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Can a Functional Appliance Grow a Mandible? by Dr. William D. Nguyen

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Introduction
As most clinicians know, the decision to treat Class II patients with a very large protrusion is not only a cosmetic decision but a preventive one as well.

An 11-year-old girl presented to my office with a chief complaint of "I have a huge overbite. Can you grow a chin for me?"

Following a clinical exam and utilizing the initial records taken, the following diagnosis and treatment plan was established.

Diagnosis
A Class II division 1 skeletal and corresponding dental malocclusion was found with the patient in the early permanent dentition stage.

The overjet was 12mm with maxillary incisor procumbency, mandibular retrognathia, and a moderately low mandibular plane angle. The patient had a great attitude towards treatment and great growth potential (CVMS II).

Some of the pertinent measurement data from the cephalometric analysis: SNA 79, SNB 74, ANB 5, U1-SN 119, U1-NA 39/9, L1-NB 16/2, SN-MP 33, FMA 23, IMPA 88, Wits +6.

Treatment plan for active care
A decision was made to utilize a Twin Block functional appliance for 9-12 months, progressing to full fixed appliances (.018 slot Roth Rx) for 12-18 months once more teeth erupt. Non-extraction therapy was determined to be the best option for this patient due to the favorable expected skeletal growth pattern.

Retention plan for care after appliance removal
Upper Hawley & L3-3 fixed lingual retainers. Monitor wisdom teeth during retention and refer for removal as needed.



Treatment sequence
Twin Block therapy was utilized from March 2014 to January 2015. The patient was instructed to wear the appliance full-time even during meals, only taking it out for oral hygiene.

The maxillary transverse screw was activated two times per week from March 2014 to July 2014. Upper and lower posterior acrylic was removed at six-week intervals to allow for sequential passive eruption of L7s, L6s and L5s.

Upper and lower arches were bonded mid-January 2015, and U16NT / L14NT were placed. U16SS was placed in early March 2015. L16SS was placed on the next month. In early May 2015 I placed U/L 16x16SS and cinched back lower.

One important factor is to differentiate these results between condylar growth versus the anterior positioning of the condyles. To do this, I would palpate the condyles by placing my fingers just anterior to the tragus and in the external auditory meatus. I would try to get a feel for the location, size and shape of the condyles, and compare this to what I see on my PANO and ceph. I would then try to manipulate the mandible and see if there is a discernible CR-CO shift.

I was able to retract upper anterior teeth by tightening the upper labial bow and reducing lingual acrylic of U2-2. I have not traced the superimposition for the maxilla between the initial ceph and the progress ceph, but I think maxillary posterior vertical control was accomplished via a "bite block" effect. I cut back the posterior acrylic sequentially on L7s, then L6s, and L5s, and trimmed upper posterior acrylic shelf accordingly to allow passive eruption of these lower posterior teeth.



Conclusion
I will be taking another progress panorex and perhaps a lateral cephalometric X-ray in a few months to ascertain root parallelism and evaluate growth. I plan to wrap things up by early 2016.

When I present this case at the next SoCal Angle meeting, I will trace the superimpositions. I did activate the labial bow from time to time during Twin Block therapy, resulting in significant reduction of maxillary incisor procumbency. I don't have imaging of the condyles other than what you see on the initial views. I would assume, and hopefully correctly so, that the condyles are seated in the fossa pre-treatment.





William D. Nguyen graduated from Case Western Reserve University in Cleveland, Ohio in 1999. Nguyen works with Dr. Joseph Andrews in Orange County, California, as part of Nguyen & Andrews Orthodontics


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