This Master Thesis is directed to the improvement of the behavior of spur gear drives related with the second type of failure, tooth brake through bending. For doing that, a study of the influence of the type of root profile on tooth bending stresses in spur gear drives is presented. Different types of root profiles will be applied through the use of the Integrated Gear Design (IGD) software developed by the Research Group of Advanced Gear Transmissions of the Universidad Polit´ecnica de Cartagena. Standardized ISO profiles will be implemented considering types A, B, C and D of this Standard. The type of root profile that the Standard considers is a trochoid, that is a curve generated by a rounded tip of the rack-cutter tooth.