Effects of dental bleaching protocols with violet radiation on the color and chemical composition of stained bovine enamel

Evaluation of Enamel Surface Properties Submitted to Bleaching With 35% Hydrogen Peroxide Associated With Titanium Tetrafluoride (TiF4)

OBJECTIVE

This study evaluated the color change, surface roughness, mineral content and morphology of enamel bleached with 35% hydrogen peroxide (HP) combined with an experimental gel containing 1% titanium tetrafluoride (TiF4).

MATERIALS AND METHODS

Bovine enamel blocks were treated with (n = 12): (TiF) experimental gel containing 1% TiF4, (HP) 35% HP, (HPT) 35% HP + 1% TiF4 and (CT) control. Bleaching with HP was performed in 3 sessions (3 × 15 min/applications). pH, colorimetric parameters, surface roughness, mineral content and enamel morphology were determined. The pH was evaluated for 45 min. The color parameters were determined before bleaching (T0), and 14 days elapsed from the last bleaching session (T4). Surface roughness was analyzed at T0 and immediately after last bleaching session (T3). Enamel mineral content and morphology were verified at T4. Data were statistically analyzed by one-way, two-way ANOVA and Kruskal-Wallis (α = 0.05).

RESULTS

TiF increased surface roughness, and no differences between HP and HPT in terms of color andCO 3 2 - -PO 4 3 - mineral content. Ti was detected only on TiF, and slight surface morphology changes were observed in bleached enamel.

CONCLUSIONS

The combination of TiF4 and 35% HP did not interfere with the enamel bleaching effect, controlled surface roughness, and kept mineral content but promoted a minor surface morphology alteration.

CLINICAL SIGNIFICANCE

Due to the adverse effects of bleaching, titanium tetrafluoride (TiF4) has gained attention for its therapeutic properties, including the ability to reverse mineral loss and neutralize remineralization of mineral structures. Therefore, TiF4's remineralizing capacity may be a good alternative for incorporation into hydrogen peroxide bleaching agents.

Effects of experimental in-office bleaching gels incorporated with co-doped titanium dioxide nanoparticles on dental enamel physical properties

To evaluate the physical properties of enamel submitted to hydrogen peroxide (HP) incorporated with titanium dioxide nanoparticles (NP) co-doped with nitrogen and fluorine and irradiated with violet LED light (LT). Enamel-dentin disks were randomly allocated (T0) into groups, according to HP (HP6, HP15, or HP35) and NP (no NP, 5NP, or 10NP) concentrations, and irradiated or not with LT. A negative control (NC) group was set. After three bleaching sessions (T1, T2, and T3), specimens were stored in saliva for 14 days (T4). Enamel surface microhardness number (KHN), surface roughness (Ra), cross-sectional microhardness (ΔS), energy-dispersive spectroscopy (EDS), scanning electron (SEM), and polarized light (PLM) microscopies were performed. Surface KHN was significantly influenced by NP over time, independently of LT irradiation. At T3 and T4, gels with 5NP and 10NP exhibited no KHN differences compared to NC and baseline values, which were not observed under the absence of NP. NP incorporation did not statistically interfere with the ΔS and Ra. PLM images exhibited surface/subsurface darkening areas suggestive of demineralizing regions. SEM demonstrated some intraprismatic affection in the groups without NP. EDS reported a higher enamel calcium to phosphorus ratio following 10NP gels applications. Gels with NP maintained the enamel surface microhardness levels and seemed to control surface morphology, upholding the mineral content. None of the proposed experimental protocols have negatively influenced the enamel surface roughness and the cross-sectional microhardness.

Effect of hydrogen peroxide versus charcoal-based whitening mouthwashes on color, surface roughness, and color stability of enamel

BACKGROUND

Patients tend to favor the whitening mouthwashes as they are easily applied and affordable. This study aimed to evaluate the effect of hydrogen peroxide versus charcoal-based whitening mouthwashes on color, surface roughness, and color stability of enamel. In the current study, the whitening mouthwashes used have the ability to stop future stains due to their white seal technology.

