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Home PRODUCTS Scientific articles The Twin Block - Case reports - Dr. W.J. Clark

The Twin Block - Case reports - Dr. W.J. Clark

Case reports

1) P.K. – Age 11 Years 4 months

Facial photographs before treatment show the listless appearance typical of many patients with severe Class II Division I malocclusion. A large overjet is frequently associated with a backward tongue position and a reduced airway.


1- Pre-treatment

2 - 3 months into TWIN-BLOCKS treatment

3 - After 11 months

4 - 5 years after retention

Treatment start

After 11 months

5 years after retention

This patient had a 17 mm overjet and a severe distal occlusion with congenital absence of a lower second premolar. Within 3 months of starting treatment a remarkable change is observed in facial appearance. The patient is more alert and there is a marked improvement in the eyes and the complexion. These fundamental physiological changes can be attributed to an improved airway with significant improvements in the patient’s general health. These aims of treatment were first recognized by Pierre Robin (1902) when he designed the monobloc.

After 11 months in treatment the overjet was reduced to 2 mm. Facial and profile changes are illustrated after 3 months, 11 months and 5 years to show the long term stability.

2) K.C. – Age 11 years 2 months

A severe Class II Division I malocclusion was associated with narrow archform and crowding in upper and lower labial segments. An initial stage of treatment using lingual appliances to correct the archform was followed by twin blocks. The rapid improvement in appearance is shown in profile photographs taken immediately before fitting twin blocks and two months later.

1 - Pre-treatment

2 - 3 months into TWIN-BLOCKS treatment

3 - 18 months after retention

A profile view 3 years 6 months later confirms the stability of the result. The final occlusion is shown 18 months out of retention.


3) J. C. - Age 8 years 9 months

This young boy presented in mixed dentition with a severe Class II division 1 malocclusion with an overjet of 15 mm. The buccal segment relationship was a full unit distal occlusion and the overbite was excessive, with the lower incisors occluding in the soft tissue of the palate 5 mm lingual to the upper incisors. (Fig. 1).Pre-treatment occlusion Fig.1

Lips were incompetent at rest, with a short upper lip and the lower lip trapped lingual to the upper incisors. In profile the maxilla appeared to be well related to the cranial base and the mandible was retrusive.

Functional orthopedic correction was achieved with twin blocks after 14 months' treatment (Fig. 2), at which stage the twin blocks were discontinued and replaced by an anterior inclined plane, to support the corrected occlusion.

Treatment start. Setting the Twin-Blocks Fig.2

The anterior inclined plane was worn full time for 6 months, and thereafter was worn at night as a retainer during the transition to permanent dentition.

At this stage, slight spacing was present distal to the upper canines, and the overbite was slightly increased at 4 mm. The buccal segments were in Class I relationship, and the overjet was stable at 3.5 mm. The facial changes were rapid in the early stages of treatment and were sustained after treatment. A short period with fixed appliances followed to detail the occlusion. (Fig. 3).

14 months into treatment Fig.3


Examination of growth increments in individual and consecutively treated cases in the Twin Block Technique supports the view that functional orthopedic therapy can influence mandibular growth, and produces highly significant growth change in treatment (Clark, 1995, 2002).

Before planning surgical correction of facial imbalance due to skeletal factors, the alternative of functional orthopedics should be considered. If the problem is within treatable limits, twin blocks can achieve a non-surgical orthopedic correction, which is much more acceptable to the patient than the combined surgical and orthodontic approach.

4 years after retention Fig.4


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