Orthodontic treatment with removal of one mandibular incisor: Outcome data and the importance of extraction site preparation

摘要

Introduction: Extraction of one mandibular incisor in adolescents and adults can simplify orthodontic treatment in 2 major circumstances: (1) severe crowding of the mandibular but not the maxillary incisors, and (2) mild anterior crossbite with good alignment in both arches. Despite its potential advantages, this method has had limited use in most practices. There have been 3 major objections: (1) the possibility of unsightly black triangles because of loss of interdental papilla height, (2) a possible tooth size discrepancy that would affect occlusal relationships, and (3) patient concerns about a visible extraction site. All 3 objections now can be overcome. Methods: For 37 consecutively treated single-incisor-extraction patients, preparation of the extraction site for the tooth to be extracted was done by tipping it lingually while simultaneously closing the space in front of it. Treatment outcomes and the effect of age at the time of treatment were evaluated. Results: In patients below age 20, this approach eliminated post-treatment black triangles and almost eliminated partial loss of the interdental papilla. It reduced the previously reported prevalence of these problems in patients aged 20-40 years and did not seem to be helpful in those aged over 40 years. This positive effect was achieved because of maintenance of alveolar crest height that supports the interdental papillae. Tooth size discrepancy caused by incisor extraction was largely compensated by the different labio-lingual orientation of maxillary and mandibular anterior teeth. The extraction space quickly disappeared during extraction site preparation. Conclusions: The new procedure of extraction site preparation described in this paper offers more favorable outcomes for post-treatment prevalence of black triangles in younger patients but shows limited efficacy in older patients. Camouflage of a mild skeletal Class III problem is the major indication for this extraction pattern. About 3% of Icelandic orthodontic patients appear to be good candidates for this treatment, and this finding should be reasonably generalizable to other populations of European descent.