Influence of pH, bleaching agents, and acid etching on surface wear of bovine enamel

Effectiveness of violet LED with or without a bleaching gel: a 12-month randomized clinical trial

Introduction

The present interventional, controlled, randomized, blind clinical study aimed to evaluate the effectiveness of an in-office bleaching procedure with violet LED associated or not with 37% carbamide peroxide, considering as response variables the degree of change and color stability over 12 months and dental sensitivity over a month.

Methods

Forty participants, according to the inclusion and exclusion criteria, were randomly divided into 2 groups (n = 20) according to the bleaching protocol conducted, in two sessions, with a 7-day interval: vLED-violet LED, without gel; vLED/CP-37% carbamide peroxide photocatalyzed with violet LED (control group). In the vLED group, in each session the bleaching was carried out by 2 consecutive irradiation cycles of 25' each (10 × 2' LED + 30" interval), with 5' interval between cycles. In the vLED/CP group, the gel was applied 5 times in the bleaching session and photocatalyzed 3 times for 2' with 30" intervals (7'30" per gel application), totaling 37'30" per session. Dental sensitivity was assessed using a visual analog scale (VAS) and the effectiveness of bleaching as a function of the degree of change and color stability (ΔE) with a spectrophotometer. The data were tabulated and submitted to statistical tests (p < 0.05).

Results

The VAS analysis showed that some individuals from both groups had mild pain (1 ≤ VAS < 4) during the time intervals evaluated, being more prevalent in the vLED/CP group. Regarding the degree of color change, the groups behaved differently over time (p < 0.0001). The ΔE observed for the vLED/CP group was superior in comparison to the vLED group at all evaluated moments.

Conclusions

Over 12 months, the vLED/CP group was more effective in relation to the bleaching effect compared to the vLED group. Both groups showed low levels of sensitivity in the studied time intervals.

Clinical Trial Registration

[https://ensaiosclinicos.gov.br/rg/RBR-6rc23h], identifier [U1111-1253-8850].

Biological action of bleaching agents on tooth structure: A review

The use of bleaching agents to remove stains is one of the main dental procedures to improve the aesthetics of teeth. This review presents the main agents used for tooth whitening, existing clinical protocols, and the structural changes that may occur through their use. The main bleaching agents consist of hydrogen peroxide and carbamide peroxide, which are used in bleaching techniques for vital teeth. These techniques can be performed in the office by a professional or by the individual in a home en-vironment under professional guidance. Bleaching agents come in a variety of concentrations and there are over-the-counter products available on the market with lower concentrations of hydrogen peroxide. Due to the chemical characteristics of the agents, changes in the organic and inorganic content of the tooth structure can be observed. These changes are related to morphological changes characterized by in-creased permeability and surface roughness, such changes compromise the mechanical resistance of the tooth. Furthermore, bleaching agents can promote molecular changes after reaching the dental pulp, resulting in oxidative stress of pulp cells and the release of pro-inflammatory mediators. Despite the bleaching effectiveness, tooth sensitivity is considered the main side effect of use. Therefore, among the heterogeneity of protocols, those that used the bleaching agent for a prolonged time and in lower con-centrations presented more harmful effects on the tooth structure.

Enhanced tooth bleaching with a hydrogen peroxide/titanium dioxide gel

BACKGROUND

This study aimed to explore the effects of the titanium dioxide (TiO2) concentration and particle size in hydrogen peroxide (HP) on tooth bleaching effectiveness and enamel surface properties.

METHODS

TiO2 at different concentrations and particle sizes was incorporated into 40% HP gel to form an HP/TiO2 gel. The specimens were randomly divided into 8 groups: C1P20: HP + 1% TiO2 (20 nm); C3P20: HP + 3% TiO2 (20 nm); C5P20: HP + 5% TiO2 (20 nm); C1P100: HP + 1% TiO2 (100 nm); C3P100: HP + 3% TiO2 (100 nm); C5P100: HP + 5% TiO2 (100 nm); C0: HP with LED; and C0-woL: HP without LED. Bleaching was conducted over 2 sessions, each lasting 40 min with a 7-day interval. The color differences (ΔE00), whiteness index for dentistry (WID), surface microhardness, roughness, microstructure, and composition were assessed.

RESULTS

The concentration and particle size of TiO2 significantly affected ΔE00 and ΔWID values, with the C1P100 group showing the greatest ΔE00 values and C1P100, C3P100, and C5P100 groups showing the greatest ΔWID values (p < 0.05). No significant changes were observed in surface microhardness, roughness, microstructure or composition (p > 0.05).

CONCLUSIONS

Incorporating 1% TiO2 with a particle size of 100 nm into HP constitutes an effective bleaching strategy to achieve desirable outcomes.

Evaluating color change and hydrogen peroxide penetration in human and bovine teeth through in-office bleaching procedures

OBJECTIVE

Assess color alteration and hydrogen peroxide (HP) penetration in human and bovine teeth using various in-office bleaching protocols with different application times.

MATERIALS AND METHODS

Thirty healthy human premolars and 30 healthy bovine incisors were divided into five groups and subjected to different bleaching protocols: 2 × 15 min, 1 × 30 min, 2 × 20 min, or 1 × 40 min, with a control group for each tooth type. All teeth were treated with 35% HP gel. Color alteration was measured using digital spectrophotometry before and 1 week after bleaching. HP concentration within the pulp was determined via UV-Vis spectrophotometry. Statistical analysis included one-way ANOVA, Tukey's, and Dunnett's tests (α = 0.05).

RESULTS

All groups exhibited significant color alteration, with no statistically differences among them (p > 0.05). However, significant differences were observed when compared with their respective control groups (p < 0.05). HP penetration into the pulp was evident in all bleached teeth compared to the control groups (p < 0.05), with the 2 × 20 group showing the highest HP levels within the pulp cavity, irrespective of tooth type (p < 0.05).

CONCLUSION

A simplified 1 × 30-min protocol can be recommended as it effectively maintains color alteration and HP penetration, irrespective of whether human or bovine teeth.

CLINICAL SIGNIFICANCE

This study suggests that an in-office dental bleaching protocol using a 1 × 30-min session is recommended, as it ensures both effective color change and no increase in the amount of HP penetration.

Bleaching efficacy of in-office dental bleaching with different application protocols: a single-blind randomized controlled trial

OBJECTIVE

This randomized controlled trial aimed to evaluate the equivalence in the color change, adverse effects, self-perception (AS) and the impact on oral condition (IO) of participants submitted to different application protocols of in-office dental bleaching.

