06 November 2019

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Orthodontic treatment with removal of one mandibular incisor

Davide Elsido

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In specific types of cases, removal of one mandibular incisor can greatly facilitate orthodontic treatment. There are 2 primary indications: (1) severe crowding in the mandibular arch but minimal crowding in the maxillary arch,
(2) mild anterior crossbite but good alignment in a patient with a skeletal Class III tendency.

ln a sense, these 2 different malocclusion patterns are variants of the same problem, a lack of dental compensation for a mild to moderate Class III malocclusion jaw relationship. ln a more severe skeletal Class III problem that requires orthognathic surgery, one mandibular incisor extraction may be still be preferred to deal with crowding in the mandibular but not the maxillary arch. lt is generally conceded that satisfactory dental occlusion can be achieved with extraction of one mandibular incisor in selected cases. Most orthodontists probably know that removing 1 mandibular incisor instead of 2 or 4 premolars in patients who could be treated either way simplifies the orthodontic treatment and tends to shorten treatment time. Why do they rarely do that? A more pressing esthetic concern is the possibility of gingival recession that leads to a black triangle because of the loss of the interdental papilla between the teeth at the extraction site. This occurs when the underlying crestal bone remodels during the space closure and the height of the interdental bone crest decreases.

In the latest issue (October 2019) of the American Journal of Orthodontics and Dentofacial Orthopedics an article was published about a technique developed by W. Proffit to solve both the visible empty space and black triangle problems, however, that is not widely recognized: the “extraction site preparation”. It decreases the effect on the crestal bone and thereby decreases the number and size of black triangles.
The purpose of the paper was to describe it and offer data both for its effectiveness and treatment time. Extraction site preparation is done in 2 steps: first, orthodontically tipping the incisor that is to be removed lingually to a safer location for its removal, and then closing most of the space in front of it before it is extracted. This moves the new extraction site away from the delicate crestal bone and usually preserves the height of the alveolar crest where the tooth used to be. lt also addresses the possible patient concern about the esthetic effect of removing an anterior tooth. With this approach, the tooth is moved out of the way quickly, and one day, it disappears without anyone noticing. Selecting the incisor to be removed can sometimes be difficult. One would want to remove a tooth that has enamel decalcification or has been shortened by attrition. But a main factor in preventing black triangles is to select for extraction the incisor with the greatest bone height around its cervical neck. lf the height of the crestal bone is about the same around all the incisors, then it is usually easiest to select an incisor that is already lingually inclined. This is likely to be the same tooth with the best bone around it and if so, that makes the selection easy. If the crowding is worse on one side, then it is sensible to select a tooth where the crowding is worst. Selecting an incisor that is labially inclined and in the front of the other incisors usually is not a good decision. These teeth often have the worst bone height and it is difficult to move them lingually out of the arch. If such a tooth is the best one to extract for other reasons, site preparation still is possible by having a dental colleague do a root canal procedure on it; then it can be slenderized with a tlame-shaped bur before moving it lingually in the usual way.

The results showed that 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.

To get more info about this useful procedure, please read the original article, which have many figures to better understand it: Orthodontic treatment with removal of one mandibular incisor: Outcome data and the importance of extraction site preparation