Effect of different storage conditions on the physical properties of bleached enamel: An in vitro vs. in situ study

Development of toothpaste formulations containing mineral clays as abrasive agents and their effects on the physical properties of dental enamel

To assess the physical properties and topographical aspect of dental enamel's surface microhardness (KHN), surface roughness (Ra), and color parameters CIELAB (∆Eab*), CIEDE 2000 (∆E00), and whiteness index for dentistry (∆WID) after toothbrushing with experimental toothpaste formulations with the following mineral clay types: kaolin, Sparclay SGY, and Tersil CGY used as abrasive component. Scanning electron microscopy (SEM) was performed for topographical analyses purposes. A total of 96 bovine incisors were used in the experiment. They were divided into eight experimental groups (n = 12), namely: NC-negative control (no treatment), CT12-Colgate Total 12®, CMP-Colgate® Máxima Proteção Anticáries, K-kaolin experimental toothpaste, SGY-Sparclay SGY experimental toothpaste; CGY-Tersil CGY experimental toothpaste, SD-SiO2 experimental toothpaste, and CC-CaCO3 experimental toothpaste. All samples were subjected to mechanical brushing protocol with 5000 cycles and kept in artificial saliva with daily exchanges. KHN was analyzed through the mixed linear model for repeated measures over time. Ra was analyzed through nonparametric Kruskal Wallis and Dunn tests to compare the groups. Paired Wilcoxon test was run to compare experimental times. ∆WID, ∆Eab*, and ∆E00 were analyzed through Kruskal Wallis and Dunn tests. All analyses were performed in R* software, at 5% significance level. EXP_SGY recorded higher KHN than EXP_SiO2 and EXP_CaCO3, whereas EXP_K showed increased Ra in comparison to CMP (p = 0.0229). ∆Eab and ∆E00 were significantly higher in the CT12, EXP_SiO2, and EXP_CaCO3 groups than in the NC and EXP_K (p < 0.0001). There were no significant changes in ∆WID (p = 0.0852). According to SEM results, toothbrushing with experimental toothpastes added with mineral clay types did not have significant impact on enamel's polishing and smoothness. CLINICAL RELEVANCE: Mineral clays have a broad application in the cosmetic industry, and recently, they have been used in the formulation of vegan toothpaste.

Analysis of Calcium and Phosphate Ion Extraction From Dental Enamel by Bleaching Gels Using Ion Chromatography, Micro-CT, and SEM

OBJECTIVES

To evaluate the volume and depth of enamel loss promoted by 37.5% and 7.5% hydrogen peroxide (HP) gels, and quantify the loss of calcium (Ca) and phosphate (P) ions by using ion chromatography (IC) analysis after bleaching.

METHODS

Sixty bovine enamel specimens were randomly divided into three groups: Control - no bleaching gel; HP37.5%, application of HP 37.5% for 45 minutes for 14 days; and HP7.5%, application of HP 7.5% for 3 applications of 8 minutes. The surface analysis (n=5) was performed using a scanning electron microscope (SEM) and dispersive energy system (EDS) to calcium and phosphorus dosage. The micro-CT was used for the enamel loss analysis (n=5). IC was used to analyze extracted Ca and P (n=10). Data were analyzed by one-way ANOVA and two-way repeated measures ANOVA, followed by Tukey and Dunnett's tests (α=0.05).

RESULTS

Significantly higher volume and depth of enamel loss were found for bleached groups compared with the control group. HP7.5% had significantly higher enamel change than HP37.5%. SEM showed higher enamel porosity for HP37.5% and HP7.5% compared to control. The IC demonstrated a significant increase of Ca incorporated into the gel, however, only HP7.5% had a higher P presence than the control group. The HP7.5% showed higher Ca and P ion exchange than HP37.5% (p<0.001).

CONCLUSION

HP37.5% and HP7.5%, caused enamel mineral changes compared with the control group. The IC method was demonstrated to be an effective methodology for detecting enamel mineral loss by the bleaching gel.

Effect of experimental bleaching gels with polymers Natrosol and Aristoflex on the enamel surface properties

Natrosol and Aristoflex® AVC polymers are widely applied in the cosmetic industry and have recently been applied as a thickener option in the composition of dental bleaching gels, with the purpose to reduce the adverse effects on enamel mineral components. The aim of this study was to evaluate the color variation (ΔE* ab, ΔE00, ∆WID), surface roughness (Ra), and mineral content quantification (Raman Spectroscopy) of dental enamel after bleaching treatment with experimental gel-based on 10% carbamide peroxide (CP), containing Carbopol, Natrosol, and Aristoflex® AVC. Sixty bovine teeth were randomly divided into 6 groups (n=10): Negative Control (NC) - no treatment; Positive Control (PC) - Whiteness Perfect 10% - FGM; CP with Carbopol (CPc); CP with Natrosol (CPn); CP with Aristoflex® AVC (CPa); NCP - no thickener. Data were analyzed, and generalized linear models (∆WID -T0 x T1) were used for repeated measurements in time for Ra and with a study factor for ΔE* ab and ΔE00. For the evaluation of the mineral content, data were submitted to one-way ANOVA and Tukey tests. For enamel topographic surface analysis the Scanning Electron Microscope (SEM) was performed. A significance level of 5% was considered. ΔE* ab and ΔE00 were significantly higher for CPc, CPn, CPa, and NCP groups. (∆WID) showed a significantly lower mean than the other groups for NC in T1. After bleaching (4-hour daily application for 14 days), Ra was higher in the CPc, CPn, and PC groups. For CPa, Ra was not altered. No significant difference was found in the quantification of mineral content. CPa preserved the surface smoothness more effectively. Aristoflex® AVC is a viable option for application as a thickener in dental bleaching gels, presenting satisfactory performance, and maintaining the whitening efficacy of the gel, with the advantage of preserving the surface roughness of tooth enamel without significant loss of mineral content.

