1. Fixed lingual arch: used to maintain the length or width of dental arch after correction.
2. Fixed lingual wire holder: the fixed lingual wire connected between two canines can be directly bonded to the lingual protrusion of the canines. It is mainly used for the limited or permanent retention of the mandibular anterior teeth after correction. It is a commonly used retention method.
3. Restoration retainer: fixed or removable restorations are generally required for restoration when the tooth mass is less than the bone mass or there is still a large gap left in the dentition due to the loss of permanent teeth, and after the auxiliary orthodontic treatment of adults. This kind of prosthesis can be regarded as a permanent retainer.
4. Extraoral force holder
