In-vitro study of cellular viability and nitric oxide production by J774 macrophages stimulated by interferon gamma with ceramic, polycarbonate, and polyoxymethylene brackets.

INTRODUCTION: Ceramic brackets are chemically inert in the oral cavity, whereas polycarbonate and polyoxymethylene brackets can degrade and release bisphenol-A and formaldehyde, respectively. More reliable tests are needed to assess the potential toxicity of these materials. In addition to traditional cytotoxicity tests, the study of nitric oxide (NO) cellular production stimulated by a specific material has been shown to be a reliable tool for evaluating cytotoxic potential. The purpose of this study was to assess, with esthetic brackets, cellular viability by 3,(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide assay (Sigma, St. Louis, Mo) in the macrophage cell line J774 stimulated with interferon gamma. Interferon gamma is a key cytokine in the activation of macrophages, plays an important role in immunologic processes, and also quantifies NO production by these macrophages. METHODS: Well plates were seeded with 2 x 104 J774 cells per well, in a volume of 100 microL, resuspended in Roswell Park Memorial Institute Supplemented Medium 1640. The macrophage cell line J774 was stimulated with interferon gamma. Ceramic, polycarbonate, and polyoxymethylene brackets were added and kept in the culture for 24, 48, or 72 hours in 5% carbon dioxide at 37 degrees C; the control samples did not include brackets. At the end of each incubation period, the supernatant was collected for posterior NO quantification, and the cells were evaluated for cytotoxicity. RESULTS: Cellular viability in all groups was higher at 72 hours than at 24 hours. The final means in the bracket groups did not show significant differences compared with the control group. NO production was significantly greater in all groups at the final time than at the initial time. However, the brackets with the interferon gamma stimulation did not result in greater NO production than did the cells in the control group.

In-vitro study of the cellular viability and nitric oxide production by J774 macrophages with ceramic, polycarbonate, and polyoxymethylene brackets.

INTRODUCTION: Studies show that ceramic brackets are chemically inert in the oral cavity, whereas polycarbonate and polyoxymethylene brackets can degrade, releasing bisphenol-A and formaldehyde, respectively. In addition to the traditional cytotoxicity tests, the study of nitric oxide cellular production stimulated by a specific material has been shown to be a reliable tool for evaluating its cytotoxic potential. METHODS: We aimed to assess cellular viability by MTT (Sigma, St. Louis, Mo): 3,(4,5-dimethylthiazol-2-yl)-2,5diphenyl tetrazolium bromide assay in a murine macrophage cell line J774 with esthetic brackets and quantify nitric oxide production by these macrophages. Cell cultures were evaluated at 3 times: 24, 48, and 72 hours. RESULTS: Cellular viability in all groups was higher at 72 hours compared with 24 hours. This increase was significant in the control and ceramic brackets groups. Final means in the bracket groups showed no significant differences compared with the control group. Nitric oxide production was significantly greater in all groups at final time. There was no significant difference between the final means of the bracket groups and the control group, although polyoxymethylene brackets showed significantly greater means at 24 and 48 hours. CONCLUSIONS: Final means in the bracket groups showed no significant differences compared with the control group.

Avaliação da citotoxidade de materiais odontológicos através do método de MTT e produção de óxido nítrico: descrição de uma técnica / Cytotoxicity citotoxicity of dental materials by the MTT assay and nitric oxide production: description of a technique

Introdução: Um dos problemas apresentados pelos materiais utilizados em Odontologia está associado à biocompatibilidade, já que poucos são totalmente inertes do ponto de vista biológico. Os materiais a serem usados em contato com tecidos humanos devem, portanto, ser testados com o objetivo de simular reações biológicas e ajudar no entendimento das respostas obtidas. Os estudos in vitro constituem a primeira etapa destes testes. A International Organization Standardization (ISO) e o Council on Dental Materials Instruments and Equipment of the American Dental Association recomendam o uso de uma bateria de testes in vivo e in vitro para estudar a biocompatibilidade dos materiais e, de acordo com as normatizações, a principal categoria de testes com este objetivo é a dos testes de biocompatibilidade. Dentre estes testes o protocolo MTT assay é um dos mais utilizados para se determinar a citotoxicidade de materiais de diversas naturezas sobre células em cultura. A citotoxicidade pode também estar relacionada às moléculas que, ao serem liberadas a partir de um determinado estímulo podem ocasionar danos aos tecidos. Estudos têm relatado a presença de uma molécula com potencial citotóxico, o óxido nítrico, em tecidos da cavidade bucal e seu envolvimento em doenças inflamatórias. Objetivo: Apresentação de uma metodologia de avaliação da citotoxicidade de materiais odontológicos através do método MTT e da análise da produção de óxido nítrico (NO), o qual está relacionado com a ação destes materiais na indução da resposta inflamatória. Conclusão: Verifica-se nesta metodologia que o ensaio de MTT pode ser facilmente adaptado para testes de citotoxicidade de materiais de diferentes composições e a mensuração da produção de óxido nítrico através do método de Griess fornece dados adicionais para a análise da citotoxicidade.