METHODS

A total of 21 permanent central incisor teeth extracted for periodontal reasons were used in the present study. Teeth roots were sectioned and crowns were mounted in self-cured acrylic resin blocks. The specimens were randomly divided into three groups (n = 7) according to the tested whitening mouthwash: Control group ‟ DW" (Distilled water), ‟OW" group: Peroxide-based mouthwash (Colgate Optic White) and ‟CP" group: Charcoal-based mouthwash (Colgate® Plax Charcoal). Regarding ‟OW" and ‟CP" groups, the specimens were immersed in 20 ml of the tested mouthwash in each corresponding group for 1 min twice daily (morning and evening) for a total of 12 uninterrupted weeks. Color change was assessed using VITA Easyshade spectrophotometer and surface roughness (Ra) was measured using a white light interferometer. The specimens were stained using black tea solution and color was measured after 24 h of immersion for assessment of color stability.

RESULTS

Color change results revealed that both whitening mouthwashes were able to restore color comparable to the control group with no significant difference between them. Regarding surface roughness, the control group showed the highest mean Ra value, followed by ‟OW" group while ‟CP" group showed the lowest mean Ra value. While color stability after staining, the control group showed a significantly higher value than the ‟CP" and ‟OW" groups.

CONCLUSION

Hydrogen peroxide and charcoal-based whitening mouthwashes improve the color of enamel with no adverse effect on the surface roughness. Both whitening mouthwashes were beneficial to maintain the color after staining and prevent future enamel stains.

Influence of bleaching gels formulated with nano-sized sodium trimetaphosphate and fluoride on the physicochemical, mechanical, and morphological properties of dental enamel

OBJECTIVES

To evaluate in vitro the effects of sodium fluoride (F) and nano-sized sodium trimetaphosphate (TMPnano) added to a 35% hydrogen peroxide (H2O2) bleaching gel on the color alteration, enamel mechanical and morphological properties, and H2O2 transamelodentinal diffusion.

MATERIALS AND METHODS

Bovine enamel/dentin discs (n = 180) were divided according to the bleaching gel: 35% H2O2 (HP); 35% H2O2 + 0.1% F (HP/F); 35% H2O2 + 1% TMPnano (HP/TMPnano); 35% H2O2 + 0.1% F + 1% TMPnano (HP/F/TMPnano) and 35% H2O2 + 2% calcium gluconate (HP/Ca). The gels were applied 3 times by 40 min; once each 7-day. The Commission Internationale de l'Eclairage (CIE) L*a*b* total color alteration (ΔE), color alteration by CIEDE2000 (ΔE00), whitening index (ΔWID), surface (SH) and cross-sectional hardness (ΔKHN), surface roughness (Ra), and transamelodentinal diffusion were determined. Enamel surfaces were evaluated by Scanning Electron Microscopy (SEM) and X-ray Dispersive Energy (EDX). Data were submitted to ANOVA, followed by the Student-Newman-Keuls test (p <0.05).

RESULTS

ΔE, ΔE00, and ΔWID were similar among the gels that promoted a bleaching effect after treatment (p <0.001). Mineral loss (SH and ΔKHN), Ra, and H2O2 diffusion were lower for HP/F/TMPnano; the HP and HP/Ca groups presented the highest values (p <0.001). For SEM/EDX, surface changes were observed in all bleached groups, but less intense with TMPnano.

CONCLUSIONS

Gels containing F/TMPnano do not interfere with the bleaching effect and reduce enamel demineralization, roughness, H2O2 diffusion, and morphological changes.

CLINICAL RELEVANCE

Whitening gels containing F/TMPnano can be used as a new strategy to increase safety and maintain clinical performance.

Effectiveness of changing the color of darker teeth is potentiated by association with violet LED light

BACKGROUND

The effectiveness of in-office bleaching protocols performed with violet LED light either combined with a bleaching agent containing 37% carbamide peroxide, or not, was determined by comparing teeth with different degrees of darkening.

