Evaluation of temperature increase during in-office bleaching

Influence of dental bleaching on the pulp tissue: A systematic review of in vivo studies

BACKGROUND

Although several studies indicate the harmful effects of bleaching on pulp tissue, the demand for this procedure using high concentrations of hydrogen peroxide (HP) is high.

OBJECTIVES

To investigate the influence of bleaching on the pulp tissue.

METHODS

Electronic searches were conducted (PubMed/MEDLINE, Scopus, Cochrane Library and grey literature) until February 2021. Only in vivo studies that evaluated the effects of HP and/or carbamide peroxide (CP) bleaching gels on the inflammatory response in the pulp tissue compared with a non-bleached group were included. Risk of bias was performed according to a modified Methodological Index for Non-Randomized Studies scale for human studies and the Systematic Review Centre for Laboratory Animal Experimentation's RoB tool for animal studies. Meta-analysis was unfeasible.

RESULTS

Of the 1311 studies, 30 were eligible. Of these, 18 studies evaluated the inflammatory response in animal models. All these studies reported a moderate-to-strong inflammatory response in the superficial regions of pulp, characterized by cell disorganization and necrotic areas, particularly during the initial periods following exposure to 35%-38% HP, for 30-40 min. In the evaluation of human teeth across 11 studies, seven investigated inflammatory responses, with five observing significant inflammation in the pulp of bleached teeth. In terms of tertiary dentine deposition, 11 out of 12 studies noted its occurrence after bleaching with 35%-38% HP in long-term assessments. Additionally, three studies reported significant levels of osteocalcin/osteopontin at 2 or 10 days post-treatment. Other studies indicated an increase in pro-inflammatory cytokines ranging from immediately up to 10 days after bleaching. Studies using humans' teeth had a low risk of bias, whereas animal studies had a high risk of bias.

DISCUSSION

Despite the heterogeneity in bleaching protocols among studies, High-concentrations of HP shows the potential to induce significant pulp damage.

CONCLUSIONS

High-concentrations of bleaching gel increases inflammatory response and necrosis in the pulp tissue at short periods after bleaching, mainly in rat molars and in human incisors, in addition to greater hard tissue deposition over time. However, further well-described histological studies with long-term follow-up are encouraged due to the methodological limitations of these studies.

REGISTRATION

PROSPERO (CRD42021230937).

Influence of blue and violet LED and infrared laser on the temperature of bleaching protocols in different concentrations of hydrogen peroxide

BACKGROUND

The photo-acceleration of bleaching gels by lights has been extensively researched. However, the induced temperature increase during this process needs to be further evaluated to prevent damage to the dental pulp. Therefore, the objective of this study was to evaluate the surface and intrapulpal temperature kinetics of different concentrations of hydrogen peroxide (HP) gels photo-accelerated by blue or violet light and infrared laser.

METHODS

The whitening gels at concentrations of HP35, HP15, and HP6 % were irradiated with blue and violet LED/laser on the surface of a human canine tooth. The surface temperature variation (∆Ts) was evaluated using a pH meter, while the intrapulpal temperature variation (∆Ti) was assessed using a digital thermometer at intervals of 1, 15, and 30 min. Statistical analysis was conducted using a Two-way repeated measures ANOVA test, and Bonferroni post-test was applied at a significance level of 5 %.

RESULTS

All violet LED photo-accelerated groups showed a higher increase in ∆Ts compared to the blue LED/laser groups. However, there were no significant differences between the groups for ∆Ti.

CONCLUSION

Although the photo-acceleration of HP35 and HP15 % gels with violet LED/laser has a greater increase in surface temperature compared to HP6 % gel, the different light systems do not significantly increase the intrapulpal temperature.

Surface and intra-pulpal temperature variation during tooth whitening photoactivated with LED/laser

This study evaluated the variation of surface and intra-pulpal temperature, during bleaching protocol, using LED/laser. The 35% (HP35), 15% (HP15) and 6% (HP6) gels were used associated with LED/laser applied every 1 min for 30 min in a human canine. The evaluation of surface temperature variation (∆Ts) was performed using a pHmeter and the intra-pulpal temperature variation (∆Ti) was performed using a digital thermometer, at times of 1-, 5-, 10- 15- and 30-min. Statistical analysis was performed using the two-way repeated measures ANOVA test and Bonferroni post-hoc test was used at a significance level of 5%. HP35 and HP15 showed greater temperature variation than HP6 up to 10 min of surface evaluation, showing no differences between them. In the intra-pulpal evaluation, no group showed differences throughout the procedure.

