Investigation of three home-applied bleaching agents on enamel structure and mechanical properties: an in situ study

Whitening Efficacy of 3% Carbamide Peroxide Gel Activated by Lactoperoxidase

Objective

The aim of this clinical study was to evaluate the effectiveness of a whitening toothpaste containing 3% carbamide peroxide and lactoperoxidase. Materials and methods. Participants were instructed to brush their teeth using an enzymatic-activated dentifrice following a particular procedure for three weeks. Color was recorded before and after treatment using a VITA Easyshade spectrophotometer. Differences in L^∗ (tooth color lightness), a^∗ (displacement along the red-green axis), and b^∗ (displacement along the yellow-blue axis) were measured before and after treatment using the paired t and the Wilcoxon signed-rank tests. Color changes (Δ_E) were calculated using the obtained measurements.

Results

Thirty-four volunteers were included. Δ_E was 4.03. For the set of 348 teeth, a greater tendency towards green (lower a^∗) and blue (lower b^∗) was observed (p < 0.05). There were no significant differences in lightness after treatment. Mandibular central incisors showed a greater tendency towards green (lower a^∗) and blue (lower b^∗). Bleaching effectiveness was observed in both the upper and lower central incisors and in the lateral mandibular incisors.

Conclusion

Based on these results, it may be concluded that brushing with an enzymatic-activated dentifrice is effective for whitening teeth.

Does comsumption of staining drinks compromise the result of tooth whitening?

Background

After dental bleaching procedures dentists commonly advise patients to reduce the consumption of beverages that may cause the teeth to stain, however, the effectiveness of teeth whitening may not be directly affected by diet.

Material and Methods

It was evaluated through in vitro study whether contact with dyes through in-office bleaching sessions with 35% hydrogen peroxide would influence the effectiveness of treatment. Sixty bovine incisors were randomly assigned into 5 groups (n = 12) according to contact frequency and type of dye solutions. All dental elements received three in-office bleaching sessions with 35% hydrogen peroxide one week apart. Except for GCTRL (control), all experimental groups were submerged in dyes (coffee or wine) for 5 min once a day. In groups GC24 and GW24 contact with the dyes was made from 24 hours after each bleaching session, while in groups GC72 and GW72, from 72 hours. The color was measured with a digital spectrophotometer. Data were expressed as statistics: mean and standard deviation.

Results

Contact with dyes during in-office bleaching treatment with 35% hydrogen peroxide did not influence the staining averages after three bleaching sessions. The speed of the whitening effect was influenced by contact with coffee from 24 hours after the sessions and with wine from 24 hours and 72 hours after the whitening session. The whitening result was reversed after one week for all groups, especially for groups that came in contact with red wine either 24 hours or 72 hours after session and coffee after 24 hours.

Conclusions

Contact with dyes during in-office bleaching treatment did not influence the final staining averages after three bleaching sessions although there was influence on speed of the whitening effect between the sessions. Key words:Tooth bleaching, hydrogen peroxide, spectrophotometry.

Adverse effects of respiratory disease medicaments and tooth brushing on teeth: A scanning electron microscopy, X-ray fluorescence and infrared spectroscopy study

The present study aims to evaluate the effect of brushing with fluoride dentifrice on teeth severely affected by erosion due to respiratory medicaments. Enamel (n = 50) and dentin (n = 50) bovine specimens were prepared and treated with artificial saliva (S-control), acebrofilin hydrochloride (AC), ambroxol hydrochloride (AM), bromhexine hydrochloride (BR), and salbutamol sulfate (SS) and subjected to cycles of demineralization (immersing in 3 mL, 1 min, three times a day at intervals of 1 hr, for 5 days) followed by remineralization (saliva, 37°C, 1 hr). Simulated brushing with fluoridated toothpaste was performed using 810 strokes in a reciprocal-action brushing simulator. Scanning electron microscopy, micro energy dispersive X-ray fluorescence (μ-EDXRF) spectroscopy and attenuated total reflection Fourier transform infrared (ATR FTIR) spectroscopy were then performed. μ-EDXRF images showed extensive erosion after treatment with all medicaments. SEM images showed enamel erosion in order SS > BR > AC = AM > S after brushing and fluoridation. FTIR results were in agreement. In case of dentin, μ-EDXRF measurements showed significant difference in mineral content (percent weight of calcium and phosphate) in SS + brushing + fluoridation treated enamel compared to control, while μ-EDXRF images showed erosive effects in the order SS > AM>BR > AC = S post brushing + fluoridation. SEM images showed erosion in the order SS > AM = BR > AC > S post brushing + fluoridation. Again, FTIR multivariate results were in agreement. Overall, our study shows that proper oral care is critical when taking certain medication. The study also demonstrates the possible use of FTIR for rapid clinical monitoring of tooth erosion in clinics.

