Lateral expansion of the maxilla has been around for decades. It is well accepted as a positive although there is much disagreement about how best to do it. Rarely, however, is there discussion about how expansion and the ensuing orthodontic treatment can “trap” the lower incisor teeth.
What does “trapping” the lower incisors mean? If the upper and lower incisor teeth touch even a fraction of a second before the posterior teeth, the mandible is forced back. This is “trapping” of the lower jaw. Distal movement of the mandibular condyle on closure is inherently uncomfortable and can produce unwanted changes to the TMJ’s including pain patterns and ultimately degenerative joint disease. It is to be avoided.
Lateral expansion of the maxilla often produces spacing of the anterior teeth. Braces or aligners can be used to close those spaces. Not infrequently this retraction causes “mandibular entrapment” as these spaces are closed. Hundreds of thousands of years ago our ancestors had end-to-end incisor relationships rather than the OB/OJ relationship we call “normal”. With an end-on-end occlusion there is no entrapment and essentially no problem with the TMJ’s. Anterior Optimization can easily calculate the arch length of both arches and predict how the teeth will fit and if trapping the mandible is a possibility. Anterior Optimization could easily advise opening small spaces distal to each upper cuspid to avoid trapping the mandible and avoid TMJ symptom patterns.
