Dental Tribune Middle East
Align Technology Inc - Middle East

Treatment of Class II division 1 malocclusion treatment with mandibular advancement features

By Dr. Barry J. Glaser
March 02, 2020

Invisalign treatment with mandibular advancement is an efficient method for correcting Class II malocclusion in growing teens with patients reporting comfort and satisfaction during the treatment. This approach uses precision wings incorporated into the upper and lower aligners to engage the mandible in an advanced edge-to-edge position while the anterior teeth are being aligned. This reduces the use of interarch elastics, and differentiates the practice by offering another Class II solution besides wires/ brackets and functional appliances like the Herbst appliance. The simultaneous correction of the bite along with dental alignment results in greater efficiency compared to treating the bite relationship and the dental alignment sequentially.

In a systematic review, Janson, et.al. noted that functional appliances were effective in correcting Class II malocclusions in growing teens, with the effects of mandibular advancement-type appliances being similar to the effects of Class II elastics. These effects can be summarized as being primarily dento alveolar, with a smaller component of the change being skeletal.

Both fixed and  removable Class II correctors have their advantages and  disadvantages. Fixed  appliances such as the  Herbst reduce the  need for patient compliance, although patient comfort and  appliance breakage can  be an issue. Furthermore, the appliance carries an additional laboratory cost. Considerable chair  time must be invested for appliance insertion and  removal. On the other hand,  removable appliances such as the  twin block  tend to be bulky and  their effectiveness are limited by frequency of wear by the  patient. Class II elastics present a simple  and  effective means of correcting Class II malocclusions, especially when paired with Invisalign clear aligners. However, patient compliance with elastics wear throughout the entire treatment is a critical  factor for achieving successful outcomes. The incorporation of mandibular advancement features directly into the  aligners reduces the  dependency on intraoral elastics and  additional appliances for successful bite correction. When elastics are needed, they  are typically used at the  end  during  additional aligners, to stabilize and  fine tune the bite correction, after the majority  of the bite correction has already been achieved with the precision wings  feature.

Patient Background

The patient is an 11 year  6 month old male  with a chief  concern of “overbite.” Diagnostic summary:

  • Class II, division 1 malocclusion (severe on the right, moderate on the left)
  • Deep overbite (moderate)
  • Moderate upper crowding
  • Mild lower crowding

Initial Records

The  slightly retroclined upper incisors and  flared lower  incisors are consistent with dental compensations for a sagittal jaw discrepancy. The skeletal vertical dimension being within normal limits suggests that the deep bite is predominantly dental in nature.

Treatment plan

The  goal was to treat the  canines and  molars to Class I. For efficiency, the Class II correction would  be accomplished during the  initial phase, using aligners with precision wings  instead of Class II elastics. Class II elastics, if needed, would  only be used during additional aligners. The  crowding would be corrected through dental expansion and  arch development (i.e., non-extraction and  without any interproximal enamel contouring). Retention would  be accomplished using Vivera® retainers worn  only at night.

Treatment Results

 

Cephalometric analysis summary (initial to end-of- mandibular advancement): The cephalometric superimposition showed that a counterclockwise rotation of the  mandibular position occurred after the  bite correction phase, with the  ANB angle improving by 2.2˚ (from 6.9˚ to 4.7˚).  The  interincisal angle decreased from 127.2˚  to 120.1˚, primarily as a result of a +6˚ change in upper incisor inclination (U1-NA increased from 17.4˚ to 23.4˚). The  lower incisor inclination increased slightly (L1-GoGn = +2˚).

After 27 aligners in both arches (11 months of treatment, 2 weeks each aligner2), the  patient was Class I canine on the  right side and  3 mm Class II canine on the  left. Aligner wear compliance was good and  oral hygiene was excellent. The  majority of the  crowding in both arches was resolved during the  mandibular advancement phase. The  bilateral posterior open bite present would  be closed by additional leveling  of the  curve of Spee, along with lingual root torque of the  upper anterior teeth. By reducing the anterior interferences, the  mandible would  be able  to autorotate into a better Class I relationship.

Additional aligners phase: One  set of additional aligners was used, which lasted 9 months (19 U/L stages, weekly aligner changes3). Reverse curve of Spee was added to the  set-up of the  lower  arch to correct the  deep bite and  remove any heavy anterior occlusion, in order to close the  posterior open bite. A 3.5 oz. Class II elastic was worn  on the  left side only for just 6 weeks, from aligner stages 14 to 19 (with precision cuts on the upper canine and  the  lower  first molar),  to complete the  sagittal correction to Class I. All remaining rotations were fully resolved during additional aligners. The  total treatment time for this patient was 21 months (11 months for the  mandibular-advancement phase, 1 month for transitional aligners awaiting additional aligners, and  9 months for additional aligners with standard Invisalign treatment), which  is well within the  expected treatment time for this severity of Class II malocclusion.

