You may believe that a retainer will suffice because it appears to be a minor gap that has to be filled. There are two types of retainers: detachable and fixed. Retainers cannot be used to bridge a gap since they are installed at the conclusion of treatment and are custom-made to suit the straight teeth form. They are also not used as interim measures while your teeth heal after undergoing orthodontic treatment. The fact is, even though a retainer can help maintain the results of your orthodontic treatment, it cannot cure what has been diagnosed as a dental problem. Therefore, if you have retained teeth or dentin hypersensitivity, then this must be addressed prior to placing a retainer. Retained teeth are those that haven't been removed during oral surgery or tooth extraction procedures. If a dentist fails to remove all of the damaged tooth tissue before installing a retainer, then these remaining tissues will continue to decay and eventually require replacement. Also, if a patient has untreated dental disease near their retained teeth, then these areas will need to be treated before putting in a retainer. Fixed retainers are appliances that are bonded to the outside of the teeth. These are useful when there is insufficient room inside the mouth for placing wires on individual teeth. In addition, the use of fixed retainers helps prevent further damage to enamel that could otherwise occur if metal wires were placed in contact with vulnerable teeth.