## 1 Introduction  
Orthodontic treatment of patients with temporomandibular disorder (TMD) due to orthopaedic instability has always been challenging. Many clinicians advocate that the ideal occlusion should be related to an ideal condyle-disk-fossa relationship, what they refer to as centric relation (CR) [1]. TMD patients often show shift between maximal intercupidation (MI) and CR [1, 2]. Moreover the degree of CR-MI discrepancy has been shown to strongly correlate with the severity of the symptoms and signs of temporomandibular disorder (TMD) and therefore, it was proposed to be a contributory factor to the development of TMD [3]. [PERSON] and [PERSON] were the first to explain how CR-MI discrepancy may lead to the development of TMD [4, 5, 6]. They declared that if CR interference exist during jaw closure, the inferior lateral pterygoid muscle is non-physiologically contracted in order to achieve MI. The contraction of the muscle distracts the condyle out of CR position resulting in hyperactivation of the elevator muscles. Imbalance between the elevator and depressor muscles can lead to consequent masticatory muscle spasm and pain [4; 5]. As stated by [PERSON]; positional stability of the joint is determined by the muscles that pull across the joint and prevent separation of the articular surfaces. The muscles' directional forces determine the optimum, orthopedically stable joint position [7]. The continuous existence of occlusal interferences can contribute to chronic muscle hyperactivity, articular disc derangement and disc displacement which causes temporomandibular joint (TMJ) clicking and further progression will result in intracapsular disorders [4; 5; 6]. Over the years, the most preferably and commonly used therapy for treating patients with TMD with orthopaedic instability has been the occlusal stabilization splint [8]. Due to its design, it can reposition the mandible to CR and switch off the neuromuscular adaptation to MI by relaxing the muscles and achieve orthopaedic stability. Therefore, in orthodontic patients reporting TMD due to orthopaedic instability these stabilization splints are recommended prior to orthodontic therapy. During the splint wear, condyle is passively seated in the fossa, resulting in altered dental occlusion; contact on the most posterior teeth and anterior open bite (AOB) will develop [9; 10]. Before the era of temporary anchorage devices (TADs), possible therapeutic solutions for adult AOB patients were camouflage treatment by extruding the anterior teeth, extraction, surgical maxillary impaction [11] and intrusion of posterior teeth by either intermaximillary [12] or extraoral appliances [13]. [PERSON] [14] was the first who used dental implants for intruding molars. In 1996, [PERSON] and [PERSON] [15] demonstrated that significant amount of true orthodontic molar intrusion can be achieved which can largely facilitate the prosthetic reconstruction of partially dedulous patients and in the absence of gingival inflammation, it can improve periodontal health as well [16; 17; 18]. Since then, many techniques have been introduced for skeletally anchored posterior teeth intrusion [19; 20; 21; 22; 23; 24; 25]. Although, in many of these articles, intrusion mechanics, force magnitudes and treatment details are precisely described, not too much attention has been paid towards the real condyle position so far. Besides, far less is mentioned about the shape and position of the condyle seen in 3D as in CBCT images. In turn, treatment started from and ended in CR-where the condyle is centered in the fossa and the disc position is correct-with orthopaedic stability, can be one of the assurances for long-term occlusal stability and temporomandibular joint (TMJ) health. Accordingly, not considering CR in these patients may query even the real start-, and endpoint of the treatment and the stability as well.