Effect of bleaching gels with different thickeners under normal and hyposalivation conditions: in situ study

BACKGROUND

Bleaching gel thickeners induce important changes in tooth enamel and these changes are reversed by saliva.

OBJECTIVE

This in situ study aimed to evaluate the effect of bleaching gels with different thickeners on tooth enamel under normal and hyposalivation conditions.

METHODOLOGY

Of 28 participants, 14 had normal salivary flow and 14 had low salivary flow. For each salivary flow, four types of treatment were performed with different thickeners: no bleaching (negative control), bleaching with a commercial 10% carbamide peroxide (CP) gel with carbopol (positive control) and bleaching with experimental 10% CP gels with natrosol and aristoflex. Participants used a palatal appliance containing bovine enamel/dentin specimens for 15 days. From day 2 to day 15, specimens were bleached extraorally. The bleaching gel was applied according to the groups for four hours. When the bleaching gel was removed, the palatal appliance was inserted again in the participants' mouth until the next day for another bleaching application. This procedure was repeated for 14 days and on day 15, surface microhardness (SMH), color (ΔE*ab and ΔE00), surface roughness (Ra), scanning electron microscopy (SEM), and energy-dispersive X-ray spectrometry (EDS) analyses were performed and data were subjected to statistical analysis.

RESULTS

Neither salivary flow nor thickeners influenced ΔE*ab and ΔE00 results. Carbopol had the lowest SMH, the highest Ra, and the lowest Ca% among all groups. For normal flow, natrosol and aristoflex had higher SMH. For low flow, aristoflex had higher SMH and natrosol and aristoflex had lower Ra. Aristoflex had higher Ca% and Ca/P and differed from carbopol for normal flow.

CONCLUSION

For normal flow, 10% CP gels with natrosol and aristoflex caused fewer surface changes, and for low flow, only the 10% CP gel with aristoflex.

Effect of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) Laser Enamel Pre-Treatment on the Whitening Efficacy of a Bleaching Agent

BACKGROUND

There are a number of different substances and treatments that are effective in mitigating the negative effects of tooth bleaching. It is essential, however, to consider whether or not the presence of these factors affects the efficiency of the bleaching agent.

AIM

The purpose of this study is to determine how the pretreated enamel with a Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser affects the bleaching effect of hydrogen peroxide at a concentration of 35%.

METHODS AND MATERIALS

Thirty samples were prepared from human-extracted permanent anterior teeth and stained using a tea solution. Based on the pre-treatment protocol, the samples were split into two equal groups (n = 15): In Group I, samples were submerged in saline solution for five minutes, while in Group II, Nd:YAG laser treatment was performed. Following pretreatment, samples from both groups were bleached with 35% hydrogen peroxide. Colour analysis of all samples was done before and after bleaching using a spectrophotometer. For the colour analysis, the CIE L*a*b* (Commission Internationale de l'Eclairage) System of colour measurement was used. For statistical analysis, Student t-tests (two-tailed, unpaired) were used to compare the means of two groups on a continuous scale.

RESULTS

Samples from both groups became lighter in colour following bleaching. After bleaching, there was no discernible difference in the total colour change between the two groups.

CONCLUSION

The application of the Nd:YAG laser before bleaching did not influence the whitening efficacy of 35% hydrogen peroxide.

EVALUATION OF MINERAL CONTENT OF TOOTH ENAMEL AFTER APPLICATION VIOLET LED ASSOCIATED WITH 35% HYDROGEN PEROXIDE

BACKGROUND

The aim of this study was to evaluate the microhardness and quantify the presence of minerals (Calcium and Phosphorous) of tooth enamel submitted to bleaching with violet LED light, either associated with 35% hydrogen peroxide gel, or not.

METHODS

Bovine incisors were selected and divided into 4 Groups according to the bleaching technique used: C- Without bleaching (Control); VL- violet LED; HP- 35% Hydrogen Peroxide; HP+VL- 35% Hydrogen Peroxide + violet LED. The response variables were surface microhardness (n=12), Energy Dispersive Spectroscopy (EDS) (n=6) and scanning electron microscopy (SEM) (n=3).

RESULTS

The 2-way ANOVA test with repeated measures showed that there was difference in the microhardness values of enamel in the specimens in all of the Groups when the values measured in the initial and final time intervals were compared, however, without significant differences between the values of the different treatments in both time intervals. The results with reference to EDS were analyzed with the 1-way ANOVA test. There was difference among the Groups only in the Ca%, with Group HP obtaining the lowest values, with significant difference from those of the C Group. SEM images showed a smooth, homogeneous enamel surface and similarity among the Groups, irrespective of the treatment performed.

CONCLUSIONS

Therefore, it was concluded that the changes caused in enamel by the use of violet LED Light, either associated with 35% hydrogen peroxide, or not, did not differ from those of non-bleached tooth enamel, showing absence of harm to the mineral content of tooth enamel resulting from the use of violet LED.

Does polishing of bleached enamel affect roughness and tooth color stability after exposure to coffee?

OBJECTIVE

This laboratory randomized study was designed to evaluate the effect of polishing on roughness and color stability of bleached teeth after coffee immersion.

