The purpose of this article was to report a clinic case of a female patient of 10 years old, which was performed pulpectomy in the tooth 75 with Mineral Trioxide Aggregate (MTA). In this article was used as for definitive obturation the Mineral Trioxide Aggregate (MTA), in order to preserve the tooth as long as possible due to the agenesis of the substitute. The tooth was clinically asymtomatic and radiographs showed a progressive repair of the apical lesion after the use of the mineral trioxide aggregate (MTA).Se reporta un caso clínico de paciente femenina de 10 años de edad, a la que se le realiza una pulpectomía del diente 75 con agregado de trióxido mineral (MTA) como material de obturación definitiva, con el fin de preservar la pieza dentaria el mayor tiempo posible debido a la agenesia del sucedáneo. Se demostró la eficacia tanto clínica como radiográfica del empleo del agregado trióxido mineral (MTA).