# Open-Bite Correction Using a Mid-Palatal TAD with an Intrusion TPA: Anteroposterior Position of TAD
## 2 Mechanics of Open-Bite Correction Using a Mid-Palatal TAD Combined with an Intrusion TPA  
Figure 4 shows the structure of the posterior intrusion method using a mid-palatal TAD and an intrusion TPA. After leveling up to 0.019 \(\times\) 0.025 stainless steel (ss), a mid-palatal TAD is placed on the center of a line connecting the contact points of the first and second molars. The intrusion TPA is removable, as it is necessary to adjust during the intrusion procedure. The palatal sheaths (tooth 17-16, 728-016-00/tooth 26-27, 728-017-00, Dentauurm, Langhorne, PA, USA) are welded to the first molar bands. It is recommended to use the maxillary first molar bands over bonding because sometimes, during the removal of the TPA for adjustment, the bonded sheath may fail. On the TPA, two hooks are soldered near the gingival margin. The gap (about 4-5 mm) between the palatal mucosa and the TPA is required to avoid mucosal impingement during the intrusion (Figure 4B). A power chain is applied tightly from the head of the screw to the hooks of the TPA. _Case 2_ (Figures 5 and 6) shows these mechanics. If the second molars require further intrusion, accessory hooks can be attached for the power chain traction of the second molars (Figure 5H). At the detailing stage after intruding posterior teeth, final occlusion is obtained by wire bending adjustment with intermaximillary elastic bands such as Class II 5/16\" 6 oz and up/down 3/16\" 6 oz. The L-shaped loops between maxillary lateral incisors and canines on the 0.019 \(\times\) 0.025 ss are used routinely at the space-closing and detailing stages for three purposes: to hook elastic bands, to control labio-lingual/vertical alignment of the lateral incisor and canine, and to apply torque for four incisors. Lateral cephalometric tracing showed the skeleton-dental changes, maxillary molar intrusion, and counterclockwise rotation of the mandible (Figure 6).  
Figure 3: Molar intrusion methods with buccal TADs. (**A**) The method of _Case 1_ used four TADs between the roots of upper posterior teeth. The palatal screws were added to prevent buccal tipping caused by the buccal TADs. (**B**) The method uses a TPA with crown lingual torque [3,4]. The TPA prevents buccal tipping caused by the buccal TADs.  
Figure 4: Mid-palatal TAD (1.6 mm \(\times\) 6.0 mm, JA type, RMO, Inc., Denver, CO, USA) and intrusion TPA (0.9 mm stainless-steel round wire). A mid-palatal TAD is placed on the center of a line connecting the contact points of the first and second molars. The main archive is 0.019 \(\times\) 0.025 ss with a slight crown buccal torque. There are two hooks on the intrusion TPA for the power chains. A stretched power chain is ligated to the screw head with a steel ligature and is hung on the hooks soldered to TPA. (**A**) is the actual case picture; (**B**) schematic diagram.  
Figure 5: _Case 2_. Open-bite correction by the molar intrusion. (**A–D**) Initial intraoral photos. There was an open bite with minor anterior crowding. Lower second premolars showed lingual tipping. (**E–H**) After leveling to 0.019 \(\times\) 0.025 ss, a TAD (1.6 \(\times\) 6 mm, JA type, RMO, Inc., Denver, CO, USA) was implanted in the mid-palatal area. Accessory hooks were soldered for the second molar intrusion’s power chain traction (**H**). A power chain was ligated tightly (300 gf for each side). (**I–L**) After 11 months, the open bite was resolved well.  
Figure 6: _Case 2_. Superimposition showing the following changes: (1) intrusion and distal tipping of the upper molar, (2) slight retroclination and extrusion of the upper incisor, and (3) counterclockwise rotation of the mandible.