Erosive effects of different acids on bovine enamel: release of calcium and phosphate in vitro

Dynamics of Dental Enamel Surface Remineralization under the Action of Toothpastes with Substituted Hydroxyapatite and Birch Extract

To address tooth enamel demineralization resulting from factors such as acid erosion, abrasion, and chronic illness treatments, it is important to develop effective daily dental care products promoting enamel preservation and surface remineralization. This study focused on formulating four toothpastes, each containing calcined synthetic hydroxyapatite (HAP) in distinct compositions, each at 4%, along with 1.3% birch extract. Substitution elements were introduced within the HAP structure to enhance enamel remineralization. The efficacy of each toothpaste formulation was evaluated for repairing enamel and for establishing the dynamic of the remineralization. This was performed by using an in vitro assessment of artificially demineralized enamel slices. The structural HAP features explored by XRD and enamel surface quality by AFM revealed notable restorative properties of these toothpastes. Topographic images and the self-assembly of HAP nanoparticles into thin films on enamel surfaces showcased the formulations' effectiveness. Surface roughness was evaluated through statistical analysis using one-way ANOVA followed by post-test Bonferroni's multiple comparison test with a p value < 0.05 significance setting. Remarkably, enamel nanostructure normalization was observed within a short 10-day period of toothpaste treatment. Optimal remineralization for all toothpastes was reached after about 30 days of treatment. These toothpastes containing birch extract also have a dual function of mineralizing enamel while simultaneously promoting enamel health and restoration.

Erosion behaviour of human, bovine and equine dental hard tissues

Dental hard tissues from different species are used in dental research, but little is known about their comparability. The aim of this study was to compare the erosive behaviour of dental hard tissues (enamel, dentin) obtained from human, bovine and equine teeth. In addition, the protective effect of the pellicle on each hard tissue under erosive conditions was determined. In situ pellicle formation was performed for 30 min on enamel and dentin samples from all species in four subjects. Calcium and phosphate release was assessed during 120 s of HCl incubation on both native and pellicle-covered enamel and dentin samples. SEM and TEM were used to examine surface changes in native enamel and dentin samples after acid incubation and the ultrastructure of the pellicle before and after erosive exposure. In general, bovine enamel and dentin showed the highest degree of erosion after acid exposure compared to human and equine samples. Erosion of human primary enamel tended to be higher than that of permanent teeth, whereas dentin showed the opposite behaviour. SEM showed that eroded equine dentin appeared more irregular than human or bovine dentin. TEM studies showed that primary enamel appeared to be most susceptible to erosion.

Sensors for in situ monitoring of oral and dental health parameters in saliva

OBJECTIVES

The oral cavity is an easily accessible unique environment and open system which is influenced by the oral fluids, microbiota, and nutrition. Little is known about the kinetics and dynamics of metabolic processes at the intraoral surfaces. Real-time monitoring of salivary biomarkers, e.g., glucose, lactate, fluoride, calcium, phosphate, and pH with intraoral sensors is therefore of major interest. The aim of this review is to overview the existing literature for intraoral saliva sensors.

MATERIALS AND METHODS

A comprehensive literature search was performed to review the most relevant studies on intraoral saliva sensor technology.

RESULTS

There is limited literature about the in situ saliva monitoring of salivary biomarkers. Bioadhesion and biofouling processes at the intraoral surfaces limit the performances of the sensors. Real-time, long-term, and continuous intraoral measurement of salivary metabolites remains challenging and needs further investigation as only few well-functioning sensors have been developed until today. Until now, there is no sensor that measures reliably beyond hours for any analyte other than glucose.

CONCLUSIONS

Saliva's complex and dynamic structure as well as bioadhesion are key challenges and should be addressed in the future developments. Consequently, more studies that focus particularly on biofouling processes and interferential effects of the salivary matrix components on sensor surfaces are required.

CLINICAL RELEVANCE

By monitoring fluids in the oral cavity, as the entrance to the digestive system, extensive information can be obtained regarding the effects of foods and preventive agents on the oral microbiota and the tooth surfaces. This may lead to a better understanding of strategies to modulate oral and general health.

The Influence of Beverages on Resin Composites: An In Vitro Study

Dental composites, through their structural diversity, represent the biomaterials frequently used in dental reconstructive therapy. The aim of our study was to observe the influence of different beverage environment conditions on seven types of obturation dental materials with different compositions. Our research focused on the surface modification analysis of the materials after the immersion in the different beverages; in this regard, we used the EDAX technique correlated with the energy-dispersive X-ray fluorescence (XRF). The pH of the drinks and that of the simulated saliva solution were determined by the titrimetric method, a sodium hydroxide solution 0.1 mol/dm3 was prepared and used for the titration. An amount of 5 mL of each analyzed solution was added to 15 mL of distilled water to obtain a dilution, to which 3 drops of phenolphthalein (as a color indicator-Phenolphthalein, 3,3-Bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone, C20H14O4 Mw: 318.32, purchased from Merck) were added for each analysis. For each solution, the experiment was repeated three times in order to obtain accurate results. The results of our study materialized into a real plea for modifying the patients' behavior in terms of diet and preferences for acidic drinks, so that their quality-of-life valence can be improved by keeping the composite materials in a long-term unalterable state on the one hand; on the other hand, systemic damage can be prevented as well.

Effect of Various Beverages on Adhesion of Repaired CAD/CAM Restorative Materials

(1) Background: The purpose of this study was to determine the effect of commonly consumed beverages on the bond strength of three different computer-aided design-computer-aided manufacturing (CAD/CAM) resin-ceramic hybrid materials repaired with resin-based composite (RBC) materials. (2) Materials and Methods: Rectangular prism specimens (N = 138) measuring 6 mm × 5 mm × 2 mm were obtained from GC Cerasmart (GC), Lava Ultimate (LU), and Vita Enamic (VE) blocks. These blocks were polished and then subjected to thermal cycling (10,000 cycles, 5 °C to 55 °C). After the surface treatment was applied, the average surface roughness value was measured. All the surfaces were repaired with RBC. Thermal cycling was performed for the second time. Each group was then distributed into three subgroups according to the beverage used: tea (t), cola (c), and distilled water (0) (n = 15). The specimens were stored in these solutions for 28 days and then subjected to the shear bond strength (SBS) test. Statistical analysis was performed using a two-way ANOVA test with Bonferroni adjustment. (3) Results: The surface roughness of the materials presented no significant difference after different surface treatments (p > 0.05). No significant difference was observed among the materials (p > 0.05). Tea and cola presented similar SBS values (p > 0.05). Both were significantly lower than distilled water (p < 0.001, p < 0.001, respectively). (4) Conclusions: Consumption of beverages reduces the bond strength in surfaces repaired with RBC to CAD/CAM resin-ceramic hybrid materials. (5) Clinical Significance: Repairing damaged resin matrix dental restorations with RBC is advantageous in terms of time and cost by achieving adequate bond strengths. Frequently consumed beverages reduce the bond strength of repaired CAD/CAM resin-ceramic hybrid materials.

Erosive potential of ice tea beverages and kombuchas

OBJECTIVES

Kombuchas and other tea-based beverages are often perceived as healthy products despite the lack of knowledge on their effects on oral health. This in vitro study determined the erosive potential of commercial kombuchas, and ice teas compared to cola drinks.

