Class II division 1

Diagnosis and presentation of case

Here is a Class II division 1 case presenting a backward shift of the lower dentition (red arrows). There is a lack of space in the maxillary arch. The lateral incisors are recessed compared to the central incisors and the upper right canine is prominent.

The cephalometric X-ray on the opposite side clearly shows the backward shift (red arrow) of the lower jaw. The lower lip is everted forward because of prominent upper incisors.

The maxillary arch is narrow (green line) and it is coordinated with the mandibular arch which is shifted backward. The treatment has the goal of correcting this front-back shift between the upper and lower dentitions. To do that, the palate must be enlarged to allow the upper dentition to stay coordinated with the lower dentition in its new position.

The external surface of the upper molars (red line) is parallel to the tangent of the arch (blue line). Normally, the molar is at an angle (15°) with the tangent of the arch.
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Mechanotherapy

Progression at 44 weeks

Forsus™ Class II correctors were used to move and maintain the lower jaw forward and reduce the distance between the upper and lower teeth. These correctors are composed of a metal rod (male part) attached to the lower right archwire by a hook engaged in a loop in the orthodontic archwire. The upper portion of the corrector is composed of a spring (female part) in which the metal rod is inserted.

This resilient, mobile and flexible mechanism allows the opening and closing of the mouth, as well as lateral movements (left and right). The patient gets used to these appliances quickly and can eat and talk normally. It is possible, for the patient, to push back the lower jaw, but the spring will encourage the anterior repositioning of the jaw.

Progression at 57 weeks

The correctors were removed after 24 weeks of use. The canines have a Class I relationship (red arrows) and the molars are overcorrected toward a Class III relationship (blue arrows), meaning that the upper first molars are more recessed compared to the lower first molars. This situation is normal and ensures room to maneuver when the dentition will lead to a rebound to its initial position. The expander was also removed and brackets were bonded to the molars to replace the bands.

Progression at 96 weeks

At 96 weeks, straight, full-size archwires ensure the finishing of dental movements in the 3 planes of space. Full size means that the orthodontic archwire is large enough to fill the bracket slot. Know that this slot has a nominal dimension of 0.022 x 0.028 thousandth of an inch. The wire, at this stage of finishing, has a dimension of 0.020 x 0.025. The ligature mechanism being ensured by a nickel-titanium alloy clip maintains the wire in the bracket slot and the tooth has no other choice but to position itself in the planes of space with regard to this attachment mechanism. Finishing bends (green arrows) are sometimes necessary to correct some isolated flaws.

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Removal of fixed appliances

The fixed appliances are removed after 110 weeks of treatment. The canines (red arrows) and the molars (blue arrows) have a normal Class I relationship. The upper dentition midline fits with the lower dentition midline. The upper incisors are over the lower incisors by 2 mm, that is the normal distance.

The final cephalometric X-ray shows the correction of the shift between the upper and lower jaws. The lower lip straightened up, because it is no longer trapped by the upper incisors.

The upper occlusal view shows a large vault compared to the above pretreatment view. The external surface of the upper first molars (red line) is at an angle with the tangent of the arch form.

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Long-term stability

A hundred (100) weeks after the fixed appliances were removed, the molar and canine relationships are stable. Even the intercuspation improved.

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Evolution of the profile

It is interesting to see the change in this young boy’s face before the treatment, at the end of the treatment and 2 years after the appliances were removed. Notice how well the profile developed over a 4-year period including 2 years of treatment. Notice that the lower lip cannot get in contact with the upper lip on the initial picture. The incisors are visible when the lips are at rest. At the end of the treatment, the lips are in contact without perioral muscle contraction. This young man’s mature face, 2 years after the treatment, shows that the orthopaedic correction is maintained and that his lips are closed in the rest position. The incisors are no longer exposed as before the treatment. The face is well proportioned.