Establishment of Incisor Position and Space Closure
The anteroposterior position of the incisors determines where the mandible will be placed relative to the maxilla at operation and therefore is a critical element in planning treatment.
This is often the major consideration in planning the closure of extraction sites.
In mandibular advancement, before rigid internal fixation was available, slight over-retraction of protruding lower incisors before surgery was the usual plan.
This was done because, while the jaws were wired together as initial healing took place, the incisors would be displaced forward relative to the jaw by the pull of stretched soft tissues.
In this situation, the occlusal relationship would be maintained, but orthodontic tooth movement would allow the mandible to slip backward.
With rigid fixation of the mandibular segments, the jaws are immobilized for only a day or two postsurgically if at all, there is little or no pressure against the teeth, and overcorrection of the incisor positions is unnecessary.
When several surgical segments are planned for the maxilla, a different consideration arises: the axial inclination of the upper incisors and canines should be established presurgically so that major rotation of the anterior segment at operation can be avoided (Fig. 20.31).
Otherwise, establishing correct torque of the incisors surgically will elevate the canines above the occlusal plane, and proper postoperative repositioning of the canines becomes difficult if not impossible.
An extraction site that will be the location of an osteotomy cut should not be completely closed before surgery to leave room for the interdental cuts, but most of the extraction space can be closed without creating difficulty for the surgeon.
Recently, an old idea from the early days of orthognathic surgery was reintroduced:
Surgery first
without any presurgical orthodontics. This method was evaluated and discarded in the 1970s. The presumed advantages now would be faster treatment because segmental osteotomies could be used to accomplish much of the presurgical tooth movement, teeth close to osteotomy sites might move more rapidly, and patients would be more satisfied because their major problem would be addressed first and total treatment time would be shorter.
Not surprisingly, both the surgical procedure (with multiple segments and often corticotomy cuts to accelerate healing) and the postsurgical orthodontics would be more difficult. There would be some limitations in anteroposterior changes because of the lack of presurgical decompensation of incisor positions that often requires TAD-supported postsurgical decompensation.
In addition, as we have noted, a longer duration of postsurgical orthodontics (9 to 12 months in most surgery-first patients) has been shown to decrease patient satisfaction with surgical treatment.
The treatment sequence with the consensus approach described earlier and surgery first is summarized in Table 20.1.
As of late 2017, most of the limited use of surgery first has been in Asia and Europe, and there still are no good data to document the claimed advantages, but it is generally acknowledged now that
patients with severely crowded teeth and deep bites are not good candidates for surgery first.
A survey showing that surgery first was less successful in reducing treatment time than many case reports had claimed, and the suggestion that limited presurgical orthodontics would facilitate early surgery, has brought this thinking back closer to the consensus method described earlier.