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Skeletal Class 2
The skeletal Class II a mandible that has been trapped, and prevented from growing to its genetic potential of skeletal Class I. There are five factors that can trap the mandible. Some patients have only one of these, and some patients have all five factors. These factors in their order of most common occurrence are:
- The transverse width of the maxilla being narrow.
- A deep vertical dimension.
- The upper incisors retroclined in a dental Division Two.
- The anterior – posterior length of the maxilla being short.
- The position of the maxilla excessively retrognathic relative to the anterior cranial base.
It is critical to eliminate all of these trapping factors, except for the deep bite, prior to distracting the mandible into the skeletal Class I. The deep vertical entrapment is eliminated when the mandible is distracted “down” and forward.
The skeletal Class II should be corrected prior to the patient completing puberty. The optimal treatment time is in the mixed dentition.
Post-pubertal Class II cases follow the same sequence of eliminating the factors entrapping the mandible, but the mandibular distraction must be done incrementally. Changes in the relationship of the mandible to the anterior cranial base occur due to remodeling and recontouring within the TMJ complex, as opposed to stimulating the epiphyseal growth plate. There are obviously limitations to these changes within the TMJ complex, and thus the need for distraction surgery for the more severe post-pubertal Class II patients.