Goals of Orthodontic Treatment

According to Roth, orthodontic treatment goals can be divided into five categories: facial esthetics, dental esthetics, functional occlusion, periodontal health, and stability.20 There is no one standard that can be used to determine ideal facial esthetics. Current desirable characteristics among Caucasians include a slightly convex profile, nasolabial angle of 90º or slightly obtuse, adequate lip support and curl, a symmetrical face, lip closure without strain, 1-2 mm of visible gingiva on smile, and high cheekbones. The contour of the profile should be slightly convex with the soft tissue of the jaws in a Class I relationship.

“Ideal” occlusion was first classified by Angle into the molar Class I, II, and III relationships previously discussed. Further dental esthetics were captured by Andrews in his “six keys to normal occlusion.”21 The first key is the molar classification, with normal being about the same as Angle’s Class I molar occlusion. Other features of normal occlusion as described by Andrews includes adequate mesiodistal tip and torque (buccolingual tip) of the teeth; no rotations, crowding or spacing; a flat curve of spee; and central and lateral incisors with flat incisal edges and a pointed cusp tip on the canine. Ideal overbite and overjet should also be obtained. Vertically, incisal edges and the gingival zeniths should be symmetrical and at ideal heights, and the widths of the teeth should follow the golden proportion. Recently the esthetics of the smile indicate that buccal corridors (the dark space between the dentition and the corners of the lips) should be modest or reduced, although not eliminated completely. The curvature created by the incisal edges of the anterior maxillary teeth is most esthetic when following the curvature of the lower lip upon smiling.22

In a functional occlusion, MI coincides with CR, cusps in the opposing arches are interdigitated, occlusal forces are equally spread among all the teeth, and lateral excursions have canine guidance (seen in Video 1). Group function in lateral excursions may be acceptable in cases with severe wear. No balancing interferences should be present. Protrusion should exhibit anterior guidance with posterior disclusion (Video 2).

Video 1. Cuspid Guidance in Lateral Excursions.
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Video 2. Posterior Disclosure on Protrusion.
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Periodontal goals include adequate alveolar bone support without dehiscences or fenestrations, good gingival crest height, no pocketing or inflammation of the attachment apparatus, adequate thickness of attached gingiva, no frenum pulls, and optimum crown-root ratios.20

Most orthodontic cases exhibit some form of change or occlusal settling during the retention period after active treatment. This is a result of continued facial growth and tissue rebound. Unwanted changes in the occlusion can be minimized by avoiding unstable movements such as overexpansion of the mandibular arch and extrusion of the anterior teeth. Overcorrecting rotations, flattening interproximal contacts, eliminating undesirable neuromuscular habits, and ensuring adequate retention will also improve the stability.