To correct mandibular deficiency, mandibular advancement is often performed via intraoral vertical ramus osteotomy (IVRO) and bilateral sagittal split osteotomy (BSSO) [2]. In IVRO, a vertical incision is made in the ramus, which divides the mandible into two parts (anterior and posterior), thereby moving the mandible to achieve a reduction effect. The advantage of IVRO is that the operation is simple and fast. However, a disadvantage is that internal fixation of the mandible cannot be achieved with artificial bone screws, and thus, bone healing must be assisted by intermaxillary fixation. Therefore, patients cannot open their mouths for about 6 to 8 weeks after surgery [3]. As for BSSO, the horizontal cutting line is located above the medial side of the ramus and above the lingua, while the vertical cutting line is located at the distal side of the second molar on the lateral side of the mandible. Next, the two cutting lines are connected along the external oblique ridge. After cutting, the mandible is divided into two parts, a proximal segment and a distal segment, and fixed with miniplates. One advantage of BSSO over IVRO is that the bone has a larger contact area and higher stability. In addition, both mandibular advancement and setback can be achieved with BSSO surgery, as desired. Therefore, mandibular advancement with BSSO is the more common approach for treating mandibular deficiency [4]. Clinically, intermaxillary fixation for several days to weeks after mandibular orthognathic surgery can be performed. However, some physicians prefer to maintain an open airway for the patient after surgery and thus decide against intermaxillary fixation [5]. Consequently, if the mandible without intermaxillary fixation experiences excessive external forces, then changes in occlusion or poor bone healing may occur.
In the present study, Young’s modulus of the miniplate and cortical bone was 110,000 and 17,000 MPa, respectively, indicating that in the overall structure, the miniplate experienced higher stress. The results of this study show that the values for the miniplate in the four groups are smaller than the yield strength of the titanium alloy (tensile strength of 1100 MPa [20]), and hence, the miniplate is not easily deformed under normal occlusion loading conditions.
After BSSO surgery, the teeth are usually fixed in the ideal occlusion position (intermaxillary fixation); however, to improve patient life quality of post operation and maintain an open airway, many clinicians have opted not to perform intermaxillary fixation in recent years [5]. According to these study findings, after BSSO, patients should be advised to consume liquids and soft foods and to avoid ICP and RMOL occlusion to reduce the force on the mandible.
https://www.hindawi.com/journals/abb/2019/4989013/
Data Availability
The data used to support the findings of this study are available from the corresponding author upon request.
Conflicts of Interest
The authors declare that there is no conflict of interest regarding the publication of this paper.
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