Sodium percarbonate as a novel intracoronal bleaching agent: assessment of the associated risk of cervical root resorption

Impact of various endodontic sealers on HPDLF Cell viability and apoptosis

This study aimed to investigate the cytotoxicity and apoptotic activity of different endodontic sealers: Sealapex, Apexit Plus, AH Plus, MTA-Fillapex and TotalFill BC Sealer in the culture of human periodontal ligament fibroblast (HPDLF) cells. The sealers were mixed, set for 24 h, and then covered with culture medium to obtain extracts, which were diluted to 1:0, 1:1, 1:2, 1:4, and 1:8. Simultaneously, HPDLF cells (1 × 104) were seeded in 96-well plates and incubated for 24 h at 37 °C 5% CO2 conditions. The cells were then exposed to 100 µL of diluted extract medium. Cytotoxicity was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to check cell viability, while apoptosis was assessed by TUNEL assay. Statistical analyses were performed using Kruskal-Wallis and Dunn post hoc tests with Mann Whitney U. In MTT and TUNEL assay cells were treated with sealers both 24 and 72 h. All materials showed higher toxicity at 72 h compared to 24 h. AH Plus exhibited the highest cytotoxicity, followed by MTA-Fillapex, Apexit Plus, Sealapex, while TotalFill BC Sealer had the lowest cytotoxicity. Consuquently, it was considered that TotalFill BC Sealer had the lowest cytotoxic potency when compared to other sealers, so it can be considered biocompatible.

Evaluation of peroxide release during nonvital bleaching using three different coronal barriers: An in vitro study

Background

Peroxide from bleaching agents can cause external cervical resorption. An intracoronal barrier is used to prevent leakage of bleaching agents into the periradicular space.

Aim

This study aims to determine and compare the amount of peroxide released, during non vital bleaching at the end of 1st and 3rd day using Glass ionomer cement (GIC), Mineral Trioxide aggregate (ProRoot MTA) and Biodentine as intracoronal barriers.

Materials and Methods

Forty-five single-rooted teeth were selected for the study and root canal therapy was performed. Three millimeters of the coronal gutta-percha were removed and according to the coronal barrier placed, samples were divided into Group A: GIC, Group B: ProRoot MTA, and Group C: Biodentine. Nonvital bleaching was done using sodium perborate and 30% H2O2. Peroxide released at the end of the 1st and 3rd day was analyzed using potassium iodide and ultraviolet spectrophotometer.

Statistical Analysis

This was done using the Wilcoxon matched pair test and the Kruskal-Wallis test.

Results

No significant difference in intergroup comparison at the end of 1st and 3rd day, respectively (P > 0.05), a significant difference was found in the MTA group at follow-up dates (P < 0.05).

Conclusion

All the three tested materials (GIC, MTA, and Biodentine) may be preferred as intracoronal barrier for nonvital bleaching.

Comparative Evaluation of Activated and Nonactivated Microbubbles on the Efficacy of Bleaching Agents

INTRODUCTION

Intracoronal bleaching serves as a conservative option for nonvital teeth that exhibit discoloration. Hydrogen peroxide (H2O2) is frequently utilized in bleaching processes owing to its capability to produce free radicals. The main drawbacks of the currently available bleaching agents are the occurrence of cervical resorption and the multiple dental visits to achieve the desired result. Therefore, in our study, to address the limitations associated with cervical resorption and extended treatment duration for badly stained teeth, an attempt was made to incorporate a whitening agent (35% H2O2) with microbubbles.

AIM

 This study aimed to compare and evaluate the effect of activated and nonactivated microbubbles on the efficacy of bleaching agents.

METHODOLOGY

 Forty-five human central incisors were collected and divided into three groups: Group I (HP), H2O2 plain (n = 15) (Control); Group II (HPM), H2O2-infused microbubbles without ultrasonic activation (n = 15) (experimental group); and Group III (HPMU), H2O2-infused microbubbles with ultrasonic activation (n = 15) (experimental group). The crowns were artificially stained. Microbubbles containing 35% H2O2 were generated using the probe sonication method. The bleaching agent H2O2 plain (0.04 mL) was syringed into the pulp chamber in group I, while H2O2-infused microbubbles (0.04 mL) were syringed into group II and group III. Group III was further activated ultrasonically. The evaluation of color shade differences was conducted using the Vita Lumin shade guide at three time points: baseline, day 7, and day 14.