MATERIALS AND METHODS

The pH and fluoride content of 7 kombuchas and 18 tea drinks were measured with ion-selective electrodes. Calcium dissolution from hydroxyapatite grains was quantified by atomic absorption spectroscopy after beverage exposure. The effect of beverages on the enamel surface was visualized by scanning electron microscopy (SEM). Distilled water, and cola drinks were used as negative and positive controls.

RESULTS

The kombuchas exhibited lower pH values (2.82-3.66) than the ice teas (2.94-4.86), but still higher than the cola drinks (2.48-2.54). The fluoride concentration varied between 0.05 and 0.46 ppm and for 7 beverages the concentration was below the detection limit. The calcium release for kombuchas was 198-746 mg/l, for ice teas 16.1-507 mg/l, and for cola drinks 57.7-71.9 mg/l. Twenty-two beverages had a significantly greater calcium release than the cola drinks (p = .009-.014). The surface etching of the enamel was seen in the SEM analysis after beverage exposure.

CONCLUSIONS

Tea-based beverages have even higher erosive potential than cola drinks. Kombuchas especially, displayed a considerable erosive potential.

A comparative study of two chemical models for creating subsurface caries lesions on aprismatic and prismatic enamel

PURPOSE

To investigate the mineral density and lesion depth of artificial caries lesions on aprismatic enamel and prismatic enamel created by lactic acid and acetic acid buffers.

METHODS

Forty bovine enamel blocks were allocated to: aprismatic enamel (Group A) and prismatic enamel (Group C) in acetic acid buffer for 192 h and aprismatic enamel (Group B) and prismatic enamel (Group D) in lactic acid buffer for 96 h. The mineral loss and lesion depth were measured using micro-computed tomography.

RESULTS

A significant difference (P = 0.01) was observed in the mineral loss (%) in the lesions on aprismatic enamel and prismatic enamel treated with lactic acid buffer while no significant difference (P = 0.51) was observed in the mineral loss (%) in the lesions on aprismatic enamel and prismatic enamel treated with acetic acid buffer. No significant difference was noted in the mean lesion depth of lesions on aprismatic enamel and prismatic enamel treated with acetic acid and lactic acid buffers (P > 0.05).

CONCLUSION

Aprismatic enamel and prismatic enamel have similar mineral loss in acetic acid while prismatic enamel showed more mineral loss compared to aprismatic enamel in lactic acid.

The dynamic interplay of dietary acid pH and concentration during early-stage human enamel and dentine erosion

Dental erosion continues to be a significant global health concern affecting nearly 30% of adults world-wide. With increasing soft drink consumption predominantly driving its prevalence, strategies for prevention and control are often implemented when erosion is severe, or rates are high in the populace. While factors affecting dental erosion such as pH on enamel has received much attention, the effect of dietary acid concentration when factored out to a commercially available pH has yet to be determined. Furthermore, understanding these effects on dentine, which is known to be more susceptible to erosion than enamel can unravel structure property relationships between acid characteristics and hard tissue types. This study aimed to develop structure-property relationships between dietary acid concentration, and pH, on the nano-textural and nano-mechanical properties of human enamel and dentine during short-term simulated drinking. To achieve this, a novel sample preparation methodology and analysis approach was developed by applying atomic force microscopy (AFM) in quantitative imaging mode. This enabled simultaneous measurement of enamel and dentine morphology and mechanical properties. Flow-cells were used to simulate drinking, exposing polished and smear layer free human enamel and dentine to 30 s repeated cycles of unbuffered citric acid 6% (pH = 1.88) and 1% (w/v) (pH = 2.55) and commercially available buffered pH = 3.8 states, for up to 180 s. The same 50 µm × 50 µm area of specimen morphology was analysed using in-house developed nanotextural analysis using the bearing area curve (BAC) with a focus on roughness (Ra), normalised peak (PA) and valley areas (VA). Mechanical properties were simultaneously measured for stiffness (N/m) after each 30 s. While all studies agree pH is a major factor in the erosion of enamel, here its dominance over the treatment time varied, with concentration surpassing the importance of pH after initial acid contact. Conversely, dentine erosion showed concentration-dependent changes in morpho-mechanical properties only. These results not only highlight the dynamic process of erosion, but how the interplay between acid characteristics and dental tissue type impact the progression of very early-stage erosion.

The impact of remineralization agents on dental bleaching efficacy and mineral loss in bleached enamel

This study evaluated the effect of remineralization agents on bleaching efficiency, enamel mineral changes, and post-bleaching color stability. A total of 112 enamel-dentin blocks were prepared from bovine teeth. Following initial color measurements, separate treatment regimens were carried out as follows: negative control (no treatment); positive control (bleaching only); bleaching, then NaF; bleaching + NaF (mix); bleaching, then CPP-ACPF; bleaching + CPP-ACPF (mix); bleaching, then nHAP+F; bleaching + nHAP+F (mix). Color measurements were repeated after immersion in distilled water for 7 days, and again after staining with coffee solution for 14 days. The CIELAB-based whiteness index was used to evaluate bleaching efficiency, and the CIEDE2000 color difference formula for color stability. Chemical investigation was performed using scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction analyses. The experimental groups showed significant increases in whiteness compared to the negative control, and the staining after bleaching did not result in statistically significant differences between the groups. Energy dispersive spectroscopic analysis revealed that bleaching protocols had no impact on elemental levels as well as the ratio of Ca/P. The combined use of bleaching agents with remineralization agents did not affect bleaching effectiveness but also did not provide an additional contribution.

The Strong Protective Action of Ce3+/F- Combined Treatment on Tooth Enamel and Epithelial Cells

We studied the toxic effects of cerium and fluoride species on human dental pulp stem cells and epithelial cells of Cercopithecus aethiops as a surrogate for the human oral mucosa. The sequential use of CeCl₃ and NH₄F solutions in equimolar sub-toxic concentrations enabled the possible toxic effects of individual components to be avoided, ensuring the preservation of the metabolic activity of the cells due to the formation of CeF₃ nanoparticles. Cerium fluoride nanoparticles and terbium-doped cerium fluoride nanoparticles exhibited neither cytotoxicity nor genotoxicity to dental pulp stem cells, even at high concentrations (10^-4 M). In millimolar concentrations (from 10^-5-10^-6 M), these nanoparticles significantly increased the expression of genes responsible for the cell cycle, differentiation and proliferation. The formation of cerium fluoride on the surface of the mucous membrane and teeth provided protection against the development of carious lesions, periodontitis, ROS attacks and other inflammatory diseases of the oral cavity. Luminescent CeF₃: Tb nanoparticles enabled the visualization of tooth enamel microcracks.

