Bleaching gel volume influences hydrogen peroxide diffusion, inflammation, and the presence of nitric oxide in the pulp tissue: in vitro and in vivo model

Abstract Objective To assess whether bleaching gel volume influences chromatic changes, hydrogen peroxide (HP) diffusion, inflammation, and oxidative stress in the pulp tissue. Methodology A total of 60 bovine teeth were divided into four groups, according to bleaching gel volume (n=15): without gel (WG); V30 (30 µL of 35% HP); V60 (60 µL); and V120 (120 μL). HP diffusion analysis was performed in the first session (T1). Chromatic changes (ΔE, ΔE00, and WID) were assessed after the first (T1), second (T2), third (T3) sessions, and 15 d (T4) after the end of treatment. Moreover, 20 rats were randomly divided into four groups (n=10) and their upper first molars were treated with different gel volumes: control (no treatment); V2 (2 μL of 17.5% HP); V4 (4 μL); and V8 (8 μL). After 24 h, rats were euthanized and the specimens processed for histological and immunohistochemical (nitric oxide synthase) evaluation. Data were analyzed using the Wilcoxon and Mann-Whitney tests (p<0.05). Results In vitro (bovine teeth), chromatic changes were not influenced by bleaching gel volume, showing similar values in all groups and sessions, except for the control group (p<0.05). The V120 group had the highest HP diffusion values (p<0.05). In vivo (pulp tissue), the V4 and V8 groups showed the highest inflammatory infiltrate in the pulp and significant oxidative stress (p<0.05). Conclusion The adverse effects on the dental pulp related to HP diffusion, pulp inflammation, and oxidative stress depend on bleaching gel volume, while the bleaching effect is not proportional to the volume used.

Estudo in vitro da ação antimicrobiana de medicações intracanal experimentais sobre biofilmes de Enterococcus faecalis / In vitro study of the antimicrobial action of experimental intracanal medications on Enterococcus faecalis biofilm

Introdução: A eliminação do Enterococcus faecalis dos canais radiculares é fundamental para o sucesso do tratamento endodôntico, uma vez que esses microrganismos são de difícil eliminação, principalmente quando organizados em forma de biofilmes. A busca por drogas ou suas combinações que possam eliminar esses microrganismos é um dos principais objetivos terapêuticos. Objetivo: O presente estudo avaliou a ação antimicrobiana de medicações intracanal experimentais sobre biofilmes de Enterococcus faecalis. Métodos: Quarenta dentes bovinos unirradiculares foram utilizados; suas coroas foram seccionadas e as raízes foram instrumentadas e esterilizadas. As raízes foram contaminadas com suspensão contendo Enterococcus faecalis, mantidas em estufa a 37°C por 30 dias e divididas em quatro grupos, de acordo com a medicação intracanal: GI) medicação experimental 1 (clorexidina [CHX] 0,2%/metronidazol, doxiciclina); GII) medicação experimental 2 (CHX 0,2%/metronidazol, minociclina); GIII) clorexidina a 2% (CHX 2%); e GIV) solução salina. As raízes foram seladas e mantidas em estufa por 7 dias, em tubos contendo TSB. Dentina foi coletada e semeada por 24 h, para formação de UFCs. Os valores obtidos foram comparados pelos testes ANOVA e Tukey (p<0,05). Quando comparados os resultados, não houve diferenças entre os Grupos I, II e III; no entanto, eles foram significativamente diferentes do Grupo IV. Conclusão: As medicações intracanal experimentais exerceram ação antimicrobiana sobre biofilmes de Enterococcus faecalis (AU).

Background: The elimination of Enterococcus faecalis of the root canals is fundamental for endodontic success, since these microorganisms are difficult to killed, especially when organized in biofilms. The search for drugs or their combinations that can eliminate these microorganisms is one of the main therapeutic aim. This study evaluated the antimicrobial action of experimental intracanal medications on Enterococcus faecalis biofilms. Methods: Forty uniradicular bovine teeth were used; their crowns were removed, and the roots were instrumented and sterilized. The roots were contaminated with suspension containing Enterococcus faecalis and kept in an oven at 37°C for 30 days. The roots were divided into 4 groups according to the intracanal medication: I- experimental medication 1 (0.2% CHX/metronidazole/ doxycycline); II- experimental medication 2 (0.2% CHX/ metronidazole/minocycline), III- 2% chlorhexidine (2% CHX), and IV- saline solution. The roots were sealed and kept in tubes containing TSB in an oven for 7 days. Dentin was collected and seeded for 24 h for perform of CFUs. The values obtained were compared using ANOVA and Tukeys tests (p<0.05). When comparing the results, there were no differences among groups I, II and III; however, they were significantly different from group IV. Conclusion: The experimental intracanal medications exerted an antimicrobial action on Enterococcus faecalis biofilms (AU).