Generating an Ideal Virtual Setup with Three-Dimensional Crowns and Roots.

T goal of orthodontic treatment is to move teeth from malocclusion to a functional, esthetic, and stable ideal occlusion in which all dental crowns and roots are in the correct threedimensional positions. Mesiodistal, labiolingual, and occlusogingival positions and axial rotations can be determined solely from the crowns of the teeth, but mesiodistal angulations and faciolingual inclinations may be better assessed by viewing both the crowns and roots.1-4 Although most of the focus in orthodontic treatment is on crown positions as determinants of esthetic appearance and occlusal contacts, improper root positions may increase the risk of relapse, periodontal damage, and undesirable tooth movements under occlusal loads.5-7 To check root alignment, 67% and 80% of U.S. orthodontists take progress and post-treatment panoramic x-rays, respectively.8 Studies have shown, however, that panoramic x-rays are imprecise as a means of identifying problems with tooth angulation.9-12 Recent advances in 3D technology and software have provided diagnostic tools for more accurate measurement of mesiodistal angulation and faciolingual inclination.13,14 Still, many of the digital systems used to fabricate customized orthodontic appliances—including Invisalign,* Incognito,** and Insignia***15-18—do not display the roots in their virtual setups. A recently reported technique has the capability of monitoring root positions at any stage of orthodontic treatment by combining a cone-beam computed tomography (CBCT) scan with either an intraoral or extraoral digital scan of the crowns.19,20 The present article describes the use of this process to evaluate and modify crown and root positions for construction of an ideal 3D setup.