MATERIALS AND METHODS

165 participants were bleached with a 35% hydrogen peroxide gel (Total Blanc Office One-Step, DFL), according to the following protocols: (1) 2 applications of 20-min each (2 × 20 min); (2) 1 × 40-min and; (3) 1 × 30-min. The color change was evaluated with the Vita Easyshade spectrophotometer, Vita Classical and Vita Bleachedguide scales. The intensity and risk of tooth sensitivity (TS) and gingival irritation (GI) were recorded using a 0-10 visual analogue scale (VAS). AS and IO was assessed before and after the bleaching procedure using the Orofacial Aesthetic Scale and Oral Health Impact Profile-14, respectively.

RESULTS

Equivalent color change were observed (p < 0.001), with no significant difference between groups. The group 2 × 20 min presented the highest risk of TS (76%, 95% CI 63 to 85), compared to the 1 × 30 min (p < 0.04). The intensity of TS and GI and the risk of GI was similar between groups (p > 0.31). Irrespectively of the group (p = 0.32), significant improvements were observed for all items of AS and IO after bleaching (p < 0.02).

CONCLUSIONS

The 1 × 30 min protocol produced equivalent color change to the other bleaching protocols with reduced risk of TS and shorter application time.

CLINICAL RELEVANCE

A more simplified application regimen of a single application of 30 min yields effective bleaching and patient satisfaction while minimizing undesirable side effects and improving patient satisfaction.

In vitro evaluation of the effect of different bleaching varnishes: Hydrogen peroxide penetration into the pulp chamber and color change

OBJECTIVE

To evaluate the penetration of hydrogen peroxide (HP) into the pulp chamber and the color change of different bleaching varnishes in low concentrations used for at-home bleaching.

MATERIALS AND METHODS

Ninety healthy premolars were used, randomly distributed into nine groups (n = 10) according to bleaching varnish (PL, PolaLuminate; VS, VivaStyle Paint On Plus; CA, Cavex Bite&White whitening pen and; AW AlignerWhite) and time (10 and 30 min), and a control group (no bleaching). The penetration of HP was evaluated by UV-Vis spectroscopy. To evaluate the color change (ΔEab , ΔE00 , ΔWID ) a digital spectrophotometer was used (α = 0.05).

RESULTS

The AW group in 10 min and the control group showed similar and lower HP penetration in the pulp chamber when compared to the other groups (p = 0.003). Increasing the application time to 30 minutes elevated the amount of HP inside the pulp chamber for all groups (p = 0.003), except for PL (p > 0.05). When applied for 30 min all bleaching varnishes showed higher color change (ΔWID ) when compared to 10 min (p = 0.04).

CONCLUSIONS

For all bleaching varnishes evaluated, PolaLuminate applied for 30 min showed lower penetration into the pulp chamber and higher bleaching effects.

CLINICAL SIGNIFICANCE

The use of bleaching varnishes seems promising for teeth bleaching, but it varies according to user product and protocol.

Can all highly concentrated in-office bleaching gels be used as a single-application?

OBJECTIVE

This in vitro study aims to evaluate of hydrogen peroxide (HP) diffusion into the pulp chamber, bleaching efficacy (BE), and pH stability (pH) of single-application high concentrated in-office bleaching gels.

MATERIALS AND METHODS

Eighty-eight healthy premolars were randomly into eleven groups (n = 8) according to the in-office dental bleaching: DSP White Clinic 35% calcium (DW), Nano White 35% (NW), Opalescence XTra Boost 40% (OB), Pola Office + 37.5% (PO), Potenza Bianco Pro SS 38% (PB), Total Blanc 35% (TB), Total Blanc One-Step 35% (TO), Whiteness Automixx 35% (WA), Whiteness Automixx Plus 35% (WP), and Whiteness HP Blue 35% (WB). A group not exposed to bleaching agents was the control group (CG). All bleaching agents were applied in one session with a single application. After the bleaching procedure, the concentration of HP diffusion (μg/mL) into the pulp chamber was assessed using UV-Vis spectrophotometry. The BE (ΔEab and ΔE00) was evaluated before and 1 week after the bleaching procedure using a digital spectrophotometer. The pH of each bleaching gel was evaluated by digital pHmeter. The one-way ANOVA and Tukey's was used for a statistical analysis (α = 0.05).

RESULTS

The concentration of HP diffusion into the pulp chamber was higher in all in-office bleaching gels when compared to CG (p < 0.0000001). However, there are a significant difference between them (p = 0.0001). A significant BE was observed in all in-office bleaching gels (p < 0.0001 for ΔEab and ΔE00), with a significant difference between them (p < 0.0001). PO, OB, TB, WP, and WB showed a higher BE when compared to DW, PB, and WA (p < 0.0001). Most bleaching gels were slightly acidic or alkaline during the total application time, while DW, PB, TB, and WA showed a high acidic behavior after 30 min of application.

CONCLUSIONS

A single application was able to produce a bleaching efficacy. However, usually, gels with slightly acidic or alkaline pH during the application time reduces the HP diffusion into the pulp chamber.

CLINICAL RELEVANCE

The single-application of bleaching gels with slightly acidic or alkaline and stable pH decreased the penetration of hydrogen peroxide into the pulp chamber in in-office bleaching and maintained the bleaching efficacy.

Microstructural effect of different concentrations of hydrogen peroxide photoactivated with LED/laser

BACKGROUND

The use of different concentrations of hydrogen peroxide (HP) photoactivated with LED/laser sources is recurrent; however, their influence on tooth structure is not yet fully elucidated. This study aimed to evaluate the pH, microhardness and surface roughness of different bleaching protocols photoactivated with LED/laser.

METHODS

Forty bovine incisors were sectioned (7×7×2mm) and randomized into four groups for analysis of pH (n=5), microhardness and roughness (n=10): HP35, HP6_L, HP15_L, HP35_L. The pH analysis was performed in the initial and final minute of the bleaching protocol. Microhardness and roughness were evaluated before and 7 days after the last bleaching session. Results were obtained from two-way ANOVA for repeated measures and Bonferroni post-test at a significance level of 5%.

RESULTS

HP6_L showed higher pH and greater stability between the initial and final evaluations, while the other groups showed similar pH with reduced values in the intragroup evaluation. No differences between groups in microhardness and roughness evaluations were observed.

