An orthodontic retainer system including retainer modules that are applied to adjacent teeth in a patient's mouth. The retainer modules may be provided in the form of mutually attracted members, such as magnets, that are temporary coupled on opposites sides of a delivery member for positioning and bonding to an adjacent pair of teeth. In one exemplary embodiment, the retainer modules have rounded and/or chamfered edges and sloped and curved lingual surfaces, and may include a magnet that is received and sealed within an enclosure or cover that has the same shape or profile as the magnet and is made of a wear-resistant biocompatible material.