RESULTS

 Data regarding color change using Vita shade were investigated for normality using the Kolmogorov Smirnov test and assessed a non-normal distribution. Intergroup comparisons at each particular time interval (baseline, day 7, and day 14) were analyzed using the Kruskal-Wallis H test followed by multiple pairwise comparisons using the Adjusted Bonferroni post hoc test. Intragroup comparisons between different time intervals were analyzed using related samples from Friedman's test followed by multiple pairwise comparisons using the post hoc Dunn test. The level of statistical significance was determined at P < 0.05. There was no statistical difference in the baseline values of all three groups. Group I (HP) exhibited an average increase of three Vita Lumin shade tabs on day 7 and day 14, respectively, whereas Group II (HPM) exhibited an average increase of six and four Vita Lumin shade tabs on day 7 and day 14, respectively, and Group III (HPMU) exhibited an average increase of 10 and 3 Vita Lumin shade tabs on day 7 and day 14, respectively.

CONCLUSIONS

 Microbubbles containing H2O2 were more efficient and faster than plain H2O2 for bleaching, and the efficacy of bleaching was enhanced when activated using ultrasonic technology.

Determination of Microhardness of Remineralized Bleached Surface Subjected to Erosion-An In Vitro Study

Objectives

The aim of this study is to evaluate the microhardness of remineralized bleached surface subjected to erosion.

Materials and methods

Fifteen samples were divided into three groups and subjected to bleaching and erosion treatment. Group I-treated with 30% hydrogen peroxide then treated with 1% citric acid solution; group II-treated with 30% hydrogen peroxide and a remineralizing agent followed by 1% citric acid solution; group III-without bleaching with 1% citric acid solution. Five samples per group, GI, GII, and GIII were subjected to the Vickers microhardness analysis. Loss of surface hardness loss (% SHL) was analyzed followed by one-way ANOVA test, post hoc multiple comparison test, Bonferroni test to compare the various group.

Result

Group II showed the lowest % SHL after the erosive phase when compared with group I.

Conclusion

Erosion which usually occurs as a consequence of bleaching can be minimized by the application of remineralizing agents after bleaching.

How to cite this article

Chandrashekhar S, Mithare SS, Bharath M, et al. Determination of Microhardness of Remineralized Bleached Surface Subjected to Erosion-An In Vitro Study. Int J Clin Pediatr Dent 2023;16(1):97-100.

Present status and future directions - Managing discoloured teeth

Managing tooth discolouration involves a range of different protocols for clinicians and patients in order to achieve an aesthetic result. There is an increasing public awareness in the appearance of their teeth and management of tooth discolouration may be inter-disciplinary and involve both vital and nonvital teeth. Vital teeth can be easily treated with low concentration hydrogen peroxide products safely and effectively using an external approach and trays. For endodontically treated teeth, the walking bleach technique with hydrogen releasing peroxide products is popular. However, there is an association with external cervical root resorption with higher concentrations of hydrogen peroxide of 30%-35%. There are also regulatory considerations for the use of hydrogen peroxide in certain jurisdictions internationally. Prosthodontic treatments are more invasive and involve loss of tooth structure as well as a life cycle of further treatment in the future. This narrative review is based on searches on PubMed and the Cochrane library. Bleaching endodontically treated teeth can be considered a safe and effective protocol in the management of discoloured teeth. However, the association between bleaching and resorption remains unclear although there is likely to be a relation to prior trauma. It is prudent to avoid thermocatalytic approaches and to use a base/sealer to cover the root filling. An awareness expectations of patients and multidisciplinary treatment considerations is important in achieving the aesthetic result for the patient. It is likely that there will be an increasing demand for aesthetic whitening treatments. Bleaching of teeth has also become increasingly regulated although there are international differences in the use and concentration of bleaching agents.