METHODOLOGY

Eighty bovine incisors were separated into groups of "light" teeth (luminosity greater than or equal to B3) and "dark" teeth (less than or equal to A3.5) to receive the protocols: HP - 35% hydrogen peroxide (Whiteness HP), CP - 37% carbamide peroxide (Whiteness SuperEndo), LED - violet LED light (Bright Max Whitening), CPLED - CP associated with the LED. For color analysis the CIEL*a*b* e WID, ΔEab, ΔE00 e ΔWID parameters were used. Data were analyzed using Mann-Whitney, Kruskal-Wallis, Dunn, Friedman or Nemenyi tests (α = 5%).

RESULTS

HP and CP resulted in similar color change values (ΔEab, ΔE00 e ΔWID) for light and dark teeth (p > 0.05). Dark teeth showed better bleaching effectiveness (ΔEab, ΔE00 e ΔWID) than light teeth when CPLED was used (p < 0.05). LED showed color change that were below the limits of acceptability and perceptibility for ΔWID.

CONCLUSION

light teeth are effectively bleached with the use of HP or CP, whereas dark teeth respond better to treatment with the CPLED protocol. Violet LED used alone did not show a satisfactory result.

Effects of experimental bleaching gels containing co-doped titanium dioxide and niobium pentoxide combined with violet light

OBJECTIVES

The objective of the study is to evaluate the bleaching potential of 6% hydrogen peroxide (6% HP) gels containing NF_TiO2 or Nb2O5 irradiated with a violet LED light and the effects on enamel mineral content and surface morphology.

METHODS

Particles were synthesized, and experimental gels were chemically analyzed by preliminary and accelerated stability tests, pH, and HP decomposition rate. Bovine enamel blocks were treated with 6% HP gels containing (n = 10): 5% NF_TiO2, 5% Nb2O5, 2.5% NF_TiO2 + 2.5% Nb2O5 or without particles (6% HP), irradiated or not with LED, and the control was treated with 35% HP. Color (∆E00) and whitening index (∆WID) variations, surface microhardness (SH), average roughness (∆Ra), Ca-P concentration (EDS), and enamel morphology (SEM) were assessed. Bleaching was performed in 3 sessions of 30 min and 7-day intervals. Data were submitted to two- (pH, decomposition rate, ∆E00, and ∆WID) or three-way ANOVA and Bonferroni (SH), Kruskal-Wallis (∆Ra), and Dunnet tests (α = 0.05).

RESULTS

No changes in the gel's color, odor, or translucency were observed. The pH (6 to 6.5) remained stable over time, and light irradiation boosted the HP decomposition rate. NF_TiO2 and Nb2O5-containing gels displayed higher ∆E00 and ΔWID when light-irradiated (p < 0.05). Nb2O5 and Nb2O5 + NF_TiO2 decreased enamel SH (p < 0.05), but no SH changes were found among groups (p > 0.05). No differences among groups were noted in ∆Ra, Ca-P content, and enamel morphology after treatments (p > 0.05).

CONCLUSION

Experimental light-irradiated 6% HP gels containing NF_TiO2 or Nb2O5 were chemically stable and exhibited bleaching potential comparable with 35% HP.

CLINICAL RELEVANCE

Low-concentrated HP gels containing NF_TiO2 or Nb2O5 and light-irradiated stand as a possible alternative to in-office bleaching.

Influence of violet LED and fluoride-containing carbamide peroxide bleaching gels on early-stage eroded/abraded teeth

PURPOSE

This study evaluated enamel with early-stage erosion/abrasion following bleaching with 20% and 45% carbamide peroxide (CP) gels containing fluoride (F) and irradiated with violet LED (LED).

