Low and high hydrogen peroxide concentrations of in-office dental bleaching associated with violet light: an in vitro study

Characterization and effects on enamel of low-concentration bleaching gels containing hyaluronic acid, NF_TiO2 nanoparticles and irradiated with violet LED light

OBJECTIVE

To characterize and evaluate experimental in-office bleaching gels containing hyaluronic acid (HA) or carbomer 940 (CAR), enriched with NF_TiO₂ nanoparticles and irradiated with a violet LED, assessing their effects on the physicochemical properties of enamel.

MATERIALS AND METHODS

Bovine enamel-dentin discs were treated according to the parameters: thickener (HA or CAR), HP concentration (1.5% or 6%), and irradiation (with or without LED), resulting in 9 experimental groups (n = 10/group). An additional control group (35%HP-commercial) was adopted, and three sessions were conducted (30 min each, with a 7-day interval). Gels were evaluated for pH, particle size, polydispersity index, zeta potential and rheological behavior. Samples were assessed for color change (ΔE00), whiteness index (ΔWID), Ca/P ratio (EDS), surface microhardness (KHN), roughness (ΔRa), and surface morphology (SEM). Data were analyzed using ANOVA three-way and Tukey/Bonferroni (α = 5%).

RESULTS

pH remained stable above 6.0. Hyaluronic-based gels exhibited higher particle size and polydispersity, but lower zeta potential and less viscous rheological behavior compared to the carbomer-based ones (p < 0.05). LED light significantly increased ΔE00 and ΔWID for all gels, with HA-1.5%HP and HA-6%HP + LED achieving comparable ΔWID to 35%HP-commercial (p > 0.05). Hyaluronic-based gels groups irradiated with LED increased Knoop microhardness (p < 0.05). No significant changes were found in ΔRa, Ca/P ratio, or enamel morphology (p > 0.05).

CONCLUSION

Experimental hyaluronic or carbomer bleaching gels incorporated with NF_TiO2 nanoparticles and irradiated with violet LED showed minimal variations in physicochemical properties, effective bleaching even at low HP concentrations, and no enamel damage.

CLINICAL RELEVANCE

Innovative bleaching gel formulations incorporating hyaluronic acid, NF_TiO₂ nanoparticles, and violet LED light irradiation exhibit high efficacy even at low hydrogen peroxide concentrations, thereby minimizing enamel damage and potentially mitigating post-operative sensitivity.

Effect of light-activation systems associated with whitening pens in the bleaching efficacy and hydrogen peroxide permeability

OBJECTIVE

To evaluate the bleaching efficacy and hydrogen peroxide (HP) permeability of whitening pens, with and without light-activation systems. Also, pulp temperature and physicochemical properties were assessed, as well as the characterization of the light sources.

MATERIAL AND METHODS

Ninety premolars were distributed into nine groups (n = 10): untreated, Colgate Optic White Pen ComfortFit LED (CF), Colgate Optic White Pen Express (CX), Equate Teeth Whitening Kit (EW) and Zimba Teeth Whitening Kit (ZW), with and without light-activation. Bleaching efficacy (WID, ΔEab, and ΔE00) was assessed using a digital spectrophotometer. HP permeability (μg/mL) was measured by UV-Vis; initial concentration (%), pH, and pulp temperature variation (ΔT, °C) by titration, pH meter, and T-type thermocouple, respectively. Light characteristics were determined using spectroradiometer and integrating sphere. Statistical analysis included ANOVA, Tukey's, and Dunnett's tests (α = 0.05).

RESULTS

ZW light device exhibited the highest power and irradiance (p < 0.05). EW and ZW emitted blue light (peak: 456 nm), while CF device emitted violet light (peak: 405 nm). Light-activation did not significantly impact WID or HP permeability (p > 0.05). However, CF and CX showed greater color changes under light, when evaluated by ΔEab/ΔE00 (p < 0.05). All groups showed acidic pH; EW and ZW exhibited the highest HP concentration and permeability (p < 0.05). Pulpal temperature variations were not significant across groups (p > 0.05).

CONCLUSIONS

Light-activation had no significant impact on bleaching efficacy (WID) or HP permeability, regardless of HP concentration or pH.

CLINICAL SIGNIFICANCE

It is not essential to combine light devices with whitening pens to achieve bleaching efficacy.

Prediction based on machine learning of tooth sensitivity for in-office dental bleaching

OBJECTIVE

To develop a supervised machine learning model to predict the occurrence and intensity of tooth sensitivity (TS) in patients undergoing in-office dental bleaching testing various algorithm models.

MATERIALS AND METHODS

Retrospective data from 458 patients were analyzed, including variables such as the occurrence and intensity of TS, basal tooth color, bleaching material characteristics (concentration and pH), intervention details (number and duration of applications), and patient age. Classification and regression models were evaluated using 5-fold cross-validation and assessed based on various performance parameters.

