Inadequate molar control is one of the difficulties that arise during mechanical treatment. When molar control is handled efficiently, it facilitates precise control of forces and moments, which increases the effectiveness of biomechanics. Knowledge of 4 x 2, 6 x 2 partial systems and the transpalatal bar with its different forms of activation offer a number of advantages that make it possible to optimize orthodontic results. The aim of this article is to clarify concepts, specify possible treatment strategies and analyze the side effects that occur with these systems.