Takashi Takaki

Postoperative Evaluation of Grafted Bone in Alveolar Cleft Using Three-Dimensional Computed Tomography Data

Objective Postoperative evaluation of bone formation in the alveolar cleft by computed tomography imaging has been reported. We quantitatively evaluated bone grafts in the alveolar cleft preoperatively and postoperatively using three-dimensional data and superimposition of images. Subjects A total of 12 patients with complete unilateral cleft lip and palate (six left-sided and six right-sided) were studied. Methods Helical computed tomography scans were taken immediately before surgery and at 6 months after surgery and the DICOM files obtained were processed using Mimics and 3-matic software for three-dimensional data analysis. The preoperative and postoperative computed tomography data were superimposed, and the position and length of the unerupted canines and width of the alveolar cleft measured. Results Strong and significant correlations were observed between bone formation in the alveolar cleft bone graft region and preoperative canine position (r = –.766, p < .01) and canine length (r = .681, p < .05). Stepwise multiple regression analysis demonstrated that only the preoperative canine position was independently and significantly correlated with bone formation in the alveolar cleft. Conclusion These results indicate that the optimal timing for surgery is when the canine cusp is close to the alveolar plane.

Hard palate thickness for temporary anchorage devices placement: Differences in sex and ethnicity

Abstract Purpose The purpose of this study is to determine variations in hard palate thickness among sexes and four ethnic groups to identify optimum area for temporary anchorage devices (TADs) placement. Materials and methods Cone-beam computed tomography (CBCT) volume data on 160 patients were selected. Patients belonged to one of four ethnic groups (Asian, African-American, Caucasian or Hispanic; 20 men and 20 women in each group, 16–45 years old). Hard palate thickness from the incisor fossa to the palatal root of the maxillary first molar was determined on each image and compared between sexes and ethnic groups. Results The data revealed that thickness was greatest at the paramedian area in the incisive canal zone (C-zone) and the median area posterior to the incisive foramen. A significant difference in thickness of palate was confirmed between sexes, and was approximately 0.5 mm and 1 mm greater in men at the median and paramedian, respectively. Among ethnic groups, a trend of decreasing thickness was as follows: Caucasian > Hispanic > African-American > Asian. Conclusion The anterior (incisive canal zone) paramedian and posterior median areas of the hard palate were thicker and suggest that these areas are appropriate for TADs placement. Some differences were also observed local to the paramedian in the C-zone among ethnicities. This indicates that sex and ethnicity should be taken into consideration in selecting sites for placement of TADs.

Three-dimensional Analysis and Evaluation in Orthognathic Surgical Cases with Facial Asymmetry

Two-dimensional cephalometric analysis is commonly used in planning and evaluating the outcome of orthognathic surgery. It is difficult to arrive at an accurate evaluation with this method, however, as the jaw bones overlap in profile. Therefore, the purpose of this study was to use 3-dimensional (3-D) orthognathic treatment planning software for measurement of distances and angles to evaluate change in dentofacial morphology and stability after orthognathic surgery in patients with jaw deformity and facial asymmetry. Computed tomography with SimPlant O&O® (Materialize Dental, Belgium) was used to obtain data at before surgery (T1) and at 1 month (T2) and 1-2 years postoperatively (T3). Reference points, reference planes, and evaluation items were set to measure angles and distances. The average values at T1, T2, and T3 and the standard deviations were obtained. The analyses of change in distance and angle between T1 and T2 in both the maxilla and mandible revealed that the amount of postoperative deviation and change was greatest in the mandible (p<0.05). These findings showed a correlation between postoperative change in position of the chin and symmetry. Only a minimal amount of change was observed between T2 and T3 in both the maxilla and mandible. The results also revealed a correlation between positional change in both the proximal and distal bone segments and stability. It was found to be possible to determine change in horizontal, vertical, and anterior/posterior angle in both the maxilla and mandible by such 3-D analysis. The results suggest that the chin is the most appropriate facial element for evaluation of symmetry after orthognathic surgery.

