The surgicalnonsurgical decision in Class III treatment

As with Class II treatment, it is important to recognize those Class III cases which have a major skeletal disproportion, either at the time of assessment, or where there is a probability of unfavorable growth. For such individuals, it will be necessary to consider a surgical/orthodontic solution. Treatment on the basis of orthodontics alone should be delayed, or discarded as a possibility.

The S'FCA of Arnett et al was discussed in Chapter 7 (p. 163). In the following theoretical consideration of some aspects of Class III treatment, the same seven measurements will be considered, for cases where it is assumed that the upper- and mid-thirds of the facial profile are close to ideal, and that the upper incisors are well positioned.

The theoretical treatment situations, A, B, and C, explain the potential difficulties:

Situation A - a surgical/orthodontic correction to an ideal result. If it is determined that mandibular surgery will be required, then the surgeon will normally wait until all growth has finished, which may be as late as 22 years of age in males. The surgeon will then require the orthodontist to decompensate the incisors. Correction will be achieved by A/P realignment of the mandible and/or maxilla, with transverse correction of the maxilla if necessary. This should lead to an optimal facial and dental result (Fig. 8.6).

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Fig. 8.6 If a combined surgical and orthodontic solution is used to treat this case, a close-to-ideal facial profile and dental outcome should be possible. A 6-mm mandibular set-back will result in measurements to true vertical line (TVL) which are within 1 SD of the ideal.

Color codes used with the Arnett soft tissue cephalometrlc analysis

Black = within 1 SD Green = within 2 SD Blue = within 3 SD Red = more than 3 SD

Fig. 8.6 If a combined surgical and orthodontic solution is used to treat this case, a close-to-ideal facial profile and dental outcome should be possible. A 6-mm mandibular set-back will result in measurements to true vertical line (TVL) which are within 1 SD of the ideal.

Situation B - orthodontic masking of a mild Class III skeletal case. As an alternative to 'A' above, if the underlying skeletal discrepancy is mild, it may be decided to follow a treatment plan based on orthodontics alone. This will allow correction to be commenced much earlier, and the patient will be informed of the possibility of late mandibular growth. The orthodontist will then solve the problem by 'masking' the underlying Class III discrepancy by dental compensation. This will involve proclination of upper incisors and/or retroclination of lower incisors. Good patient cooperation with Class III elastics and/or a face mask will normally be needed in this type of treatment. This should lead to an acceptable dental and facial outcome without the need for orthognathic surgery, which patients wish to avoid (Fig. 8.7).

TVL

TVL

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Black = within 1 SD iH Green = within 2 SD ¿2 Blue = within 3 SD

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Fig. 8.7 In this mild Class III case, a treatment plan can be based on orthodontic tooth movements to mask the slight underlying skeletal discrepancy. This can lead to a good dental outcome, and some'improvement in facial profile measurements. In this theoretical representation, the upper incisors were proclined 2° and the lowers were retroclined 8°.

Situation C - late mandibular growth. After orthodontic masking of a mild Class III malocclusion, late mandibular growth can occur, especially in males. This is a difficult situation to manage. Sometimes the patient will find the late change in dental and facial outcome acceptable, and seek no further treatment. However, if mandibular surgery is deemed necessary, there is limited scope for facial improvement from the surgery, because of the dentally compensated teeth (Fig. 8.8). The incisors will need to be decompensated by orthodontics before surgery, if there is to be an optimal facial benefit from the surgery.

TVL !TVL

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Fig. 8.8 In some cases, late mandibular growth occurs after the type of treatment shown in 'B' above. This is difficult to manage. If a decision is made to carry out mandibular surgery, it is often necessary to provide further orthodontic treament to decompensate the incisors, before the surgery.

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