Identifying severe Class II cases

Orthodontics can be relied upon to achieve a good outcome for most patients with Class I or mild Class II skeletal bases. I Iowever, it is important to recognize those Class II cases which have a major skeletal disproportion at the time of assessment. For such individuals, it will be necessary to consider a surgical/orthodontic solution (Fig. 7.2). Treatment on the basis of orthodontics alone should be discarded as a possibility, unless there is a real prospect, in a growing individual, of achieving favorable skeletal change with functional appliances.

The theoretical Class II/1 treatment situations, A, B and C, on the opposite page show some of the potential difficulties.

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Fig. 7.2 In the above diagrams, the different colors of the Arnett analysis help to highlight the areas and quantity of facial disproportion. The right example is normal. The center example is a moderate Class 11/1 malocclusion which may be considered for treatment by orthodontics alone. In the example on the left, it is clear that the severity of the problem may require a combined orthodontic and surgical assessment, and that treatment on the basis of orthodontic treatment alone may need to be discarded as a possibility, unless major skeletal change can be achieved, for a growing individual, with functional appliances (Case TS, pp 198-205).

Situation A - orthodontic masking of a mild Class II. If the underlying skeletal Class II discrepancy is mild, it may be decided to follow a treatment plan based on orthodontics alone. The orthodontist will provide correction by 'masking' (he underlying Class II discrepancy with dental compensation. T his will involve slight retroc.lination of upper incisors and/or proclination of lower incisors. Good patient cooperation with Class II elastics and/or a headgear will normally be needed in this type of treatment. Treatment should lead to a good dental and an acceptable facial outcome (Fig. 7.3).

Color codes used with the Arnett soft tissue cephalometric analysis

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

Fig. 7.3 In the theoretical situation A, good correction has been achieved by dental compensation, assisted by a small amount of favorable growth. Many mild Class II cases can be successfully managed in this way, in growing individuals.

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Situation B - attempted orthodontic masking of a more severe Class II skeletal problem. If the underlying skeletal Class II discrepancy is moderate to severe, a treatment plan based on orthodontics alone carries risks. If the orthodontist attempts correction of the bite by 'masking' the Class II discrepancy with dental compensation, there is a probability of over-retraction of the upper incisors and a ver)' unfavorable change in facial profile (Fig. 7.4). This also leaves the upper and lower incisors in a position which is unsuitable for successful orthognathic surgery, if this is to be provided later. Further orthodontic, treatment will be required to decompensate the anterior teeth, so that maximum benefit can be obtained from surgery.

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Fig. 7.4 In the theoretical situation B, an attempt has been made to correct a severe Class II problem by orthodontics alone, and there has been unfavorable change in facial profile. This is clearly seen in the increased number of red Arnett measurements in the right diagram. There has been flattening of the upper lip, with reduced convexity, to give the 'orthodontic look' which has been much criticized in the past. The STCA clearly shows this.

Situation C - combined orthodontic and surgical correction of a severe Class II/l malocclusion. Patients are understandably anxious to avoid surgery, but for many severe cases, in non-growing individuals, it offers the best possible outcome in dental and facial terms (Fig. 7.5). If mandibular advancement surgery is deemed necessary, the surgeon may wish to delay this until age 16 or later, to allow maturation of the temporomandibular joints, so they are able to support the position of the corrected mandible.

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Fig. 7.5 The theoretical situation C is the same at the start as situation B. However, the severe Class II problem has been corrected by combined surgery and orthodontics. The favorable change in facial profile is clearly seen in the black Arnett measurements in the right diagram. Although patients are anxious to avoid surgery, it may offer the best possible outcome in dental and facial terms for severe cases, and it is appropriate to inform the patient of this.

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