Correction of skeletal class II severe open bite with temporomandibular joint disorder treated by miniscrew anchorage and molar extraction: a case report

Our patient, a Japanese woman aged 42 years and 6 months, visited our dental hospital with a chief complaint of impaired masticatory function due to anterior open bite. She also experienced pain in the TMJ while chewing and mouth opening. Her open bite had worsened gradually and she also had tongue thrust. She was previously recommended orthodontic treatment with orthognathic surgery by an orthodontist, but she did not want to undergo the surgery.

Her pretreatment facial appearance revealed a convex profile, and suggested hypermentalis activity associated with lip closure. The initial intraoral photographs revealed a − 6.0-mm anterior open bite and occlusal contact between only the second molars. The right molar occlusal relationship was class II, while that of the left was a more severe type of class II. There was crowding in either arch and the upper dental midline had shifted to the right by 4 mm. The lower midline coincided with the facial midline (Figs. 1 and 2). A panoramic radiograph revealed the existence of three third molars except the upper right third molar (Fig. 3). A severe skeletal class II relationship of angle of point A-nasion-point B (ANB), 11.5° and a steep Frankfort-mandibular plane angle (FMA, 47.5°) with lingual inclination of upper incisors of upper incisor-Frankfort plane angle (U1-FH), 104.6° was noted in the cephalometric measurements (Table 1). The DDwoR of both TMJs was evident in the magnetic resonance imaging (MRI) images (Fig. 4a, b). Schüller’s view showed flattening of both condyles, but there was no restriction of jaw movement (Fig. 5a, b). Based on this information, our patient was diagnosed to have a skeletal class II open bite with TMD. Informed consent was obtained from all individual participants included in the study.

A stabilization occlusal splint was used before the orthodontic treatment to reduce the TMJ pain on masticatory movement. Because our patient refused surgical treatment, it was decided to correct the anterior open bite and achieve an ideal occlusion with class I molar relationship via orthodontic treatment alone (without orthognathic surgery). The treatment plan was as follows.

Before the orthodontic treatment, a stabilization occlusal splint was placed for 3 months to reduce the TMJ pain. After our patient confirmed alleviation of TMD symptoms, the four premolars were extracted and 0.018-inch (0.457-mm) standard edgewise brackets were bonded on the maxillary and mandibular teeth. This was followed by placement of two self-drilling titanium alloy miniscrews (2.0 mm in diameter and 6 mm in length, Dual Top Auto Screw; Jeil Medical Corp., South Korea) into the palatal region of the maxillary first molar, under local anesthesia, to intrude the maxillary posterior teeth. A transpalatal arch was also placed in order to maintain the maxillary molar width (Fig. 6). The molars were connected by an elastic chain to intrude them and to avoid the loss of anchorage. Distal movement of the maxillary canines and mandibular first premolar was then initiated.

After 24 months, the extraction spaces of premolars had closed. The maxillary dental midline had shifted to the right by 3 mm. However, the left canine and molar relationship continued to be class II, while the right side had nearly progressed to a class I relation (Fig. 7). Hence, the maxillary left first molar was extracted to correct the midline and the left molar relationship. The maxillary left premolars were moved distally using a miniscrew (1.6 mm in diameter and 8 mm in length) which was inserted into the maxillary left buccal alveolar bone.

After 36 months, the anterior open bite was corrected to 1.5 mm and the teeth had attained a class I molar relationship (Figs. 8 and 9). All the orthodontic appliances and miniscrews were then removed, and lingual bonded retainers were affixed on both arches. In addition, a Begg-type retainer with tongue crib was also affixed in the maxilla to avoid tongue thrust. Our patient did not have any TMD symptoms during the active treatment and the retention period. The occlusion continued to be stable at 24 months from the initiation of the retention.

After orthodontic treatment, the overbite increased to 1.5 mm, while the molar and canine relationships changed to class I on both sides. The maxillary and mandibular dental midlines coincided, and the arch alignment was well corrected. There was no major variation in the posttreatment facial profile compared with the pretreatment profile. Although, the posttreatment panoramic radiograph suggested minor root resorption of the maxillary incisors, all roots were aligned in parallel (Fig. 10). On the cephalometric pretreatment and posttreatment superimposition, the upper and lower anterior teeth were distalized by 5 mm and 3 mm, respectively, and extruded by 2 mm and 3 mm, respectively. The maxillary molars were intruded by 1 mm (Fig. 11). The ANB angle had changed from 11.5° to 10.1°, and the FMA had changed from 47.5° to 46.5° (Table 1). Posttreatment Schüller’s view revealed no change in condyle shape and jaw movement (Fig. 12a, b). Our patient did not experience any symptoms of TMD, such as pain on mouth opening, during the orthodontic treatment.