CONCLUSIONS

Although HP6_L showed higher alkalinity and pH stability, none of the protocols reduced the microhardness and surface roughness of bovine enamel.

Bleaching effectiveness and cytotoxicity of new experimental formulation of niobium-based bleaching gel

OBJECTIVES

The development of new bleaching agents with minimum concentration of hydrogen peroxide (HP), without adverse effects, and with bleaching effectiveness, has great clinical relevance. The aim of this study was to evaluate the bleaching efficacy and cytotoxicity of a new niobium-based bleaching gel, compared to already available HP-based gels.

MATERIALS AND METHODS

For the bleaching efficacy analysis, 40 bovine incisors were randomly divided into 4 groups according to the established bleaching protocol: control, untreated; 35HP, 35% HP bleaching gel; 6HP, 6% HP bleaching gel; NbHP, niobium gel associated with 3% HP gel. The color variation was measured in a spectrophotometer and the values of ΔL, Δa, Δb, and ΔE obtained. For the cell viability assay by MTT, MC3T3 cells were exposed to bleaching gel extracts (1:500, 1:250, 1:125 dilutions; immediately and 24 h). Statistical tests were performed (P < 0.05).

RESULTS

The color alteration for all bleaching gels was significant compared to control (P < 0.05), but the NbHP gel showed a significant ΔE than other gels, with expressive color alteration at 14 days (P < 0.05). The 35HP showed high cytotoxicity regarding control and the most groups in all periods and extracts analyzed (P < 0.05), while the NbHP showed greater cell viability than control in the immediate period, dilution of the 1:500 and superior to 6HP in the most extracts at 24 h.

CONCLUSION

The new experimental niobium-based gel has bleaching efficacy similar to that of gels with a high concentration of HP, and it has high cytocompatibility.

CLINICAL RELEVANCE

The use of this new generation of niobium-based whitening gel associated with a low concentration of hydrogen peroxide represents the possibility of a tooth whitening with lower dentin sensitivity.

Application Tip and Concentration of a Self-mixing Bleach: Hydrogen Peroxide Inside the Pulp Chamber, Color Change, and Amount of Bleaching Gel Used

PURPOSE

The objective of this study was to evaluate if the application method (tip with brush or tip without brush) and hydrogen peroxide (HP) concentration (6% or 35% self-mixing) of in-office bleaching gel influences the penetration of HP into the pulp chamber, color change, and the amount of bleaching gel used.

METHODS

Forty healthy premolars were randomly divided into the following five groups (n=8): no treatment; HP6% using a tip with a brush, HP6% using a tip without a brush, HP35% using a tip with a brush, and HP35% using a tip without a brush. After treatments, the HP concentration (μg/mL) within the pulp chamber was determined using UV-Vis spectrophotometry. The color change (ΔEab, ΔE00, and ΔWID) was evaluated using a digital spectrophotometer. The amount of gel used (g) in each group was measured using a precision analytical balance. Data from each test were submitted to parametric tests (α=0.05).

RESULTS

The tip with a brush resulted in a lower amount of HP inside the pulp chamber and less gel used when compared with the tip without a brush, regardless of HP concentration (p<0.05). However, regarding the tip used, although no significant difference was observed when HP35% was used (p>0.05), a higher whitening effect was observed when the 6% HP was applied without a brush as opposed to with a tip brush (p<0.05).

CONCLUSIONS

The use of a tip with a brush, regardless of the in-office bleaching gel concentration (6% or 35% self-mixing), presented a lower penetration and lower volume of spent gel when compared to a tip without brush. However, the whitening effect depended on the concentration of HP used.

The Effect of In-Office Bleaching with Different Concentrations of Hydrogen Peroxide on Enamel Color, Roughness, and Color Stability

The aim of this study is to evaluate the effectiveness of in-office bleaching in esthetic dentistry on the roughness and color stability of the enamel surface, using different concentrations of hydrogen peroxide (HP). Fifty human incisors were randomly divided into 5 groups (n = 10). No bleaching was performed in the control group. For these groups, concentrations of 40% HP with fluoride (F), 35% HP with calcium (Ca), 25% HP with nano-hydroxyapatite (nHA) and 18% HP with nHA were used for bleaching in the test groups. Surface roughness was assessed at baseline after bleaching occurred. Color measurements were first obtained at baseline, then after the first and second sessions of bleaching, and, finally, after the staining protocol. Scanning electron microscopy and atomic force microscopy were performed. Statistical analysis was conducted with a one-way ANOVA, followed by a post hoc Tukey's test and a paired-samples t-test (p < 0.05). All the bleaching gels used exhibited a similar color change (p > 0.05). Bleaching gels containing 18% HP with nHA and that containing 35% HP with Ca caused less surface roughness of the enamel. Of these concentrations, 25% HP with nHA caused the most surface roughness and no significant difference was observed, compared with 40% HP with F. The highest coloration after bleaching was observed in 40% HP with F and 25% HP with nHA. The lowest coloration was obtained in 35% HP with Ca and 18% HP with nHA but no significant difference was observed between them and the control group. A concentration above 18% HP does not increase the bleaching effectiveness. The results show that 18% HP with nHA and 35% HP with Ca resulted in the least increase in enamel surface roughness when compared to high-concentrate HP; however, it also prevented recoloration after bleaching.

Violet LED associated with high concentration hydrogen peroxide: Effects on bleaching efficacy, pH, and temperature

BACKGROUND

This study aimed to evaluate the bleaching efficacy, pH, and temperature of 35% hydrogen peroxide (HP) gel used alone or associated with violet LED.

METHODS

Sixty bovine crowns were sectioned (5 × 5 × 2mm). After staining with black tea, the specimens were randomized into four groups (n = 10) according to the bleaching protocol: HP35R: 3 × 15 min 35% HP; HP35: 1 × 45 min 35% HP; HP35VR: 3 × 8min 35% HP + Violet LED; HP35V: 1 × 24 min + Violet LED. Two bleaching sessions were performed for all the groups. Color change was evaluated before, 24h after each session, 7 days and 15 days after the last session. The variables ∆E₀₀ [CIEDE2000] and W_ID were used for color analysis. The pH variation (initial and final) and the temperature of the gel were recorded (n = 5). ANOVA two-way for repeated measures and Bonferroni post-test was used at a significance level of 5%.