MATERIALS AND METHODS

Ninety bovine crowns were randomly allocated to six groups (n = 15), according to bleaching protocols: At-home: standard protocol using 10% hydrogen peroxide (HP) or In-office: standard protocol using 35% HP; and with polishing protocols: (1) no polishing, (2) bleached enamel polished with #0.5 μm or (3) #2-4 μm diamond particles grit pastes. Samples were daily immersed into coffee solution for 45 min followed by mechanical brushing simulation (30 s) for 30 days. The surface roughness (Ra) and color alteration, expressed by ΔEab , ΔE00 , and whitening index (WI) were analyzed at baseline, after bleaching/polishing protocols and after coffee solution staining. The surface from each group was examined using a scanning electron microscope. Data were analyzed by two-way repeated measure analysis of variance followed by the Tukey test (α = 0.05).

RESULTS

Staining increases Ra, ΔEab , ΔE00 , and decreases WI values. Polishing after bleaching did not prevent staining, however, tooth polished with #0.5 μ-grit polishing paste showed better performance than #2-4 μ-grit (ΔEab : p = 0.001/ΔE00 : p = 0.003). Scanning electron microscope revealed a more irregular surface after coffee staining for all groups regardless bleaching/polishing protocols.

CONCLUSIONS

Using #0.5 μ-grit diamond paste to polish 35%HP in-office bleached enamel reduces the roughness and tooth staining. However, polishing after 10%HP at-home bleached enamel neither affects roughness nor improves tooth color stability after exposure to coffee.

CLINICAL SIGNIFICANCE

Polishing after at-home bleaching does not have benefits but after 35% hydrogen peroxide in-office bleaching, the polishing with #0.5 μ-grit polishing paste is indicated to reduce roughness and the tooth staining over time.

One-year follow-up comparing at-home bleaching systems outcomes and the impact on patient's satisfaction: Randomized clinical trial

OBJECTIVE

To compare at-home systems with reduced daily time of use (10% hydrogen peroxide [HP] gel with prefilled (PT) or customized trays (CT), and 10% carbamide peroxide [CP] gel), with the conventional nightguard vital bleaching (10% CP). Bleaching efficacy, adverse effects, and patient's satisfaction were evaluated.

METHODS

Sixty participants were randomly divided into treatments (14 days): Opalescence GO (OGO)-10%HP PT-30 min, White Class-10%HP CT-30 min, Opalescence PF-10%CP CT-2 h, and Opalescence PF-10%CP CT-8 h. Color difference (visual and spectrophotometer), tooth sensitivity (visual analogue scale), gingival condition (Löe index), enamel mineralization (laser fluorescence), and patients' satisfaction (questionnaire) were assessed. Statistical tests were applied (5%).

RESULTS

After 1 year, color difference was similar for the groups (p > 0.05). All groups showed similar sensitivity risk (p > 0.05). The intensity of sensitivity and gingival irritation was mild for all gels, but higher for OGO. Fluorescence after bleaching remained similar to those of sound enamel. All participants were satisfied with treatments.

CONCLUSIONS

All systems produced similar bleaching efficacy, which was maintained after 1 year. Patients were satisfied with bleaching outcomes. Tooth sensitivity occurred in all groups, but with overall mild intensity. No relevant gingival irritation and enamel demineralization was observed.

CLINICAL SIGNIFICANCE

Bleaching with 10% HP gels in prefilled and CTs represent efficacious alternative for tooth color change, with patients' acceptance similar to conventional 10% CP. Patients must be warned about the mild sensitivity and gingival irritation potential, mainly with PTs.

In-office tooth bleaching with chitosan-enriched hydrogen peroxide gels: in vitro results

OBJECTIVE

This study aimed to evaluate the effects of adding chitosan to 35% hydrogen peroxide gels (for in-office bleaching), with or without calcium gluconate, on tooth properties and bleaching efficacy.

METHODS

Bovine enamel/dentin specimens (4 × 4 × 2.5 mm) were randomly allocated into groups (n = 10): negative control (unbleached), bleaching with 35% hydrogen peroxide gel (35% HP, commercial gel); 35% HP with 2% chitosan (% wt) (35% HP + chitosan), 35% HP and calcium (35% HP + Ca, commercial gel), and 35% HP + Ca + 2% chitosan. Variation of surface profile (ΔRa) and color analyses (ΔL*, Δa*, Δb*, ΔE*_ab, ΔE₀₀, and ΔWID) were performed comparing specimens at baseline (initial) and 24 h after of storage in artificial saliva (final). Surface microhardness (KHN) values and scanning electron microscopy (SEM) images were obtained on conclusion. The data were analyzed by ANOVA and Tukey's tests (KHN), generalized linear models (ΔL*, ΔE_ab, ΔE₀₀, ΔWID, ΔRa), and Kruskal-Wallis and Dunn tests (Δa*, Δb*) (α = 0.05).

RESULTS

Considering ΔL*, Δa*, Δb*, ΔE*_ab, ΔE₀₀, and ΔWID values, the bleached groups differed from negative control. For ΔRa, chitosan-based groups showed lower variation in surface roughness compared to 35% HP, without significant difference from negative control. For KHN, chitosan groups did not differ from negative control (unbleached control = chitosan groups > 35% HP + Ca > 35% HP). For SEM, slight surface changes were observed in all bleached groups, but the intensity varied according to gel used (35% HP > gels with Ca > gels with chitosan).

CONCLUSION

Chitosan-enriched hydrogen peroxide gels can reduce negative impacts on tooth properties without affecting bleaching efficacy.

CLINICAL RELEVANCE

Although commercial gels containing remineralizing agents such as calcium reduce the negative effects on the properties of teeth, the addition of chitosan appears to be a promising approach to preservation of dental properties without interfering in bleaching efficacy.

