A soft-tissue cephalometric analysis and its use in orthodontic treatment planning. Part II.
To summarize, the soft-tissue profile can vary in many ways and still be in balance and harmony. There is a wide range of acceptability regarding soft-tissue chin position in the profile. Both the lips and the chin should line up near the H line, but we need to look at the upper lip from a different perspective or in its relation to a line perpendicular to the Frankfort plane and tangent to the vermilion border to be certain that we are planning the best possible lip support for the case at hand. The H angle, allowing a few degrees for soft-tissue thickness variability, must increase as the basic skeletal convexity increases, and as the convexity increases, the lower incisors will need to be left farther forward than in a straight or concave skeletal profile. A thick integumental covering in the chin area can also effectively align the lower facial profile where lower incisors are farther forward than we are accustomed to seeing them. This principle can also be applied by surgically moving the bony chin forward until the three key soft-tissue points line up. Because there are wide variations in skeletal convexity, standardizing the position of the lower incisor to its apical base support as measured in the Frankfort mandibular incisor angle fails to recognize that upper incisors can be retracted too far, leaving a "streamlined" upper lip which is not esthetically pleasing. Locating the lower incisor in relation to the expected point A to pogonion line is somewhat better but still fails to recognize the wide range of variability in the thickness of the lips and soft-tissue chin. We must also guard against "dishing" those cases having good facial balance with quite normal skeletal convexity and only 5 mm or 6 mm of lower arch length discrepancy. Finally, it is completely practical as a treatment-planning procedure to approach the proposed orthodontic changes from a soft-tissue analysis perspective, making changes only to the point where the best possible soft-tissue profile is established, and then compute the tooth movement necessary to develop ideal profile relationships. The visualized treatment objective, or VTO, is the vehicle that I use to accomplish this.
D000328:Adult; D002508:Cephalometry / Q000379:methods*; D002648:Child; D005145:Face / Q000033:anatomy & histology*; D005147:Facial Bones / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology; D008046:Lip / Q000033:anatomy & histology; D008297:Male; D008310:Malocclusion / Q000503:physiopathology / Q000628:therapy*; D008445:Maxillofacial Development; D010347:Patient Care Planning; D014087:Tooth Movement Techniques / Q000379:methods