Class III Skeletal Pattern & DeClerk Mechanics

The interesting case that I wanted to discuss today is this gal that came into the clinic that has a Class III skeletal pattern. She has an under bite of approximately 2-3 millimeters, and appears to be progressing as she grows into a worse and worse Class III skeletal pattern. If left unchecked, this patient likely will require some Orthognathic surgery, either a Le Fort I or a bilateral sagittal split osteotomy setback in order to correct this discrepancy. This patient was referred from a fantastic orthodontist to place skeletal anchorage. This anchorage will be used over an extended period of time with elastics to provide a force to try to modify grown.

What was done as this patient was brought into the clinic and was NPO, she was sedated. Initially, a couple of plates were placed in the mandible and actually on the mandible in the canine 1st bicuspid area. In the anterior mandible, an incision was made that was vertical with a small horizontal limb that allowed access to this part of the mandible. An L-plate, that's a plate that's in the shape of an L, was then contoured and adapted, and three screws were used for each plate, one on the right, one on the left. One of the eyelets of the L-plate was actually cut to allow for an elastic to either engage or for at least the orthodontist to grab onto this portion of the L-plate that was then transmucosal and above the gum tissue that allows access.

These screws provide absolute anchorage and have to be attached to the maxilla. I've done this several ways in the past. The classic version of this, using Bollard plates and De Clerck mechanics, is by placing a plate in the zygomaticomaxillary buttress. I found multiple times that this bone tends to be soft, and the retention and the long-term stability of these plates is somewhat sketchy and unpredictable.

What we've headed towards now is placing a palatal implant. In fact, in this gal I placed a 4.3 by 8 millimeter Nobel Biocare or Replace Select implant in the palate at the junction between the premaxilla and the palate. There's some really stable, strong, dense bone in this area, and the implant went in quite nicely. The key here, of course, is to place it within bone and to not damage the roots in this area. I have some pictures that verify that. The implant was put in position and a healing abutment was placed.

What the orthodontist will do is take an impression and fabricate a transpalatal arch that will be luted onto the 1st molars bilaterally, and then some hooks on the facial aspect will then be used to engage the plates in the mandible. The palatal implant immobilizes those 1st molars by attaching it, and essentially creates absolute anchorage. Now the force applied between the maxilla and mandible will be there preferably through her growth phase and modify and provide forces hoping to restrict growth of the mandible and accelerate growth of the maxilla, eliminating her Class III discrepancy.

There's some really good research and papers out there using the De Clerck mechanics to modify growth and to help these patients avoid Orthognathic surgery and, worst-case scenario, at least minimize the amount of movement required with that jaw surgery. This patient tolerated the procedure quite nicely.

If you go here, you can find a really nice breakdown of the case with some intraoral photos and pictures. Once the orthodontist is done using this hardware, the hardware will be removed, which is surprisingly straightforward. I want you also to know that the morbidity, the pain and the tenderness after this, is pretty reasonable for patients. For instance, way easier than, say, 3rd molars.

For the full "Class III Skeletal Pattern & DeClerk Mechanics" podcast episode click here.

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