Energy-Saving One-Step Pre-Treatment Using an Activated Sodium Percarbonate System and Its Bleaching Mechanism for Cotton Fabric

The traditional pre-treatment of cotton fabric hardly meets the requirement of low carbon emissions due to its large energy consumption and wastewater discharge. In this study, a low-temperature and near-neutral strategy was designed by establishing a tetraacetylethylenediamine (TAED)-activated sodium percarbonate (SPC) system. First, the effects of SPC concentration, temperature and duration on the whiteness index (WI) and capillary effect of cotton fabrics were investigated. Particularly, excess SPC's ability to create an additional bleaching effect was studied. The optimized activated pre-treatment was compared with the traditional pre-treatment in terms of the bleaching effect and energy consumption. Further, the degradation of morin, which is one of the natural pigments in cotton, was carried out in a homogeneous TAED/SPC system to reveal the bleaching mechanism. Lastly, the application performance of the treated cotton was evaluated by characterizing the dyeability, mechanical properties, morphology, etc. The research results showed that temperature had a significant influence on both the WI and capillary effect, followed by the SPC concentration and duration. The WI was positively correlated with the SPC concentration, but excess SPC could not produce an obvious additional effect. The WI of the fabric increased by 67.6% after the optimized activated bleaching using 10 mmol/L SPC and 15 mmol/L TAED at 70 °C for 30 min. Compared with the traditional process performed at 95 °C for 45 min, the activated process produced approximately 39.3% energy savings. Research on the bleaching mechanism indicated that the reactive species that participated in degrading the morin were the hydroxyl radical and superoxide radical, and the contribution degree of the former was larger than that of the latter. Two degradation components with molecular weights of 180 and 154 were detected using mass spectroscopy. Based on this, the bleaching mechanism of the TAED/SPC system was proposed. Moreover, the fabric after the activated pre-treatment had a suitable dyeability and strength, a lower wax residual and a smoother and cleaner fiber surface. The encouraging results showed that TAED/SPC is a promising bleaching system that is conducive to the sustainable advance of the textile industry.

Insights into a novel CuS/percarbonate/tetraacetylethylenediamine process for sulfamethazine degradation in alkaline medium

This work presents a novel CuS/percarbonate/tetraacetylethylenediamine (CuS/SPC/TAED) process for the degradation of sulfamethazine (SMT). Results indicated that the CuS/SPC/TAED process enabled the efficient generation of peracetic acid (PAA), which can be efficiently activated by CuS in alkaline reaction media, and 93.6% of SMT was degraded in 30 min. Mechanism study revealed that the available reactive oxygen species (ROS) including hydroxyl radical (^•OH), carbonate radical (CO₃^•-), superoxide radical (O₂^•-), singlet oxygen (¹O₂), and organic radicals (R-O^•). Among them, R-O^• (acetyloxyl radical (CH₃CO₂^•) and acetylperoxyl radical (CH₃CO₃^•)) were confirmed to be the primary species that contributed to SMT degradation. Simultaneously, the role of sulfur species and carbonate ions were explored. It was found that the reductive O₂^•- and sulfur species rendered the efficient redox of Cu species. Besides, the effects of key influencing factors including SPC/TAED mole ratio, CuS dosage, initial pH, temperature, and nontarget matrix constituents on SMT degradation were examined. Finally, the degradation intermediates of SMT was identified, and the toxicity of these products was estimated by quantitative structure-activity relationship (QSAR) analysis. Overall, this work offers a new and simple strategy for antibiotic-polluted water remediation.

Evaluation of the penetration of intracoronal bleaching agents into the cervical region using different intraorifice barriers

Background

The present study aimed to make a comparison between the effects of 35% hydrogen peroxide gel (HP) and sodium perborate with distilled water (SP) bleaching agents on the sealing characteristics of glass ionomer cement (GIC), TheraBase, ProRoot MTA and Biodentine intraorifice barriers.

Methods

One hundred and twelve single-rooted mandibular human premolar teeth extracted from young patients (14–25 years) were chosen. Root cement and cementoenamel junction (CEJ) of teeth were examined under a stereomicroscope at 10 × magnification to ensure there was no cement defect or dentin gap in CEJ. After the endodontic access cavities were opened on the occlusal surfaces of the teeth, the working length was determined. Instrumentation of each root canal was performed with a ProTaper Gold rotary system in the determined working length and filled with gutta-percha + AH Plus with a single cone technique using. Root fillings were removed 3 mm short of the CEJ and sealed with one of the following intraorifice barrier materials (n = 30/group): 1. GIC; 2. TheraBase; 3. ProProot-MTA; 4. Biodentine. In each of the sub-groups, either HP or SP was used to perform intracoronal bleaching on days 1, 4, and 7. All outer surfaces of the specimens except the 3 mm cervical region were covered with nail polish and modeling wax layers. Specimens were immersed in a 5 ml Eppendorf tube that contained 2 mL of distilled water. The penetration of peroxide release was measured using the colorimetric ferric thiocyanate method. Statistical analysis of the data was performed with Three-way ANOVA and Tukey’s test (P = 0.05).