RESULTS

HP35VR and HP35V the most noticeable color change(p < 0.05). The final values of pH were lower than the initial ones, but with no difference between the groups (p > 0.05). Groups HP35VR and HP35V showed an increase in temperature in relation to HP35R (p < 0.05).

CONCLUSIONS

Violet LED improved the bleaching efficacy of 35% HP in a time-saving manner without negatively affecting the pH and temperature of 35% HP. The renewal of HP did not influence the outcomes.

The influence of hydrogen peroxide concentration on the chemical kinetics of photo-accelerated tooth whitening

BACKGROUND

The bleaching procedure consists of chemical principles of free radical release that react with chromophores, which results in an amount of energy released in this process. However, the evaluation of the electrical potential generated in these protocols has not yet been thoroughly investigated in the literature. Thus, this study aimed to examine variations in pH, mV, and temperature of different concentrations of hydrogen peroxide in the presence or absence of an intermittent LED/LASER photo acceleration system.

METHODS

The study was divided into six groups (n = 9) according to the concentration of hydrogen peroxide (6%, 15%, and 35%), associated or not with the photo acceleration system LED/LASER. We followed the variation of pH, mV, and temperature at 1, 5, 10, 15, and 30 min after gel manipulation. Data were evaluated by two-way ANOVA of repeated measures (α =0.05).

RESULTS

pH, mV, and temperature of the groups showed statistical differences both in the light and bleach and in the interaction between the two factors (p < 0.0001), where pH and mV were more influenced by the bleach and light factor, while the temperature was influenced by the bleach factor associated with light. HP15 presented the most significant change in pH, mV, and temperature.

CONCLUSION

The use of LED/laser increased the temperature of the gels and altered the pH and mV kinetics of HP6 and HP15, which did not occur in HP35, possibly due to the high ionic potential linked to the concentration.

Whitening efficacy of low concentration hydrogen peroxide photoactivated with blue or violet LED

BACKGROUND

Bleaching protocols using low concentration hydrogen peroxide (HP) photoactivated with LED sources have been widely discussed. We evaluated the whitening efficacy of 15% HP photoactivated with blue or violet LED compared to 35% HP.

METHODS

Thirty bovine crowns were sectioned into 5 × 5 × 2mm specimens. After staining in black tea, the specimens were randomized into three groups (n=10): 35% HP, 15% HP + blue LED and 15% HP + violet LED. Two bleaching sessions were performed and the color assessment (∆L*, ∆a*, ∆b*, ∆E_ab [CIELab], ∆E₀₀ [CIEDE2000] and WI_D) was performed before, 24h after each session, 7 days and 1 month after the last session. Data were evaluated by two-way repeated measures ANOVA and Bonferroni post-test at a significance level of 5%.

RESULTS

All groups showed effective and similar results over 1 month of follow-up (p > 0.05), with only intragroup differences among the time intervals (p < 0.05).

CONCLUSIONS

The use of 15% HP photoactivated with blue or violet LED showed similar whitening efficacy compared to 35% HP. Thus, the association of low concentration bleaching gels with LED sources can provide a successful and less aggressive treatment in terms of color change.

Effects of tooth bleaching protocols with violet LED and hydrogen peroxide on enamel properties

BACKGROUND

This study evaluated the color change, enamel surface roughness and microhardness after different tooth bleaching protocols, using hydrogen peroxide (HP) and/or violet LED.

METHODS

Forty bovine specimens (7 × 7 × 2 mm) were randomly distributed into 4 groups: 35% HP, 6% HP, 6% HP + violet LED and violet LED alone. First, the specimens were stained with black tea and then submitted to two bleaching sessions of 30 min with an interval of 7 days. Color change (∆L*, ∆a*, ∆b* and ∆E00) after 24 h of each session and 1 week after the last session was evaluated. Enamel roughness and microhardness were evaluated immediately before the sessions, 24 h and 1 week after the last session. Data were evaluated by ANOVA for repeated measures and Bonferroni post-test or Kruskall-Wallis and Dunn tests (α = 0.05). Representative specimens from each group were analyzed by scanning electron microscopy.

RESULTS

6% HP + violet LED and 35% HP showed the highest color change, while violet LED alone had the lowest results. Enamel roughness analyses showed that 6% HP + violet LED and 35% HP showed changes after two bleaching sessions. No differences were observed regarding enamel microhardness.

CONCLUSIONS

The use of 6% HP + violet LED showed enhanced bleaching efficacy compared to 35% HP. However, violet LED used alone exhibited the lowest color change. 6% HP + violet LED and 35% HP promoted changes on enamel roughness, while no microhardness changes was observed for any group.

A Titanium Tetrafluoride Experimental Gel Combined with Highly Concentrated Hydrogen Peroxide as an Alternative Bleaching Agent: An In Vitro Study

This in vitro study evaluated color change, mineral content, and morphology of enamel, pH and cytotoxicity of experimental bleaching agents containing 35% hydrogen peroxide (HP), titanium tetrafluoride (TiF4), Natrosol, and Chemygel. Sixty enamel/dentin blocks were randomly treated with (n = 10) HP; HP+Natrosol+Chemygel with different TiF4 concentrations: 0.05 g HPT0.5, 0.1 g HPT1, 0.2 g HPT2, 0.3 g HPT3, 0.4 g HPT4. Bleaching was performed in three sessions (3 × 15 min application). Color change (CIELab-ΔEab, CIEDE2000-ΔE00, ΔWID) and Knoop microhardness (KHN) were evaluated. Enamel morphology and composition were observed under scanning electron microscopy and energy-dispersive spectrometry (EDS), respectively. Cell viability of keratinocyte cells was evaluated using MTT assay. Data were analyzed by one-way ANOVA and LSD and Tukey tests, and two-way repeated measures ANOVA and Bonferroni (α = 5%). The pH and EDS were analyzed descriptively. Lightness-L* increased, and a* and b* parameters decreased, except for HPT3 and HPT4 (b*). HPT0.5, HPT1, and HPT2 exhibited ΔEab and ΔWID similar to HP. ΔE00 did not present statistical difference. HP, HPT0.5, and HPT1 promoted higher KHN. HPT0.5 exhibited no changes on enamel surface. Keratinocyte cells were viable when treated with T0.5, and weak viable for T1. Experimental agents exhibited acidic pH and Ti elements. HPT0.5 exhibited bleaching efficacy, maintained KHN without enamel alterations, and did not increase cytotoxicity.