Human Enamel Fluorination Enhancement by Photodynamic Laser Treatment

Poor oral hygiene leads to serious damages of theteeth’s surface enamel such as micro-abrasions and acid erosion. These alterations combined with bacterial plaque result in cavity appearance. Prophylactic measures include various techniques for enamel surface restoration. Fluorination is one of the most important treatments for this purpose. Therefore, in the present research, we investigated the classical fluorination treatment compared with laser photodynamic fluorination performed on human enamel samples with poor surface quality. Three sample groups were investigated: veneer (F), inlay (I), and crowns (C). The general morphologic aspect was investigated by scanning electron microscopy (SEM), and the specific details such as the fine microstructure and nanostructure were investigated by atomic force microscopy (AFM) of the surface roughness. The samples were also investigated by Fourier transformed infrared attenuated total reflectance (FTIR-ATR) to evidence the fluorination effect on the enamel surface. Results showed that all initial samples had an altered state with micro-abrasions and erosion with mineral loss, which increase the surface roughness. The F group was the most damaged, having a higher roughness, and the I group was less damaged. Classic fluorination treatment partially restored the enamel by local re-mineralization, but did not obtain the parameters of healthy enamel. However, a significant decrease of the roughness was observed (statistical relevance p = 0.001 with the Breusch–Pagan Test). This fact was supported by the presence of newly formed fluorides in the FTIR-ATR spectra. The photodynamic laser fluorination restores the enamel in an enhanced manner by a strong re-mineralization, which implies a significant roughness value decrease comparable to healthy enamel. The Breusch–Pagan Test confirmed the relevance with p = 0.001. This is due to an extended re-mineralization abundant in fluoride crystals as observed by AFM and FTIR. Statistical p-values regarding laser application were in the range of 0.02–0.06, supporting its relevance in the fluorination effect. The final conclusion is that the photodynamic effect is able to favor the newly formed fluoride deposition onto the affected sites of the enamel surface.

Unveiling the Solubilization of Potassium Mineral Rocks in Organic Acids for Application as K-Fertilizer

Organic acids produced by soil microorganisms can be useful to promote the release of potassium (K) from potassium mineral rocks (KR), but the complexity of low reactivity minerals limits K solubilization and their use as fertilizer. Here, we investigate the ways that different organic acids (gluconic, oxalic, and citric) can affect the solubilization of potassium minerals, in order to propose process strategies to improve their solubility. For this, evaluations were performed using the model minerals KR_polyhalite (sedimentary mineral), KR_feldspar (igneous mineral), and KCl (commercial fertilizer). For KCl and KR_polyhalite, complete solubilization was achieved using all the organic acids, while for KR_feldspar, the highest K⁺ solubilization (34.86 mg L^-1) was achieved with oxalic acid. The solubility of KR_feldspar was further investigated under submerged cultivation with the filamentous fungus Aspergillus niger, as well as after a mechanochemical grinding treatment. The biotechnological route resulted in solubilized K up to 63.2 mg L^-1. The mechanochemical route, on the other hand, increased the release of K by about 8.6 times (993 mg L^-1) compared to the natural mineral, due to the greater fragmentation of the particles after the treatment (with a surface area about 2.5 times higher than for the in natura KR_feldspar). These findings demonstrated the potential of applying biotechnological and mechanochemical routes with organic acids to improve the solubilization of K present in low reactivity mineral rocks, indicating the possible use of these minerals in more sustainable agricultural practices.

Adsorption of malic acid at the hydroxyapatite/aqueous NaCl solution interface

The aim of the study was the basic incidence on the phenomenon of adsorption that occurs at the hydroxyapatite/malic acid interface, leading to a change in the surface properties of hydroxyapatite, Analytical methods used in the research: X-ray diffraction (XRD) as well as by the, adsorption–desorption of nitrogen (ASAP), potentiometric titration. The specific adsorption of malic acid ions at the hydroxyapatite interface was investigated by means of the radioisotope method. The zeta potential of hydroxyapatite dispersions was determined by electrophoresis with Zetasizer Nano ZS90 by Malvern. The particle sizes of hydroxyapatite samples were analyzed using Masteriszer 2000 Malvern. Studies on the kinetics of malic acid on hydroxyapatite from a solution with an initial concentration of 1 mmol/dm3 have shown that the adsorption process is initially fast, followed by a slow adsorption step. An increase in the pH of the solution causes a decrease in the malic acid adsorption as a result of competition with hydroxyl ions. The presence of adsorbed malic acid was confirmed by the FTIR measurements. The effect of malic acid adsorption on the zeta potential and particle size distribution of hydroxyapatite in the NaCl solution was investigated.

The Influence of Popular Beverages on Mechanical Properties of Composite Resins

Currently, composite resins are used in many restorative procedures. Previous studies showed that drinking beverages may affect the mechanical properties such as microhardness or flexural strength of dental composite resins. The aim of the present study was to investigate the influence of common beverages on the mechanical properties of composite resins. Samples of the materials were prepared according to the ISO 4049:2010 standard and producer’s recommendations. The samples were next conditioned in tested fluids: distilled water, sparkling water, Coca-Cola, Red Bull and orange juice for 7 days. Vickers microhardness and flexural strength testing was performed after 7 days. Performed statistic tests confirmed the significance of microhardness changes of the tested materials in terms of both different conditioning of the samples and different composite materials. The mean flexural strength of composites was highest in distilled water and it was reduced after one week in different beverages. We conclude that all tested beverages influenced on Vickers microhardness of tested composite resins. Flexural strength only in one material was statistically significantly influenced by tested beverages. The results of this study should be taken into consideration by a dentist preparing recommendations for the patients after dental treatment with usage of composite material or after cementing composite based fixed dentures.

Adsorption of the Tartrate Ions in the Hydroxyapatite/Aqueous Solution of NaCl System

The research on the interaction of tartrate ions with the surface of hydroskyapatite was presented, including the measurements of the kinetics of tartrate ion adsorption and tartrate ion adsorption as a function of pH. The adsorption of tartrate ions was calculated from the loss of tartrate concentration in the solution as measured by a radioisotope method using C-14 labeled tartaric acid. In order to explain the mechanism of interaction of tartrate ions with hydroxyapatite, supplementary measurements were carried out, i.e., potentiometric measurements of the balance of released/consumed ions in the hydroxyapatite/electrolyte solution system, zeta potential measurements, FTIR spectrophotometric measurements and the hydroxyapatite crystal structure and particle size distribution were characterized. It was found that the adsorption of tartrate ions occurs as a result of the exchange of these ions with hydroxyl, phosphate and carbonate ions. Replacing the ions with the abovementioned tartrate ions leads to the appearance of a negative charge on the surface of the hydroxapatite. On the basis of XRD study and particle size distribution, a decrease in the size of crystallites and the diameter of hydroxyapatite particles in contact with a solution of 0.001 mol/dm³ of tartaric acid was found.

Baseline Specimens of Erosion and Abrasion Studies

The difficulty in obtaining human teeth that are caries-free that have similar environmental exposure, e.g., diet intake and water fluoridation has lead researchers to opt for bovine teeth as a substitute for erosion studies. Bovine mandibular incisors are readily available at abattoirs and often originate from the same region and are likely to consume similar dietary intake. The bovine teeth for erosion or abrasion studies usually undergo specimen preparation to produce a "flat surface" baseline specimen. Among other terms used to define baseline specimens for erosion and abrasion studies include phrases like "optically flat" and "flat and smooth surface." However, these terms might have no quantitative value as it does not justify the actual surface characteristics of the prepared flattened surface. In dentistry, roughness average (Ra) is the most commonly used parameter when reporting the roughness of specimens Reporting Ra alone might not be sufficient as it does not provide information regarding the surface texture as there is no distinction between valleys and peaks, nor does it provide information about the core structure of a material unlike the bearing area curve. The incorporation of Ra and BAP values in baseline specimens has the potential in predicting the wear or lubricating potential of these specimens. Furthermore, standardization of baseline specimens by acknowledging its surface roughness values ensures comparability of erosion and abrasion studies as different specimen preparation technique might influence the outcome or results of research.