Enamel sample preparation for AFM: Influence on roughness and morphology

Human dental enamel is organized by prisms that are structured between 3 and 6 µm in diameter. Determining the relationships between different treatments on the surface of enamel using ultrastructural analysis is the purpose of many in vitro experiments. Different sample pretreatments have been reported in the literature. Grinding and polishing are common procedures for enamel preparation. They provide a flat and standardized surface, which is imperative for the use of some techniques such as ATR-FTIR. However, for morphological analysis, SEM and AFM represent easier methods to measure and reduce the biological sample variation. Therefore, the objective of this study was to establish how different forms of enamel preparation can influence the advent of artifacts during ultrastructural observation, especially by AFM analysis. Four groups (n = 10) were tested: (a) without preparation; (b) polishing with a diamond paste; (c) grinding with decreasing granulations of silicon carbide papers; (d) grinding with polishing. Images were obtained using the Peak-Force Tapping mode. After the first images were obtained, all fragments were acid etched with 37% phosphoric acid for 30 seconds, rinsed for 60 seconds, and dried intensively. Upon grinding and polishing, the exposure of the inner enamel surfaces provided a less mineralized layer that was marked by scratches and a higher susceptibility to treatments. Moreover, using native enamel provided more valuable information on the surface and the roughness changes for clinical applications. In addition, phosphoric acid is an option for observing the prismatic arrangement after grinding and/or polishing changes the morphology. RESEARCH HIGHLIGHTS: The use of native enamel samples to investigate the effects of different treatments on surface should be preferred in research, when the technique allows it.

Hydrogen Peroxide Might Bleach Natural Dentin by Oxidizing Phosphoprotein

Recent studies suggested that bleaching agents may whiten teeth by oxidizing the fluorescent materials, which are the proteins located in the organic-inorganic interface. Therefore, we postulated that fluorescence of dentin came from dentin phosphoprotein (DPP) and that bleaching agents might bleach dentin by oxidizing DPP. Fifty-six specimens were randomly divided into 4 groups and exposed to distilled water, hydrogen peroxide (HP), ethylenediamine tetraacetic acid disodium salt (EDTA), and acetic acid for 24 h. After measuring the organic and inorganic components, fluorescence, and color characteristics of dentin before and after exposure, we found that when DPP was removed from dentin by EDTA, fluorescent intensity declined proportionally with the reduction in Raman relative intensity, and dentin was whitened considerably, with an Δ E value 6 times higher than that of the distilled water group. On the contrary, due to the incapability of acetic acid to dissolve DPP during decalcification, fluorescent intensity values and tooth color remained nearly unchanged after exposure to acetic acid. Dentin exposed to neutral HP showed no obvious morphologic and organic/inorganic component changes except for the destruction of DPP. Similarly, dramatically decreased fluorescent intensity and lightened color were found in the HP group. Moreover, DPP solution of the HP group exhibited decreased ultraviolet absorbance, especially between 250 and 300 nm, which arose from aromatic amino acids. The results indicated that DPP was responsible for the fluorescent properties of dentin and that HP might bleach dentin by the oxidization of aromatic amino acids in DPP. These findings are of great significance in promoting our further understanding of the mechanism of tooth bleaching and the fluorescent property of normal dentin.

