Since gears are essential in modern mechanical and industrial applications, their research is one of the most demanded areas.In various design conditions (meshing conditions and geometric sizes), where the gears are used to transmit load and motion, the two teeth of a gear can be in contact simultaneously. In this study, the additional von Mises stress created at the root of one of the teeth by force applied to the other Tooth is considered.For this, the von Mises stress generated in the Tooth root is calculated by first applying a force to one Tooth, and then the same amount of force is applied to the second Tooth, and after that, the von Mises stress in the root of the first Tooth is calculated again. After the computation, the difference between the initial and final value is indicated, and the effects created by single and Double contact are compared. After that, a calculation is applied to both spur and helical gears with the same geometrical parameters, and it is investigated whether Double contact is more desirable for spur or helical gear from the point of view of the structural reliability of the gear Tooth. Solidworks Simulation Software models each gear and von Mises stress calculation, and finally, the percentage of effects created by Double contact for the helical and the spur gear is calculated.