Effect of tooth bleaching and application of different dentifrices on enamel properties under normal and hyposalivation conditions: an in situ study

OBJECTIVE

The purpose of this in situ study was to evaluate different dentifrices on enamel after bleaching under normal and hyposalivatory conditions.

MATERIALS AND METHODS

Twenty-four participants were assigned of which 12 had normal and 12 had low salivary flow. The study was conducted in 6 in situ experimental phases of 24 h duration: placebo, NaF, SnF₂, F/Sn/Chitosan, F/Arginine, and F/Bioactive Glass. The specimens were previously bleached in vitro. Microhardness (SMH), roughness (Ra), and color analyses (CIELAB and ΔE₀₀) were performed at baseline (T1), after bleaching (T2) and after in situ phase (T3). Scanning electron microscopy (SEM) and the elemental levels (wt%) of Ca, P, and Na and the proportion between Ca and P were determined using an energy-dispersive X-ray spectrometer (EDS) in T3. The SMH and Ra were analyzed by mixed models for repeated measures and Tukey Kramer. The color and Na% were analyzed by split-plot ANOVA and Tukey test. The EDS were analyzed by Mann's Whitney nonparametric, Friedman, and Nemenyi tests (p<0.05).

RESULTS

The dentifrices placebo and NaF in the low flow presented lower SMH and higher Ra in T3 and lower Ca% compared to the same dentifrices in normal flow. For normal flow, SnF₂ resulted in greater SMH. For low flow, SnF₂, F/Sn/Chitosan, and F/Bioactive Glass resulted in higher SMH in T3 and did not differ from T1. F/Bioactive Glass showed lower Ra among the dentifrices evaluated for both salivary flows, whereas SnF₂ showed the highest. F/Bioactive Glass showed a statistically significant difference from placebo for Ca%, P%, Na%. For ΔE^*_ab and ΔE₀₀ (T1×T3), no differences were found for the dentifrices and salivary flows.

CONCLUSION

The low salivary flow had less capacity for remineralization of bleached enamel compared to normal flow. Overall, the dentifrice with bioactive glass had the best performance in bleached enamel under low and normal salivary flow condition.

CLINICAL RELEVANCE

It is recommended to use a bioactive glass-based dentifrice after bleaching to promote tooth enamel recovery for patients with or without impaired salivary flow.

Effect of over-the-counter whitening strips and toothpaste on shear bond strength of orthodontic brackets

Background

To investigate: 1) the effects of over-the-counter white strip enamel bleaching and 2-Step whitening toothpaste application on the shear bond strength of orthodontic brackets at 24-hours and 7-days post-bleaching latent period; and 2) the correlation between amount of bleaching and shear bond strength.

Material and Methods

Sixty human premolar teeth were randomly assigned into two bleaching groups, white strip group treated with Crest® 3D WHITE™ LUXE Professional Effects Whitestrips (Proctor & Gamble, Greensboro, NC), and whitening toothpaste group, treated with Crest® 3D WHITE™ BRILLIANCE 2-Step Toothpaste (Proctor & Gamble, Greensboro, NC). The groups were further divided into 4 subgroups A, B, C, D (n=15 per group). Subgroups A and C were bonded 7 days after bleaching while subgoups B and D were bonded 24 hours after bleaching. Differences in shear bond strength between the subgroups and an unbleached control group (n=15) were compared using the Kruskal-Wallis test. Spectrophotometric color changes were recorded pre- and post-bleaching.

Results

The mean shear bond strength for the white strip groups were 10.35±3.6 MPa and 11.69±4.33 MPa for the 7-day and 24-hour delayed bonding periods, respectively. Means for the whitening toothpaste groups were 11.01±4.31 MPa and 10.83±3.79 MPa for the 7-day and 24-hour delayed bonding periods. The mean for the control group was 9.59±3.32 MPa. There were no significant differences in shear bond strength between the groups at 7-days and 24-hour (P=0.650). There was a significant difference between teeth bleached with white strips as compared to those bleached with toothpaste and controls. The correlations between color change and shear bond strength were not significant (P=0.448).

Conclusions

There is a significant difference in the amount of whitening achieved by over-the-counter white strips compared to toothpaste; however, no significant effects on shear bond strength occurred after bleaching with white strips and toothpaste at 24-hours and 7-days.

Key words:Bleaching, shear bond strength, orthodontics, over-the-counter.

Adhesion and whitening effects of P11-4 self-assembling peptide and HAP suspension on bovine enamel

OBJECTIVES

This study evaluated the adhesion and whitening effects of a combination of P11-4 self-assembling peptide and hydroxyapatite (peptide-HAP) on bovine enamel.

METHODS

Forty-six caries-free bovine teeth were selected, and 40 teeth were randomly allocated to one of five groups (n = 8). First, the effects of application frequency, exposure time, and storage in saliva on the whitening effects of an experimental low-concentrated peptide-HAP suspension (0.5 wt% HAP; Curodont, Credentis) were evaluated and compared with a commercial bleaching agent (VivaStyle Paint on Plus, VS, Ivoclar Vivadent). Tooth color was measured using a spectrophotometer (Gretag MacBeth), and color changes ΔE were statistically analyzed. Second, the effects of peptide-HAP concentration (low versus high: 6.25% HAP; Curodont Protect), and its interactions with saliva and postapplication restaining, were investigated. Third, enamel surfaces (n = 2) were treated with low concentration peptide-HAP and high-concentration peptide-HAP in polymeric and monomeric forms (Curodont Protect & Curodont Repair, Credentis) and analyzed by SEM.