Continuous vs fractionated violet LED light protocols for dental bleaching: evaluations of color change and temperature of the dental pulp and buccal surface

BACKGROUND

Dental color change and the temperature of the pulp chamber and of the buccal surface were evaluated during bleaching with 37% carbamide peroxide (CP) with continuous vs fractionated violet LED light protocols.

METHODOLOGY

Bovine incisors received in-office bleaching for 30 minutes using different light protocols (Bright Max Whitening, MMOptics). Teeth were separated into groups (n=10): HP) 35% hydrogen peroxide (Whiteness HP, FGM)/no light; CP) 37% carbamide peroxide (Whiteness SuperEndo, FGM)/no light; CP10) CP+10 min of continuous light; CP20) CP+20 min of continuous light; CP30) CP+30 min of continuous light; CPF) CP+20 cycles of 60 s light / 30 s no light (fractionated). Color evaluations were performed at different times. Evaluations of pulp and buccal surface temperatures were performed before and throughout the 30 minutes of bleaching.

RESULTS

Generalized linear models for repeated measures over time were applied to the data (α=5%). After the 1st session, CP20 and CP30 had significantly lower b* values ​​than CP and CP10 (p=0.0071). For ΔE_ab and ΔE₀₀, CPF, CP20 and CP30 showed the highest color change among the treatments after the third bleaching (p<0.05). For temperature evaluations, CP30 showed higher pulp and buccal surface temperatures than the other protocols (p<0.0001) after 20 min.

CONCLUSION

Fractionated or continuous application of violet LED for 20 or 30 min leads to greater effectiveness of color change. All protocols with the application of LED led to an increase in pulp and buccal surface temperatures during bleaching, although the fractionated application appeared to be safer than the use of continuous light.

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.

Direct dentin bleaching: Would it be possible?

This study aims to evaluate in vitro the effect of violet LED when applied directly to dentin tissue pigmented by different substances. We analyzed the chromatic alteration, the bleaching effect and the temperature variation. Hence, 60 bovine dentin tissue discs were divided into five groups: NNatural Pigmentation; T-Black Tea; C-Soluble Coffee; W-Red Wine; B-Equine Blood. Individualized pigmentation protocols were performed and all groups reached the same chromatic change value. Subsequently, we simultaneously performed a bleaching session and measured temperature variation using a K-type thermocouple device. Data on chromatic change (∆E, ∆E00, ∆a, ∆b and ∆L), whitening effect (WID) and temperature variation were subjected to one-way Anova and Tukey's post-test at a 5% significance level. The C group showed the most relevant chromatic change values, similar to the N group, responding positively to the treatment. However, the B group differed from the control group, which showed difficulty to respond to the treatment. Regarding the whitening index, only the W group showed lower results than the others. The B group showed the greatest temperature changes. We conclude that the violet LED offered chromatic change, which generated a bleaching effect. Pigmentations with red wine and blood showed the greatest difficulty to respond to treatment, also promoting a higher temperature rise in teeth pigmented with blood.

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.

Surface Morphology Changes of Bleached Dental Ceramics

Tooth whitening is one of the most conservative procedures for increasing the aesthetics of patients, but the effect of bleaching on ceramic restorations has not been extensively studied. In this study, the bleaching effect on three dental restoration materials (polished/glazed lithium disilicate glass ceramic, leucite reinforced glass ceramic and zirconium dioxide ceramic) has been investigated in terms of surface roughness changes of the exposed samples. Philips Zoom NiteWhite 16% carbamide peroxide, Philips Zoom 6% hydrogen peroxide with following LED illumination and Pola Office 6% hydrogen peroxide have been used for ceramic bleaching. The experimental investigation and performed statistical analysis revealed that the highest surface roughness changes of all investigated ceramics were caused by the hydrogen peroxide and the lowest by carbamide peroxide. These findings correlated well with the colour changes observed in the same bleached dental ceramic samples indicating potential of carbamide peroxide as the most prospective bleaching agent.

Expanding the applications of photodynamic therapy-tooth bleaching

OBJECTIVES

The current tooth bleaching materials are associated with adverse effect. Photodynamic method based on a novel photosensitizer alone, without combining with peroxides, is evaluated for tooth bleaching application.