METHODS

Enamel blocks were immersed in 1% citric acid (5 min) and artificial saliva (120 min) three times to produce early-stage enamel erosion. Simulated toothbrushing was performed only after the first saliva immersion, to provoke enamel abrasion. The erosive/abraded enamel samples were submitted to (n=10): LED/CP20, CP20, LED/CP20_F, CP20_F, LED/CP45, CP45, LED/CP45_F, CP45_F, LED, and control (without treatment). The pH of the gels was assessed, and color (ΔE₀₀) and whiteness index (ΔWI_D) changes were calculated after cycling (T₁), and 7 days from bleaching (T₂). Enamel surface roughness average (Ra) and Knoop microhardness (kg/mm², %SHR) were evaluated at baseline (T₀) at T₁ and T_2. Scanning electron microscopy evaluated the enamel surface morphology at T₂.

RESULTS

The gels' pH was neutral and CP20 and CP45 exhibited no differences in ΔE₀₀ and ΔWI_D (p>0.05) but LED increased these parameters for CP20_F and CP45. Erosion/abrasion significantly decreased mean kg/mm², and the LED group was the only one not increasing microhardness after bleaching (p>0.05). None of the groups fully recovered the initial microhardness. All groups exhibited %SHR similar to the control (p>0.05) and the increase in Ra was detected only after erosion/abrasion. CP20_F groups exhibited a more preserved enamel morphology.

CONCLUSION

Light irradiation combined with low-concentrated CP gel promoted a bleaching effect comparable to the high-concentrated CP. The bleaching protocols did not adversely impact the surface of early-stage eroded/abraded enamel.

Effect of non-vital tooth bleaching photoactivated with blue or violet LED on color and microhardness

BACKGROUND

To evaluate the efficacy of non-vital dental bleaching protocols using 35% hydrogen peroxide photoactivated with violet LED on color and microhardness of endodontically treated teeth.

METHODS

Forty specimens were selected and randomized into 4 groups (n = 10): C - Control, HP - 35% hydrogen peroxide, HP + BL - 35% hydrogen peroxide + blue LED, HP + VL - 35% hydrogen peroxide + violet LED. Three bleaching sessions were performed for each group. Color analysis was performed 7 days after each bleaching session. Two-way repeated measure ANOVA and Bonferroni test were used to evaluate the effect of different bleaching protocols and evaluation times on the dependent variables (∆E and ∆L). Dentin microhardness was measured 24 hours after the third bleaching session. Data were evaluated by ANOVA and Tukey's test at a significance level of 5%.

RESULTS

Differences on ∆E and ∆L were verified after the first and second bleaching sessions (p < 0.05) and showed stability after the third one, for all the groups. No differences were observed among HP, HP + BL, and HP + VL groups, regardless of the evaluation time (p > 0.05). HP and C showed the greatest and smallest reduction in dentin microhardness (p < 0.05), respectively. No difference between HP + BL and HP + VL protocols (P > 0.05) was observed.

CONCLUSIONS

High concentration hydrogen peroxide (35%) photoactivated with violet LED bleached endodontically treated teeth effectively. However, the same protocol negatively affected the dentin microhardness, but not in the same level of 35% HP solely used.

Effect of tobacco and nicotine in causing staining of dental hard tissues and dental materials: A systematic review and meta-analysis

INTRODUCTION

Dental staining is a common concern for tobacco users. However, little is known about which components of tobacco are responsible for the staining and whether nicotine may be implicated. This is of increasing relevance with the popularity of novel products such as heated-tobacco products and electronic cigarettes (E-cigarettes).

OBJECTIVES

This systematic review aimed to establish the evidence base for the effect if any, of the various tobacco and nicotine products in causing staining of dental hard tissues and materials.

MATERIAL AND METHODS

This systematic review was performed in accordance with the preferred reporting items for systematic reviews and meta-analyses guidelines. There were four structured population intervention comparison outcomesquestions. A search was conducted up to December 2021 in three databases: MEDLINE, EMBASE, and Web of Science, and manual searching of relevant sources was also completed. Two researchers individually reviewed the titles then abstracts and finally full articles. A reporting quality appraisal was conducted appropriately to the study methodology.