Response of pulp cells to resin infiltration of enamel white spot-like lesions

OBJECTIVES

To investigate the trans-enamel and trans-dentinal biological effects of treating enamel white spot-like lesions (EWSLs) with resin infiltration components (RICs) on odontoblast-like cells (MDPC-23) and human dental pulp cells (HDPCs).

METHODS

EWSLs were induced in 60 enamel/dentin discs (4.0 ± 0.2 mm thick) using S. mutans. The discs were adapted into artificial pulp chambers and MDPC-23 were seeded on the dentin surface. The components of a resin infiltration system (Icon) were applied individually or in combination on the enamel surface as following (n = 10/treatment): Etch, Infiltrant, Etch+Infiltrant, or Etch+Dry+Infiltrant. The application of water or hydrogen peroxide served as negative and positive controls, respectively. After 72 h, MDPC-23 viability was evaluated. The extracts were exposed for 72 h to pre-cultured MDPC-23 and HDPCs in 96-well plates to evaluate cell viability, alkaline phosphatase activity (ALP), mineralized nodule formation (MN), and the expression of inflammatory cytokines (ICs) and mineralization-related genes (MRs). Data were analyzed by ANOVA complemented with Tukey or Games-Howell post-hocs (α = 5%).

RESULTS

Cell viability, ALP activity, and MN formation were significantly reduced in response to the RICs, presenting intermediate values compared to positive and negative controls. Likewise, ICs were upregulated, whereas MRs were downregulated. Among the RICs, the Etch component caused the most notorious detrimental effects.

SIGNIFICANCE

Resin infiltration of EWSLs negatively affected the metabolism of pulp cells in vitro. Therefore, even though resin infiltration is a micro-invasive therapy for non-cavitated caries in enamel, it should be closely followed up seen that components may diffuse and unbalance pulp homeostasis.

The effect of red wine in modifying the salivary pellicle and modulating dental erosion kinetics

This study investigated the potential of red wine in modulating dental erosion kinetics in the presence or absence of salivary pellicle. Polished human enamel specimens were used in two conditions; presence or absence of acquired enamel pellicle; and subdivided according to exposure: red wine, orange juice, apple juice, or citric acid. The specimens were incubated in clarified whole human saliva (presence of acquired enamel pellicle) or in a humid chamber (absence of acquired enamel pellicle) for 2 h at 37°C, then in the test substances for 1 min, at 25°C, under shaking. This was repeated four times. Surface hardness was measured initially and after each cycle and surface reflection intensity was measured initially and after all cycles. In the presence of acquired enamel pellicle, red wine caused the least surface hardness loss, followed by orange juice, apple juice, and citric acid. Statistically significantly less surface reflection intensity loss was observed for red wine and orange juice than for apple juice and citric acid. In the absence of acquired enamel pellicle, red wine and orange juice caused less surface hardness loss than apple juice and citric acid. Orange juice showed the least surface reflection intensity loss, followed by red wine, citric acid, and apple juice. The polyphenol composition of these drinks can notably modulate the erosion kinetics.

Efficacy of silver diamine fluoride and sodium fluoride in inhibiting enamel erosion: an ex vivo study with primary teeth

PURPOSE

To assess the efficacy of silver diamine fluoride (SDF) and sodium fluoride (NaF) in inhibiting enamel erosion in primary teeth.

METHODS

80 primary canine teeth were immersed for 24 h in 2% NaF, 10% SDF, or distilled water. Afterward, some of them underwent a 10-min acid challenge using either 1% or 10% citric acid while others did not. Specimens selected for negative controls were immersed in distilled water but not exposed to the acids, whereas those selected for positive controls were not only immersed in distilled water, but also exposed to the acids. Following, 3-mL samples were collected for calcium and phosphorus analysis by an atomic emission spectrometer.

RESULTS

1% acid caused higher phosphorus loss in the positive control group than in the others (no differences between them). Regarding 10% acid, the SDF group showed lower phosphorus loss compared to the positive control and NaF groups. From calcium loss analysis, SDF and NaF groups presented no significant difference when compared to the positive control groups after both acidic challenges.

CONCLUSION

Considering phosphorus loss values, 10% SDF seems to be effective in inhibiting enamel erosion after 1% and 10% citric acid challenges, whereas 2% NaF only after 1% citric acid challenge. Regarding calcium loss values, both fluoride agents seem to have no impact on inhibiting enamel erosion after 1% and 10% citric acid challenges.

Stannous Fluoride Preventive Effect on Enamel Erosion: An In Vitro Study

The aim of this in vitro study was to evaluate the effects of a single dose application of two daily toothpastes on enamel exposed to acid attack. The research was conducted on human molars enamel fragments (n = 72). The two different toothpastes active ingredients were sodium fluoride (NaF) and stannous fluoride (SnF₂). They were compared in protecting the surface of the enamel exposed to three acids: citric acid, lactic acid and hydrochloric acid. A spectrophotometer was used to measure the calcium ions and phosphate released in the solutions by the enamel specimens. Afterward, ionic concentrations were analyzed through the t-Student test, in order to estimate the significance level (p < 0.05) of the solubility differences obtained between the treatment and control groups. Finally, sample surfaces were analyzed with scanning electron microscopy and X-ray energy dispersive spectroscopy (SEM/EDX). The two analyzed toothpastes did not reveal any statistically significant variation in the release of calcium and phosphate (p > 0.05). Nevertheless, acid-resistant deposits were detected in samples treated with stannous fluoride and exposed to lactic acid, though the presence of tin ion deposits on samples treated with stannous fluoride was not shown. A single dose of a fluoride-based toothpaste before different acids attack, in simulated oral cavity conditions, did not show a significant preventive effect.

Vinegar inhibits the formation of oral biofilm in situ

Background

Vinegar has been recognized as an effective antimicrobial agent for long. This study intended to elucidate the effect of commercially available vinegar on in situ pellicle formation and existing 24-h biofilms.

Methods

In situ biofilm formation took place on bovine enamel slabs mounted in individual splints and exposed intraorally over 3 min and 24 h, respectively. After 5 s rinsing with vinegar, all samples were analyzed via fluorescence microscopy (FM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, salivary samples were collected and analyzed via FM. Samples with water rinsing served as controls.

Results

Vinegar caused destruction of the pellicle. Compared to the control group, vinegar rinsing reduced the outer globular layer of the pellicle (p < 0.001), and resulted in formation of subsurface pellicle. Also, vinegar rinsing could reduce bacterial viability and disrupt the 24-h biofilm. Total bacteria amount of saliva samples decreased remarkably (p < 0.001) after vinegar rinsing within 30 min. Reduction of bacterial viability was observed even 120 min after vinegar rinsing in both biofilm and saliva sample (p < 0.001).

Conclusion

This in situ study reveals that rinsing with vinegar for only 5 s alters the pellicle layer resulting in subsurface pellicle formation. Furthermore, vinegar rinsing will destruct mature (24-h) biofilms, and significantly reduce the viability of planktonic microbes in saliva, thereby decreasing biofilm formation.