MATERIALS AND METHODS

Teeth samples were randomly divided into 3 groups with different treatment schemes, including negative control group (group A, physiological saline), experimental group (group B, ZnPc(Lys)5), and the positive control group (group C, hydrogen peroxide). Tooth color, surface microhardness, and roughness were determined at baseline, right after the first and second phase of bleaching, as well as 1 week and 1 month post-bleaching. Four samples in each group was randomly selected to evaluate the changes in surface morphology using the scanning electron microscope.

RESULTS

The color change values (ΔE) in group B (7.10 ± 1.03) and C (12.22 ± 2.35) were significantly higher than that in group A (0.93 ± 0.30, P < 0.05). Additionally, surface microhardness and roughness were significantly affected in group C, but not in the group A and B. Furthermore, the scanning electron microscope images showed no adverse effect of enamel in the group A and B while the group C demonstrated corrosive changes.

CONCLUSIONS

ZnPc(Lys)5 had a satisfactory bleaching effect and is promising to be a new type of tooth bleaching agent.

CLINICAL RELEVANCE

The current tooth bleaching materials give a satisfactory clinical outcome and long-term stability, but associated with some adverse reactions. Photosenstizer ZnPc(Lys)5 eliminated the main side effects observed in hydrogen peroxide-based agents on the enamel, and also had a satisfactory bleaching effect and provide a novel selective bleaching scheme for clinical use.

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.

Evaluation of Tooth Sensitivity of In-office Bleaching with Different Light Activation Sources: A Systematic Review and a Network Meta-analysis

OBJECTIVES

A systematic review and network meta-analysis were performed to answer the following research question: Are there differences in the risk and the intensity of tooth sensitivity (TS) among eight light activation systems for in-office bleaching in adults?

METHODS

Randomized controlled trials (RCTs) that compared at least two different in-office bleaching light activations were included. The risk of bias (RoB) was evaluated with the RoB tool version 1.0 from the Cochrane Collaboration tool. A random-effects Bayesian mixed treatment comparison (MTC) model was used independently for high- and low-concentration hydrogen peroxide. The certainty of the evidence was evaluated using the GRADE (Grading of Recommendations, Assessment, Development and Evaluations) approach. A comprehensive search was performed in PubMed, Bridge Base Online (BBO), Latin American and Caribbean Health Sciences Literature database (LILACS), Cochrane Library, Scopus, Web of Science, and grey literature without date and language restrictions on April 23, 2017 (updated on September 26, 2019). Dissertations and theses, unpublished and ongoing trials registries, and IADR (International Association for Dental Research) abstracts (2001-2019) were also searched.

RESULTS

After title and abstract screening and the removal of duplicates, 32 studies remained. Six were considered to be at low RoB, three had high RoB, and the remaining had an unclear RoB. The MTC analysis showed no significant differences among the treatments in each network. In general, the certainty of the evidence was graded as low due to unclear RoB and imprecision.

CONCLUSION

There is no evidence that the risk and intensity of TS are affected by light activation during in-office bleaching.

Change of dental color and temperature through two bleaching agents boosted with light emitted by diodes

INTRODUCTION

The use of light sources during the application of bleaching can reduce the time and improve the results, but at the same time this can increase the dental temperature. The objective of this study was to evaluate the performance of two bleaching agents and the increase in dental temperature with the use of light emitted by diodes (LED)-unit.

MATERIALS AND METHODS

Forty third molars were obtained and randomized: the whiteness without lamp (WHN) and Pola office without lamp (PON) groups, two bleaching systems based on 35% hydrogen peroxide were used, according to manufacturer specifications. For the whiteness with lamp (WHL) and Pola office with lamp (POL) groups the same bleaching agents were light boosted. A spectrophotometer and ∆WI_D equation was used to record and analyzed teeth color. An infrared thermometer was used to record the external and internal temperature. A ∆T was obtained by the difference of the temperature of the groups with and without LED (WHN-WHL and PON-POL). For statistical analysis Kruskal-Wallis test and Anova test were performed.

RESULTS

The WHN, PON, WHL, and POL groups reported ∆WI_D values of 4.88 ± 1.08, 9.26 ± 3.27, 5.70 ± 2.48, 12.08 ± 5.44, respectively. The dates of internal temperature were 1.01 and 1.07°C, and for external temperature were 1.61 and 1.15°C respectively.

CONCLUSIONS

With the limitations of this study, both bleaching agents reported a significant increase in ∆WI_D with and without association of light. Significant temperature increases were also observed. The highest average temperature increase was approximately 1.61°C.

CLINICAL SIGNIFICANCE

Bleaching agents boosted with LED may improve the results of bleaching, but it is not essential to obtain good results.

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.