RESULTS

Of the 815 records titles identified, 56 full-text articles were assessed for eligibility, of which 27 were included for analysis. The included studies were mainly laboratory studies of varying reporting quality. There was evidence from 18 studies that tobacco exposure caused staining of dental hard tissues (pooled results from three studies- enamel/dentine; mean difference [MD]: 16.22; 95% confidence interval[12.11, 20.32; I2 : 96%)and materials (pooled result from four studies-resin composite; MD: 11.90; 95% CI: 11.47, 12.34; I2 : 100%). There was limited evidence that E-cigarettes 99%) and heated tobacco products (HTPs; pooled results from three studies--1.07, 6.54; I2 : 99%) cause staining, but this was lower than with traditional tobacco/found 11 compounds, of which 8 were terpenoids, from tobacco products implicated in causing staining. Finally, there was some evidence that resin composites stained more than other materials.

CONCLUSIONS

Tobacco smoking causes dental staining. There was limited evidence that E-cigarettes and HTPs did cause dental staining that was less intense than that caused by traditional tobacco products.

Effects of black tea tooth staining previously to 35% hydrogen peroxide bleaching

Aim: To determine if the artificial staining with black tea (BT) influences the enamel microhardness before in-office bleaching and if BT staining is necessary to evaluate the efficacy of bleaching with 35% hydrogen peroxide Methods: Enamel/dentin blocks were randomized into groups according to the staining protocol (n=5/group): (CO) control – maintained in artificial saliva solution (AS); (BT4) immersed in black tea solution for 4 h; (BT24) immersed in black tea solution for 24 h. After the staining protocols, all specimens were kept in AS for one week, followed by bleaching (three sessions of HP application for 40 min). Knoop surface microhardness (kgF/mm2) was determined at baseline (T0), after staining (T1), after 7 days of storage in AS (T2), and after bleaching (T3). The color (ΔE00) and coordinate changes (ΔL, Δa, Δb) were measured using a digital spectrophotometer at T0 and T3. Data were submitted to one-way (ΔE00, ΔL, Δa, Δb) or two-way ANOVA repeated measures (kgF/mm2) and Tukey’s test (a=5%). Results: The staining protocols (BT4 and BT24) promoted significantly lower microhardness (T1 and T2, p<0.05) than CO, whereas CO was the only group to maintain microhardness values over time. Bleaching promoted perceptible ΔE00 without a significant difference among the groups regardless of the staining protocol (p=0.122). CO and BT4 showed no differences in terms of ΔL and Δa (p>0.05), but BT4 displayed a higher Δb than CO. Conclusion: The artificial staining with BT negatively affected the enamel surface microhardness and was not essential to evaluate the efficacy of 35% hydrogen peroxide bleaching.

Novel Experimental In-Office Bleaching Gels Containing Co-Doped Titanium Dioxide Nanoparticles

The present study reports on the development and testing of novel bleaching agents containing co-doped metaloxide nanoparticles (NP; 0%, 5%, 10% v/w) and hydrogen peroxide (HP, 0%, 6%, 15%, and 35%). Bovine blocks (n = 200, A = 36 mm2) were obtained and randomly distributed into experimental groups (n = 10/group). NPs were incorporated into gels before bleaching (3 sessions, 7 days apart, 30 min/session, irradiated with violet light-LT). Color changes (ΔE00, ΔWID), mineral content (CO32−, PO43−), and topography were assessed (spectrophotometer, ATR-FTIR, and AFM) before and after bleaching procedures (14 days). Metabolic status and three-dimensional components of non-disrupted Streptococcus mutans biofilms were investigated using a multimode reader and confocal microscopy. The results indicate that ΔE00 and ΔWID significantly increased with NPs’ concentrations and LT. The enamel’s mineral ratio was adversely impacted by HP, but alterations were less pronounced when using NP-containing gels. The enamel’s topography was not damaged by the bleaching protocols tested. The bioluminescence results show that bleaching protocols do not render latent antibacterial properties to enamel, and the confocal microscopy results demonstrate that the 3-dimensional distribution of the components was affected by the protocols. The proposed nanotechnology improved the bleaching efficacy of experimental materials independent of hydrogen peroxide or irradiation and did not adversely impact the enamel’s surface properties or its chemical content.

