Over 4 years in development, Invisalign Treatment with Mandibular Advancement is now available for use in the United States. The appliance features Precision Wings on both the upper and lower aligners which engage in such a way as to advance the mandible, replicating the mechanism of action of a functional appliance. Designed for growing teen patients with mandibular retrognathism, Invisalign Treatment with Mandibular Advancement provides the orthodontist with an esthetic and comfortable alternative for Class II correction in growing teen patients.
As the Principal Investigator for the multi-center North American study, I have a unique perspective on the development of the appliance and application of the technique. As the study progressed, we learned a great deal about how to best approach mandibular advancement patients. One of the facets of the treatment protocol that is critically important, but easily overlooked, is the pre-mandibular advancement (Pre-MA) phase.
The initial treatment happens in three phases; pre-mandibular advancement, mandibular advancement (with precision wings), and transitional aligners. You may be very anxious to get your patients into precision wings right away so that the Class II malocclusion may be corrected as soon as possible. In fact, you may prescribe precision wings at aligner stage 1. Be aware that this may not be wise, as there are certain movements that should happen on the pre-MA phase that will allow for more successful treatment. Let’s review three critical moves:
- Mesial-out rotation of the upper first molars
- Leveling of the lower curve of Spee
- Proclination of the upper incisors in Class II div. 2 cases
First, mesial out-rotation of the upper first molars not only helps in attaining a Class I molar relationship, it also accommodates proper positioning on the precision wings. In fact, there are some cases where pre-MA upper molar rotation is required for the precision wings to fit. In these cases, a minimum of four pre-MA stages will be provided.
Second, leveling of the lower curve of Spee prior to advancing the mandible is critically important to allow for advancement of the mandible in a horizontal direction, which is desirable in retrognathic patients. Failure to flatten the lower curve of Spee will result in advancing the mandible in a more vertical direction, leading to undesirable lengthening of the lower facial height, increasing facial convexity, and the development of a posterior open bite.
Third, it is necessary to procline the upper incisors in Class II div. 2 cases to allow for sufficient overjet to accommodate an advanced mandibular position.
Make sure you prepare your mandibular advancement patients and their families for the possibility of several months of pre-MA aligners by explaining that the position of the teeth needs to be properly set up to accommodate advancement. Learning to recognize the clinical conditions that require pre-MA will help your mandibular advancement cases proceed in a smoother fashion with better clinical outcomes. OP
Barry Glaser, DMD, Glaser Orthodontics, Cortlandt Manor, NY
