## 1 Introduction  
Open bite is considered to be one of the most difficult malocclusions in orthodontic treatment; therefore, in open bite cases, decision of treatment method, mechanics, and maintenance have been the topic of focus [1, 2, 3, 4, 5]. This is due to the fact that open bite can be associated with many complex problems such as TMD and tongue habits, which make treatment and maintenance difficult. In addition, the approach to open bite varies depending on skeletal type and dental type [6].  
Conventionally, skeletal open bite has been corrected by surgically repositioning the maxilla or mandible [7] (Figure 1), and dental open bite by extruding the anterior teeth [8, 9] (Figure 2). In recent years, however, the use of temporary anchorage devices (TADs) in orthodontics has changed the treatment of open bite cases--specifically, intruding the molars using TADs to rotate the mandible counterclockwise and improving open bite [10, 11, 12] (Figure 3). This treatment method has been reported in many cases and has shown good results and long-term stability [1, 13, 14]. Therefore, molar intrusion has been established as one of the treatment methods for open bite cases.  
Figure 1: A schema of surgical orthodontic treatment. **(A)** Orthognathic surgery; Le Fort 1 osteotomy and sagittal split ramus osteotomy. **(B)** Superimposition of cephalometric trace changes pre- and post-treatment.  
Figure 3: **(A)** A schema of orthodontic treatment of open bite with intruding molars using a multi-bracket appliance system and TADs. **(B)** Superimposition of cephalometric trace changes pre- and post-treatment.  
Figure 2: **(A)** A schema of orthodontic treatment of open bite with extruding anterior teeth using a multi-bracket appliance system and vertical elastics. **(B)** Superimposition of cephalometric trace pre- and post-treatment.  
In orthognathic surgery for skeletal open bite, only the mandible is positioned anteriorly and upward to the occlusal plane of the maxillary dentition, or the mandible is positioned anteriorly and upward with counterclockwise rotation by impacting the posterior region of the maxilla [15]. In other words, surgical orthodontic treatment reduces the lower facial height and surgically improves the vertical skeletal discrepancy. Therefore, this new treatment approach involving molar intrusion has been reported as a treatment method for skeletal open bite cases, mainly because it improves open bite by the same mechanism as surgical orthodontic treatment [16].  
However, not all cases of skeletal open bite have been treated with molar intrusion, and there have been no reports on the criteria for the use of TADs in molar intrusion. [PERSON] et al. classified the structure of open bite into low position of anterior teeth, high position of molars, and vertical skeletal disharmony [17]. However, the main cephalometric assess points that determine the treatment strategy are unclear, and a comprehensive assessment is required to diagnose and make a decision on the treatment plan. In this study, we will report the treatment strategy for open bite cases by mainly examining the criteria for the indication of molar intrusion treatment as a retrospective study.