RESULTS

The ΔE of the low-concentration peptide-HAP suspension did not differ from that of VS. Application frequency, exposure time, and storage in saliva did not have any significant impact on whitening efficacy of the peptide-HAP suspension. Increasing the concentration of the suspension did not promote overall ΔE. SEM observations confirmed the presence of the newly generated peptide and HAP on the enamel surface.

CONCLUSIONS

The peptide-HAP suspension is a mild tooth whitener, and the adhesion of peptide-HAP to enamel is concentration dependent.

CLINICAL RELEVANCE

This peptide-HAP suspension is effective in offsetting discoloration caused by restaining after treatment.

Influence of Prolonged Dental Bleaching on the Adhesive Bond Strength to Enamel Surfaces

The objective of this in vitro study was to assess the influence of prolonged bleaching pre- and postrestoration on the bond strength (microshear) to enamel using 4% hydrogen peroxide (PH4). In the postrestorative bleached specimens evaluation, the composite cylinders were assembled after bleaching, while in the prebleached specimens, the cylinders were assembled before. Therefore, in the postbleached specimens, 60 bovine teeth were randomly assigned as follows: G1: control; G2: 14 days bleaching before bond strength (BS) testing; G3: 21 days; and G4: 28 days. In prebleached specimens, 180 bovine teeth were randomly assigned as follows: G1: control; G5: 14 days bleaching, storage in artificial saliva (AS) for 24 h before BS testing; G6: 14 days beaching, AS storage for 7 days before BS testing; G7: 21 days bleaching, AS storage for 24  h before BS testing; G8: 21 days bleaching, AS storage for 7 days before BS testing; G9: 28 days bleaching, AS storage for 24 hours before BS testing; and G10 : 28 days bleaching, AS storage for 7 days before BS testing. The results were submitted to ANOVA one-way (postrestoration bleaching) and two-way (prerestoration bleaching) and Tukey's post hoc test (p ≤ 0.05). In the postrestoration bleaching, no statistical difference between times was found. However, when bleached groups were compared to the control (G1), an expressive difference was detected (p ≤ 0.0001). For prerestoration bleaching, all experimental groups were statistically different from G1 (p ≤ 0.05), except G6 (p ≥ 0.01), and for G5 and G6, statistical differences were found (p ≤ 0.01). There were no significant differences between G7 and G8 and between G9 and G10, regardless of the AS storage times (p ≥ 0.05). It was concluded that prolonged bleaching with PH4 decreased adhesion resistance regardless of the moment of the bleaching (post- and prerestoration bleaching).

Effect of in-office bleaching gels with calcium or fluoride on color, roughness, and enamel microhardness

Background

Commercial bleaching gels with remineralizing agents were developed to reduce the adverse effects of dental bleaching. The present study evaluated the effects on teeth of in-office bleaching gels containing 35-40% hydrogen peroxide (HP) with Calcium (Ca) or Fluoride (F).

Material and Methods

Bovine enamel/dentin blocks (4x4x2.5 mm) were randomly divided into the following groups (n=12): no treatment (control); 35% HP (Whiteness HP, FGM); 35% HP with Ca (Whiteness HP Blue, FGM); 40% HP with F (Opalescence Boost, Ultradent). The specimens were analyzed for color (ΔL*, Δa*, Δb*, and ΔE), roughness (Ra), and Knoop microhardness (KHN). The color and KHN data were submitted to ANOVA and Tukey’s test, while Ra values were analyzed using mixed models for repeated measures and Tukey-Kramer’s test (α=0.05).

Results

The bleached groups did not exhibit statistical differences among them for color. For roughness, 35% HP provided a slight increase of Ra, which was statistically different from the control. For microhardness, 35% HP and 40% HP with F presented KHN values that were statistically lower from the control, while the 35% HP with Ca did not statistically differ from the control.

Conclusions

The presence of Ca or F in bleaching gels did not interfere with bleaching efficacy. However, only the enamel exposed to the bleaching gel containing Ca obtained microhardness values similar to unbleached enamel.

Key words:Hydrogen peroxide, tooth bleaching, tooth bleaching agents, laboratory research.

Effect of tooth enamel staining by coffee consumption during at-home tooth bleaching with carbamide peroxide

Abstract Introduction Obtaining the result expected during tooth bleaching requires a correct diagnosis of the type of staining presented. The causes of tooth staining differ depending on the etiological factor. Objective To assess the color change caused by the immersion of bovine teeth in coffee solution during at-home tooth bleaching using a 16% carbamide peroxide gel. Material and method Thirty-three sound bovine teeth were assigned to three groups of eleven teeth each: 1 – Teeth bleached (TB) four hours per day for 21 days; 2 – TB four hours per day for 21 days and immersed in coffee solution immediately after tooth bleaching; 3 – TB four hours per day for 21 days and immersed in coffee solution four hours after the end of tooth bleaching. Immersed in coffee was performed for 15 minutes and tooth color was assessed before the start of the bleaching procedure and after 21 days with an intraoral spectrophotometer. Test Shapiro-Wilk was used to assess homoscedasticity and data were submitted to one-factor Analysis of Variance (ANOVA) and Tukey’s test (p <0.05). Result The color change observed in group 1 (5.76 ± 2.74)A was not statistically different from group 2 (8.83 ±5.11)A, which was immersed in coffee solution immediately after tooth bleaching, and from group 3, which was immersed in coffee solution four hours after tooth bleaching (8.20 ±3.71)A. Conclusion Coffee did not interfere with the tooth bleaching results, regardless of the time after the procedure. Hence, diet restrictions are not necessary during tooth bleaching.

