Expanding the Lower Arch: Is it Really a Forbidden Frontier?

The position of the lower incisors at the center of the mandibular symphysis has been proposed for decades as ideal in orthodontic treatments, supposedly providing adequate periodontal support and stability. Nevertheless, there are many clinical conditions in which lower incisor proclination, as well as the expansion of the lower arch in the canine and premolar region are necessary. Understanding the limits for proclination and expansion of these teeth, with the purpose of protecting the supporting tissues, is critical for orthodontic treatment planning. With CBCTs, the alveolar bone can be analyzed in three dimensions, bringing a whole new diagnostic perspective to this subject instead of only relying on radiographic or clinical judgement of periodontal biotype, which may be misleading. Thus the main purpose of this presentation is to discuss the possibilities, consequences and stability of lower incisor proclination and canine and premolar expansion based on modern diagnostic tools and how current scientific evidence has contributed to change the areas of concern regarding expansion of the lower arch.

Learning Objectives:

• Define cases where expansion in the lower arch is necessary.
• Apply current diagnostic tools to determine lower arch expansion.
• Recognize how 3D imaging broadened anatomic concerns regarding expansion of the lower arch.