Relationship between Changes in Chemical Composition of Enamel Subsurface Lesions and the Emitted Nonlinear Optical Signals: An in vitro Study

The development of new diagnostic technologies based on the light scattering and autofluorescence properties of dental tissues is required to improve the diagnostic ability of initial caries lesions earlier than previously done and promoting the potential of treatment without surgical intervention. The aim of this study is to correlate fluorescence-based results provided by multiphoton microscopy (MPM) with confocal Raman microscopy records using phosphate level at 960 cm-1 and the organic matrix at ∼2,931 cm-1 in healthy and demineralized human enamel. Measurements on 14 teeth were made using two incident lights of different wavelengths, released by confocal Raman microscopy and MPM. Raman phosphate peak intensity at 960 cm-1 along with organic to mineral ratio at (2,931/430 cm-1) and nonlinear optical signals (second harmonic generation [SHG] and intrinsic two-photon excited fluorescence [I2PEF]) were recorded from the demineralized and healthy enamel sites. Raman spectral maps showed that the higher the organic/mineral ratio in the demineralized enamel, the lower the intensity of mineral component in the same zone. MPM revealed new optical indicators of carious lesion as shown by the presence of a red-shifted fluorescence peak in the 650- to 750-nm area of the fluorescence spectrum of demineralized enamel. Moreover, on sample regions with insignificant autofluorescence, the emergence of the SHG signal could be noted. By comparing I2PEF images with the structural motifs observed by the confocal Raman imaging system, the morphological similarity of the acquired images was quite evident. Any change in the I2PEF spectra reflects alterations in the chemical composition of enamel. These findings may provide an important basis for potentially valuable applications of photonic tools in the clinical diagnosis of tooth pathological conditions, besides exposing the fundamental role of organic matrix in enamel integrity and reparation.

Prevention of Enamel Softening by Rinsing with a Calcium Solution before Dental Erosion

OBJECTIVES

This in situ study aimed to evaluate whether rinsing with a calcium-containing solution prior to an erosive attack reduces the softening of enamel.

MATERIALS AND METHODS

A total of 240 bovine enamel samples with determined baseline surface microhardness (KHN) were allocated to 5 runs in which each of the 12 volunteers performed the following experiment: 4 enamel samples were inserted in a custom-made intraoral appliance and carried in the mouth (upper jaw) for 30 min before each volunteer either rinsed his mouth for 60 s with a fluoride- and stannous ion-containing dental erosion protection mouth rinse as positive control (run 1), milk (run 2), a solution prepared from a 500-mg calcium effervescent tablet dissolved in 100 mL (run 3) or 200 mL (run 4) water, or did not perform any rinsing with a test solution before the erosive attack (run 5, negative control). To simulate the erosive attack, volunteers rinsed their mouth with a commercial soft drink (Sprite Zero) for 60 s and afterwards with water to stop the erosive process. Finally, surface microhardness was measured again and hardness loss (ΔKHN) calculated. A mixed effect model was fitted to the data set to investigate whether the different runs showed differences with respect to ΔKHN.

RESULTS

No significant difference in softening of enamel (mean of ΔKHN; lower confidence level/upper confidence level) was observed between the negative control run 5 (50.7; 60.8/40.6), run 2 (50.7; 60.8/40.6), run 3 (38.7; 48.8/28.6) and run 4 (40.7; 50.8/30.6) (p > 0.05, respectively). Enamel softening in the positive control run 1 (25.4; 35.6/15.3) was significantly lower compared to the softening in run 5 (p < 0.001). No significant difference was observed between run 1 and run 3 (p = 0.09).

CONCLUSION

Other than the fluoride- and stannous ion-containing dental erosion protection mouth rinse, none of the investigated calcium-containing solutions is able to significantly reduce erosion-induced softening of enamel.

Dentin tubule obturation of a bioglass-based dentin desensitizer under repeated exposure to lactid acid and brushing

Background

Dentin hypersensitivity is a frequent finding especially in periodontitis patients. Conventional treatment aims for obstruction of dentin tubules by disabling liquid and osmotic fluctuation to and from the pulpal chamber. A novel bioglass-based desensitizer was shown to obstruct tubules and to resist periodic exposure to lactic acid. Whether this obstruction is resistant to brushing had not been tested so far. Accordingly, the present study aimed to assess dentin tubule obstruction after repeated acid exposure and brushing.

Methods

Sixty dentin discs were cleaned with 17% EDTA, mounted into a pulp fluid simulator and randomly divided into 3 groups: No surface treatment in Group A, Seal&Protect® in group B and DentinoCer in group C. Discs were exposed to 0.1 M non-saturated lactic acid thrice and standardized brushing twice a day for 12 days. At baseline and after 2, 4 and 12 d samples were removed from the setting and prepared for top-view SEM analysis to assess tubule obstruction using the Olley score. Discs were then vertically cut and the section surface morphologically assessed using backscatter imaging. For both vertical and sectional surfaces EDX analysis was used to characterize the surface composition in the tubular and inter-tubular area.

Results

Group A showed clean tubular lumina at all time points. From day 2 onwards dentin showed exposed collagen fibers. Group 2 initially showed a complete surface coverage that flattened out during treatment without ever exposing tubules. At baseline, samples of Group C displayed a complete homogeneous coverage. From day 2 on tubules entrances with obstructed lumen became visible. While on day 4 and 12 the dentin surface exposed collagen fibers the lumina remained closed. EDX analysis of the vertical and horizontal views showed that P and Ca were predominant elements in both the inter- and tubular dentin while Si peaks were found in the tubule plugs.

Conclusion

While group B displayed a packed layer on the surface during the whole investigation time group C samples lost their superficial layer within 48 h. Tubule plugs containing considerable Si proportions indicated previous presence of DentinoCer, while high Ca and P proportions suggest obturation by dentin-like material.

Surface analysis of etched enamel modified during the prenatal period

Structural changes in the enamel surface subjected to induced demineralization and assessment of the influence of prenatal administration of β-hydroxy β-methylbutyrate (HMB) on enamel resistance were investigated. The examination was conducted on five sets of teeth from one-day-old spiny mice (Acomys cahirinus), one from the control and four from the experimental groups. Surface structure, molecular arrangement and crystalline organization of offspring's enamel both before and after etching were studied. Obtained results revealed that the physical and molecular arrangements of enamel were altered after the prenatal supplementation, and significantly affected its final structure and resistance against acid action. The enamel of incisors from the offspring which mothers were supplemented with HMB in a high dose (0.2 g/kg_bw) and in the late period of gestation (26th-39th day) showed the highest endurance against acid treatment demonstrating only vestigial changes in their surface structure after acid action. Comparing to the remaining experimental groups, it was characterized by a reduced roughness and fractal dimension, significantly lower degree of demineralization and simultaneous lack of notable differences in the Raman spectra before and after acid etching. The results suggest that an increased enamel resiliency was the effect of a relatively high degree of mineralization and higher organization of the surface.