Nonprescription Bleaching versus Home Bleaching with Professional Prescriptions: Which One is Safer? A Comprehensive Review of Color Changes and Their Side Effects on Human Enamel

OBJECTIVES

 This study evaluates the efficacy and safety of the professionally prescribed and nonprescription over-the-counter (OTC) bleaching agents.

MATERIALS AND

METHODS:  Extracted human upper central incisors were prepared and stained with red wine for 14 days before being subjected to four different bleaching agents: professionally prescribed opalescence PF 15%, VOCO Perfect Bleach 10%, nonprescription OTC Crest 3D Whitestrips, and Whitelight Teeth Whitening System. Colorimetric measurement was performed with Vita Easyshade Handheld Spectrophotometer, enamel surface microhardness measured using Vickers Hardness machine, and surface roughness was evaluated with profilometer, before and after bleaching. Scanning electron microscope (SEM) evaluation and atomic force microscopy were conducted postbleaching.

STATISTICAL ANALYSIS

 The data were analyzed with t-test, two-way ANOVA, one-way ANOVA, and Turkey's test at a significance level of 5%.

RESULTS

 All bleaching products have the same efficacy to whiten stained enamel. Opalescence PF 15% showed significant increase in the microhardness (92.69 ± 68.316). All groups demonstrated significant increase in surface roughness (p < 0.05). SEM evaluation showed that Opalescence PF 15% resulted in same microscopic appearance as unbleached enamel, while VOCO Perfect Bleach 10%, Whitelight Teeth Whitening System and Crest 3D Whitestrips demonstrated mild to moderate irregularities and accentuated irregularities, respectively.

CONCLUSION

 Professionally prescribed bleaching agent of Opalescence PF 15% is effective tin whitening the teeth, while the other bleaching products may be effective but also have deleterious effects on the enamel.

Effect of ammonium acryloyldimethyltaurate copolymer on the physical and chemical properties of bleached dental enamel

OBJECTIVE

To analyze the effect of bioadhesive polymer, Aristoflex® AVC, on enamel physical and chemical properties.

MATERIALS AND METHODS

Bovine enamel blocks were divided into CP 10% with carbopol-Whiteness Perfect® (WP-FGM), CP 10% with Aristoflex (A + CP 10%), CP 10% with carbopol (C + CP 10%), Aristoflex (A), carbopol (C), carbamide peroxide 10% (CP 10%) and control (no treatment). The treatment was performed for 4 h during 14 days. The colour (ΔE, ΔL*, Δa* and Δb*), profilometry (Ra) and surface microhardness (KHN) were performed before and after the bleaching treatment. The concentrations of Ca and P were performed on the 1st, 3rd, 7th and 14th days by inductively coupled plasma optical emission spectrometry for the groups WP, A + CP 10%, C + CP 10%, A, C and CP 10% (control without thickener) and the morphology by scanning electron microscopy.

RESULTS

All groups with CP 10%, regardless of polymer, differing statistically to ΔE, ΔL*, Δa* and Δb* compared to control group. The group A + CP 10% maintained low values of roughness and microhardness after bleaching. Higher concentration of Ca and P was found in the 1st day of treatment for the WP group compared to the groups A + CP 10% and C + CP 10%.

CONCLUSION

The 10% CP associated with the bioadhesive polymer Aristoflex® AVC was effective on the bleaching treatment without changing the physical properties of the dental enamel. Also, this experimental gel caused less mineral loss than the group CP 10% with carbopol (WP-FGM).

CLINICAL RELEVANCE

Because the change of Carbopol by Aristoflex, a bioadhesive polymer, does not interfere with the effectiveness of bleaching treatment, it is a promising agent associated to carbamide to maintain the physical properties of enamel after bleaching.

Effect of sodium metabisulfite gel on the bond strength of dentin of bleached teeth

Objective

This study aimed to evaluate the effect of the application of sodium metabisulfite (SMB) on the bond strength of bleached teeth.

Materials and Methods

The study was divided into two parts. The first part evaluated the application of various concentrations of SMB for 1 h prior to the completion of bonding procedures. Fifty blocks were divided into five groups (n = 10): control; bleaching with 35% hydrogen peroxide (HP); HP + 5% SMB; HP + 12.5% SMB; and HP + 25% SMB. The second part evaluated the application of 25% gel SMB to either enamel or dentin, including the application time. Sixty blocks were divided into six groups (n = 10): control; bleaching with 35% HP; HP + 25% SMB for 1 h in enamel; HP + 25% SMB for 1 h in dentin; HP + 25% SMB for 10 min in enamel; and HP + 25% SMB for 10 min in dentin.

Statistical Analysis

Following the completion of microshear bond testing, data were analyzed using one-way analysis of variance as well as Tukey's and Dunnett's tests.

Results

In part 1, data analysis revealed statistical differences (P < 0.0001) between HP and HP + 5% SMB. No statistical differences were found between the control and both HP + 12.5% SMB and HP + 25% SMB. Part 2 revealed a statistical difference (P = 0.001359) only between the bleached group and others.

Conclusions

The use of 25% SMB gel immediately after bleaching was able to reverse the deleterious effect of bleaching on the bond strength of dental composites to dentin.