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.

Assessment of the temporal variation of electrical potential and pH of different bleaching agents

INTRODUCTION

Tooth whitening procedures are under continuous investigation to improve esthetic outcomes and reduce bleaching sensitivity (BS) precipitating from treatments. During the dental bleaching process it is known that the release of free radicals degrades the organic pigment molecules of the tooth and with this an amount of energy is released. Nonetheless, previous studies have never investigated the temporal correlation between of pH and electric potential (EP) generated in this treatment.

OBJECTIVES

Therefore, the objective of the present study was to investigate temporal variations of pH and EP associated with three different commercially available bleaching gels and the correlation levels between parameters of interest to provide relevant information regarding the kinetics of oxidation reactions in dental bleaching procedures.

METHODS

The study was divided into 3 groups (n = 9) in function of hydrogen peroxide concentration (either 6%, 15% and 35%). The temporal evolution of pH and EP values were determined using a highly-accurate and previously calibrated pH meter at specific time-points (5, 10, 15 and 30 min).

RESULTS

Data obtained were submitted to one-way ANOVA of repeated measures with Bonferroni post-test (α = 0.05). The results of the study showed difference in the factor gel concentration (p < 0,0001), time (p < 0,0001) and interaction (gel/time) (p = 0.002) while throughout the intervals evaluated the groups remained relatively stable and without significant difference in the intragroup variation of pH (p < 0.05) and in EDP only with significant difference in the 5 min interval of the 35% concentration. A 2nd order polynomial relationship test showed high correlation levels.

CONCLUSION

It can thus be concluded that there is a negative relationship between EP and pH variation in the different gel concentrations.

CLINICAL SIGNIFICANCE

The findings of the present study suggest that bleaching gels of higher concentration may provoke BS that are more intense and durable due to significant electric depolarization of neuronal extensions of pulpal tissues.

Comparison of the Effect of Agitation on Whitening and Tooth Sensitivity of In-Office Bleaching: A Randomized Clinical Trial

OBJECTIVE

This single-blind, split-mouth, randomized trial was aimed at evaluating the bleaching efficacy (BE) and tooth sensitivity (TS) of a 20% hydrogen peroxide (HP) bleaching agent used under active or passive application.

METHODS AND MATERIALS

Twenty-two patients with canines darker than C2 were selected. Teeth were bleached in two sessions, with a one-week interval between treatments. The bleaching agent was applied using active (HPactive) or passive (HPpassive) application. Each tooth in the HPactive-allocated hemiarch received bleaching gel with sonic activation after 10 and 30 minutes from the start of treatment, with rounded movements all over the buccal surface. The color changes were evaluated by subjective (Vita Classical and Vita Bleachedguide) and objective (VITA Easyshade Spectrophotometer) methods at baseline and 30 days after the second session. TS was recorded up to 48 hours after treatment using a 0-10 visual analog scale. Color change in shade guide units (SGUs) and ΔE was analyzed using a Wilcoxon test (α=0.05). The absolute risk and intensity of TS were evaluated using McNemar test and a Wilcoxon test, respectively (α=0.05).

RESULTS

Significant whitening was observed in both groups after 30 days of clinical evaluation. The activation did not significantly influence BE (ΔSGU HPpassive=5.6 and HPActive=5.8; p=0.98; and ΔE HPpassive=10.6 and HPactive=10.3; p=0.83). Absolute risk of TS (HPactive=36.4% and HPpassive=31.8%; p=0.94) was similar for both groups (Fisher exact test). TS intensity (visual analogue scale) was higher during the bleaching sessions and up to 24 hours thereafter for both groups, with no differences between groups (twoway analysis of variance and Tukey).

CONCLUSION

The active application of a 20% HP gel did not improve BE and TS.

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.

Assessment of a novel bleaching agent formula containing 35% hydrogen peroxide and titanium tetrafluoride: an in vitro study

This study developed experimental gels containing titanium tetrafluoride (TiF4) combined with commercial 35% hydrogen peroxide (HP), and evaluated bleaching efficacy and pH of the gels, and mineral content and morphology of enamel submitted to these treatments. In phase-1, different stock gels mixed with TiF4 were combined with HP. In phase-2, the selected gels were tested on enamel/dentin specimens (n=8): HP; HP and Natrosol+TiF4 (HPnT); HP and Natrosol+Chemygel+TiF4 (HPncT); HP and Aristoflex+TiF4 (HPaT). Bleaching was performed in four sessions (3x15min-application/session). Color (CIEL*a*b*) and whiteness index (WID) were measured after each session, whereas whiteness index differences (ΔWID), color alteration (CIELab-ΔE, CIEDE2000-ΔE00), enamel morphology and pH, at end of bleaching therapy. The change in Knoop microhardness (ΔKHN) was compared before and after bleaching. Data were analyzed by two-way repeated measures ANOVA and Bonferroni (CIEL*, a*, b*), one-way ANOVA and Tukey (ΔWID, ΔE, ΔE00), and LSD (ΔKHN) tests (α=5%). SEM and pH measurements were submitted to descriptive analysis. No differences were observed in lightness (L*) or WID among the groups (p > 0.05), but HP exhibited lower b* values (p<0.05), higher ΔWID than HPnT, and the highest ΔE among the groups (p < 0.05). No differences in ΔE00 were observed between HP and HPncT (p > 0.05), and HPncT showed higher ΔKHN than HP (p < 0.05). HP presented pH values closer to neutral (6.9), whereas experimental agents showed acidic pH values (2.3-3.9). No morphological changes were observed in HP or HPncT groups. HPncT was able to bleach the enamel and maintain enamel microhardness and surface integrity, even at low pH.

Bleaching and microstructural effects of low concentration hydrogen peroxide photoactivated with LED/laser system on bovine enamel

BACKGROUND

Tooth whitening protocols with low concentration hydrogen peroxide (HP) appear to minimize the microstructural effect on teeth. In addition, light sources have been used to enhance bleaching efficiency. This study evaluated the color change and microhardness of a protocol with 6% HP photoactivated by LED/laser in comparison with 35% HP.

METHODS

Twenty bovine incisors were randomized in two groups: 6% HP + LED/laser and 35% HP (n=10). Teeth were submitted to staining using dark tea. Three whitening sessions were carried out according to the manufacturer's instructions. Enamel microhardness (VHN) and color change evaluation (∆L*, ∆a*, ∆b*, ∆E₀₀ [CIEDE2000], and WI_D) before 24 hours and 7 days after the last whitening session were performed. Two-way repeated ANOVA and Bonferroni post-test was used (α = 0.05).