Erosion-Protective Capacity of the Salivary Pellicle of Female and Male Subjects Is Not Different

This study aimed to analyse if the erosion-protective potential of the salivary pellicle is different between female and male subjects. Bovine enamel and dentin specimens (each n = 3) were exposed to the oral cavity of healthy female or male volunteers (each n = 25, females: 25.8 ± 3.5 years, males: 26.7 ± 4.0 years) for 120 min to form a salivary pellicle. Subsequently, each 2 enamel and 2 dentin specimens were eroded with hydrochloric acid (pH 2.6, 60 s). Specimens of the control group (each n = 30) were eroded without presenting a salivary pellicle. Calcium release into the acid was determined photometrically. Additionally, total protein content in the pellicle (each n = 1 enamel and dentin specimen/volunteer) and different salivary parameters (flow rate, pH, buffer capacity, protein, albumin, calcium, phosphate, fluoride) were assessed. Statistical analyses were performed by one-way ANOVA, t tests, multiple linear regressions and Pearson correlations (p < 0.05). The erosion-protective capacity was not significantly different among female (calcium release [% of control]: enamel: 82.6 ± 28.1, dentin: 80.7 ± 24.0) and male (enamel: 76.0 ± 27.5, dentin: 87.1 ± 34.9) subjects. The protein content of the pellicle was not different between female and male subjects. The protein content and pH of unstimulated saliva were significantly reduced in female compared to male volunteers. Calcium release was neither correlated with the protein content of the salivary pellicle nor with salivary parameters. Under the conditions of the present study, the erosion-protective capacity of the salivary pellicle of female and male subjects is not different.

Effect of fluoride mouthrinses and stannous ions on the erosion protective properties of the in situ pellicle

The particular feature of this study is the investigation of effects of pure fluoride- or stannous ions based mouthrinses on the erosion protective properties and the ultrastructure of the in situ pellicle (12 volunteers). Experimental solutions were prepared either from 500 ppm NaF, SMFP, AmF or SnF₂ or 1563 ppm SnCl₂, respectively. After 1 min of in situ pellicle formation on bovine enamel slabs, rinses with one of the preparations were performed for 1 min and intraoral specimens’ exposure was continued for 28 min. Native enamel slabs and rinses with bidestilled water served as controls. After oral exposure, slabs were incubated in HCl (pH 2; 2.3; 3) for 120 s and kinetics of calcium- and phosphate release were measured photometrically; representative samples were analysed by TEM and EDX. All mouthrinses reduced mineral loss compared to the native 30-min pellicle. The effect was pH-dependent and significant at all pH values only for the tin-containing mouthrinses. No significant differences were observed between the SnF₂- and the SnCl₂-containing solutions. TEM/EDX confirmed ultrastructural pellicle modifications. SnF₂ appears to be the most effective type of fluoride to prevent erosive enamel demineralisation. The observed effects primarily have to be attributed to the stannous ions’ content.

Effect of Toothpaste Use Against Mineral Loss Promoted by Dental Bleaching

AIM

To investigate the effect of different toothpaste formulations used prior to dental bleaching with 35% hydrogen peroxide (HP) on the mineral content and surface morphology of enamel.

METHODS

Seventy bovine enamel blocks (4×4×2 mm) were submitted to in vitro treatment protocols using a toothbrushing machine prior to dental bleaching or a placebo procedure (n=10) as proposed in the following groups: unbleached control (PLA), bleached control (HP), and brushing with differing toothpastes prior to HP bleaching, including: potassium nitrate toothpaste containing sodium fluoride (PN), sodium monofluorophosphate/MFP toothpaste (FT), arginine-carbonate (8% arginine) (PA) or arginine-carbonate (1.5% arginine) toothpaste (SAN), and toothpaste containing bioactive glass (NM). Phosphorus concentration in gel ([P]) was evaluated (μg of P/mg of gel), and the elemental levels (wt%) of Ca, P, and Na as well as the proportion between Ca and P and spectra graphics were determined using an energy-dispersive X-ray spectrometer (EDS). The surface morphology was assessed using scanning electron microscopy (SEM). The data were subjected to analysis of variance and the Tukey test (α=0.05).

RESULTS

HP demonstrated the greatest [P] values in gel, being statistically different from PLA. The [P] of NM was statistically similar to PLA. HP showed a significant decrease in the Ca% and Ca/P values when compared to PLA in EDS analysis. PA showed Ca/P values statistically different from HP. In accordance with SEM analysis, the PA, SAN, and NM groups presented a smooth and uniform enamel surface, while HP and FT demonstrated some alterations in morphology.

CONCLUSION

The toothpastes containing bioactive glass or arginine carbonate used prior to dental bleaching were effective in protecting enamel against mineral loss promoted by the whitening procedure.

Obtaining scratch-free specimens of dental enamel prepared by sectioning, grinding, polishing, and acid etching for scanning electron microscopy

The aim of the present study was to identify the stage during acid etching of dental enamel where scratches introduced by sectioning and grinding procedures were eliminated. Nitric acid was used as etchant. Four hundred 2-3 mm-thick longitudinal sections of human third molar crowns were assigned to 80 groups, each group differing with respect to grinding procedure (silicon carbide paper grit 600; 1,000; 1,200; and 1,200 + polishing), acid concentration (0.1%, 1%, 2.5%, and 5%) and etching time (15, 30, 45, 90, and 180 s). Observation of the specimens with scanning electron microscopy (SEM) showed that elimination of scratches was facilitated by increasing fineness of grinding paper and polishing, and by increasing acid concentration and increasing etching time. An acid concentration of 0.1% did not remove scratches totally irrespective of grinding procedure or etching time, 1% acid removed most scratches after 45-90 s, while 2.5% and 5% acids removed most scratches after 30-45 s. It is proposed that the scratches are eliminated/obscured through a combined effect of the acid and the inherent structure of the enamel. The results of the present study may serve as a guide in choosing the best procedures for obtaining scratch-free enamel surfaces through acid etching with the least possible loss of enamel substance. Research highlights Sectioning and grinding produce scratches in dental enamel. Scratches are eliminated by acid etching prior to SEM studies of enamel structure. Scratch elimination increases with increasing acid strength and etching time and is facilitated by finer grit grinding paper and polishing.

The effect of aspartame and pH changes on the erosive potential of cola drinks in bovine enamel: An in vitro study

BACKGROUND

The aim of this study was to clarify the mechanism behind the different erosive potential of regular and light cola drinks: pH difference and/or aspartame presence.

MATERIAL AND METHODS

Sixty bovine enamel blocks were randomly divided into 5 groups: RC - regular cola, RCpH - addition of base to increase regular cola pH, RCAS - addition of aspartame to regular cola, LC - light cola, and LCpH - addition of acid to decrease light cola pH. Two-thirds of the blocks surface was coated with nail varnish for reference. The samples were daily subjected to four erosive challenges for 2 minutes. Between the erosive challenges (2h) and overnight the samples were maintained in artificial saliva. The response variable was the percentage surface hardness change (%SHC) after 1st experimental day and enamel surface loss (µm) measured at the 5th day by profilometry. Data were analyzed by ANOVA and Tukey's test (p<0.05).

RESULTS

Independently of the cola modifications, all groups promoted similar hardness change of enamel surface. RC promoted higher enamel loss (6.69±0.71µm) than LC (4.80±0.77µm). The acid addition to light cola (LCpH: 6.60±1.78µm) significantly enhanced its erosive potential, which did not differ from RC. The base addition to regular cola (RCpH-4.00±0.64µm) resulted in similar wear to LC. The addition of aspartame to the regular cola (RCAS 5.44±0.65µm) resulted in similar wear to LC and RC.

CONCLUSIONS

The data suggest that the pH alteration has a major impact on the erosive potential of cola drinks, however, the sweetener also has some influence. Key words:Tooth erosion, dental enamel, soft drinks, ph, sweetener.

