RESUMEN Introduccion: Las resinas dentales basadas en siloranos, son el resultado de la union quimica de siloxanos y oxiranos. Dentro del proceso de evolucion de las resinas, se han modifcado sus formulaciones para optimizar sus propiedades fisicas, mecanicas y esteticas. Sin embargo, aun presentan problemas como la contraccion de polimerizacion, problemas alergicos y toxicologicos. Objetivo: Determinar el potencial efecto citotoxico de las resinas a base de siloranos sobre la viabilidad celular en un cultivo de fbroblastos de la linea L929. Metodologia: Se estudio la exposicion de fbroblastos de raton L929 a resinas dentales a base de siloranos Filtek p90 y metacrilatos Filtek p60 en tres tiempos de fotocurado durante 6 dias. Se evaluo el efecto sobre la viabilidad celular mediante pruebas de exclusion vital, micrografias electronicas y composicion elemental de superfcie (Mg, Na, K y Ca) por ESEM/EDAX. Resultados: La resina Filtek p90 mostro un mayor efecto citotoxico a tiempos de fotocurado prolongados (20 segundos o mas) respecto a la resina Filtek p60. El efecto resulto mas marcado para 20 segundos de fotocurado, ya que las concentraciones de Ca y K en la superfcie celular fueron las mas afectadas. Conclusiones: La resina dental Filtek p90 ejerce un efecto citotoxico relativamente bajo sobre las celulas de fbroblastos L929 (p<0.01). Su uso en la practica odontologica se puede considerar bioseguro, pero un tiempo de fotocurado prolongado con la resina dental a base de siloranos puede afectar signifcativamente la viabilidad de los tejidos dentales. Palabras clave: citotoxicidad, viabilidad celular, Fibroblastos, Microscopia electronica de barrido. Evaluation of the cytotoxic effect of a silorane-based dental resin on fibroblasts L929 ABSTRACT Introduction: The resins dental based on siloranes, are the result of chemical bonding between siloxanes and oxiranes. In the process of evolution of the resins, they have changed their formulations to optimize their physical, mechanical and aesthetic properties. However have problems as polymerization shrinkage, allergic and toxicological problems. objective: determine the potential cytotoxic effect of siloranes based resins on cell viability in cultured fbroblast line L929. Methodology: The exposure of mouse L929 fbroblasts to commercial dental resins based on either, methacrylate Filtek P60 or silorane Filtek P90 for three curing times was assessed throughout 6 days. Its effect on the cell viability was determined by vital exclusion tests, electron micrographs and ionic composition (Mg, Na, K and Ca) by ESEM/EDAX. Results: The dental resin Filtek p90 displayed a higher cytotoxic effect for prolonged curing times (20 seconds or more) than the resin Filtek P60. Moreover, such an effect was stronger at 20 seconds of curing, as long as the concentration of Ca and K on the cell’s surface were the more affected. Conclusions: The dental resin Filtek p90 exerts a relatively low cytotoxic effect on L929 fbroblast cells (p <0.01), and then, its use can be considered biologically safe in practical dentistry but a prolonged curing time of the silorane-based resin could signifcantly affect the viability of dental tissues. Keywords: cytotoxicity, cell viability, Fibroblast, Scanning Electron Microscopy.