Influence of Staining Solutions on Color Change and Enamel Surface Properties During At-home and In-office Dental Bleaching: An In Situ Study

The purpose of this in situ study was to evaluate the influence of staining solutions (coffee and cola) on the color change, microhardness, roughness, and micromorphology of the enamel surface during at-home and in-office dental bleaching. One hundred and thirty-five enamel bovine blocks were prepared to perform the evaluations. Fifteen volunteers used an intraoral appliance with nine enamel blocks for 15 days. The enamel blocks were randomly assigned among the different groups according to the three treatments: in-office bleaching with high hydrogen peroxide concentration (Opalescence Boost PF 40%, Ultradent) for 40 minutes in three sessions (first, eighth, and 15th days of treatment), at-home bleaching with low carbamide peroxide concentration (Opalescence PF 10%, Ultradent) for 60 minutes daily for 15 days, and a control group (no bleaching agent applied). The enamel blocks were immersed daily in different staining solutions (coffee or cola) for 30 minutes for 15 days or were not submitted to staining (control) to obtain a factorial scheme (3×3) of the dental bleaching treatment and staining solution (n=15). The microhardness analyses (Knoop), roughness evaluations (Ra), surface micromorphological observations, and color measurements (using the CIELAB system and the VITA Classical scale) were made before and after the bleaching treatments to assess immersion in staining solutions. Mixed model tests showed that there was a decrease in enamel microhardness after exposure to cola compared with coffee and the control group (p<0.0001) for both bleaching techniques. Roughness was higher for the cola groups (p<0.0001), and there was no significant difference between the coffee and the control groups. Generalized linear models showed that when no staining solution was applied, lighter color scores were found for the VITA Classical scale (p<0.0001). Without the staining solutions, there was an increase in luminosity (ΔL) (p=0.0444) for in-office bleaching. Lower values of Δa (p=0.0010) were observed when the staining solutions were not used. The Δb (p=0.3929) did not vary significantly between the bleaching agents, but when cola was applied, the values were significantly higher than for the control (p=0.0293). Higher values of ΔE (p=0.0089) were observed for in-office bleaching without staining solutions, while lower values of ΔE were observed for the in-office associated with coffee immersion. Regardless of whether being submitted to bleaching, the enamel stained with cola showed a decrease in microhardness, an increase in roughness, and changes in the micromorphology. The efficacy of the bleaching agents was greater when no staining solution (cola or coffee) was used, and in-office bleaching showed greater color change than the at-home bleaching technique.

Influência do gel de clareamento e do uso de agente remineralizante na perda mineral em esmalte e na eficácia do tratamento clareador

Objetivo: O objetivo neste estudo foi investigar a ação de diferentes géis de clareamento dental e de um agente remineralizante na dureza em esmalte associada ao clareamento. Método: Dentes bovinos foram utilizados para confeccionar os espécimes de esmalte e armazenados em vinho tinto para promover o manchamento dos mesmos. Após, foram submetidos a três sessões de clareamento com peróxido de hidrogênio 35%. Três grupos (n= 9) foram utilizados para avaliação comparativa: gel de clareamento sem cálcio, gel de clareamento com cálcio e gel de clareamento com cálcio e aplicações de um agente para remineralização. As variáveis de desfecho avaliadas foram o percentual de diminuição da dureza superficial do esmalte em diferentes tempos de armazenamento (7, 14, 21 e 28 dias após o clareamento) e alteração de cor. Os dados foram avaliados com ANOVA (perda mineral) e estatística descritiva (alteração de cor). Resultados: As diferenças de perda mineral entre os grupos não foram estatisticamente significativas em todos os tempos avaliados. Em relação aos valores colorimétricos, todos os grupos apresentaram clareamento substancial após o tratamento. Conclusão: Concluiu-se que não houve influência do produto de remineralização utilizado ou gel clareador na perda mineral em esmalte.

Effect of Mouth Rinse Treatments on Bleached Enamel Properties, Surface Morphology, and Tooth Color

OBJECTIVE:

To evaluate, in vitro, the effect of mouth rinse exposure on bleached enamel.

METHODS:

Enamel/dentin bovine blocks (4×4×2 mm) were bleached with 35% hydrogen peroxide (HP) and were submitted to immersion twice daily for 14 days with different rinses (n=10), including those involving: distilled water (C [control]), 225-ppm NaF (FM, Colgate Plax Classic), essential oil (EM, Listerine Tartar Control), 1.5% hydrogen peroxide (HPM, Colgate Plax Whitening), and 2% hydrogen peroxide, pyrophosphates, and 225-ppm NaF (HPM+P, Colgate® Luminous White). The specimens were stored in a remineralizing solution during all experiments. Analyses of color (ΔE, L*, a*, b*) and roughness (Ra) were performed at the baseline, after HP, and after exposure to the rinse. The cross-sectional microhardness (CSMH) and images by scanning electron microscopy (SEM) were assessed at the end. The data were subjected to analysis of variance (ANOVA) (ΔE), repeated measures ANOVA (Ra), and split-plot ANOVA (CSMH), followed by the Tukey test. The L*, a*, and b* values were analyzed by generalized linear models (α=0.05).

RESULTS:

Color changes were not statistically different in the groups. Ra increased in all groups after bleaching; however, it was reestablished in C, FM, and HPM+F and increased in EM after 14 days of the rinse. EM and HPM reduced the CSMH values differing from C and promoted alterations on the enamel surface visualized by SEM.

CONCLUSION:

The mouth rinses did not affect the whitening efficacy or promote benefits on bleached enamel properties. Moreover, the 1.5% hydrogen peroxide- or essential oil-based mouth rinses affected the bleached enamel properties, promoting an alteration in morphologic surface and mineral loss in depth.

In situ Effect of Nanohydroxyapatite Paste in Enamel Teeth Bleaching

AIM

Evaluate in situ the effect of nanohydroxyapatite paste (nano-HAP) before bleaching with hydrogen peroxide 35% (HP35%) by ion chromatography (IC) Knoop hardness number (KHN) and tristimulus colorimetry (TC).

