The posterior region is formed of the first premolars, second premolars and first, second and third molars. The premolars are found behind the canines only in the permanent dentition, and occupy the area occupied by the molars in the temporary dentition. They usually have a single root, with the exception of the superior first premolars which may have two, and their occlusal anatomy corresponds to a transition between canines and molars, presenting two cusps and a central groove. The upper premolars present certain differences with respect to the inferior premolars. They are slightly larger, particularly in the buccolingual diameters. With respect to the occlusal surface, the upper premolars have a pentagonal form whereas the lower ones are ovoid in the first premolar and pentagonal in the second (6)(7).