Final Records

Treatment Summary

Total  treatment time: 21 months (includes 1 month in between mandibular advancement phase and  additional aligners)

  • Pre-mandibular advancement aligners: not used in this treatment
  • Mandibular advancement aligners: upper: 27, lower: 27, changed biweekly (11 months total)
  • Additional aligners: Upper: 19, Lower: 19, changed weekly (9 months total)
  • Retention: Vivera retainers at night only

Discussion

The  Invisalign treatment with mandibular advancement can be  a routine treatment modality for any growing Class II teen. This treatment approach enables the  incisors to be  aligned at the  same time that the  bite is being advanced. Proper incisor alignment was the  key to success in this case, since removing any anterior interferences allowed the  mandible to come forward into an ideal  overbite and  overjet relationship. Setting up the mandibular advancement in the  ClinCheck treatment plan to a “super” Class I or mild Class III cuspid relationship would  be  recommended for treating any similar cases in the  future, in order to further reduce the use of Class II elastics during additional aligners. Adding  sufficient lingual root torque to the  upper incisors is also  recommended, so that enough clearance in the  overjet is present for a stable Class I position to be  established. Having  a posterior open bite during the  mandibular advancement phase is common, and  can be  corrected through arch leveling  with additional aligners, or by initially leveling  the  arches with aligners through a pre-mandibular advancement phase.

Summary

Overall thoughts and learnings about how to be successful with using the mandibular advancement feature, and what to focus on during the mandibular advancement phase:

Remove anterior interferences through dental alignment, leveling  of the curve of Spee, and  lingual root torque of the  upper incisors.

Case selection recommendations when starting to use this feature:

A good malocclusion to initially target is a dental Class II with a skeletal Class I normo-divergent or mildly hyperdivergent growth pattern. An ANB < 5 degrees and  mild-to-moderate mandibular retrognathism are also helpful.

What kind of cases to try after that:

As your  familiarity  with the  mandibular advancement feature increases, try treating growing teens with more severe Class II malocclusions, and with more severe hyperdivergent growth patterns. Patients with severe skeletal Class II or severe vertical growth patterns can be  treated, but results so far have been progressively less predictable with worsening skeletal patterns.

What kind of conditions are favorable and unfavorable for treatment using this aligner feature?

The  more easily  the  lower  jaw can move straight forward without interfering with the  upper jaw, the  better. Identify  any interferences (anterior and  transverse usually)  and  eliminate them as early  as possible during the  alignment phases of treatment.

For patients with deeper overbites and/or retroclined upper incisors, using a series of pre-mandibular advancement aligners to reduce anterior interferences is key to correcting the  sagittal relationship.

What was learned from  treating this particular case?

  1. Setting up the bite correction goal to a “super” Class I in the  ClinCheck treatment plan  may reduce or eliminate the  need for Class II elastics during the  additional aligner phase.
  2. Greater leveling of the curve of Spee in a pre-mandibular advancement phase may reduce the  likelihood  of having  a posterior open bite at the end  of the  mandibular advancement phase.

Common challenges/problems experienced during teen treatment with this aligner feature:

Leveling the  curve of Spee and  mandibular advancement cannot be accomplished simultaneously during the  bite correction phase, so these corrections need to be  done sequentially instead.

How to avoid or correct these issues?

Spend the  first 3 to 5 months leveling  and  aligning  the  arches with aligners in a pre-mandibular advancement phase.

Three key take away points:

  1. A pre-mandibular advancement phase to level, align, and flatten the  curve of Spee can reduce the  chances of having a posterior open bite after the  bite correction phase.
  2. Overcorrect the  sagittal relationship in the  ClinCheck set- up to a “super” Class I during the  mandibular advancement phase, in order to reduce the  need for interarch elastics during refinement.
  3. Build precision cut  elastic hooks into the  additional aligners just in case Class II elastics are needed at or near the  end of treatment. Having  the  majority of the  Class II correction accomplished with the  precision wings  feature means that any Class II elastics used are mostly for stabilizing and  fine tuning the  bite during additional aligners.

 


 

ABOUT THE AUTHOR

Barry  J. Glaser, DMD received his doctorate in dental medicine from The  University of Pennsylvania School of Dental Medicine and  earned a certificate of Advanced Graduate Studies in Orthodontics from Boston University.  He served as associate director of orthodontics at Montefiore Medical Center in New York City from 1992 to 1995. He has been in private practice in Cortlandt Manor,  NY, since 1994. Dr. Glaser was an early adopter of Invisalign Teen®  and  has extensive experience with treating teens and  adults of all malocclusions using Invisalign aligners.

© 2020 - All rights reserved - Dental Tribune International