CASE REPORT the palatal separator. Also, a Hick-ham chin cup, which pushes back on the mandible as it pulls forward on the maxilla, may be used. A force of 8 to 16 ounces should be exerted. At first, wearing time should be 22 to 24 hours. Later, “at home” time, including sleep, should be observed until there is an over correction of the Class III. When this is accomplished, night wear only should be exercised for about four months. Total antici-pated treatment for this young patient is approximately one year. In the young patient, correction occurs about 75% in the maxilla. A small portion of this is due to tooth movement, while a majority of correction is in the orthopedic movement of the bony structure. About 25% of correction occurs in the mandible by a clockwise rotation of the mandible as the vertical height of the lower one-third of the face increases. The benefits to the patient are a larger nasal airway, aiding in airway function, and the expanded maxilla gives added space for aligning crowded teeth. Be advised, there is much patient resis-tance to the appliance, and there is always a tendency toward relapse. Rare cases of TMJ problems in young children, due to distal pressure on the mandible, have been reported. In adults, most Class III maloc-clusion is occasioned by a protru-sive mandible; a lesser number by an insufficiently developed maxilla. In most cases there is a combina-tion of these problems. When the major cause of a severe Class III malocclusion is insufficient maxillary develop-ment, full correction must be done surgically. However, in less severe cases there are some orthodontic procedures which may be used successfully. These include widen-ing the maxilla with a large overlay arch (.036 or .040 -a” Big Daddy”) and advancing the upper anteriors with Class III elastics. Recently, by the same principle, “TADs” have been employed to move the upper anteriors forward for maxillary advancement. Their use has replaced the more expensive and invasive use of mini-plates. When the anteriors in the maxilla have been moved forward, a lip bumper must then be used to run interfer-ence for the soft vascular bed so that the bony structure, along with the roots of the teeth, can be brought forward. While severe cases of Class III malocclusions caused by an under-developed maxilla need to be treated surgically, this is not the preferred treatment if the cause is primarily a protrusive mandible. Surgery for a protrusive mandible, whether to shorten or lengthen it, can have a detrimental effect on the TMJ. The mandible is cut into three pieces, and when these pieces are screwed back together, it is impossible to tell how the condyles will fit in the fossa, or if they will function properly in this new position. There is a great tendency to relapse, particularly in surgically treated Class III cases. This is why surgeons will ask a participating dentist to use some Class II mechanics prior to surgery, thus making the Class III malocclusion worse. This gives a slight “relapse” cushion. The dentist involved needs to understand why the surgeon has made this request. Class III patients rarely have TMJ problems. I contribute this to the fact that nearly all of them have a significant forward slide on final closure, thus giving plenty of space in the retrodiscal area. Conversely, I have treated some Class III cases in which, after treatment, their bites have slightly deepened, forc-ing the mandible distally. Then they come back with a TMJ prob-lem! Beware of this possibility when correcting Class III malocclusions. There are many variations of severity in Class III malocclusions. ᕡ Some adults who are edge-to-edge anteriorly, or only slightly Class III, can be treated by removing one lower central; or even at times, with only lower anterior stripping. ᕢ In slightly worse cases, the removal of the lower first bicus-pids may suffice. ᕣ The best non-surgical treat-ment I have found for more severe Class III cases in older children and adults is the removal of both lower six year molars. (In such cases, the patient must have lower eights, though they need not be erupted at the time.) The lower second molars are pulled forward to a Class I position, partially occupying the original space of the first molars. At the same time, the lower anteriors and lower bicuspids are moved distally, as a unit, to a Class I position, thus occupying the remaining space of the original first molars. Rarely is a case the same on both sides. Therefore, Class III or Class II elastics -whichever is indicated -are used to finish the case to Class I. When the lower eights have not erupted, it will be necessary to use a special upper retainer to prevent the upper second molars from erupting into the space of the second lower molar which the developing lower eight must occupy. The upper eights are left so they can exert forward pressure on the upper dentition. Once the desired Class I occlusion has been achieved, the upper eights should be removed as they now have nothing on which to occlude. Once the case is finished, and the lower eights are in place, the fact that the lower six year molars are gone is hardly noticeable. In this orthodontic method of Class III correction for a protrusive mandible, the jaw is not moved back, but the teeth are in a Class I relationship. If desired, the patient can then have genioplasty to move the chin button back, or back and up. This is a good surgical proce-dure which can be done in the surgeon’s office, and will have little or no effect on the TMJ; whereas in bilateral sectioning of www.orthodontics.com March/April 2013 19
Journal of the American Orthodontic Society March-April 2013: Page 19