Characterization and effectiveness of a violet LED light for in-office whitening

OBJECTIVES

This study characterized a violet LED light (V-LED; bright max whitening) tooth whitening device and evaluated its efficacy on stained enamel compared to hydrogen peroxide (HP).

MATERIALS AND METHODS

Characterization of the V-LED beam profile was performed using a laser beam-profiler. The irradiance was measured throughout an exposure cycle at 0- and 8-mm distances using an integrating sphere and a spectral radiometer. Bovine enamel/dentin blocks stained with black tea (BT), cigarette smoke (CS), or without staining (CONT) were subjected to V-LED or 40% HP (n = 10/group). Color parameters (ΔL, Δa, Δb, and ΔE₀₀) were measured using a digital spectrophotometer. Light transmission was estimated through 1-mm-thick bovine enamel slices (n = 5). ΔL, Δb, ΔE₀₀, and irradiance were analyzed by two-way ANOVAs and Tukey's tests, Δa by Kruskal-Wallis and Mann-Whitney tests, and light transmission by t-test (α = 5%).

RESULTS

Heterogeneous beam distribution was observed for the emitting V-LED chips. After 20 sequential exposures, irradiance levels were reduced 25-50%, regardless of the distance from V-LED. Localized irradiance values were statistically different between beam locations and different distances from the target. V-LED produced lower ΔE_00, ΔL, Δa, and Δb values than HP for CONT and BT, with no differences for CS. Light transmittance decreased approximately 98% through 1-mm thick enamel.

CONCLUSIONS

V-LED irradiance was heterogeneous and decreased throughout the exposure cycles and was also greatly reduced with increasing tip distance. V-LED produced a significantly lower whitening effect on BT and control teeth.

CLINICAL RELEVANCE

This study contributes to the knowledge of V-LED and its clinical use.

Effects of 45S5 bioactive glass on the remineralization of early carious lesions in deciduous teeth: an in vitro study

Background

Early childhood caries has been designated as a serious public health problem. The traditional restoration method is very challenging, especially in uncooperative patients. Non-invasive therapy, like remineralization agents, which have been developed to reverse the demineralization progress at the early stage of caries, may be a better choice. This study aimed to evaluate the remineralization efficacy of different concentrations of 45S5 bioactive glass (BAG) on artifical carious lesions of deciduous enamel.

Methods

65 caries-like enamel lesions of the deciduous teeth were assigned to 5 groups (n = 13) and transported to a 14 days pH-cycling: Group A: 2%BAG, Group B: 4%BAG, Group C: 6%BAG, Group D: 8%BAG, and Group E: deionized water (DDW, negative control). 8 sound (Group F) and 8 demineralized teeth (Group G) were prepared for contrast. The recovery power of mechanical property was evaluated by Vickers hardness test through the recovery of enamel microhardness (%REMH). Surface morphology, mass fraction of Ca and P ions, and Ca/P atomic ratio were analyzed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (EDX). Moreover, Fourier transform infrared spectroscopy equipped with attenuated total reflectance was used to identify the chemical structure of newly formed compounds.

Results

% REMH were (42.65 ± 1.35), (52.59 ± 2.96), (57.40 ± 1.72), (52.91 ± 2.55), (12.46 ± 2.81) in 2%BAG, 4%BAG, 6%BAG, 8%BAG, and DDW groups respectively. Micro-spherical particles were deposited in all BAG groups and 6% BAG showed the densest and most uniform surface. EDX analysis identified significantly higher Ca(wt%) and P(wt%) in four BAG groups than in the demineralized group (p < 0.005), while 6% BAG showed the highest mineral gain efficacy. The infrared spectrum demonstrated that newly mineralized crystals were consisted of type-B hydroxycarbonate apatite.

