The aim of this study was to evaluate the effects of the tongue and lip pressure on dentofacial morphology. The subjects comprised 194 patients with malocclusion. Anterior and posterior tongue elevation and lip pressures were evaluated using the Iowa Oral Performance Instrument (IOPI) device. The lateral cephalograms of each subject were traced and digitized to perform the analysis. Statistical analysis was used to investigate the relationship between perioral muscle force and the cephalometric variables. Anterior and posterior tongue pressure was both higher in males than in females. No sex difference in lip pressure was observed. The group with a low posterior tongue pressure showed a short ramus height, short posterior facial height, and clockwise-rotated mandible. On the other hand, lip pressure had a significant influence on maxillary incisor angulation. Skeletal pattern was not found to be significantly related with lip pressure. The anterior tongue pressure appeared as a mixed pattern of the two results. Tongue pressure was related to skeletal measurements, such as short posterior facial height, and lip pressure was related to the angulation of the anterior teeth. This study suggests that there may be differences in dentofacial morphology according to the differences in perioral muscle force.

Mechanics using a mid-palatal temporary anchorage device (TAD) and an intrusion transpalatal arch (TPA) were applied to correct the open bites. Two different intrusion patterns could be obtained according to the anteroposterior position of mid-palatal TADs. When the TAD was placed posterior to the first molar, the posterior teeth were intruded (“posterior intrusion”), and the open bite was corrected efficiently. This is commonly used in most open bites. However, sometimes, in an open bite with a gummy smile, intrusion of the maxillary anterior teeth, as well as the posterior teeth, may be necessary. In this case, the TAD was placed anterior to the first molar, and a “total intrusion” was obtained, including anterior intrusion. In conclusion, the intrusion pattern of the maxillary teeth differs depending on the anterior–posterior position of the mid-palatal TAD, necessitating posterior intrusion or Total intrusion.