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From Dr. Sug-joon Ahn : You can simply decompensate inclination of the mandibular incisors by the upside down reverse positioning of the mandibular incisor brackets. In case of MBT prescription, mandibular incisor brackets have minus six degrees of inclination. When you position the brackets upside down, inherent inclination of mandibular incisor brackets changes from minus six degrees to positive six degrees. As a result, you can get about 12 degrees of extra inclination of the mandibular incisors (Please refer the lecture slides #70-74)

From Dr. Sug-joon Ahn : You’d better ask a surgeon. Orthodontists cannot decide surgical procedures.

From Dr. Sug-joon Ahn : Since many patients with Class III malocclusion exhibit maxillary deficiencies, there is not enough room for the teeth to be arranged in the maxilla, which leads to anterior crowding. Therefore, extraction of the maxillary teeth can be decided according to the amount of crowding and inclination of the maxillary incisors. Occasionally, extraction may be required the mandible, but most of mandibular crowding can be solved through proclination of the mandibular incisors. In contrast, mild crowding, normal angulation of the maxillary incisors, and sufficient amount of surgical movement are contraindication for non-extraction. • Indication for extraction planning - severe crowding, - severe labioversion of the maxillary incisors (dental compensation), - a small amount of surgical movement, - narrow width of the maxillary arch • Indication for non-extraction planning - mild crowding, - normal angulation of the maxillary incisors, - sufficient amount of surgical movement, - no transverse problem

From Dr. Sug-joon Ahn : The instrumentation and procedure errors during CR registrations, face-bow transfer, the mounting of casts, and the use of average values for the hinge axis must be considered when using an articulator. You’d better ask a prosthodontist the procedure.

From Dr. Sug-joon Ahn : The paper surgery is a kind of virtual surgery. I am sorry to say that it is not possible to explain the procedure online. You’d better refer to the textbook (Proffit WR and White Jr RP. Contemporary Treatment of Dentofacial Deformity. Mosby).

From Dr. Sug-joon Ahn : I use Korean cephalometric norms to determine the position of the maxillary incisors. You have to consider inclination of maxillary incisors on the sagittal plane. Then, the center of maxillary central incisors should correspond to facial midline at the frontal position. Angulation of the maxillary incisors should be considered, which is associated with canting correction of the maxilla. In addition, display of the maxillary incisor (2 mm at rest) and gingiva (about 2 mm during smile) should be also considered.

From Dr. Sug-joon Ahn : TVL is a vertical reference plane at natural head position. After a horizontal reference plane is made using the vertical reference plane (for example, a plane pass by Sella and perpendicular to TVL), antero-posterior dental and skeletal relationships are determined (Please refer to the journal; Arnett GW, Bergman RT. Facial keys to orthodontic diagnosis and treatment planning. Part 1. Am J Orthod Dentofacial Orthop 1993;103:299-312). However, a possibility to change the TVL after an orthognathic surgery, I do not like to use the TVL as the reference plane. AB to mandibular plane angle is used to determine if a patient need surgical orthodontic treatment after the end of growth. If a Korean patient with a class III malocclusion has AB to mandibular plane less than 60 degrees, the patient will have a high possibility to undergo a surgical orthodontic treatment.

From Dr. Sug-joon Ahn : Please refer the lecture slide #51. In general, a double jaw surgery is recommended in the following situations: 1. there is a severe anteroposterior skeletal discrepancy more than 10 mm. In this case, a double jaw surgery is considered because the skeletal discrepancy is difficult to solve by a single jaw surgery alone. 2. there is a severe skeletal asymmetry, specifically maxillary asymmetry. Most patients with skeletal asymmetry have asymmetries in both maxilla and mandible, so a double jaw surgery is needed. 3. The same is true of a severe vertical dysplasia, such as anterior open bite and/or excessive incisal display. 4. Patients with a severe vertical problem need a maxillary impaction procedure to reduce a facial height.

From Dr. Sug-joon Ahn : Please specify.

From Dr. Sug-joon Ahn : In general, soft tissue tension, such as cheek and buccinator muscle is the most important factor.

From Dr. Sug-joon Ahn : You’d better ask your surgeon. As long as I know, three-pieces osteotomy is generally needed when posteror expansion is needed without expansion of anterior segment (Please refer to the figures below). But, I am telling you again that surgical expansion is the least stable surgical modality and you have to avoid surgical expansion if possible.

From Dr. Sug-joon Ahn : The amount of surgical expansion is not important. Overcorrection is more important. Due to a great relapse tendency, you should avoid surgical expansion of the maxilla. However, surgical expansion is inevitable in some cases. In these cases, about 40% of overcorrection of the amount of surgical expansion should be considered. Either symmetric or asymmetric expansion is possible. You can choose symmetric and asymmetric expansion after discussing the issue with a surgeon.

From Dr. Sug-joon Ahn : It depends on the occlusal plane angle, inclination of the maxillary incisor, and surgeon’s skill. It should be important that the occlusal plane angle and inclination of the maxillary incisor should be within the normal range after surgical orthodontic treatment. In addition, it is not easy to impact the maxillary posterior area because there are a lot of nerves and blood vessels in the superior and posterior area of the maxilla. Therefore, the surgeon’s skill is one of the most important factors to rotate the maxillary plane.