Two-Phase Treatment

Phase 1 usually consists of activator (any type), plate-headgear, headgear, any type of distalizing devices (Carriere, Beneslider, Pendulum, distal-jet, etc.), maxillary expansion (forced/rapid), extraction of premolars, etc. Subsequently, this Phase 1 is followed by Phase 2 by means of aligner treatment.

This protocol has the following advantages:

• Parallel to the initial sagittal correction, movements which are less predictable with aligners alone, such as correction of severe deep bites or transversal discrepancies, can be improved simultaneously. The subsequent Phase 2 with aligners will be easier, more predictable, and shorter.

• The estimation of compliance is more precise: a patient who wears headgear respecting the protocol will most likely also wear aligners as required.

• Starting Phase 1 during mixed dentition allows starting the aligner treatment in the permanent dentition and, therefore, the necessity of an MCC is significantly reduced. Almost all patients starting the aligner treatment during mixed dentition will need an MCC, whereas an MCC after start in the permanent dentition is rare when the planning was correct.

Distalization of Upper Posterior Teeth

With a sophisticated aligner system, the distalization of upper posterior teeth can be performed in a very predictable way. Studies have shown that no significant tipping of teeth will occur when the distal movement of molars is up to 2.5 mm. Clinical experience shows that even movements up to 4.5 mm can routinely be performed successfully. It is recommended to place rectangular vertical attachments on the molars in order to prevent tipping if the distalization exceeds 2.5 mm.

In all cases, use of Class II elastics is mandatory. The standard procedure is to fix buttons on the lower first molars and attach the elastics from these points to hooks located at the upper canines, which are cut directly into the aligners (Fig. 4.2). On both sites, it is possible to place buttons or cuts in order to attach the elastics. The inclination of the incisors will remain very stable for both kinds of attachments of the elastics, cuts and buttons. The decision whether to put cuts or buttons is influenced mainly by the form and the height of the clinical crown of the teeth and by personal preference.

If the skeletal base is only moderate Class II, 12 hours/day of elastic wear can be sufficient for anchorage. Generally, it is recommended to always start with Class II elastics which are worn full-time (24 hours/day). Depending on the progress, the duration can be reduced during treatment. Careful monitoring is always required for both tipping of teeth and sagittal relation.

The distalization has to be carried out sequentially. A maximum of two pairs of teeth should be distalized simultaneously at the same time. All the other teeth serve as anchorage.

Effect of Class II Elastics Alone

The final result of growth modification alone, in order to correct Class II malocclusions, is highly dependent on the compliance to wear Class II elastics and on growth itself. Both factors are difficult to foresee, and careful steady monitoring is mandatory.

While the inclination of the lower incisors remains very stable, this force system will produce a slight posterior rotation of the maxilla (comparable to a Herren-type activator). Probably, when attaching the elastics on buttons on the teeth, the inclination of the incisors will remain more stable compared to the attachment of the elastics directly on the aligners. However, no scientific data covering this topic are available yet.

Combination of Distalization in the Maxilla and Effect of Class II Elastics

For most cases with Class II malocclusion, the strategy of combining both distalization and skeletal effect of Class II elastics seems to be the most suitable.

The predictability of growth is limited. Therefore, clinically we can see more or less of growth modification by the effect of Class II elastics than expected or than the treatment plan requires.

The amount of distalization of the upper posterior teeth could be too much if the effect of the elastics is higher than planned or if more sagittal growth occurs than included in the treatment plan. Should this be the case, it is necessary to undertake an MCC.

It is recommended to correct Class II malocclusion 2/3 by distalization in the maxilla and 1/3 by effect of Class II elastics. If the treatment plan is designed accordingly, the clinician has more flexibility during the treatment phase.

Extraction of Premolars

In cases with severe crowding, the extraction of upper first and lower second premolars can be useful in order to obtain a Class I molar and canine relationship. This treatment will require attachments and auxiliaries to prevent undesired molar tipping, particularly in the mandible (see Section 4.3 and Section 4.6.1).

Mandibular Advancement Feature

Align Technology has released this newly designed treatment option for Class II treatments with aligners for teens. The aligners are constructed comparable to a Twin Block appliance.

The precision wings (Fig. 4.3) keep the mandible in a slightly protruded position.

Advantages:

• The appliance is worn for 22 to 24 hours (only removed for eating and cleaning), which makes it more effective than comparable appliances worn at nighttime.

• The anterior teeth can be fully aligned at the same time.

• Reduced treatment time.

First clinical studies show:

• A good effect on the sagittal relation.

• No posterior rotation of the maxilla.

• No unwanted proclination of the lower incisors.

• Very good control of the incisors in both jaws in all dimensions.

First Phase Treatment of Class III

According to the present skeletal pattern, either maxillary deficiency or mandibular protrusion or a combination of both, different appliances have been designed. Clinically and cephalometrically, it is difficult, however, to separate the effects of an appliance, for example, the Delaire face mask, to the jaws. We will always find effects in both dental arches/jaws.

Clinically, the focus should be on growth modification (skeletal effect) and avoiding camouflage or compensation. It is important not to protrude the upper incisors when trying to obtain or keep a positive overjet.

Aligner treatment in this phase consists of a pair of passive aligners provided with buttons for the application of Class III elastics. In the lower jaw, it is recommended to bond buttons or hooks directly on to the first primary molars. This prevents the lower aligner from disconnecting. In the upper jaw, alternatively, a palatal plate can be used. This device has the advantage that the position of the upper incisors can simultaneously be improved (mainly derotation of lateral incisors) and some expansion can be done when needed. Poncini clasps are strong enough to keep the plate in place with the elastics hooked directly on them. To improve compliance, the labial arch can be left out.

Aligner therapy in the first phase of Class III treatment is advantageous due to the following reasons:

• The appliance can be worn full time, showing faster and higher effect.

• Lower forces are needed (4 ounces instead of 12 ounces recommended for the Delaire mask).

• Compliance is much higher as the appliance is less bulky and much less visible than all other Class III appliances.

• The costs are much lower, even when the aligners have to be replaced when worn out.