Some patients and even some surgeons have the misconception that the narrowing effect is proportional to the amount of mandible reduction [2]. That is, some believe that if more amount of angular bone is resected, the more slimming effect will be expected. However, if the mandibular angle is excessively resected during the surgery, an unnatural or hollow lower face contour may be resulted. Also the balance between the chin and the rest of the mandible or between the lower face and the rest of the face will be lost. In some severe cases, an alloplastic implant should be inserted to the overly resected mandible site to restore its natural contour. Figure 13.3 shows examples of various ready-made Medpor^® implants manufactured by Stryker^® (Kalamazoo, MI, USA). Individually customized implants are also available recently.

During a conventional mandibular angle reduction surgery, if the ostectomy is abruptly stopped somewhere in the middle of the mandible body, an unnatural and unsmooth jawline, namely, a ‘secondary angle,’ may form and result in an unaesthetic outcome. A long, smoothly curved ostectomy should have been performed to prevent this condition, as in some troublesome cases an additional bone contouring is required to smoothen the secondary angle. In some cases, a narrowing genioplasty may be accompanied with the procedure.

Figure 13.4 shows a 33-year-old female patient with a prior surgical history of a conventional mandibular angle reduction. As seen on the oblique view of the preoperative medical photographs, a secondary angle is formed in the middle of the mandibular body. This is caused by a short and straight-lined ostectomy that leaves an unnatural jawline. This postoperative secondary angle was improved by a secondary mandibular mini V-line surgery. As the chin was further narrowed with a T-osteotomy technique, the lower border of the mandibular body was further contoured and smoothened for a slim and smooth facial contour.

In patients with pre-existing jawline asymmetry, bone resection should be differentially carried out. However, if the asymmetry is failed to be noticed preoperatively, the resultant surgical outcome will also leave asymmetry. Or even in patients with a symmetric jawline, if the ostectomy procedure was carried out differentially, postoperative asymmetry and a dissatisfactory outcome will be resulted. Thorough preoperative analysis and accurate intraoperative procedures are required to avoid postoperative asymmetry, and differently sized ‘guarded’ oscillating saws can be helpful in such situations [1]. However, if a noticeable asymmetry is complained by the patient after a prior mandibular contouring surgery, a secondary bone contouring with or without a concomitant genioplasty should be carried out.