The planning of jaw defomity has been established for postoperative stability of maxilla and mandible. However, there are many types of jaw deformity, and there are many types of mandibular prognathism such as mandibular prognathism with mandibular asymmetry or open bite. The purpose of this study was to evaluate the postoperative stability of the mandibular position.
The subjects were 94 patients (34 males and 60 females) who underwent treatment of mandibular prognathism by sagittal splitting ramus osteotomy (parallel method). Cases of mandibular asymmetry and open bite were excluded. In the selected subjects, bone fragments were fixed using a total of 4 A-0 bone-penetrating screws (2 on each side). Cephalometric radiographs of the patients were taken before surgery and 1 month, 3 months, 6 months, 1 year, and 2 years after surgery.
Straight posterior movement parallel to the occlusal plane of the mandible were 5.7mm on average at point B and 6.2 mm on average at the Pogonion 1 month after surgery. The Lower incisors were moved posteriorly 7.4mm on average and were inclined to the lingual side 2.8°on average 1 month after surgery.
The mandibular body showed anterior movement of 1.5mm on average at point B and 2.3mm on average at the Pogonion 2 years after surgery. However, almost no change was observed at the ANS-Menton. Anterior movement of the mandibular body during the first 6 months of the postoperative period correlated to the operative movement of the mandibular body. Incisor overjet was decreased 1.0mm on average in the first year after surgery. Incisor overbite tended to increase during the 2 years after surgery. The occlusal relationship in the anterior teeth was maintained for 2 years after surgery. The lower molar teeth showed anterior movement of 1.0 mm on average. Their movement correlated with the postoperative movement of the mandibular body during the 2 years after surgery. The maxillary and mandibular anterior teeth were both inclined to the labial side 2 years after surgery. Upon measurement, almost all movement tended to be observed during the first year after surgery.
Mandibular bodies, corrected by sagittal splitting ramus osteotomy, acquired a new position during the first year after surgery. In our cases, mandibular replacement was allowed at clinical levels, and there were no signs or evidence that suggested relapse.

View full abstract

Three-dimensional (3-D) modelling from computed tomography (CT) data is an ideal method of obtaining information about the bony structures of the oral and maxillofacial region for plastic surgery or reconstructive surgery. This proved to be useful for preoperative diagnosis, selection of surgical procedures, simulated surgery, educating young surgeons and reducing operation time. If precise occlusion is necessary, dental impressions are taken, and dental arches of the 3-D models are replaced by dental plaster models using a labiobuccal impression system at our institution. However, the accuracy of the 3-D models has not been established. Errors in the 3-D model are roughly divided into three categories. One category includes errors produced during the process of data accumulation by CT and CAD data fabrication using a workstation. The next category concerns errors produced during model fabrication utilizing the milling machine and lastly, those involving replacement by dental plaster models.
This study investigated errors occurring in the 3-D milling models especially during replacement of the dental plaster models using cephalogram. Two cephalograms were compared, one obtained from the patient and the other obtained from the 3-D model painted with contract medium. The results of the study indicated that the accuracy of the milling models integated with dental plaster models is not always sufficient and cephalometric analysis should be recommended in individual cases for clinical use.

View full abstract

Mandibular lengthening by distraction osteogenesis was performed on two females (6 and 9 years old) with hemifacial microsomia to correct facial asymmetry. The follow up was done by cephalometric analysis for 3 years.
The results were as follows:
1) Three years after distraction, the morphological symmetry corrected by distraction had almost been maintained.
2) However, a slight amount of deviation on affected side was noticed at the Menton.
3) In lateral chepharogram, ∠SN-Pog did not changed for 3 years after distraction.
4) Downward growth of the maxilla on the affected side was not observed. Open bite at lengthened side seemed to be closed by eruption of the permanent molars.

View full abstract

Six patients with maxillary asymmetry with inclination of occlusal plane were treated by a unilateral Le Fort I osteotomy technique for the correction of maxillary asymmetry which can be performed through horizontal bone-cut of the unilateral maxilla and median palatine suture splitting. This technique allows lateral expansion and downward rotation of the osteotomized maxilla.
Patients with maxillary asymmetry who have no maxillary horizontal deficiency on clinical and lateral cephalometric examination and exhibit no deviation of median line between upper central incisors, are potential candidates for the unilateral Le Fort I osteotomy. The unilateral Le Fort I osteotomy is a useful technique because of easier repositioning of the osteotomized maxilla by a prefabricated splint, obtaining good stability.

View full abstract

The symptoms of temporomandibular joint disorder (TMD) in 33 patients indicative for surgical orthodontic treatment (8 males and 25 females, mean age of 22.5 years) were evaluated before treatment, during presurgical orthodontic and after treatment respectively through the questionnaires and the study casts. The patients were divided into 18 mandibular prognathism, 4 mandibular retrusion, 15 asymmetry, and 4 open bite cases.
1. There was a significant difference in incidence of TMD symptoms between before (81.8%) and after (48.5%) treatment in all the patients.
2. Incidence of TMD disorders decreased from 86.7% to 60.0% in asymmetry, from 72.2% to 27.8%(p<0.05) in mandibular prognathism and from 50% to 25% in open bite from before to after treatment, while in mandibular retrusion it remained 75% before and after treatment.
3. The incidence of joint noise was 100% in mandibular retrusion and 46.7% in asymmetry before and after treatment, while it decreased from 44.4% to 22.2%(p<0.05) in mandibular prognathism and from 25% to 0% in open bite. Joint noise showed various changes during presurgical orthodontics in each malocclusion.
4. The incidence of difficulty in mouth opening remained 50% in mandibular retrusion before and after treatment, while it decreased from 26.7% to 6.7% in asymmetry and from 16.7% to 5.6% in mandibular prognathism from before to after treatment. The open bite patients did not show difficulty in mouth opening both before and after treatment. Incidence of difficulty of opening tended to decrease in asymmetry and mandibular prognathism during presurgical orthodontics, while it worsened in mandibular retrusion.
5. Mean value of VAS (Visual analog scale) in mandibular retrusion, which was used as an indicator for pain of temporomandibular joint, decreased from 60.0±42.4 to 40.4±14.1 from before treatment to presurgical prthodontics, however, it increased and showed 65.0±21.2 after treatment. Although VAS in asymmetry and mandibular prognathism showed 27.5±23.3 and 30.0±22.9 before treatment, and 27.0±17.9 and 27.5±19.4 presurgical orthodontics respectively, it decreased to 6.7±2.9 and 5.0 after treatment respectively. Open bite did not show pain of TMJ before and after treatment.
These results suggested that symptoms of TMD in asymmetry and mandibular prognathism tend to be improved by surgical orthodontic treatment, but there were some cases of mandibular retrusion that did not improve.

View full abstract