The article, “Severe complication of a bonded mandibular lingual retainer,” in the September issue (Pazera P, Fudalej P, Katsaros C. Am J Orthod Dentofacial Orthop 2012;142:406-9) was interesting. The authors carefully documented a complication with a broken lingual flexible spiral wire retainer. Four years after treatment, the root of a canine had moved out of the buccal cortical bone. Cone-beam computed tomography sections of the canine before and after retreatment beautifully demonstrated partial recovery of the labial cortical plate. The authors concluded that buccal bone regeneration and recoverage of parts of a root can occur and stated that “to our knowledge, this has never been documented before.”
It is admittedly difficult to be aware of all relevant published literature, particularly in a field bordering other specialties, but several research teams have reported the same or similar findings. Experimental studies have demonstrated that, when a tooth is tipped, torqued, or moved bodily through the cortical plate, a labial bone dehiscence might develop. Such perforations can occur, eg, (1) for mandibular incisors due to excessive frontal expansion, (2) in the maxilla associated with retraction and lingual root torque of the maxillary incisors in patients with large overjets, (3) in the maxillary posterior region during lateral expansion of crossbites, and (4) by pronounced traumatic jiggling of teeth.
Independent researchers have reported bone apposition when malpositioned teeth expanded through the cortical plate are moved or relapse back to or toward their optimal positions in the arch. Apparently, the soft tissues labial to an orthodontically produced dehiscence can contain soft-tissue components (vital osteogenic cells) with the capacity to form bone after repositioning of the tooth. The dehiscence might be repaired even if the repositioning occurs several months later. On the other hand, dehiscences produced by labial tooth movement do not regenerate if the teeth are retained in their displaced positions, even though the forces are discontinued.