Effect of photo-thermal acceleration on in-office bleaching

The purpose is to evaluate the effect of photo-thermal acceleration on in-office bleaching efficiency using a bleaching agent without photocatalysts in vitro. Artificially discolored bovine lower incisors were prepared, and the mixed in-office bleaching material contained hydrogen peroxide 23% was applied by following treatment for 10 min: high-(HI group) and low-intensity LED lights (LI group), oven at 38 °C (OV group), and room temperature at 23 °C (RT group). Color was measured before and after bleaching and color difference (∆E*) was calculated. The data were statistically analyzed using a two-way ANOVA and Tukey’s post hoc test. The temperature change (∆T) of applied bleaching agent in HI and LI groups was measured using a thermography and was analyzed using a T test. The bleaching procedures were repeated 6 times. Irradiation in the HI group resulted in the highest ΔE, followed by the LI group whose ΔE was significantly lower. Both irradiated modes exhibited higher ΔE compared to non-irradiated OV and RT groups which were not significantly different from each other. The average temperature rise of bleaching agents in HI and LI groups after 10 min irradiation was 15.00 °C and 11.80 °C, respectively. The effect of photo-thermal acceleration was proved for an in-office bleaching agent without photocatalysts in vitro.

The Whitening Effect and Histological Safety of Nonthermal Atmospheric Plasma Inducing Tooth Bleaching

Various light sources have been applied to enhance the bleaching effect. This study was to identify the histological evaluation in oral soft tissues, as well as tooth color change after tooth bleaching by nonthermal atmospheric pressure plasma (NAPP). Nine New Zealand adult female rabbits were randomly divided into three groups (n = 3): group 1 received no treatment; group 2 was treated with NAPP and 15% carbamide peroxide (CP), which contains 5.4% H₂O₂, and group 3 was treated with 15% CP without NAPP. Color change (ΔE) was measured using the Shade Eye NCC colorimeter. Animals were euthanized one day later to analyze the histological responses occurring in oral soft tissues, including pulp, gingiva, tongue, buccal mucosa, and hard and soft palates. Changes in all samples were analyzed by hematoxylin and eosin staining and Masson's trichrome. Teeth treated with plasma showed higher ΔE than that obtained with bleaching agents alone. Overall, the histological characteristics observed no appreciable changes. The combinational treatment of plasma had not indicated inflammatory responses as well as thermal damages. NAPP did not cause histological damage in oral soft tissues during tooth bleaching. We suggest that NAPP could be a novel alternative energy source to conventional light sources for tooth bleaching.

Effect of violet LED light on in-office bleaching protocols: a randomized controlled clinical trial

Objective

This study evaluated the clinical effect of violet LED light on in-office bleaching used alone or combined with 37% carbamide peroxide (CP) or 35% hydrogen peroxide (HP).

Methodology

A total of 100 patients were divided into five groups (n=20): LED, LED/CP, CP, LED/HP and HP. Colorimetric evaluation was performed using a spectrophotometer (ΔE, ΔL, Δa, Δb) and a visual shade guide (ΔSGU). Calcium (Ca)/phosphorous (P) ratio was quantified in the enamel microbiopsies. Measurements were performed at baseline (T ₀ ), after bleaching (T _B ) and in the 14-day follow-up (T ₁₄ ). At each bleaching session, a visual scale determined the absolute risk (AR) and intensity of tooth sensitivity (TS). Data were evaluated by one-way (ΔE, Δa, ΔL, Δb), two-way repeated measures ANOVA (Ca/P ratio), and Tukey post-hoc tests. ΔSGU and TS were evaluated by Kruskal-Wallis and Mann-Whitney, and AR by Chi-Squared tests (a=5%).

Results

LED produced the lowest ΔE (p<0.05), but LED/HP promoted greater ΔE, ΔSGU and Δb (T ₁₄ ) than HP (p<0.05). No differences were observed in ΔE and ΔSGU for LED/CP and HP groups (p>0.05). ΔL and Δa were not influenced by LED activation. After bleaching, LED/CP exhibited greater Δb than CP (p>0.05), but no differences were found between these groups at T ₁₄ (p>0.05). LED treatment promoted the lowest risk of TS (16%), while HP promoted the highest (94.4%) (p<0.05). No statistical differences of risk of TS were found for CP (44%), LED/CP (61%) and LED/HP (88%) groups (p>0.05). No differences were found in enamel Ca/P ratio among treatments, regardless of evaluation times.

