Spectrophotometric evaluation of peroxide penetration into the pulp chamber from whitening strips and gel: An in vitro study

The effect of ascorbic acid and cranberry on the bond strength, surface roughness, and surface hardness of bleached enamel with hydrogen peroxide and zinc phthalocyanine activated by photodynamic therapy

AIM

To evaluate the effect of different bleaching methods 40% (hydrogen peroxide) HP and Zinc Phthalocyanine (ZP) activated by photodynamic therapy (PDT) with the utilization of diverse procedures of reversal (10% ascorbic acid and 6% cranberry solution) on bond values, surface microhardness and surface roughness of bleached enamel surface.

MATERIAL AND METHODS

An aggregate of 60 extracted human mandibular molars was gathered and the buccal surface of each specimen was exposed to 2 mm of enamel surface for bleaching with chemical and photoactivated agents with the use of reversal solutions. Specimens were divided into six groups (n = 10) at random- Group 1: samples bleached with 40% HP with 10% ascorbic acid (reversal agent), group 2: ZP activated by PDT with 10% ascorbic acid (reversal agent), group 3: 40% HP with 6% cranberry solution as a reversal agent, group 4: ZP activated by PDT with 6% cranberry solution, group 5: 40% HP and group 6: ZP activated by PDT with no reversal agents. Resin cement restoration was performed via etch and rinse technique and SBS was estimated by using the universal testing machine, SMH by using Vickers hardness tester, and Ra by stylus profilometer. Statistical analysis was executed using the ANOVA test and the Tukey multiple tests (p<0.05).

RESULTS

Enamel surface bleached with 40% HP reversed with 10% ascorbic acid displayed the highest SBS while 40% HP with no reversal agent use showed the least SBS. For SMH, ZP activated by PDT when applied on the enamel surface and reversed with 10% ascorbic acid showed the highest SMH while when bleached with 40% HP and reversed with 6% cranberry solution showed the least SMH value. For Ra, Group 3: samples bleached with 40% HP with 6% cranberry solution as reversal agent showed the highest Ra value while bleaching of enamel surface with ZP activated by PDT with 6% cranberry displayed the least Ra value.

CONCLUSION

Bleached enamel surface with Zinc Phthalocyanine activated by PDT with the application of 10% ascorbic acid as reversal solution has demonstrated the highest SBS and SMH with acceptable surface roughness for bonding adhesive resin to the enamel surface.

Hydrogen Peroxide Diffusion through Dental Tissues-In Vitro Study

Whitening products commonly utilize hydrogen peroxide (HP) as an active principle, which can penetrate dental tissues with potential side effects due to its low molecular weight. This study aimed to evaluate the HP diffusion of two in-office whitening products, namely 6% VivaStyle Paint On Plus (VS) and Opalescence Boost 40% (OP), in different tooth types. Additionally, the influence of the area of exposure, dental tissue thickness and pulp chamber volume was assessed. Each group consisted of eighteen intact anterior (A), premolar (PM) and molar (M) human teeth, and a positive pulpal pressure model was employed. The samples were analyzed using spectrophotometry, and results were expressed as the mean and 95% confidence interval. Statistical tests and linear regression models were appropriately applied at α = 5%. The total HP (µg) retrieved was as follows: VS-A, 1.333 [1.214, 1.452]; OP-A, 1.538 [1.457, 1.620]; VS-PM, 1.208 [1.123, 1.291]; OP-PM, 3.628 [3.401, 3.855]; VS-M, 2.560 [2.297, 2.823]; and OP-M, 4.197 [3.997, 4.396], with statistically significant differences in diffusion kinetics between whitening products for PM and M. Several HP concentrations attained a minimum cytotoxicity value of 2.22 µg/mL. The regression model shows that OP exposed the pulp chamber to 1.421 µg of HP more than that of VS. Different whitening products can cause cytotoxic HP concentrations in the pulp chamber, with a higher risk observed in molars.

A review on dental whitening

OBJECTIVES

To provide a narrative review on vital dental whitening chemistry, toxicity and safety, vital dental whitening techniques, whitening systems, potential side effects of whitening and cyclic whitening using products with a range of concentrations and pH values. In addition, new developments and recommendations in the field of vital dental whitening will be presented to help clinicians understand the whitening process, its advantages, limitations, and the impact of whitening concentration and pH on enamel providing guidance in tailoring whitening treatments.

DATA

Data were gathered using the following keywords: dental whitening, roughness, hardness, sensitivity, hydrogen peroxide, whitening pH, whitening concentration, whitening chemistry, colour, and toxicity.

SOURCES

An electronic search was performed using PubMed and Scopus databases. Bibliographic material from papers reviewed was then used to find other relevant publications.

CONCLUSIONS

The effectiveness of vital dental whitening depends on many factors, such as the concentration/pH of the whitening agent, application duration, chemical additives, and re-mineralising agents used. Developing new whitening products and technologies such as nano-additives and alternative carrier systems is showing promising results, and might prove efficient in maximising whitening benefits by accelerating the whitening reaction and/or minimising expected reversible/irreversible enamel structural damage.

Dental Bleaching Techniques; Hydrogen-carbamide Peroxides and Light Sources for Activation, an Update. Mini Review Article

Hydrogen and carbamide peroxides have been successfully used for many years; in the past century the dental bleaching technique suffered several changes and almost 10 years before new millennium the technique was finally recognized by the international agencies of regulation.

It is important that Dentists handle the peroxides with the essential knowledge, because it is demonstrated that satisfactory final results of this technique depend on the correct diagnosis of stains, management of the substrates (enamel and dentin) and as well sensitivity.

Dentists are exposed to several dental bleaching techniques, products and brands, and in the last 2 decades the devices for light activation of the peroxides have become an extensive catalog. Today, the technique is also suffering changes based on the effectiveness of the different light sources for peroxide activation and its relation to satisfactory final results of the technique.

The purpose of this literature review is to explain the determinant factors that influence satisfactory final results of the techniques and provide a general overview, in order to achieve a treatment decision based on evidence.

Influence of concentration and activation on hydrogen peroxide diffusion through dental tissues in vitro

This study evaluated the effect of physical and chemical activation on the diffusion time of different concentrations of hydrogen peroxide (HP) bleaching agents through enamel and dentin. One hundred and twenty bovine cylindrical specimens were divided into six groups (n = 20): 20% HP; 20% HP with light activation; 20% HP with manganese gluconate; 35% HP; 35% HP with light activation; and 35% HP with manganese gluconate. The specimens were fixed over transparent epoxy wells with internal cavities to simulate a pulpal chamber. This chamber was filled with an enzymatic reagent to simulate pulpal fluid. The bleaching gels were applied on enamel surface and the image of the pulpal fluid was captured by a video camera to monitor the time of peroxide penetration in each specimen. ANOVA analysis showed that concentration and type of activation of bleaching gel significantly influenced the diffusion time of HP (P < 0.05). 35% HP showed the lowest diffusion times compared to the groups with 20% HP gel. The light activation of HP decreased significantly the diffusion time compared to chemical activation. The highest diffusion time was obtained with 20% HP chemically activated. The diffusion time of HP was dependent on activation and concentration of HP. The higher concentration of HP diffused through dental tissues more quickly.