An alternative 2-step cementation technique to reduce polymerization shrinkage stress in root canals: a case report.

The functional rehabilitation of teeth with endodontic involvement and substantial loss of coronal structure can be a challenging scenario. The use of fiber-reinforced posts (FRPs) promotes retention and supports the restoration. The main cause of failure associated with the use of FRPs is the debonding of the post, mainly due to polymerization contraction or incorporation of voids in the thick resin cement layer during the cementation protocol. This case report describes a simple 2-step cementation technique to reduce polymerization shrinkage of the resin cement and improve the fit of the FRP inside the root canal. In the first cementation step, the FRP is wrapped in a polyvinyl chloride film and placed in the canal, self-curing glass ionomer cement is injected in the canal, and the cement is allowed to cure. In the second cementation step, the FRP is removed from the canal, unwrapped, and tried in the canal again. If it fits correctly, it is removed from the canal, and a self-etching resin cement is mixed and injected into the canal. The post is reinserted, excess resin cement is removed, and the cement is polymerized. This technique reduces the volume of resin cement required in each step and consequently the polymerization contraction stress. The 2-step technique is a simple method and a useful option for flared root canals.

Edemogenic test and hydrogen peroxide degradation rate of bleaching gels with different desensitizing agents / Teste edemogênico e taxa de degradação do peróxido de hidrogênio de géis clareadores com diferentes agentes dessensibilizantes

Objective: The at-home bleaching technique leads to the intimate contact of the bleaching gel with gingival tissues, so this study evaluated the immediate inflammatory response, through the edemogenic test, induced by at-home bleaching gels of 10% carbamide peroxide with different desensitizing agents, the quantification of hydrogen peroxide released and bleaching gels pH. Material and Methods: Forty-eight rats were divided into groups (n=12): CTRL-control group, WP-Whiteness Perfect 10% (FGM Produtos Odontológicos, Joinville, SC, Brazil), OPA-Opalescence 10% (Ultradent Products Inc., South Jordan, IT, USA), and PB-Power Bleaching (BM4, Palhoça, SC, Brazil). For the edemogenic test, all rats received an intravenous injection of Evan's Blue; after 30 min, 0.2 mL of each bleaching gels was injected into the subcutaneous tissue of the rats, and the results of the vascular permeability were assessed after 3 and 6h. The amount of HP released and pH of each product was also determined. Data were submitted to statistical test (p <0.05 ). Results: At 3h, the PB showed higher vascular permeability than the other groups. At 6h, the PB produced similar vascular permeability than WHI, and higher than OPA and CTRL groups. The OPA group had a higher vascular permeability at 6h compared to 3h; there is no difference in other groups. The PB group had higher HP concentrations than the other groups. Conclusion: In general, the PB caused a more considerable amount of inflammatory edema and higher amount of HP released. This results suggesting that these bleaching gels cause greater aggression in soft gingival tissues that eventually ends up in contact with bleaching products. (AU)

Objetivo: A técnica de clareamento domiciliar leva ao contato íntimo do gel clareador com tecidos gengivais, assim, este estudo avaliou a resposta inflamatória imediata, através do teste edemogênico, induzido por gel de clareamento caseiro à base de peróxido de carbamida a 10% com diferentes agentes dessensibilizantes, a quantificação de peróxido de hidrogênio liberado e o pH dos géis branqueadores. Material e Métodos: Quarenta e oito ratos foram divididos em 4 grupos (n = 12): grupocontrole CTRL, WP-Whiteness Perfect 10% (FGM Produtos Odontológicos, Joinville, SC, Brasil), OPA-Opalescence 10% (Ultradent Products Inc., South Jordan, IT, EUA) e PB-Power Bleaching (BM4, Palhoça, SC, Brasil). Para o teste edemogênico, todos os ratos receberam uma injeção intravenosa de Evan's Blue; após 30 min, 0,2 mL de cada gel clareador foi injetado no tecido subcutâneo dos ratos, e os resultados da permeabilidade vascular foram avaliados após 3 e 6 horas. A quantidade de HP liberada e o pH de cada produto também foram determinados. Os dados foram submetidos ao teste estatístico (P <0,05). Resultados: Às 3h, o PB apresentou maior permeabilidade vascular que os demais grupos. Às 6h, o PB produziu permeabilidade vascular semelhante ao WHI e maior que os grupos OPA e CTRL. O grupo OPA apresentou maior permeabilidade vascular às 6h em relação às 3h; Não existe essa diferença em outros grupos. O grupo PB apresentou maiores concentrações de HP que os demais grupos. Conclusão: Em geral, o PB causou maior quantidade de edema inflamatório e maior quantidade de HP liberado. Estes resultados sugerem que estes géis branqueadores causam maior agressividade nos tecidos gengivais moles que eventualmente acabam em contato com produtos de branqueamento. (AU)

Color alteration, hydrogen peroxide diffusion, and cytotoxicity caused by in-office bleaching protocols.

OBJECTIVES: This study evaluated the color alteration, cytotoxicity, and hydrogen peroxide (HP) diffusion associated with different in-office bleaching protocols. MATERIALS AND METHODS: Bovine enamel/dentin disks were subjected to three bleaching sessions with 35 % HP (three 15-min applications), 35 % HP (one 45-min application), or 20 % HP (one 45-min application). The control group was not bleached. Before bleaching, the disks were adapted to artificial pulp chambers positioned in compartments containing 1 ml of acetate buffer or medium, so that the dentin remained in contact with these substances. Immediately after bleaching, the HP that diffused through the disks was stabilized by acetate buffer and was quantified (two-way repeated measures ANOVA/Fisher's protected least significant difference (PLSD) test; α = 5 %). Cells of mouse dental papilla cell-23 (MDPC-23) were incubated in this culture media for 1 h, followed by analysis of cellular metabolism (methyl tetrazolium assay) (one-way ANOVA/Tukey test; α = 5 %) and morphology (scanning electron microscopy). The specimen color alteration (ΔE) was analyzed by reflection spectrophotometry (two-way repeated measures ANOVA/Fisher's PLSD test; α = 5 %). RESULTS: All protocols showed equal effectiveness at the end of the treatment. HP diffusion was significantly higher in the groups bleached with 35 % HP. Reapplication of 35 % HP resulted in increased diffusion only in the first session; however, the decrease in cell metabolism was similar for all studied protocols. CONCLUSION: Despite greater peroxide diffusion in the groups treated with 35 % HP, all protocols showed the same effectiveness and were cytotoxic to MDPC-23 cells. CLINICAL RELEVANCE: Bleaching protocols using high HP concentrations should be avoided because they exert aggressive actions on odontoblast-like cells.