Conclusions

Violet LED alone produced the lowest bleaching effect, but enhanced HP bleaching results. Patients treated with LED/CP reached the same efficacy of HP, with reduced risk and intensity of tooth sensitivity and none of the bleaching protocols adversely affected enamel mineral content.

Decomposition Rate, pH, and Enamel Color Alteration of At-Home and In-Office Bleaching Agents

Abstract This study evaluated the decomposition rate (DR), pH, enamel color alteration (DE) and whiteness index (DWI) promoted by at-home and in-office bleaching. Enamel surface was submitted to (n=10): at-home (10%, 15%, 20% carbamide peroxide - CP, 6% hydrogen peroxide -HP) and three 35% HP agents with light irradiation (LED, laser, and halogen) or no treatment (control). The DR and pH of agents were measured after 0, 2, 4, 6 and 8 h (at-home) or after 5, 15, 20, 30 and 40 min (in-office). Color parameters (L*, a*, b*, DE, DWI) were determined at baseline and after bleaching. DR, pH, L*, a*, b* data were analyzed by one-way (at-home) or two-way (in-office) repeated measures ANOVA and Tukey test. DE and DWI, by one-way (at-home) or two-way (in-office) ANOVA and Tukey test. DR of at-home agents was similar after 6 and 8 h (p>0.05), with pH close to neutral (6.5 to 6.9, CP) or acid 5.9 (6% HP). From 4 to 8 h, DE was higher for 15% and 20% CP compared with 10% CP (p<0.05). After 40 min, DR of 35% HP agents was similar and all exhibited significant DE in one application (p<0.05), regardless light irradiation. DWI indicated whitening effect with no differences among groups (p>0.05). One 35% HP showed alkaline pH, and the others, pH < 5.5. At-home agents could be applied for 2 h (15%, 20% CP, 6% HP) and 4 h (10% CP) and the in-office agents, up to 40 min in one application, without light.

In vitro evaluation of visible light-activated titanium dioxide photocatalysis for in-office dental bleaching

The evaluation of the photocatalysis of visible light activated titanium dioxide employed in hydrogen peroxide (H₂O₂) was carried using seven H₂O₂ solutions (3.5 and 35%) and/or methylene blue (MB), with or without light irradiation (LI); the absorbance of MB was the bleaching indicator. Color analysis was performed on bovine teeth (n=12) using two different concentrations of H₂O₂, 6 and 35% associated with titanium dioxide (TiO₂). Data were analyzed with one and two-way ANOVA, and significance level of p<0.05. Solutions containing MB, H₂O₂ at 3.5 or 35%, and TiO₂, followed by LI, showed significant difference when compared with other groups. Greater MB reduction was found in 35% concentration. H₂O₂ 35%+TiO₂ gel showed no difference in comparison to control group. All groups for the color analysis assay showed ΔE higher than 3.3. In conclusion, TiO₂ and H₂O₂ association is a promisor alternative for reducing the clinical time of in-office dental bleaching.

Influence of different types of light on the response of the pulp tissue in dental bleaching: a systematic review

OBJECTIVES

This systematic review (PROSPERO register: CRD42016053140) investigated the influence of different types of light on the pulp tissue during dental bleaching.

MATERIALS AND METHODS

Two independent authors conducted a systematic search and risk of bias evaluations. An electronic search was undertaken (PubMed/Medline, Embase, The Cochrane Library, and other databases) until May 2017. The population, intervention, comparison, outcomes (PICO) question was: "Does the light in dental bleaching change the response of the pulp to the bleaching procedure?" The intervention involved pulp tissue/cells after bleaching with light, while the comparison involved pulp tissue/cells after bleaching without light. The primary outcome was the inflammation/cytotoxicity observed in pulp after bleaching.

RESULTS

Out of 2210 articles found, 12 articles were included in the review; four were in vivo studies (one study in dogs/others in human), and eight were in vitro studies (cell culture/with artificial pulp chamber or not). The light source used was halogen, light-emitting diode (LED), and laser. Only one in vivo study that used heat to simulate light effects showed significant pulp inflammation. Only two in vitro studies demonstrated that light influenced cell metabolism; one using halogen light indicated negative effects, and the other using laser therapy indicated positive effects. Given that animal and in vitro studies have been identified, there remain some limitations for extrapolation to the human situation. Furthermore, different light parameters were used.

CONCLUSIONS

The effects of dental bleaching on the pulp are not influenced by different types of light, but different light parameters can influence these properties.

CLINICAL RELEVANCE

There is insufficient evidence about the influence of different types of light on inflammation/cytotoxicity of the pulp.