Prevention of erosive tooth wear: targeting nutritional and patient-related risks factors

This article provides an overview of the nutritional and patient-related risk factors involved in the aetiology of erosive tooth wear (ETW) and the preventive strategies to counteract them. The first step is to diagnose clinical signs of ETW and to recognise causal factors. Low pH and high buffer capacity of foods/drinks are the major risk factors, while the calcium concentration is the main protective factor. Reduction of frequency of consumption and contact time of erosive foods/drinks with the teeth, use of straws appropriately positioned and consumption of dairy products are advisable. Oral hygiene has a role in the development of ETW, however, postponing toothbrushing is not clinically advisable. In cases of drug abuse, chronic alcoholism, GERD or bulimia, the patient must be referred to a doctor. Immediately after vomiting, patients might be advised to rinse the mouth. Saliva has an important protective role and patients with reduced salivary flow can benefit from the use of chewing gum. Recent studies have focused on improving the protective capacity of the acquired pellicle as well as on the role of protease inhibitors on dentine erosion. However, the degree of evidence for these preventive measures is low. Clinical trials are necessary before these measures can be recommended.

The presence of acquired enamel pellicle changes acid-induced erosion from dissolution to a softening process

Erosive wear undermines the structural properties of enamel resulting in irreversible enamel loss. A thin protein layer formed from natural saliva on tooth surfaces, acquired enamel pellicle (AEP), protects against erosive wear. The exact components in saliva responsible for such protection are not yet known. We prepared three solutions containing different components: proteins and ions [natural saliva (NS)], minerals with no proteins [artificial saliva (AS)] and neither proteins nor ions [deionised water (DW)]. To assess the protection of the three solutions against citric acid enamel erosion, enamel specimens were immersed in the corresponding solution for 24 h. All specimens were then exposed to five erosion cycles, each consisted of a further 30 min immersion in the same solution followed by 10-min erosion. Mean step height using a non-contacting profilometer, mean surface microhardness (SMH) using Knoop microhardness tester (final SMH), and roughness and 2D profiles using atomic force microscopy were measured after five cycles. The final SMH values were compared to the starting values (after 24 hr). NS group had significantly less tissue loss but greater SMH change (P < 0.0001) than AS and DW groups. Specimens in NS were softer and rougher (P < 0.001) but less eroded than specimens in AS and DW.

Are grape juices more erosive than orange juices?

AIMS

To evaluate the chemical characteristics of grape and orange juices, and their erosive potential in the decrease of microhardness and the loss of enamel structure.

METHODS

Five grape and orange juices were evaluated for pH, titratable acidity, calcium, phosphate, and fluoride concentration. De-ionised water and Cola soft drink were used as a negative and positive control, respectively. Twelve specimens of bovine enamel were immersed in beverages for 10 min at 37 °C, 3 times/day for 7 days. Erosive potential was quantified using microhardness and loss of enamel structure. Anova One Way, Student's t test, Multiple Regression and Spearman Correlation (p < 0.05) were used to analyse the results.

RESULTS

Powdered grape juice showed the lowest pH (3.18 ± 0.03) and pure grape juice presented the highest titratable acidity (5.48 ± 0.06 mL NaOH/100 mL). Fresh orange juice and soya-based grape juice revealed the lowest calcium (0.77 ± 0.12 mmol/L) and phosphate concentrations (0.35 ± 0.06 mmol/L), respectively. Among juices, powdered orange juice caused the greatest decrease in surface microhardness (SMH) (127.99 ± 40.47 ΔSMH) and grape juice from concentrate caused the greatest loss of enamel structure (13.30 ± 3.56 μm).

CONCLUSIONS

All of the evaluated juices contributed to dental erosion. Grape juices presented greater erosive potential than orange juices. Pure, powdered and concentrated grape juices showed similar loss of enamel structure to the Cola soft drink. The erosive potential of beverages was statistically correlated to pH, titratable acidity, calcium, phosphate and fluoride concentrations.

Evaluation of the effectiveness of micro-Raman spectroscopy in monitoring the mineral contents change of human enamel in vitro

The purpose of this in vitro study was to investigate the efficacy of micro-Raman spectroscopy on detecting mineral content change during the demineralization and de/remineralization cycling process. The enamel samples (n = 55) were randomly divided into three groups and separately treated with demineralization solution (n = 20), de/remineralization cycling solution (n = 30), and distilled water (n = 5). Micro-Raman spectroscopy, microhardness (MHS), and the released calcium ions concentration were performed before and after treatment, respectively. A one-way analysis of variance (ANOVA) with a post hoc Tukey test was used to analyze the results. The Spearman correlation coefficients among the parameters of Raman relative intensity decrease (RRI_D%), the percentage of MHS loss (PML), and the released calcium ions concentration were also analyzed. In demineralization group, RRI_D%, PML, and released calcium ions concentration were highly correlated with each other (r = 0.979, p < 0.001; r = 0.984, p < 0.001; and r = 0.983, p < 0.001, respectively). While for the de/remineralization cycling group, there also existed a high correlation between RRI_D% and PML (r = 0.987, p < 0.001). In conclusion, micro-Raman spectroscopy could effectively monitor the mineral content change, and its efficacy was validated by the measurement of released calcium ions concentration and MHS.

Effect of Tannic Acid on the Protective Properties of the in situ Formed Pellicle

OBJECTIVES

In the present in situ/ex vivo study the impact of tannic acid on the erosion-protective properties of the enamel pellicle was tested. Additionally, the antiadherent and antibacterial effects of tannic acid were evaluated.

METHODS

The pellicle was formed in situ on bovine enamel samples fixed on individual splints worn by 6 subjects. Following 1 min of pellicle formation the volunteers rinsed for 10 min with tannic acid. After further oral exposure for 19 min, 109 min, and 8 h overnight, respectively, slabs were incubated in HCl ex vivo (pH 2.0, 2.3, 3.0) over 120 s. Subsequently, kinetics of calcium and phosphate release were measured photometrically. Samples after a 1-min fluoride mouth rinse as well as enamel samples with and without a 30-min in situ pellicle served as controls. Antiadherent effects were evaluated after a 1-min rinse with tannic acid and oral exposure of the slabs overnight. DAPI (4',6-diamidino-2-phenylindole) combined with concanavalin A staining and live/dead staining was used for fluorescence microscopic visualization and quantification of adherent bacteria and glucans. Modification of the pellicle's ultrastructure by tannic acid was evaluated by transmission electron microscopy (TEM).

RESULTS

Tannic acid significantly improved the erosion-protective properties of the pellicle in a pH-dependent manner. Bacterial adherence and glucan formation on enamel were significantly reduced after rinses with tannic acid as investigated by fluorescence microscopy. TEM imaging indicated that rinsing with tannic acid yielded a sustainable modification of the pellicle; it was distinctly more electron dense.

CONCLUSION

Tannic acid offers an effective and sustainable approach for the prevention of caries and erosion.

Techniques to Evaluate Dental Erosion: A Systematic Review of Literature

This article reviews different techniques for evaluating dental erosion, weighs the advantages and disadvantages of these techniques, and presents the latest trends in the study of dental erosion. In May 2014, an initial search was carried out in the PubMed/MEDLINE database of indexed journals from 1975 to 2013 using the following keywords: dental erosion; dental erosion In-vitro; and dental erosion in-vivo. Bibliographic citations from the papers found were then used to find other useful sources. The authors categorize the techniques into three classes: in-vitro, in-vivo and in-vitro/in-vivo. The article discusses the instrumentation required to use each of these techniques, as well as their rationale, merits and applications. The emergence of in-vitro/in-vivo techniques offers the potential to accurately quantify tooth wear in clinical situations. Cross-sectional as well as longitudinal studies show that these techniques will improve diagnosis, treatment planning and management of dental erosion.