RESULTS

For the predictive classification task (occurrence of TS), the developed models achieved a maximum area under the receiver operating characteristic curve (AUC) of 0.76 [0.62-0.88] on the test data, with an F1-score of 0.80 [0.71-0.87]. In cross-validation, the highest AUC reached 0.86 [0.84-0.88], and the highest F1-score was 0.78 [0.75-0.83]. For predicting TS intensity, the regression models demonstrated a minimum mean absolute error (MAE) of 1.76 [1.45-2.06] and a root mean square error (RMSE) of 2.38 [2.06-2.69] on the test set. During cross-validation, the lowest MAE was 1.84 [1.67-2.03], with an RMSE of 2.39 [2.20-2.58].

CONCLUSIONS

The supervised machine learning model for estimating the occurrence and intensity of TS in patients undergoing in-office bleaching demonstrated good predictive power. The Gradient Boosting Classifier and Support Vector Machine Regressor algorithms stood out as having the greatest predictive power among those tested.

CLINICAL RELEVANCE

These models can serve as valuable tools for anticipating tooth sensitivity in this patient population, facilitating better post-treatment management and control.

Bleaching efficacy of in-office bleaching with violet light using low-concentration hydrogen peroxide nanoparticulate photocatalyst gel: A randomized controlled trial

OBJECTIVE

This randomized controlled trial aimed to evaluate the bleaching efficacy and tooth sensitivity (TS) of participants submitted to different application protocols of in-office bleaching with violet light using 6 % hydrogen peroxide (HP) nanoparticulate photocatalyst gel.

MATERIALS AND METHODS

Sixty-six participants were randomized and bleached using either a 6 % HP (Nano White, DMC), and/or violet light (Bright Max Whitening, MMOptics), according to the following protocols: 1) only violet light (VIOL); 2) only bleaching gel application (BG) and; 3) combined bleaching gel application + violet light (BG+VIOL). The bleaching efficacy was evaluated with the Vita Easyshade spectrophotometer, Vita Classical and Vita Bleachedguide scales. The risk and intensity of TS were recorded using a 0-10 visual analogue scale (VAS) and a 0-4 numerical scale (NRS). Color change and intensity of TS values were compared using one-way ANOVA and Tukey's test were used. The absolute risk of TS was compared using the Chi-square test (α = 0.05).

RESULTS

A significant and higher degree of bleaching was observed in the BG and BG+VIOL groups compared to the VIOL group (p < 0.003). Despite no significant differences in the risk (p > 0.07) and intensity (p > 0.28) of TS among groups, a higher risk of TS was observed in the BG and BG+VIOL groups.

CONCLUSIONS

Using VIOL reduced the risk of TS but did not improve bleaching. However, BG+VIOL with low-concentration HP nanoparticulate photocatalyst gel achieved equal efficacy and was less likely to cause TS compared to BG.

Synthesis and characterization of different nano-hydroxyapatites and their impact on dental enamel following topical application for dental bleaching

OBJECTIVE

This study aims to synthesize, characterize, and assess the penetration of hydrogen peroxide (HP), color change (CC), and surface morphology changes after the application of two distinct nano-hydroxyapatite (nano-HAp).

METHODS

Two nano-HAp were previously synthesized by co-precipitation: one with rod-shaped particles (RS) and the other with spherical-shaped particles (SS). The surface charge of the nano-HAp particles was determined at varying pH levels and characterized by X-ray diffraction patterns and Fourier transform infrared spectroscopy. The morphology of the samples was assessed using scanning electron microscopy (SEM). The nano-HAp particles were applied before the dental bleaching procedure. Forty teeth were divided into four groups (n = 10) according to the bleaching treatment: no treatment, bleaching with 35 % HP only, RS application and bleaching with 35 % HP, and SS application and bleaching with 35 % HP. HP concentration (µg mL-1) was measured using UV-Vis, while CC was evaluated with a digital spectrophotometer (ΔEab, ΔE00 and WID). Additionally, four teeth from each group were selected for SEM analysis. Statistical analysis encompassed one-way ANOVA, Tukey's, and Dunnet's tests.

RESULTS

RS and SS were successfully synthesized by coprecipitation, primarily differing in pH during synthesis. Both variations of nano-HAp morphology significantly reduced HP diffusion into the pulp chamber (p < 0.001). Regarding enamel morphology, groups analyzed post dental bleaching exhibited greater HAp deposition on the enamel surface. Notably, this deposition did not impede CC.

SIGNIFICANCE

The utilization of different nano-HAp morphologies prior to dental bleaching appears to be a promising strategy for mitigating adverse effects associated with dental bleaching procedures.