Results

In the HP groups, GIC showed the greatest peroxide release when compared with other tested groups on day 1 (P < 0.05). Biodentine and ProRoot MTA displayed a significantly lower peroxide leakage when compared to GIC and TheraBase on days 1 and 4 (P < 0.05). While GIC and TheraBase were used, HP observed higher peroxide penetration when compared with SP on days 1 and 4 (P < 0.05).

Conclusions

Peroxide diffusion was significantly influenced by the kind of intracoronal bleaching agents and intraorifice barrier materials used.

A review on percarbonate-based advanced oxidation processes for remediation of organic compounds in water

Sodium percarbonate (SPC) is considered a potential alternative to liquid hydrogen peroxide (H₂O₂) in organic compounds contaminated water/soil remediation due to its regularly, transportable, economical, and eco-friendly features. The solid state of SPC makes it more suitable to remediate actual soil and water with a milder H₂O₂ release rate. Apart from its good oxidative capacity, alkaline SPC can simultaneously remediate acidized solution and soil to the neutral condition. Conventionally, percarbonate-based advanced oxidation process (P-AOPs) system proceed through the catalysis under ultraviolet ray, transition metal ions (i.e., Fe²⁺, Fe³⁺, and V⁴⁺), and nanoscale zero-valent metals (iron, zinc, copper, and nickel). The hydroxyl radical (^•OH), superoxide radical (^•O₂^-), and carbonate radical anion (^•CO₃^-) generated from sodium percarbonate could attack the organic pollutant structure. In this review, we present the advances of P-AOPs in heterogeneous and homogeneous catalytic processes through a wide range of activation methods. This review aims to give an overview of the catalysis and application of P-AOPs for emerging contaminants degradation and act as a guideline of the field advances. Various activation methods of percarbonate are summarized, and the influence factors in the solution matrix such as pH, anions, and cations are thoroughly discussed. Moreover, this review helps to clarify the advantages and shortcomings of P-AOPs in current scientific progress and guide the future practical direction of P-AOPs in sustainable carbon catalysis and green chemistry.

Establishing an ultrasound-assisted activated peroxide system for efficient and sustainable scouring-bleaching of cotton/spandex fabric

This study presents a high-efficient and cost-effective ultrasound-assisted strategy for one-bath one-step scouring and bleaching of cotton/spandex fabric using sodium percarbonate (SPC) and tetraacetylenediamine (TAED) couple. SPC plays both roles of pH regulator and H₂O₂ donor to initiate the peracetic acid (PAA) release from TAED. The significance and interaction effects of operating parameters (TAED concentration, temperature and time) on the WI (Whiteness Index) of fabrics were investigated through a central composite design. The bleaching mechanism was studied by exploring the relationship between WI and PAA and hydroxyl radical (HO·) concentrations. The mechanical and dyeing performances of treated fabrics were also evaluated. Results show that temperature exerted a significant impact on WI followed by TAED concentration and time. The PAA concentration decreased and HO· concentration increased upon the temperature rise. Both PAA and HO· were significant to upgrade WI and ultrasound was effective in enhancing their bleaching efficiency. The fabric treated only with 15 mmol/L TAED and 10 mmol/L SPC at 40 °C for 40 min under ultrasound could achieve a WI of 68.6 (43% higher than greige fabric), which was almost equivalent to that of the fabric treated at 60 °C without ultrasound. This verifies the contribution of ultrasound technology in reducing bleaching temperature for energy-saving purpose. Moreover, the treated fabric displayed less than 5% tensile strength loss, having a marginal impact on the apparel performance. The wettability of fabric was greatly improved leading to a good dyeing performance. Encouraging results demonstrate the high efficiency of the ultrasound-assisted pre-treatment process of cotton/spandex fabric, which contributes to the sustainable production of textiles.