# An Orthodontic Treatment Case of a TMD Patient with Maximly Posterior Intrusion Using TsADs
## 3 Discussion
### Considerations for Orthodontic Tooth Movement after Stabilization  
[PERSON] et al. reported that splint therapy in TMD patients resulted in increased open bite as condyles moved in the anterosuperior direction of the articular fossae [38]. [PERSON] et al. studied 19 patients with TMD symptoms who had stabilization splints applied full-time until the symptoms were relieved and discovered that their condyles moved superiorly from the condylar position, indicating instrumentation data [24]. [PERSON] et al. also claimed in their report that if an occlusal interference persists, a protective co-contraction in the masticatory system can occur, and positional changes of the mandibular condyles can be produced, which are generally caused by the uncontrolled contraction of the lower lateral pterygoid muscles and the hyperactivation of the surrounding elevator muscles [6]. When etiologic factors are resolved by a stabilization splint, and the harmful protective co-contraction is eliminated, the mandibular condyles gradually move superoateriorly in the articular fossae [1; 34; 39]. This position is naturally guided by the vector sum of the three major elevator muscles: masseter, temporalis, and medial pterygoid muscles [2; 6; 9; 14]. If the condyles move superiorly in the articular fossae after a stabilization splint has been used, the posterior teeth act as fulcrum points that produce a clockwise rotation of the mandible and cause a bite opening and/or more severe Class II tendency. [PERSON] et al. reported that, after the splint therapy, orthodontic patients with large MIP-CRO discrepancies showed a greater difference in ANB, a larger overjet, and a steeper mandibular plane [5]. In some cases, these patients require orthognathic surgery due to the dramatic occlusal changes, such as severe open bite and a retrognathic mandible. The vulnerable joint structures in TMD patients, however, may not be strong enough to tolerate the mechanical loads produced after osteotomies for mandibular advancement. If the mechanical loads to the TMJ structures exceed the biological adaptability, unexpected condylar resorptions or the progressive positional change of the condyles could also occur. Therefore, in some cases, clinicians might have to consider using orthodontic camouflage treatment [2, 40, 41, 42]. In the orthodontic camouflage treatment of patients showing anterior open bite and Class II occlusal relationship, two requisite considerations should be kept in mind: the maxillary anterior teeth exposure and the inclination of the maxillary occlusal plane [1]. The appropriate exposure of the maxillary anterior teeth is closely related to smile esthetics [43]. If the exposure of the maxillary anterior teeth is excessive, the patient will present an unesthetic gummy smile, while if it is not sufficient, the patient will look older. The inclination of the maxillary occlusal plane influences both on the function of mastication and facial esthetics [44, 45]. If a patient has a steep maxillary occlusal plane, the chances that occlusal interference occurs during the mandibular movements will increase [46]. When the point of early contact on the mandibular teeth acts as a fulcrum, the displacement of the mandibular condyles can result. The anteroposterior chin position is also affected by the inclination of the maxillary occlusal plane. The more the maxillary occlusal plane is steepened, the more convex the facial profile is presented. In contrast, the more the maxillary occlusal plane is flattened, the more pronounced the chin point is presented [47]. [PERSON] et al. reported in their investigation that the vertical position of the maxillary posterior teeth should be positioned such that the inclination of the maxillary occlusal plane to the patient's true vertical line is 100\({}^{\circ}\) and claimed that, with this inclination, the occlusal function and esthetics could be optimized [48]. The use of intermaximillary elastics to correct a Class II open bite could be detrimental to TMD patients. [PERSON] et al.