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Introduction The objective of this research was to analyze the effect of orthodontic treatment with maxillary permanent first molar extraction on the occlusal stress distribution and displacement in the human skull. Methods A 3-dimensional finite element model was constructed on the basis of a computed tomography scan, and it was used as the pretreatment model. The software used for geometric modeling was Solid Works (Dassault Systemes, Paris, France). For the extraction model, the maxillary permanent first molar was removed, followed by a repositioning of the anterior and posterior segments to create a space closure model. Stress distribution was evaluated under the simulation of 1000 N for occlusal forces and 400 N for masseter muscle force. Results The highest von Mises stress was observed at the zygomatic process of the temporal bone across all 3 models (25 MPa), whereas stress at the pterygomaxillary suture area was almost 50% less. However, the stress in the pterygomaxillary suture area was lowest in the extraction model (18%) and space closure (30%). Stress in the zygomatic process of the frontal bone and frontal process of the maxilla increased from pretreatment to extraction model followed by space closure model. Conclusions The occlusal forces were transferred through maxillonasal, maxillozygomatic, and maxillopterygoid stress trajectories. The mesial displacement of the molars may weaken the role of maxillopterygoid stress trajectory while strengthening the role of maxillonasal stress trajectory.

Introduction The purpose of this study was to compare the pattern and amount of stress and displacement between maxillary protraction with miniplates placed at the infrazygomatic crest and the lateral nasal wall. Methods Three-dimensional finite element models for the skull and the curvilinear type of miniplate were constructed. After a protraction force (500 g/side) was applied to the distal end of the miniplate with a forward and 30° downward vector to the maxillary occlusal plane, stress distributions in the circummaxillary sutures and displacements of the surface landmarks were analyzed. Results There was a difference in the maximum stress distribution area according to the site of the miniplate: infrazygomatic crest and middle part of the maxilla in the infrazygomatic crest and paranasal area adjacent to the pyriform aperture in the lateral nasal wall. Stress values of the frontonasal, frontomaxillary, zygomaticomaxillary, and pterygomaxillary sutures were greater in the infrazygomatic crest than in the lateral nasal wall. The site of the miniplate produced differences in the major displacement areas: infrazygomatic crest, maxillary dentition, anterior maxilla, and upper part of the maxillary tuberosity in the infrazygomatic crest and the lateral nasal wall, maxillary dentition, anterior maxilla, and lower part of the maxillary tuberosity in the lateral nasal wall. The lateral nasal wall exhibited forward, downward, and outward displacements of ANS, Point A, and prosthion. However, the infrazygomatic crest showed forward and upward displacements of ANS, Point A, and prosthion, and outward displacement of the zygomatic process of the maxilla and the maxillary process of the zygomatic bone. Conclusions The site of miniplate placement should be considered to obtain proper stress and displacement values in different areas with maxillary hypoplasia.

This case report demonstrates the efficient use of implant anchorage in a patient with mesially inclined mandibular molars and an overerupted maxillary molar. A 14-year-old girl had an overerupted maxillary right first molar, possibly because of severely inclined mandibular right molars. Two-step use of miniplate anchorage in the right zygomatic process was proposed. As the first step, the overerupted maxillary first molar was intruded with elastic chains from the miniplate for 10 months. Then the maxillary right molars were distalized by using the miniplate to correct the Class II molar relationship. In the mandible, the first molar was extruded with intermaxillary elastics applied from the miniplate to the molar for 7 months after the uprighting of the mandibular right second molar. The results suggest that the use of 2-step implant anchorage is efficient for intrusion and distalization of maxillary molars and extrusion and uprighting of mandibular inclined molars.

Introduction: The objective of this study was to evaluate a new method for superimposition of 3-dimensional (3D) models of growing subjects. Methods: Cone-beam computed tomography scans were taken before and after Class III malocclusion orthopedic treatment with miniplates. Three observers independently constructed 18 3D virtual surface models from cone-beam computed tomography scans of 3 patients. Separate 3D models were constructed for soft-tissue, cranial base, maxillary, and mandibular surfaces. The anterior cranial fossa was used to register the 3D models of before and after treatment (about 1 year of follow-up). Results: Three-dimensional overlays of superimposed models and 3D color-coded displacement maps allowed visual and quantitative assessment of growth and treatment changes. The range of interobserver errors for each anatomic region was 0.4 mm for the zygomatic process of maxilla, chin, condyles, posterior border of the rami, and lower border of the mandible, and 0.5 mm for the anterior maxilla soft-tissue upper lip. Conclusions: Our results suggest that this method is a valid and reproducible assessment of treatment outcomes for growing subjects. This technique can be used to identify maxillary and mandibular positional changes and bone remodeling relative to the anterior cranial fossa. (Am J Orthod Dentofacial Orthop 2009; 136: 94-9)

Orthodontists have been, and are, interested in influencing facial growth, specifically, mandibular growth. The purpose of this investigation is to enhance condylar growth by means of electric stimulation. Eight growing cats were bilaterally condylotomized and unilaterally at random received electric stimulation. Before the condylotomy bonemarkers were implanted in the zygomatic process and above the condylotomy site. The condylotomy effectively separated the head of the condyle from the body of the mandible, thus unloading the head. After 5 weeks, implant separation indicated increased condylar growth on the treated side of all eight cats. Histologically, the treated condyles of six cats were different from the controls in that the hypertrophic zone was irregular and vascularization increased. The treated condyle showed significantly more bonemarker separation than the control condyle. On average, the treated condyle showed 1.24 mm more separation than the control ( p = 0.001 by the paired sample t test). (A M J O RTHOD D ENTOFAC O RTHOP 1995;108:599-606.)

The purpose of this study was to determine if there are discernable, stable, anatomic landmarks in the maxilla that may reliably be used for maxillary superimposition. It was hypothesized that, through the evaluation of cephalometric radiographs of patients with metallic implants, such anatomic landmarks could be identified. The material for this study consisted of pairs of cephalometric radiographs from 50 subjects, 23 males and 27 females ages 8.7 to 20.3 years. All films were taken at least 3 years apart. The mean age at the time of the first film was 11.9 ± 1.4 years, and the mean age at the time of the second film was 16.0 ± 1.7 years. The two serial tracings from each subject were superimposed on the implants and evaluated for best fit of anatomic structures. The maximum distance that the structures varied from perfect superimposition was measured. Rotational changes of the maxilla relative to the cranial base and of the palatal plane relative to the maxilla were evaluated. In the vertical plane, the floor of the orbit raised more than the palatal plane lowered by an average ratio of 1.5 to 1 mm. The maxilla demonstrated varying degrees and directions of rotation relative to the cranial base. The palatal plane demonstrated varying degrees and directions of rotation within the maxilla. Internal structure of the palate was of limited value as a stable area of registration. Infraorbital foramen, PTM, ANS, PNS, A point, and superior and inferior borders of the palate were not found to be stable landmarks for maxillary superimposition. The posterior and anterior portions of the zygomatic process of the maxilla were found to be the most reliable anatomic landmarks for cephalometric superimposition.