Current status of whitening agents and enzymes in Dentistry

Abstract This study reviews the knowledge on the use of conventional dental whitening and the use of enzymes as a new approach in bleaching. A review of the literature was based on academic articles and on patents related to the use of enzymes in dental bleaching. Tooth whitening techniques used nowadays are well reported in the literature, and its mechanism of action consists of an oxidoreduction reaction with the release of free radicals. The great instability of radicals, when in contact with the tissues, promotes oxidation and reduction in the size of the pigment chains incorporated into them. These pigments are eventually broken down into smaller and smaller molecular chains and end up being diffused from the dental structure. In turn, the use of enzymes aimed at tooth whitening can be a less harmful alternative to the tooth because their specificity regarding the substrate makes them of great interest to perform specific reactions, reducing collateral effects. The use of proteolytic enzymes and oxidoreductases paired with the application of peroxides, can be a promising alternative for obtaining even better results in the dental bleaching process.

Avaliação do cimento resinoso autoadesivo como tampão cervical para clareamento interno / Evaluation of a self-adhesive resin cement as a cervical barrier in intracoronal bleaching

Objetivo: Avaliar capacidade seladora de um cimento resinoso autoadesivo como tampão cervical para clareamento interno. Métodos: Quarenta incisivos inferiores bovinos recém-extraídos foram tratados endodonticamente. Após 72 horas, foi realizada a desobturação parcial do canal radicular para confecção de tampão cervical dividido em quatro grupos aleatório (n = 40), cada um contento dez amostras (n = 10), com os seguintes materiais: cimento resinoso autoadesivo, cimento resinoso adesivo, cimento de óxido de zinco sem eugenol com presa por água e cimento de ionômero de vidro quimicamente ativado (grupo controle). Após 24 horas de presa dos materiais, os elementos dentais foram submetidos ao clareamento interno com perborato de sódio misturado com água destilada pelo período de 7 dias em câmara umidificadora a 37 ºC. Posteriormente, o material clareador foi removido e um corante (fucsina básica 0,5%) foi colocado no interior da câmara pulpar, sendo renovado de 8 em 8 horas, pelo período de 24 horas. Os elementos dentais foram seccionados no sentido longitudinal em máquina de corte para avaliação quantitativa em um microscópio óptico sob aumento de 20x. O grau de penetração do corante foi analisado ao longo do tampão cervical (topo até base). Resultados: Não houve diferença significativa entre os materiais tamponantes utilizados (p = 0,5997). Conclusão: O cimento resinoso autoadesivo apresentou baixo grau de infiltração, sendo uma opção de material alternativo com finalidade de tampão cervical.

Aim: To evaluate the sealing ability of a self-adhesive resin cement as a cervical barrier for internal bleaching. Methods: Forty recently extracted bovine lower incisors were endodontically treated. After 72 hours, partial disobturation of the root canal was performed, a cervical barrier was placed, and the teeth were divided into four random groups (n = 40), each containing ten samples (n = 10), using the following materials: self-adhesive resin cement, adhesive resin cement, zinc oxide cement without eugenol cured by water, and chemically activate glass ionomer cement (control group). Twenty-four hours after the materials were cured, the teeth were subjected to internal bleaching with sodium perborate and distilled water for a period of seven days in a humidified chamber at 37°C. After, the bleaching material was removed and a dye (0.5% basic fuchsin) was placed inside the pulp chamber and renewed every eight hours for a period of 24 hours. The teeth were sectioned longitudinally in a cutting machine for quantitative evaluation using an optical microscope under 20x magnification. The degree of dye penetration was evaluated through the cervical barrier (top to bottom). Results: No significant difference was observed among the cervical barrier materials used in this study (p = 0.5997). Conclusion: The self-adhesive resin cement had low degree of leakage and represents an alternative material option to be used as a cervical barrier.

Tooth whitening recovers the color of pre-stained composites

Aim: To assess the effect of home-whitening on aged and stained composite. Methods: Fifteen disc-shaped specimens (10 mm diameter x 2 mm thick) of Filtek Z350XT, shade A2E were fabricated, polished and embedded in wax, leaving exposed the top surface. The specimens were allocated to three groups (n=5): A ­ the specimens remained dry; B ­ conditioning in distilled water and; C ­ conditioning in distilled water and coffee. They were next subjected to whitening with 10% carbamide peroxide (Whiteness Perfect) for 4 h daily for 1, 2 and 4 weeks. Shade was measured with a spectrophotometer Easyshade and expressed based on the CIE L*a*b* system (ΔE*). Surface roughness was measured with a roughness meter (Ra-µm). Data were analyzed with two-way ANOVA and Tukey's test (α=0.05). Results: Conditioning, grouping and the interaction between both, influenced the ΔE* (p<0.0001), which exceeded the 3.3 threshold for visible color change after conditioning of Group C in black coffee. Whitening for 1 week significantly reduced ΔE* in this group. There were no significant changes in surface roughness. Conclusions: Home-whitening did not alter significantly the color of the nanocomposite, except when it was previously stained. One-week whitening was sufficient to recover color change to an acceptable level (Au)