Effect of Inula viscosa on the pellicle's protective properties and initial bioadhesion in-situ

OBJECTIVES

The present in situ study investigated the effect of Inula viscosa tea on the pellicle's acid protective properties and on initial oral biofilm formation.

DESIGN

Biofilm formation was performed on bovine enamel slabs on individual maxillary splints. Following 1min of pellicle formation, eight subjects rinsed for 10min with Inula viscosa tea and the splints remained for 8h intraorally. Samples carried after 1-min rinsing with CHX (0.2%) or without rinse served as controls. BacLight™ staining, 4',6-diamidino-2-phenylindole (DAPI)-staining and fluorescence in situ hybridization (FISH) were used for fluorescence microscopic detection of adherent bacteria. For investigation of acid protective properties, three subjects rinsed for 10min with Inula viscosa tea after 1min pellicle formation and kept the splints intraorally for further 19min. Physiological 30-min pellicles and native enamel samples served as controls. After HCl incubation of the samples ex-vivo over 120s (pH 2.0, 2.3, 3.0) calcium- and phosphate release were quantified photometrically. Potential influences on the pellicle's ultrastructure by Inula viscosa tea were evaluated by transmission electron microscopy (TEM).

RESULTS

Application of Inula viscosa tea yielded a significant reduction of adherent bacteria on all enamel samples as detected by fluorescence microscopy. For calcium- and phosphate release no significant effect was recorded. TEM investigation indicated a modification of the pellicle's ultrastructure, but no enhanced protection against erosive noxae.

CONCLUSION

Rinsing with Inula viscosa tea influences the bacterial colonization on enamel in situ over 8h but has no impact on acid protective properties of the pellicle.

Application of Plant Extracts for the Prevention of Dental Erosion: An in situ/in vitro Study

OBJECTIVES

Antiadherent and antibacterial effects of certain plant extracts have been proven to be beneficial in preventive dentistry. In the present in situ/in vitro crossover study, the impact of plant extracts rich in polyphenols on the erosion-protective properties of the in situ pellicle was evaluated.

METHODS

Individual splints were prepared for 12 subjects for intraoral exposure of bovine enamel specimens. Following formation of a 1-min pellicle, watery plant extracts (leaves of the wild form of Ribes nigrum, the wild form of Origanum as well as a combination of both) were administered for 10 min in situ. Alternatively, a mouth rinse with fluorides (Elmex Kariesschutz) was performed for 1 min. After further oral exposure for 19/28 min, respectively, slabs were removed and incubated with HCl in vitro over 120 s (pH 2, 2.3, 3). The resulting calcium and phosphate release was quantified photometrically. Slabs with and without a 30-min in situ pellicle served as controls. The modification of pellicle ultrastructure was evaluated by transmission electron microscopy (TEM).

RESULTS

Plant extracts modulated the erosion-protective properties of the native in situ pellicle in all test groups in a pH-dependent manner. The combination of R. nigrum leaves and Origanum enhanced the protective properties of the pellicle at all pH values; the administration of this preparation was comparable, yet superior, to the effect of the fluoridated mouth rinse. TEM images indicated that rinsing with R. nigrum leaves/Origanum yielded a distinctly thicker and more electron-dense pellicle.

CONCLUSION

The combination of certain plant extracts offers a novel approach to the complementary prevention of dental erosion.

In vitro effects of hydrogen peroxide combined with different activators for the in-office bleaching technique on enamel

OBJECTIVE

The aim of this study was to evaluate the alteration of human enamel bleached with high concentrations of hydrogen peroxide associated with different activators.

MATERIALS AND METHODS

Fifty enamel/dentin blocks (4 × 4 mm) were obtained from human third molars and randomized divided according to the bleaching procedure (n = 10): G1 = 35% hydrogen peroxide (HP - Whiteness HP Maxx); G2 = HP + Halogen lamp (HL); G3 = HP + 7% sodium bicarbonate (SB); G4 = HP + 20% sodium hydroxide (SH); and G5 = 38% hydrogen peroxide (OXB - Opalescence Xtra Boost). The bleaching treatments were performed in three sessions with a 7-day interval between them. The enamel content, before (baseline) and after bleaching, was determined using an FT-Raman spectrometer and was based on the concentration of phosphate, carbonate, and organic matrix. Statistical analysis was performed using two-way ANOVA for repeated measures and Tukey's test.

RESULTS

The results showed no significant differences between time of analysis (p = 0.5175) for most treatments and peak areas analyzed; and among bleaching treatments (p = 0.4184). The comparisons during and after bleaching revealed a significant difference in the HP group for the peak areas of carbonate and organic matrix, and for the organic matrix in OXB and HP+SH groups. Tukey's analysis determined that the difference, peak areas, and the interaction among treatment, time and peak was statistically significant (p < 0.05).

CONCLUSION

The association of activators with hydrogen peroxide was effective in the alteration of enamel, mainly with regards to the organic matrix.

Enamel structural changes induced by hydrochloric and phosphoric acid treatment

PURPOSE

The aim of this study was to evaluate enamel acid-induced structural changes after 2 different treatments, by means of Raman and infrared (IR) spectroscopy analyses, and to correlate these findings with permeability measured as fluid discharge from outer enamel.

METHODS

Two different treatments were investigated: 10 enamel slices were etched with 15% hydrochloric acid (HCl) for 120 seconds and 10 slices with 37% phosphoric acid gel (H3PO4) for 30 seconds, rinsed for 30 seconds and then air-dried for 20 seconds. Powders of enamel treated as previously described were produced. Replicas of enamel subjected to the same treatments were obtained to evaluate the presence of fluid droplets on enamel surface.

RESULTS AND CONCLUSIONS

Raman and IR spectroscopy showed that the treatment with both hydrochloric and phosphoric acids induced a decrease in the carbonate content of the enamel apatite. At the same time, both acids induced the formation of HPO42- ions. After H3PO4 treatment, the bands due to the organic component of enamel decreased in intensity, while they increased after HCl treatment. Replicas of H3PO4 treated enamel showed a strongly reduced permeability. Replicas of HCl 15% treated samples showed a maintained permeability. A decrease of the enamel organic component, as resulted after H3PO4 treatment, involves a decrease in enamel permeability, while the increase of the organic matter (achieved by HCl treatment) still maintains enamel permeability.The results suggested a correlation between organic matter and enamel permeability. Permeability was affected by etching technique and could be involved in marginal seal, gap and discoloration at the enamel interface, still causes of restoration failure.

Possible ways of reducing dental erosive potential of acidic beverages

Frequent consumption of acidic beverages is related to excessive tooth wear, namely dental erosion. Preventive measures may involve reduction or elimination of acidic drink consumption. However, the success of this approach is difficult to achieve as it is highly dependent on patient compliance. Therefore, a practical way of minimizing the erosive potential of popular acidic drinks may be their chemical modification. The aim of this article was to review the different methods of modification and their shortcomings. The available literature demonstrates that the erosive potential of most acidic beverages could be reduced. To date, the effectiveness of soluble calcium salts supplementation is the best established. However, modification can reduce the sensorial quality of the drink and shorten its shelf-life. There is also a need to evaluate the lowest effective and safe dose of the additive.