The Orthodontics Professors
the latest in contemporary & evidence-based orthodontics
Management of Class III Malocclusion using Bone Anchors: True Orthopedics Part II – Clinical Technique
BY TUNG T. NGUYEN, DMD, MS
The following article outlines our protocol for early treatment of Class III malocclusion using Bone Anchored Maxillary Protraction (BAMP). In a future post, we will include more clinical tips and tricks, as well as information on how to handle unusual complications.
Age of the Patient
The typical age for BAMP treatment for a patient who has a Class III skeletal relationship with a component of maxillary retorgnathia is 11-14 years. Broadly stated, the younger the patient, the better the chance for orthopedic protraction of the maxilla and midface. The success of BAMP treatment is primarily dependent on 2 factors:
Surgical Management – Placement of the Plates
We recommend the Bollard plate with the Y-Design (center plate in the image below). The Standard (screw holes in-line) design can also be used with success.
The maxillary bone plates are inserted in the infrazygomatic crest, with the plate arm emerging through attached tissue near the maxillary molars. The mandibular bone plates are inserted between the mandibular lateral incisors and canines – again with the intraoral attachment emerging from attached tissue. For the placement of both the maxillary and mandibular plates, a small flap is raised with a design that maintains good blood flow to the tissue. We refer all plate placement to qualified oral and maxillofacial surgeons familiar with the technique and treatment goals.
Ideally 1.5-2.0 mm of cortical plate thickness is needed to ensure both short-term and long-term stability of the plates. For these reasons, we often delay BAMP treatment until the age of 11. In the mandible, extraction of primary canines (M & R) will expedite the eruption of the permanent canine to help provide the inter-radicular space needed for the plates and screws.
If the permanent mandibular canines have not yet erupted, the mandibular plates can still be placed, however. In these special circumstances, we use the maxillary plates with 3 screw holes (in-line, not the Y-Design) and utilize the bottom 2 screws with the most apical hole placed just beneath the lateral incisor root. The plates are placed with a distal angulation – so that the hooks on the plates still emerge into keratinized gingiva in the region just buccal and apical to where the permanent canine crown will erupt.
The screws can either be inserted with the surgeon making small pilot holes or using self-drilling screws. We recommend the use of a pilot hole, as it decreases the mechanical stress on the bone and facilitates faster healing.
The plates are loaded 3-4 weeks after surgery, if they are stable. We test stability clinically at each plate before loading.
Initial traction is 100g per side for 6 weeks. The patient is instructed to wear the elastics 24/7 and to change the elastics at every meal. Make sure that the patient does not experience sharp or dull nagging pain when wearing the elastics. If the patient experiences sharp pain upon elastic loading, instruct them to discontinue elastic wear immediately. Sharp pain usually indicates plate instability. Stopping traction is most often the best way to allow the plates to re-stabilize.
After 6 weeks of initial loading, the traction force can be increased to 150g per side for an additional 6 weeks. The final loading force is 250g per side about 6 weeks later.
Often, patients who have a Class III skeletal relationship with a deepbite and anterior crossbite require some sort of bite-opening appliance to allow the crossbite to be most efficiently corrected. To accomplish this goal, we place temporary bite turbos on the mandibular first molars, but a retainer with a posterior bite plate is also effective.
Most often, we start BAMP treatment with a full fixed appliance in the lower arch to decompensate the mandibular incisors. Our experience suggests that young patients are more motivated to wear elastics until the anterior crossbite is corrected. By simultaneously decompensating (proclining) the lower incisors with a fixed appliance, we know the true amount of orthopedic correction needed in order to obtain positive overjet with an aligned mandibular arch.
Once positive overjet is obtained, we place full maxillary appliances and continue elastics to overcorrect to ~4mm overjet or ½ cusp Class II. Elastics can then be decreased to only night time wear for retention of the orthopedic improvement until mandibular growth is completed. After debond, the patient is seen every 6 months for growth observation. If the overjet decreases, we increase elastic wear to full time in order to help account for continued Class III mandibular growth. In the rare instances in which the overjet increases, the patient can cut elastic wear to every other night. The plates and screws can often be maintained successfully for several years and then removed in conjunction with 3rd molar extractions, if indicated.
In summary, the clinical protocol is as follows:
11/13/2017 08:11:26 am
Colleagues have reported effective results but I can't help but wonder the long-term effects and health of the TM joints.
11/13/2017 11:35:00 am
I understand your concerns with TMJ loading. The loading force for the BAMP protocol is pretty low at 250g to get overjet correction. Historically Reverse Pull Facemask have 2-3X that force level and there is published data showing long-term TMJ damage. After that they only wear the elastics at night time. We are following these patients long-term and preliminary data shows the the volume of the condyle is stable even with night time loading forces. We also have a small sample of BAMP patients with MRI and there appears to be no loss of the capsular or subcapsular space. We will continue to follow these patient to make sure they do not develop TMD.
11/13/2017 06:10:10 pm
5/31/2018 12:07:32 pm
Yes, you can load sooner with pre-drill. Dr. DeClearck often loads at 3 weeks where as I load at 4-6 weeks because my surgeon uses self drilling screws. Check to make sure the anchors are firm before loading. Push the anchor in a distal direction and see if the patient reports sharp pain.
5/30/2018 04:08:05 pm
Great article! I have tried a few mini plate orthopedic correction cases and I have been not very successful. My surgeon did not use the bollard plates, however. I had issues with loose plates on a few of the cases. Is there a specific reason the bollard plates should be used over another plate manufacturer? TIA
5/31/2018 12:16:47 pm
I have used Stryker, KLS Martin, and Surgitec plates. I don't like the Stryker plates as much since they are more flexible. Your surgeon is likely choosing it because it is cheaper or they have a deal with that manufacturer. That said a plate is a plate as long as the arm emerges in keratinized tissue and it is stable. The 2 most common cause of plate loosening is poor bone quality and poor surgical technique. Younger kids (10 yo) often have thinner bone at the infrazygomatic crest. Ideally they should have 2mm of bone thickness at the site to assure stability. Self-drilling screws then to fail more because they introduce more micro-fractures in the bone especially if the cortical plate isn't thick. The 3rd article has suggestion if the plates become loose. Good luck
12/23/2021 11:28:26 pm
Do you have any experience with protracting adults? Many people have become very interested in protraction after the recent widespread of the MSE device which can loosen up the fully developed sutures. Of course higher loads would be required which I am not sure whether the bollards can sustain. Kind regards.
1/21/2022 07:21:28 pm
How difficult is it for your patients to get US medical insurance to pay especially because of the restriction on paying for “jaw surgery” in growing children and hospital expenses because of general anesthesia preference?
8/7/2022 05:08:24 pm
Thanks for shharing this
Leave a Reply.
Tate H. Jackson, DDS, MS