Titanium dioxide in dental enamel as a trace element and its variation with bleaching

Background

Titanium is a less studied trace element in dental enamel. Literature relates an increased Titanium concentration with a decreased enamel crystal domain size, which in turn is related to a higher color value. The aim of our study was to analyze the effect of tooth bleaching agents on its concentration in dental enamel by means of confocal Raman spectroscopy.

Material and Methods

Human teeth were randomly distributed in six experimental groups (n=10) and submitted to different bleaching protocols according to the manufacturer´s instructions. Confocal Raman spectroscopy was carried out in order to identify and quantify the presence of titanium dioxide molecules in enamel prior to and during whitening. Statistical analysis included repeated measures analysis of variance (p≤0.05) and Bonferroni pairwise comparisons.

Results

Titanium dioxide concentration was negatively affected by the longer bleaching protocols (at-home bleaching gels). All in-office whitening products increased significantly the studied molecule (p≤0,05).

Conclusions

All dental specimens depicted the presence of titanium dioxide as a trace element in dental enamel. Bleaching gels that have to be applied at higher concentrations but for shorter periods of time increase the concentration of titanium dioxide, whilst at-home whitening gels used for longer periods of time despite the lower concentration caused a loss in titanium.

Key words:Bleaching, whitening, hydrogen peroxide, carbamide peroxide, Raman spectroscopy, titanium dioxide.

In Situ and In Vitro Effects of Two Bleaching Treatments on Human Enamel Hardness

The aim of this study was to evaluate in vitro and in situ the effects of two bleaching treatments on human enamel surface microhardness. Sixty enamel slabs from recently extracted thirty molars were used. The specimens were polished with sandpapers under water-cooling. The enamel samples were randomly divided in four groups, treated with 10% hydrogen peroxide (HP) or Whitening Strips (WS) containing 10% hydrogen peroxide and using two conditions: in vitro or in situ model. For in situ condition, six volunteers wore an intra-oral appliance containing enamel slabs, while for in vitro condition the specimens were kept in deionized water after the bleaching protocols. The bleaching treatments were applied one-hour daily for 14 days. Similar amounts of bleaching agents were used in both conditions. Before and after bleaching treatments, microhardness was measured. Statistical analysis (ANOVA and Tukey test) showed that in the in situ condition there was no statistically significant microhardness reduction in the bleached enamel (p>0.05). Significant decrease in hardness was observed for enamel slabs bleached with both treatments in the in vitro condition (p<0.05). Regarding the bleaching agents, in situ results showed no difference between HP and WS, while in vitro WS produced the lowest hardness value. It could be concluded that there was no deleterious effect on enamel produced by any of the bleaching protocols used in the in situ model. The reduction of hardness was only observed in vitro.

Effect of tooth-bleaching on the carbonate concentration in dental enamel by Raman spectroscopy

Background

There are not many studies evaluating the effects of surface treatments at the molecular level. The aim of this in vitro study was to analyze the concentration of carbonate molecules in dental enamel by Raman spectroscopy after the application of in-office and home whitening agents.

Material and Methods

Sixty human teeth were randomly divided into six groups and exposed to three different home bleaching gels (Day White) and three in-office whitening agents (Zoom! Whitespeed and PolaOffice) according to the manufacturer´s instructions. The concentration of carbonate molecules in enamel was measured prior to and during the treatment by means of Raman spectroscopy. Statistical analysis included repeated measures analysis of variance (p≤0.05) and Bonferroni pairwise comparisons.

Results

At home bleaching agents depicted a decrease in the carbonate molecule. This decrease was statistically significant for the bleaching gel with the highest hydrogen peroxide concentration (p≤0,05). In-office whitening agents caused an increase in carbonate, which was significant for all three groups (p≤0,05).

Conclusions

In-office bleaching gels seem to cause a gain in carbonate of the enamel structure, whilst at-home whitening gels caused a loss in carbonate.

Key words:Bleaching, whitening, hydrogen peroxide, carbamide peroxide, Raman spectroscopy, carbonate.