MATERIALS AND METHODS

A total of 60 fragments were obtained from third molars included (3 mm × 3 mm × 3 mm) and the specimens were divided into three groups (n = 20): Gas chromatography (CG) (negative control group) = no bleaching; HP35% (positive control group) = HP35% whitening (whiteness HP35%); nano-HAP = application for 10 minutes before bleaching treatment + HP35%. The specimens were fixed to the volunteers' molars. The KHN and TC were measured before and after bleaching. For IC, the dentin layer was removed, leaving the enamel that was crushed, and autoclaved for chemical quantification (calcium, fluorine, and phosphorus). The results of KHN and TC were analyzed statistically by analysis of variance (ANOVA) followed by Tukey test (p < 0.05).

RESULTS

The HP35% group showed reduction of the Ca, F, and P ions. The initial and final KHN mean of the CG and nano-HAP did not differ statistically; however, the group of HP35% did differ statistically. The mean ΔE of the HP35% and nano-HAP groups did not differ statistically from each other. However, they differed from the CG.

CONCLUSION

The nano-HAP paste preserved the KHN, promoted the lower loss of Ca and P ions and an increase of F ions when compared with the CG, but did not influence the effectiveness of the bleaching treatment.

CLINICAL SIGNIFICANCE

Nano-HA is a biomaterial that has shown positive results in the prevention of deleterious effects on the enamel by the action of the office bleaching treatment.

Effect of 10% Strontium Chloride and 5% Potassium Nitrate with Fluoride on Bleached Bovine Enamel

Background:

Dental whitening has been increasingly sought out to improve dental aesthetics, but may cause chemical and morphological changes in dental enamel surfaces.

Objective:

This study evaluated in vitro the effect of 10% strontium chloride and 5% potassium nitrate with fluoride on bovine enamel, through tristimulus colorimetry, Knoop microhardness (KHN), and roughness after bleaching with 35% hydrogen peroxide (HP).

Methods:

The specimens were divided into three groups (n=15): GControl received bleaching treatment with 35% HP; GNitrate received bleaching with 35% HP followed by the application of 5% potassium nitrate with 2% sodium fluoride; and GStrontium received bleaching with 35% HP followed by the application of 10% strontium chloride on the enamel. Next, five specimens of each experimental group were subjected to KHN and tristimulus colorimetry tests, and 10 specimens were subjected to surface roughness (SR) tests. The values obtained for the different groups were compared through analysis of variance (ANOVA) followed by a post-hoc Tukey-Kramer test in addition to Student’s T-test for paired data.

Results:

In the intergroup comparison, KHN final differed statistically (p<0.05). The mean SR final of the experimental groups differed statistically from the GControl group (p<0.05). In addition, the groups did not differ in color variation (p>0.05).

Conclusion:

10% strontium chloride and 5% potassium nitrate combined with 2% fluoride downplayed morphological changes to the enamel, without interfering with the effectiveness of the bleaching process.

Salivary acquired pellicle-inspired DpSpSEEKC peptide for the restoration of demineralized tooth enamel

Salivary acquired pellicle (SAP) is a layer of proteins and glycoproteins of salivary origin that tightly coat the tooth surface. Statherin is an important part of the SAP. The initial six-peptide sequence DpSpSEEK (where pS denotes phosphorylated serine) of the N-terminus of statherin can be immobilized on a hydroxyapatite (HAP) surface and the negatively charged domains of the DpSpSEEK side chain can catch free Ca²⁺ in saliva due to the charge adsorption effect. In order to prepare more functional materials based on DpSpSEEK, we designed a cysteine-labeled peptide sequence DpSpSEEKC, which could conjugate other macromolecules by forming a sulfur-based linkage. In this work, we measured the adsorption of DpSpSEEKC to HAP by various methods. We also coated DpSpSEEKC on a demineralized tooth enamel surface to evaluate its biomineralization capacity. The DpSpSEEKC-coated samples were characterized after immersion in artificial saliva for 2 weeks. The results showed that DpSpSEEKC has a strong adsorption capacity to HAP and could induce remineralization on the demineralized tooth enamel surface due to its carboxyl and phosphate groups. Compared with the control samples, the mechanical properties of the DpSpSEEKC-coated samples were obviously improved. In conclusion, DpSpSEEKC can provide a potential method for restoring demineralized tooth enamel.

Impact of hydrogen peroxide activated by lighting-emitting diode/laser system on enamel color and microhardness: An in situ design

Background:

Hydrogen peroxide (HP) at lower concentration can provide less alteration on enamel surface and when combined with laser therapy, could decrease tooth sensitivity. This in situ study evaluated the influence of 15% and 35% HP gel activated by lighting-emitting diode (LED)/laser light for in-office tooth bleaching.

Materials and Methods:

Forty-four bovine enamel slabs were polished and subjected to surface microhardness (load of 25 g for 5 s). The specimens were placed in intraoral palatal devices of 11 volunteers (n = 11). Sample was randomly distributed into four groups according to the bleaching protocol: 15% HP, 15% HP activated by LED/laser, 35% HP, and 35% HP activated by LED/laser. The experimental phase comprised 15 days and bleaching protocols were performed on the 2^nd and 9^th days. Surface microhardness (KHN) and color changes were measured and data were analyzed by ANOVA (α = 0.05).

Results:

There were no significant differences in microhardness values neither in color alteration of enamel treated with 15% HP and 35% HP activated or not by LED/laser system (P > 0.05).

Conclusions:

Both concentrations of HP (15 or 35%), regardless of activated by an LED/laser light, did not affect the surface microhardness and had the same effectiveness in enamel bleaching.