Conclusion

BAG possessed a promising remineralization effect on artificial lesions in deciduous enamel by recovering enamel surface mechanical property, morphology and chemical elements. Among them, 6% BAG performed the greatest overall efficacy. Acting as a new caries-arresting biomaterial, 45S5 BAG has the potential to facilitate the adaptation of better carious prevention strategies in children.

LED/laser photoactivation enhances the whitening efficacy of low concentration hydrogen peroxide without microstructural enamel changes

BACKGROUND

The association of low concentration hydrogen peroxide (HP) and a light source has been widely used to achieve efficient bleaching. We investigated the colorimetric and microstructural changes of bovine enamel bleached with 6% HP associated or not with a hybrid light source system of violet light and laser (LED/laser).

METHODS

Twenty bovine crowns were used to obtain specimens of 7 × 7 × 2 mm. Then, they were randomized in two groups (n=10): 6% HP and 6% HP + LED/laser. After staining with dark tea solution, three bleaching sessions were performed. Colorimetric evaluation (∆L*, ∆a*, ∆b*, ∆E₀₀ [CIEDE2000] and WI_D) after 24 hours of each session and 7 days after the final bleaching session was performed. Enamel Vickers microhardness at baseline, 24 hours and 7 days after the last bleaching session were also evaluated. Two-way repeated measures ANOVA and Bonferroni post-test was used at a significance level of 5%.

RESULTS

6% HP and 6% + HP LED/laser showed satisfactory bleaching results. The group photoactivated showed higher WI_D values (p<0.05). Differences between groups were observed for ∆E₀₀, ∆L* and ∆a* (p<0.05), except for ∆b* (p>0.05). Intra-group differences were also found (p<0.05). Regarding microhardness, no inter or intra-group differences were observed (p>0.05).

CONCLUSIONS

The photoactivation with LED/laser enhanced the whitening efficacy of 6% HP compared to the group without photoactivation. Thus, the LED/laser activation appears to be a good option when using low concentration HP-based agents. In addition, both bleaching protocols did not cause changes on enamel microhardness.

Colorimetric evaluation after in-office tooth bleaching with violet LED: 6- and 12-month follow-ups of a randomized clinical trial

OBJECTIVES

To evaluate the long-term outcomes of in-office bleaching with violet LED light (LED) alone or combined with carbamide (CP) or hydrogen (HP) peroxides.

METHODS

Volunteers of a previous short-term study were recalled for 6- and 12-month follow-ups, according to the following interventions (n = 18/group): LED, CP, LED/CP, HP, and LED/HP. The objective color (ΔE_ab, ΔE₀₀) and whiteness index (ΔWI_D) changes were calculated applying the CIELab coordinates' values obtained using a spectrophotometer. A visual shade guide determined the tooth's subjective color change (ΔSGU). Data were submitted to one-way ANOVA or Welch's ANOVA, following appropriate post hoc tests (α = 5%).

RESULTS

The LED and CP groups exhibited the lowest ΔE_ab, ΔE₀₀, and ΔSGU (p < 0.05), but the LED group displayed a significantly lower ΔWI_D. After 12 months, the LED/CP group presented a higher ΔE_ab and ΔE₀₀ than the CP group (p < 0.05). ΔE_ab, ΔE₀₀, ΔSGU, or ΔWI_D means did not differ statistically between the LED/CP and HP groups. The LED/HP group presented a higher ΔE₀₀ than the HP group, regardless of the time.

CONCLUSIONS

The bleaching efficacy of LED alone was significantly lower compared to the LED/CP and HP-containing protocols. After 12 months, the LED/CP and HP groups did not differ in bleaching efficacy. LED irradiation only increased the objective color change of bleaching gels.

CLINICAL RELEVANCE

LED alone promoted a long-term perceptible bleaching, but not compatible with that of high-concentrated HP. The bleaching outcomes of violet irradiation to 37% CP were maintained over time, with LED/CP demonstrating comparable results to HP even after 12 months.

NATIONAL CLINICAL TRIALS REGISTRY (REBEC)

RBR-5t6bd9.

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.