A simple, sensitive and non-destructive technique for characterizing bovine dental enamel erosion: attenuated total reflection Fourier transform infrared spectroscopy

Although many techniques are available to assess enamel erosion in vitro, a simple, non-destructive method with sufficient sensitivity for quantifying dental erosion is required. This study characterized the bovine dental enamel erosion induced by various acidic beverages in vitro using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Deionized water (control) and 10 acidic beverages were selected to study erosion, and the pH and neutralizable acidity were measured. Bovine anterior teeth (110) were polished with up to 1 200-grit silicon carbide paper to produce flat enamel surfaces, which were then immersed in 20 mL of the beverages for 30 min at 37 °C. The degree of erosion was evaluated using ATR-FTIR spectroscopy and Vickers' microhardness measurements. The spectra obtained were interpreted in two ways that focused on the ν1, ν3 phosphate contour: the ratio of the height amplitude of ν3 PO4 to that of ν1 PO4 (Method 1) and the shift of the ν3 PO4 peak to a higher wavenumber (Method 2). The percentage changes in microhardness after the erosion treatments were primarily affected by the pH of the immersion media. Regression analyses revealed highly significant correlations between the surface hardness change and the degree of erosion, as detected by ATR-FTIR spectroscopy (P<0.001). Method 1 was the most sensitive to these changes, followed by surface hardness change measurements and Method 2. This study suggests that ATR-FTIR spectroscopy is potentially advantageous over the microhardness test as a simple, non-destructive, sensitive technique for the quantification of enamel erosion.

Bioactive calcium phosphate cement with excellent injectability, mineralization capacity and drug-delivery properties for dental biomimetic reconstruction and minimum intervention therapy

CPC could be used as a promising biomaterial to reconstruct the breached enamel on exposed dentin through a biomimetic and minimally invasive way.

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.

Compositional, structural and mechanical comparisons of normal enamel and hypomaturation enamel

Hypomaturation amelogenesis imperfecta is a hereditary disorder of the enamel that severely influences the function, aesthetics and psychosocial well-being of patients. In this study, we performed a thorough comparison of normal and hypomaturation enamel through a series of systematical tests on human permanent molars to understand the biomineralization process during pathological amelogenesis. The results of microcomputed tomography, scanning electron microscopy, Fourier transform infrared, Raman spectroscopy, microzone X-ray diffraction, thermal gravimetric analysis, energy diffraction spectrum and Vickers microhardness testing together show dramatic contrasts between hypomaturation enamel and normal enamel in terms of their hierarchical structures, spectral features, crystallographic characteristics, thermodynamic behavior, mineral distribution and mechanical property. Our current study highlights the importance of the organic matrix during the amelogenesis process. It is found that the retention of the organic matrix will influence the quantity, quality and distribution of mineral crystals, which will further demolish the hierarchical architecture of the enamel and affect the related mechanical property. In addition, the high carbonate content in hypomaturation enamel influences the crystallinity, crystal size and solubility of hydroxyapatite crystals. These results deepen our understanding of hypomaturation enamel biomineralization during amelogenesis, explain the clinical manifestations of hypomaturation enamel, provide fundamental evidence to help dentists choose optimal therapeutic strategies and lead to improved biofabrication and gene therapies.

Safety issues of tooth whitening using peroxide-based materials

In-office tooth whitening using hydrogen peroxide (H₂O₂) has been practised in dentistry without significant safety concerns for more than a century. While few disputes exist regarding the efficacy of peroxide-based at-home whitening since its first introduction in 1989, its safety has been the cause of controversy and concern. This article reviews and discusses safety issues of tooth whitening using peroxide-based materials, including biological properties and toxicology of H₂O₂, use of chlorine dioxide, safety studies on tooth whitening, and clinical considerations of its use. Data accumulated during the last two decades demonstrate that, when used properly, peroxide-based tooth whitening is safe and effective. The most commonly seen side effects are tooth sensitivity and gingival irritation, which are usually mild to moderate and transient. So far there is no evidence of significant health risks associated with tooth whitening; however, potential adverse effects can occur with inappropriate application, abuse, or the use of inappropriate whitening products. With the knowledge on peroxide-based whitening materials and the recognition of potential adverse effects associated with the procedure, dental professionals are able to formulate an effective and safe tooth whitening regimen for individual patients to achieve maximal benefits while minimising potential risks.