RESULTS

Both groups showed perceptible color changes, being more pronounce for 35% HP. Differences were observed for ∆a*, ∆b* and ∆E₀₀ (p≤0.027), except for ∆L* (p>0.05). Differences were also found in the comparison among the evaluation times within the same group (p≤0.027), except for ∆a* results (p>0.05). WI_D showed that 35% HP exhibited high whiteness values. Regarding microhardness, the groups did not show significant differences (p>0.05). However, 35% HP showed decreased values after 7 days of the last whitening session compared to the baseline (p≤0.027).

CONCLUSIONS

6% HP + LED/laser promoted perceptible color change, but not comparable with 35% HP. No differences on enamel microhardness were observed between the whitening protocols. However, 35% HP showed decreased hardness after 7 days of whitening compared to baseline.

[Ph stability of four hydrogen peroxide bleaching gels at different time intervals]

Objective

The aim of this in vitro study was to evaluate the pH of four bleaching agents based on high concentration hydrogen peroxide (30-35%) Whiteness HP Maxx (HPM), Lase Peroxide (LP), Whiteness HP Automixx (HPA) and Dash (DA) in different clinical periods (baseline, 15', 30' and 45').

Materials and methods

40 specimens (bovine teeth) were divided into 4 groups; one group for each bleaching agent. Each bleaching agent was prepared according to the manufacturer's instructions and was applied on the vestibular surface. The pH of the bleaching agent was measured with a digital pH meter at baseline, 15, 30 and 45 minutes. ANOVA, Friedman and Wilcoxon tests were applied.

Results

The pH values showed a trend to decreasing from the initial time of application to the final time, except for the DA group, which showed increasing pH values over time. The HPM group showed significant differences between baseline and the remaining periods. The LP group LP showed significant difference between 15' and the other periods. The HPA group showed significant differences between baseline and the remaining periods. Finally, the DA group, showed a significant difference between baseline and 45'.

Conclusions

The pH values of 3 of the bleaching agents decreased over time, with the exception of Dash which increased in the different time periods.

Longitudinal, Randomized, and Parallel Clinical Trial Comparing a Violet Light-Emitting Diodes System and In-Office Dental Bleaching: 6-Month Follow-Up

Objective: This in vivo study compared two bleaching techniques with regard to the degree of tooth sensitivity (TS), color change, and treatment stability for a 6-month follow-up period. Materials and methods: Sixty volunteers were selected according to inclusion and exclusion criteria and submitted to in-office bleaching. For group 1, we performed one bleaching session with a 35% hydrogen peroxide gel and a second bleaching session after 7 days; for group 2, we performed two bleaching sessions with two applications per session, each session with a 7-day interval, using a light-emitting diodes (LEDs) device emitting violet light (405-410 nm) without employing peroxide-containing bleaching gel. TS was recorded immediately before and immediately after each bleaching session using the Variance Analogic Scale. The color of upper central incisors and upper canines at baseline was recorded immediately after each bleaching session, after 15, 30, and 180 days, with a value-oriented shade guide used by two well-trained observers. Results: The two whitening protocols results were similar regarding the immediate effectiveness and 6-month stability of tooth whitening. Dental bleaching with violet LED did not promote postoperative pain sensitivity at any of the evaluated times. However, dental bleaching performed with 35% hydrogen peroxide promoted higher postoperative pain sensitivity. Conclusions: The violet light alone provided dental bleaching and had the clinical advantage of promoting less immediate postoperative sensitivity; however, an unwanted repigmentation occurred after dental bleaching with light alone.

Do bleaching gels affect the stability of the masking and caries-arresting effects of caries infiltration-in vitro

Objectives

The aim of this study was to evaluate the influence of different bleaching gels on the masking and caries-arresting effects of infiltrated and non-infiltrated stained artificial enamel caries lesions.

Materials and methods

Bovine enamel specimens (n = 240) with each two sound areas (SI and SC) and each two lesions (DI and DC) were infiltrated (DI and SI), stained (1:1 red wine-coffee mixture,70 days), and randomly distributed in six groups to be bleached with the following materials: 6%HP (HP-6), 16%CP (CP-16), 35%HP (HP-35), 40%HP (HP-40), and no bleaching (NBl,NBl-NBr). Subsequently, specimens were pH-cycled (28 days, 6 × 60 min demineralization/day) and all groups except NBl-NBr were brushed with toothpaste slurry (1.100 ppm, 2×/day, 10 s). Differences in colorimetric values (ΔL, ΔE) and integrated mineral loss (ΔΔZ) between baseline, infiltration, staining, bleaching, and pH cycling were calculated using photographic and transversal microradiographic images.

Results

At baseline, significant visible color differences between DI and SC were observed (ΔE_baseline = 12.2; p < 0.001; ANCOVA). After infiltration, these differences decreased significantly (ΔE_infiltration = 3.8; p < 0.001). Staining decreased and bleaching increased ΔL values significantly (p ≤ 0.001). No significant difference in ΔΔE was observed between before staining and after bleaching (ΔE_bleaching = 4.3; p = 0.308) and between the bleaching agents (p = 1.000; ANCOVA). pH-cycling did not affect colorimetric values (ΔE_pH-cycling = 4.0; p = 1.000). For DI, no significant change in ΔZ during in vitro period was observed (p ≥ 0.063; paired t test).

Conclusions

Under the conditions chosen, the tested materials could satisfactorily bleach infiltrated and non-infiltrated stained enamel. Furthermore, bleaching did not affect the caries-arresting effect of the infiltration.

Clinical relevance

The present study indicates that bleaching is a viable way to satisfactorily recover the appearance of discolored sound enamel and infiltrated lesions.

Effect of bleaching agents on hardness, surface roughness and color parameters of dental enamel

Background

In this study was evaluated the effect of carbamide peroxide (CP) and hydrogen peroxide (HP) in different concentrations on hardness, roughness, and color parameters (color change - ΔE, lightness - ΔL, and yellow-blue axis - Δb) of bovine teeth.

