching pattern (type 1-2) to appear. The former was a transitional type between the prismless enamel and type 2 prisms. These etched surfaces show type 2 prisms after deeper etching. Small dome-shaped structures, slightly elevated on the attrited enamel surfaces, were found only in deciduous teeth. After acid etching, such areas which retained the prismless enamel rose to the underlying surfaces of cone-shaped prisms.

Effect of acid etching technics on the adhesion of composite resins applied to the enamel

The purpose of this study is to evaluate the generally accepted enamel etching procedure for the composite resin restoration and to develop a more useful one. The flat ground enamel surfaces of human teeth were treated with varying exposure period to various etchants and different washing pressures. The tensile bond strength of the adhesive resin applied to the enamel was determined. After testing, the enamel surface and the interfacial resin structure were observed by SEM. The bond strength would greatly depended upon the microfine irregularity resulting from the individual enamel crystal rather than much greater irregularity due to the preferential loss of prism periphery. The bond strength was remarkably reduced when the dissolution products deposited on the etched enamel surface. These products were generated by long etching with orthophosphoric acid solution or citric acid containing FeCl3. Compared with the acid solution, the gel-like liquid generally required a longer etching to produce such a microfine irregularity contributing to bonding. A new etching technique with two applications of the gel-like liquid for 5 seconds each succeeded in efficiently producing the microfine irregularity resulting in the marked increase of the bond strength. This double etching technique was found very practical for clinical use.

Regional and Age-related Variations in Solubility and Fluoride Concentraion on the Surface of Human Tooth Enamel

The purpose of this study was to examine the regional and age-related variations in the enamel solubility and the fluoride concentration on the surface of women's lower first premolars and to develop a technique to determine both enamel solubility and fluoride concentration using dissolved enamel from the same point on the tooth surface.The following results were obtained.1) Both the enamel solubility and the fluoride concentration could to be determined at the same window of enamel (3-mm diameter) on tooth surface.2) Fluoride concentration on the approximal surfaces were higher in older persons than in younger persons. The fluoride concentrations on the buccal surface increased transiently after eruption and then decreased. The decrease of fluoride concentration appeared to be most remarkable near the biting edge of the buccal surface in earlier stage.3) The differences in the fluoride concentrations between the approximal surfaces and the buccal surface in the group of unerupted teeth were not significant, but in the older group the approximal surface showed significantly higher fluoride concentrations than the buccal surface.4) The gourp of unerupted teeth showed significantly lower fluoride concentrations than the: group of erupted teeth, and the most scattered value of all.5) Enamel solubility tended to decrease first and then to drop to a plateau shortly after eruption.6) There were no differences in the enamel solubility between the approximal surfaces and the buccal susface, but in the older group the approximal surface. showed lower enamel solubility than the buccal surface.7) The group of unerupted teeth showed the least scattered values of all in the enamel solubility. The enamel solubility of the approximal surfaces tended to be more dispersed than that of the buccal surface.8) There was a reverse relationship between fluoride concentration and enamel solubility.

Charged particle analysis of fluorine distributions in the surface of human tooth enamel

The E p = 340 keV resonance in the 19 F( p, αγ) 16 O reaction was used to measure the fluorine depth distributions, up to a maximum of 1.4 μm, and the lateral distributions in three contralateral pairs of human incisors. The maximum concentration was just below the surface at 0.18 μm, followed by a rapid decrease at greater depths. To quantify the shapes of these depth profiles a ‘one micron reduction factor’ was defined. Highest concentrations and the flattest profiles were near the cervical margin for all samples. The hypothesis is offered of transport via pumping action along inter-crystal spaces particularly in interprism regions.

The effect of tooth wear on the distribution of fluoride in the enamel surface of human teeth

Distribution curves, describing the change in fluoride concentration from the surface to the interior of enamel, were determined in different regions of the tooth surface in a large number of permanent human anterior teeth of different ages and types, from districts with and without fluoride in the water supply. The distribution curves varied considerably from place to place in the tooth surface, often being shallow towards the biting edge of the tooth and steeper in cervical and approximal regions. These differences in the shape of the curves seemed largely attributable to wear. There was also a variation in the curves with age and type of tooth. The lost fluoride was not apparently restored by post-eruptive uptake, even in teeth from a district where the fluoride concentration of the water supply was relatively high.