Three-dimensional Finite Element Analysis of Bone Fixation in Bilateral Sagittal Split Ramus Osteotomy Using Individual Models

The purpose of this study was to investigate factors involved in stress on locking mini-plate/screws used in orthognathic surgery based on patient-specific 3-dimensional finite element analysis. Data were obtained from 10 patients undergoing mandibular advancement by bilateral sagittal split ramus osteotomy. All underwent osteosynthesis with 2.0-mm titanium locking mini-plate/screws. A 3-dimensional finite element model of the mandible was created for each patient and each model subjected to the same loading conditions, which produced different stress values on locking mini-plate/screws. When the contact area of the proximal and distal bone segments was narrower and bone mineral density (BMD) lower, the von Mises stress values on the plate/screws were higher (contact area, p<0.01; BMD, p<0.05). The present results suggest that bone contact area and BMD should be considered as plate stress factors.

Implant Treatment after Sagittal Splitting Ramus Osteotomy and Alveolar Ridge Augmentation in Patient with Mandibular Prognathism and Multiple Missing Maxillary Teeth

An abnormal maxillomandibular ridge relationship frequently hinders oral implant treatment in patients with jaw deformities. Here, we describe a patient who was experiencing difficulty using dentures due to multiple maxillary tooth loss and mandibular prognathism. Treatment comprising sagittal splitting ramus osteotomy and alveolar ridge augmentation using bone grafts harvested from the mandibular ramus followed by implant treatment yielded good outcomes. The patient was a 47-year-old woman presenting with an unstable upper partial denture. Although prior prosthetic treatment for mandibular prognathism had resulted in normal overbite, she had since lost an increasing number of teeth due to advanced periodontal disease, impairing support for the denture. She was referred to the Department of Oral Implantology at the Tokyo Dental College Chiba Hospital in October 2008. Subsequent treatment comprised implant treatment following maxillary alveolar ridge augmentation and sagittal splitting ramus osteotomy to correct the maxillary-mandibular relationship. In January 2010, sagittal splitting ramus osteotomy and alveolar bone augmentation using a bone graft from the mandibular ramus were performed under general anesthesia. In July and August 2010, a total of 7 implants were placed in the maxilla and implant superstructure preparation started after 3 months. Taking both the patients wishes and ease of maintenance into account, retrievable superstructures made of Auro Galvano Crown were fitted in April 2011. The jaw-to-jaw alveolar ridge relationship was improved by sagittal splitting ramus osteotomy, rendering subsequent treatment, from implant placement to superstructure preparation, feasible by conventional methods. The use of surplus bone generated during sagittal splitting ramus osteotomy for bone augmentation avoided the need to harvest bone from another area.

Incidental findings during head and neck MRI screening in 1717 patients with temporomandibular disorders

ObjectiveMagnetic resonance imaging (MRI) plays an important role in the evaluation of temporomandibular disorders (TMDs). At our institution, we perform additional head and neck screening using head coils when performing MRI screening of the temporomandibular joint (TMJ) to detect lesions in areas other than the TMJ (lesions discovered by chance, or incidental findings; IFs) and to conduct a diagnosis of exclusion. The objective of this study was to determine the number and frequency of IFs detected during head and neck screening, according to sites and diseases.Materials and methodsThe study evaluated 1717 patients with clinically suspected TMDs who underwent MRI of the TMJ. IFs were assessed on horizontal sections of images of the craniofacial region obtained by the short tau inversion recovery imaging technique.ResultsThe patients undergoing MRI of the TMJ comprised 433 males and 1284 females. Among the patients, at least one IF was detected on images in 461 patients. The most common IF site was the maxillary sinus. Based on diagnostic imaging, there were 21 IFs (1.2%) associated with TMD symptoms, or for which an association with TMD symptoms could not be ruled out.ConclusionsCombination of conventional MRI imaging of the TMJ with craniofacial MRI screening may allow detection of lesions other than TMDs, thereby confirming the usefulness of MRI. Detection of IFs may require development of different therapeutic strategies than those for TMDs.

Our Team’s Safety Management of the Sagittal Splitting Method of the Mandibular Ramus

Orthognathic surgery is performed for congenital anomalies, growth of jaw abnormalities, and tumor and trauma after jaw treatment. The sagittal splitting method of the mandibular ramus is performed most commonly in the world, but resulting complications are increasing. The sagittal procedure and perioperative care have been established, however, complications of orthognathic surgery have been reported in many hospitals. Therefore, we should perform the surgery safely, with careful consideration, and eventually we need to improve the surgery. Our treatment goal is to improve the facial form and to attain appropriate occlusion. Accordingly, we need to understand the patients background as a useful reference for drawing up the treatment plan. This paper reports on a safe sagittal splitting method of the mandibular ramus performed by our team.