Material and Methods

Fifty square dental blocks (7 x 7 x 2 mm) were submitted to initial readings of Knoop hardness, surface roughness (Ra), and color parameters. Specimens were divided into 5 groups (n = 10): control group was kept in artificial saliva during the experimental period; CP 20% was bleached for 2 h daily for 14 days, HP 9.5% was bleached for 30 min daily for 14 days, HP 38% the bleaching gel was applied for 15 min, gel was removed and it was reapplied for two more times, the bleaching session was repeated for another 2 times every 7 days, totaling three sessions, and in CP 45% three sessions of 30 min each were performed of 7 in 7 days. All groups after the bleaching procedures had the bleaching gel removed, washed, and kept in artificial saliva. At the end of bleaching treatment, the hardness, roughness, and color parameters (ΔE, ΔL, and Δb) were re-evaluated. Data were analyzed by ANOVA, Tukey, and Dunnett tests (α = 0.05).

Results

Bleaching promoted a reduction in hardness, the CP 45% showed the lowest hardness and the CP 20% the highest, the HP 9.5% and HP 38% showed intermediate values of hardness. Bleaching agents did not affect the roughness. CP 20% and HP 38% promoted the highest values of ΔE and higher reduction of yellowish tone of tooth. Lightness increase after bleaching treatment for all groups.

Conclusions

All the bleaching agents tested showed effectiveness, but with reduced hardness.

Key words:Carbamide peroxide, hydrogen peroxide, tooth whitening, hardness, roughness.

Experimental gel containing bioactive glass-ceramic to minimize the pulp damage caused by dental bleaching in rats

Objectives

This study evaluated if the use of a bioactive glass-ceramic-based gel, named Biosilicate (BS), before, after or mixed with bleaching gel, could influence the inflammation of the dental pulp tissue of rats’ molars undergoing dental bleaching with hydrogen peroxide (H₂O₂).

Methodology

The upper molars of Wistar rats (Rattus norvegicus, albinus) were divided into Ble: bleached (35% H₂O₂, 30-min); Ble-BS: bleached and followed by BS-based gel application (20 min); BS-Ble: BS-based gel application and then bleaching; BS/7d-Ble: BS-based gel applications for 7 days and then bleaching; Ble+BS: blend of H₂O₂ with BS-based gel (1:1, 30-min); and control: placebo gel. After 2 and 30 days (n=10), the rats were euthanized for histological evaluation. The Kruskal-Wallis and Dunn statistical tests were performed (P<0.05).

Results

At 2 days, the Ble and Ble-BS groups had significant alterations in the pulp tissue, with an area of necrosis. The groups with the application of BS-based gel before H₂O₂ had moderate inflammation and partial disorganization in the occlusal third of the coronary pulp and were significantly different from the Ble in the middle and cervical thirds (P<0.05). The most favorable results were observed in the Ble+BS, which was similar to the control in all thirds of the coronary pulp (P>0.05). At 30 days, the pulp tissue was organized and the bleached groups presented tertiary dentin deposition. The Ble group had the highest deposition of tertiary dentin, followed by the Ble-BS, and both were different from control (P<0.05).

Conclusion

A single BS-based gel application beforehand or BS-based gel blended with a bleaching gel minimize the pulp damage induced by dental bleaching.

Chemical composition and roughness of enamel and composite after bleaching, acidic beverages and toothbrushing

Background

In this study was assessed the surface roughness and chemical composition of tooth enamel and composite resin after bleaching treatment, immersion in acidic beverages, and simulated toothbrushing.

Material and Methods

One hundred and twenty dental blocks (10 x 10 x 3 mm) were randomly assigned (n = 10) according to surface treatment [none (N), bleaching (B), toothbrushing (T), and B+T] and storage medium [saliva (S), whiskey (W), and orange juice (O)]: experimental groups - N+S, N+W, N+O, B+S, B+W, B+O, S+T, W+T, O+T, B+S+T, B+W+T, and B+O+T. Two bleaching sessions were conducted using 38% hydrogen peroxide (3 applications). Surface roughness was measured using a roughness tester and composition was determined by micro energy-dispersive X-ray fluorescence spectrometry (µ-EDXRF) before and after treatments. Calcium/phosphorus (Ca/P) ratio in enamel and silica (Si) content in composite were evaluated. Data were statistically analyzed by ANOVA and Tukey’s test (α = 0.05).

Results

Overall, increased values of surface roughness for enamel and composite were observed mainly after immersion in orange juice and bleaching/toothbrushing association. Moreover, this association and immersion in whiskey resulted in lower Ca/P ratio and after aging methods, bleached and bleached/toothbrushed groups showed decreased in Ca/P ratio compared to initial values. All groups showed Si content decrease at the end, except the group without surface treatment and immersed in saliva, and bleaching followed by immersion in orange juice and toothbrushing caused the highest Si reduction.

Conclusions

Bleaching and toothbrushing combination strengthened the effects caused by acidic drinks on roughness and chemical composition of enamel and composite.

Key words:Tooth bleaching, toothbrushing, physical properties, chemical properties.

Effects of pH and Application Technique of In-office Bleaching Gels on Hydrogen Peroxide Penetration into the Pulp Chamber

Objective:

This in vitro study aimed to quantify the penetration of hydrogen peroxide (HP) into the pulp chamber in teeth submitted to in-office bleaching with varied pH and application techniques. The color change and pH of the in-office bleaching product during application was also evaluated.

Methods and Materials:

Ninety-six human premolars were used and randomly divided into 10 groups (n=9) according to the following combination of factors: pH of in-office bleaching agents (two neutral/alkaline pH: Opalescence Boost 38% and Whiteness HP Blue 35% and three acidic pH: Whiteness HP Maxx 35%, Lase Peroxide Sensy 35%, and Total Blanc Office 35%) and application modes (for 3 × 15 minutes [3×15] and 1 × 45 minutes [1×45]). An additional group of non-bleached teeth (control; n=6) was added. First, all teeth were sectioned 3 mm from the cementoenamel junction and the pulp tissue was removed. An acetate buffer was placed in the pulp chamber of all teeth. After bleaching, this solution was transferred to a glass tube in which HP was allowed to react with other components, resulting in a pink solution. The optical density of this pink solution was measured using ultraviolet-visible spectroscopy and converted into amount of HP. Color change before and 1 week after bleaching was evaluated using a digital spectrophotometer. A pH meter with a 6-mm circular and flat surface was used in contact with the enamel surface to quantify the pH of the bleaching gels during application. Data were analyzed using two-way analysis of variance and Tukey tests (α=0.05).

