The purpose of this study was to evaluate hard and soft tissue changes in mandibular prognathic patients with open bite following different orthognathic surgery.
Twenty adult patients who underwent orthognathic surgery to correct mandibular protrusion and open bite were selected for this study. The subjects were divided into the following two groups based on surgical method: 12 subjects who underwent mandibular setback osteotomy with the sagittal split technique (one jaw group) and 8 subjects who underwent mandibular setback osteotomy with the sagittal split technique and combination (Le fort I and horseshoe) osteotomy in bimaxillary surgery (two jaw group). A pair of pre- and post-operative lateral cephalograms was used for hard and soft tissue analysis. Statistical analysis using a paired t test was performed for comparative study.
No significant differences were observed in the pre-operative anterior occlusion, dento-skeletal pattern and facial profile between the two groups. Anterior occlusion was improved in both groups following surgery and no significant differences were observed in the post-operative overjet and overbite between the two groups. However, significant differences were observed both in the dento-skeletal and facial profile changes between the two groups. The amount of mandibular up-backward movement, especially the chin portion in the two jaw group was significantly larger than that in the one jaw group due to the clockwise rotation of the maxillary occlusal plane following superior repositioning of the maxillary posterior portion. In accordance with this larger mandibular up-backward movement coupled with maxillary advancement in the two jaw group, more harmonized bimaxillary skeletal relationship as well as better facial profile were achieved in the two jaw group in comparison with that in the one jaw group. It is suggested that a combination of Le fort I and horseshoe osteotomy in bimaxillary surgery is a useful technique to treat mandibular prognathic patients with open bite.

View full abstract

Aim: The aim of this study is to introduce our newly developed three-dimensional system of analyzing the lip movement using a video-based tracking system, and its preliminary clinical application.
Materials and methods: Motions of black foamed styrol balls (10mm in diameter) placed on bilateral medial and distal canthal points, bilateral commissural points, and center point of the upper and lower lips, were tracked by two video cameras (Dejimo VCC-277) with a three-dimensional device for analyzing animation images (Dejimo D4202-01-T). After establishing the three-dimensional coordinate system using bilateral medial and distal canthal points to correct head motion, the lip movement was measured in these coordinates. Measurement reliability of this system was evaluated in comparison with values measured by a contact three-dimensional measuring unit (Mitsutoyo MXF203). For clinical application, during phonation of a long vowel/a/the lip movement was analyzed in 15 healthy adult subjects. The average standardized locus pattern of bilateral commissural points and center point of the lower lip was computed respectively. Based on this average standardized locus pattern, changes in the lip movement before and after orthognathic surgery were examined in two patients with facial asymmetry and mandibular protrusion.
Results: The mean measurement reliability of this system was nearly 0.6mm in the X, Y, and Z axes, suggesting the mechanical accuracy. A marked deviation of the lip movement found in the affected commissural point and center point of the lower lip was improved in both patients after surgery. The amount of pre-operative deviation as well as that of post-operative improvement, was different in the two cases.
Conclusion: Application of the method demonstrated clinical feasibility for the dynamic analysis of changes in lip movement after orthognathic surgery.

View full abstract

Le Fort I osteotomy followed by distraction osteogenesis using the Rigid External Distraction (RED) system has been a useful method for facial and occlusal improvement of maxillary hypoplasia. Although an arch wire jointed to the stainless steel traction rod has been commonly fixed to the upper teeth in the RED system, some disadvantages, such as drifting of the teeth, have been pointed out in this method. Recently, the Leipzig retention plate, which is directly fixed to the maxilla, was reported and we also have been using this plate in our department. However, distraction osteogenesis using the RED system with these devices sometimes takes a long distraction time to get the expected amount of distraction because of the difference in the actual and expected amounts of maxillary advancement. One of the causes of this difference may be the deflection of the devices caused by the traction force.
In this study, we examined the deformation of the devices caused by the traction force. The bending stiffness of the stainless steel rod of the teeth-fixing wire and the square rod of the Leipzig retention plate were determined by a three-point bending test. The elastic modulus of the stainless rod was lower than that of the square rod. On another examination of the deflection of the stainless steel rod and the square rod, which were bent into a U-shape, the deflection-load ratio of the stainless steel rod was higher than that of the square rod.
We next studied the deformation of the teeth-fixing wire and Leipzig retention plate fixed to the dental arch model. Furthermore, the vertical rod and Halo frame of the RED system were fixed to the cranial model and their deformation was evaluated. We found that the teeth-fixing wire showed a greater deformation than the Leipzig retention plate on the dental arch model. The deformation of the vertical rod plus Halo frame was not observed when the traction force was less than 40N.
These results indicated that the Leipzig retention plate was more useful than the teeth-fixing wire in the RED system because of the lower extent of deformation as well as the lack of teeth drifting. In addition, our results indicated that the deformation of the external fixation devices of the RED system could be negligible.

View full abstract

Osteogenesis imperfecta is a hereditary bone disorder with friable bone and is caused by gene mutation of type 1 collagen. Clinical features are multiple fractures, bone deformity, blue sclera, dentinogenesis and so on. Complications are abnormal fracture, bleeding tendency, and malignant hyperthermia. These problems make surgery difficult.
This case report describes osteogenesis imperfecta with a mandibular prognathic patient who had marked changes in the occlusion and profile after sagittal splitting ramus osteotomy.

View full abstract

A 13-year-old female with facial asymmetry and fibrous dysplasia on the right side of the mandible complained of cross bite and facial asymmetry due to a shift of the mandible to the left. The problems were: 1. Cross bite of the left side and scissors bite of the right side; 2. A 9.0 degree tilt of the occlusal plane; 3. Spaced dental arch of the right molar region of the mandible; 4. Facial asymmetry; and 5. Fibrous dysplasia of the mandible.
Orthodontic treatment followed by surgical procedures was performed. Before the orthognathic surgery, the upper arch was aligned in two segments; one segment, including canine, premolars, and molars of the right side, was prepared for alveolar segmental osteotomy. After alignment of the upper and lower dental arches, the posterior maxillary alveolar segmental osteotomy on the upper right segment and SSRO were performed. The upper right segment was moved to the planned position to enable expansion and elongation, and the mandible was also moved to enable a mandibular shift. Post-operatively, detailing and finishing were performed in the orthodontic treatment, after which the fibrous dysplasia of the mandible was reduced by operation, and the final result was an improved occlusion.

View full abstract