Class IIIClass III dentofacial deformitySFAPrognathismComparison
The conventional dentofacial deformity management sequence, using orthognathic surgery, is presurgical orthodontic treatment, orthognathic surgery, and postsurgical orthodontic treatment. This approach has been the standard for achieving stable and predictable results in correcting dentofacial deformities; few studies have investigated possible modifications to this approach. Although the conventional approach has many advantages, some disadvantages exist, such as the length of the presurgical orthodontic treatment, related delays in orthognathic surgery, and possible aggravation of facial aesthetics during the presurgical period, especially in patients with Class III dentofacial deformities. However, if a surgery-first orthognathic approach is possible, these presurgical drawbacks can be avoided [1–5].
The presurgical orthodontic treatment aims to reveal the true extent of skeletal discrepancies by correctly positioning teeth in the basal bone, which is done during the dental decompensation process (Fig. 11.1). However, complete decompensation may not be possible because of mastication function and force as well as spontaneous dental compensation, which occurs opposite to the iatrogenic decompensation and makes the postsurgical orthodontic treatment, in addition to presurgical treatment, generally necessary (Fig. 11.2) [6–10].
Therefore, we hypothesized that orthognathic surgery followed by postsurgical orthodontics, without any presurgical orthodontics, may be as effective as the standard approach for correcting dentofacial deformities.
When orthognathic surgery is performed without a decompensation procedure, the body’s natural compensatory adaptation process coincides with the postsurgical dental decompensation procedures [16–25]. Moreover, if the surgery-first approach is applied with postsurgical orthodontics, a regional accelerated phenomenon (RAP), which is known to facilitate the postsurgical dental movement, might maximize the dental movement effect of the postsurgical orthodontic treatment (Fig. 11.4). Therefore, orthognathic surgery, without presurgical compensation, maybe a valid treatment modality in patients with Class III deformities. Consequently, the surgery-first approach has been performed on our dentofacial patients, since 2007 (Fig. 11.3).
Our surgery-first approach is based on presurgical simulation using a dental model. Although our approach does not require preoperative orthodontic treatment, dental model simulation before the orthognathic surgery provides us with predictions that avoid possible postoperative occlusal instability.
In order to persuade you to understand the efficacy of the surgery-first orthognathic approach, I will address one of investigation with the comparison between the traditional approach and our surgery-first approach . This prospective study investigated the surgical outcomes of 22 standard and 32 surgery-first approaches. The included patients had skeletal Class III deformities and underwent orthognathic surgery between December 2007 and July 2010 at the Seoul Asan Medical Center, University Medical Center (Fig. 11.5). Patients were placed in the surgery-first group after consideration of the inclusion and exclusion criteria. The indications were based on presurgical simulations using the dental model. This preoperative simulation setup allowed us to evaluate the possibility of a surgery-first orthognathic approach. In addition, we excluded patients with severe dental crowding, arch discrepancies, syndromic patients, and those with cleft-related dentofacial deformities, based on our presurgical model setup; patients not followed for at least 18 months were also excluded. Patients were not randomized, but cephalometric analyses were used to evaluate the dental and preoperative skeletal parameters of the two groups to validate the intergroup homogeneity of these parameters. Subsequently, changes in cephalometric landmarks, reflecting the vertical and horizontal skeletal patterns and the dental patterns, were compared between the standard and surgery-first groups in the preoperative, immediate postoperative, and 1-year postoperative periods. In the surgery-first approach, presurgical orthodontic treatment was not performed, except for the application of a bracket for intermaxillary fixation. However, simulated surgeries, using a dental model, were performed before surgery to create the appropriate wafer and estimate the extent of the postsurgical orthodontic treatment. This presurgical procedure was a critical step in our surgery-first approach.
The overall procedure was carried out in the following sequence: (1) Preoperatively, the standard model mounting process was performed to assess the patient’s occlusion. (2) In the model setup, teeth that were already adapted to the skeletal discrepancy were simulated and reorganized into their predicted locations. This was done by analyzing, simulating, and separating each tooth in the model, as in the real presurgical orthodontic treatment. (3) Simulation of the actual orthognathic surgery, similar to that for the standard approach, was performed. For example, in Class III cases, the maxillary impaction or advancement and mandibular setback processes were simulated. These processes indicate the possible occlusion outcomes, after presurgical orthodontics and orthognathic surgery, in the model. (4) At this time, if the positioning of the teeth is reverted to that which existed before the presurgical orthodontic treatment on the dental model, using the original teeth model, we get a model reflecting the condition of the teeth before orthognathic surgery, without presurgical orthodontics. This process is referred to as the “surgical temporary occlusion” and is made possible using unique magnetic mounting plates that were designed to produce these changes in the dental model. (5) Based on the simulated model surgery, the intermediate and final wafers used for orthognathic surgery, without presurgical orthodontics, are made (Fig. 11.6).