Results:

Overall, lower mean HP penetration values were observed for Opalescence Boost 38% and Whiteness HP Blue 35% compared with other bleaching gels (p&lt;0.05). Opalescence Boost 38% and Whiteness HP Blue 35% were not influenced by the application technique (p&gt;0.05). However, lower mean HP penetration values were observed for Whiteness HP Maxx 35%, Total Blanc Office 35%, and Lase Peroxide Sensy 35% when using the 3×15 application technique compared with the 1×45 technique (p&lt;0.05). Significant whitening was detected and no significant difference of color change was observed between groups (p&gt;0.54). The pH did not change during the 3×15 application technique; however, all acidic bleaching gels significantly decreased in pH when applied for 1×45 (p&lt;0.01).

Conclusions:

The amount of HP that reaches the pulp chamber was lower when neutral/alkaline pH gels were used, independently of the application technique. When considering acidic pH gels, it is preferable to use the 3×15 application technique, mainly because longer application time (1×45) results in lower pH. No difference was observed between groups with regards to color change.

Effect of pH conditioners on tooth bleaching

The purpose of this study was to evaluate the effect of pH conditioners on tooth bleaching using hematoporphirin-stained paper and artificially discolored bovine tooth model. Experimental bleaching gels containing 23% hydrogen peroxide, adjusting pH 7.0 by different pH conditioners (NaOH, NaHCO3, Na2CO3, KOH, KHCO3, and K2CO3), were prepared. Each bleaching gel was applied on a hematoporphirin-stained paper, and the light was exposed for 5 min. Before and after bleaching, color was measured and color difference was calculated. Artificially discolored bovine tooth samples were prepared and bleached by four experimental bleaching gels containing NaOH, NaHCO3, Na2CO3, or KHCO3. The bleaching time was 10 min with light exposure, and bleaching was repeated 10 times. The color of bleached surface was measured at each bleaching period, and color difference was calculated. In the experiment using hematoporphirin-stained paper, degrees of color difference were KHCO3 > NaHCO3 > KOH > NaOH > Na2CO3 ≥ K2CO3. In the experiment using bovine teeth, degrees of color difference were KHCO3 > NaHCO3 > NaOH > Na2CO3. It was concluded that the bleaching materials with same pH and different pH conditioners showed different bleaching effects and that both cation and anion in the pH conditioners affected bleaching effect.

In-office bleaching with a commercial 40% hydrogen peroxide gel modified to have different pHs: Color change, surface morphology, and penetration of hydrogen peroxide into the pulp chamber

OBJECTIVE

In-office bleaching gels are usually marketed in different pHs. This study is aimed at evaluating the efficacy, enamel surface morphology and concentration of hydrogen peroxide (HP) in the pulp chamber of teeth bleached with 40% HP with different pHs.

MATERIALS AND METHODS

Forty premolars were randomly divided according to bleaching gel pH: 5.1, 6.3, 7.0, and control (no bleaching). Teeth were prepared, an acetate buffer was placed in the pulp chamber and teeth were bleached with two 20-minutes applications. The amount of HP was determined on a UV-VIS spectrophotometer. Color change was assessed by using a digital spectrophotometer before and 1 week after bleaching treatment. Five additional premolars were divided into four parts, assigned to the same groups above for analysis under scanning electron microscope. Data were subjected to anova and Tukey's tests (alpha = 0.05).

RESULTS

The group pH 5.1 showed the highest HP diffusion in the pulp chamber (P < .001). No significant difference was detected in color change (P = .51). All groups presented the same pattern of enamel demineralization.

CONCLUSIONS

The bleaching agent with pH 5.1 presented the highest HP amounts in the pulp chamber, but color change and enamel morphology were similar among groups.

CLINICAL SIGNIFICANCE

Regardless of the pH, the bleaching effect can be observed in teeth submitted to high concentrations of HP, but a higher permeability of HP was found in the pulp chamber of teeth bleached with more acidic bleaching agents. Based on that, we suggest the use of alkaline gels for in-office bleaching to minimize damage to the pulpal tissue.

Development of a bioadhesive nanoformulation with Glycyrrhiza glabra L. extract against Candida albicans

Glycyrrhiza glabra L. is considered an important source of bioactive compounds. This study aimed at the development of an efficient solution for the treatment of oral candidiasis. Several extracts of Glycyrrhiza glabra L. were prepared using different solvents and their potential in vitro antifungal activity was assessed. Ethanolic extracts showed the most promising results against C. albicans. This extract was incorporated into mucoadhesive nanoparticles (PLA, PLGA and alginate), which were further included in an oral gel, an oral film and a toothpaste, respectively. The results showed that nanoparticles were successfully produced, presenting a mean size among 100-900 nm with high encapsulation efficiency. In vitro studies showed that the most bioadhesive formulation was the oral film with extract-loaded PLGA nanoparticles, followed by the toothpaste with extract-loaded alginate nanoparticles and the oral gel with extract-loaded PLA nanoparticles.

Mucoadhesive assessment of different antifungal nanoformulations

Oral candidiasis is an important opportunistic fungal infection and polyenes and azoles are still the most used antifungal agents. However, the oral absorption resulting from most available treatments is generally poor and, consequently, a very high frequency of administrations of antifungal agents is strongly required. Therefore, the major challenge is to improve the retention of the antifungal agents in buccal mucosa, and the encapsulation into mucoadhesive systems may be considered as a possible strategy to achieve this objective. Three types of mucoadhesive polymeric nanoparticles (polylactic acid (PLA), polylactic-co-glycolic acid (PLGA) and alginate) were prepared using nystatin as model drug. The drug-loaded nanoparticles were then included in toothpaste, oral gel and oral films, respectively. The results demonstrated that the loaded nanoparticles were successfully produced, presenting a mean size between 300-900 nm and with a negative surface charge. Also, the determination of the encapsulation efficiency of all nanoparticles showed values above 70%. In terms of the in vitro mucoadhesion, the best formulation was the oral film loaded with the PLGA nanoparticles followed by the oral gel with PLA nanoparticles and thirdly the toothpaste with alginate nanoparticles. This was confirmed in an in vitro rinsing model with mucus producing HT29-MTX cells, where the percentage of nystatin retained to the cells after 40 min of simulated saliva flow was between 10-27% when formulations were used and only 4% for free nystatin. Further studies will include in vivo testing using animal models.