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Bilateral Sagittal split ramus osteotomy (BSSRO) represents the majority of mandibular osteotomies. Intraoperative risks associated with BSSRO include unfavorable fractures, major bleeding episodes, and inferior alveolar nerve (IAN) and lingual nerve damage. In particular, injury to the IAN during BSSRO is a well-documented complication. However, reports of immediate microneural repair of transected IAN are scarce. In this report, we describe a case of neurosensory disturbance due to transection of the IAN during BSSRO. A 20-year-old woman underwent BSSRO at our hospital. Intraoperatively, the IAN was transected during osteotomy, and immediate microneural repair of the IAN was performed combined with polyglycolic acid (PGA) sheet. We performed the stellate ganglion block (27 times), and prescribed 6.6 mg of dexamethasone sodium phosphate postoperatively from the day of the surgery for 14 days and Vitamin B12 for 6 months postoperatively. We evaluated the response to touch sensation using the Semmes-Weinstein monofilaments test (SW test) and two-point discrimination (2PD), pain sensation, and temperature sensation. The right mental nerve did not respond to any quantitative test and sensation of pain just after the operation. One year and three months postoperatively, the SW value was 2.83 and 2PD distance was 11 mm, which were similar to the values on the normal side. The patient responded to sensations of heat and cold and 2-g pain sensation similar to that before the surgery. All responses to sensations were restored to normal one year and three months postoperatively. The postsurgical evaluation revealed marked improvement and significant recovery in sensations of the IAN, following immediate neurorrhaphy combined with PGA sheet during SSRO.

Background Mesiodentes are the most common supernumerary teeth. The cause is not fully understood, although proliferations of genetic factors and the dental lamina have been implicated. Mesiodentes can cause delayed or ectopic eruption of permanent incisors, which can further alter occlusion and appearance. Careful attention should be paid to the position and direction of the mesiodentes because of possible damage to adjacent roots in the permanent dentition period, errant extraction in the deciduous and mixed dentition periods, and damage to the permanent tooth embryo. To avoid these complications, we applied mixed reality (MR) technology using the HoloLens® (Microsoft, California). In this study, we report on three cases of mesiodentes extraction under general anesthesia using MR technology. Results The patients ranged in age from 6 to 11 years, all three were boys, and the direction of eruption was inverted in all cases. The extraction approach was palatal in two cases and labial in one case. The average operative time was 32 min, and bleeding was minimal in all cases. No intraoperative or postoperative complications occurred. An image was shared preoperatively with all the surgeons using an actual situation model. Three surgeons used Microsoft HoloLens® during surgery, shared MR, and operated while superimposing the application image in the surgical field. Conclusions The procedure was performed safely; further development of MR surgery support systems in the future is suggested.

Objective In clinical dentistry, tooth extraction is one of the most fundamental techniques learned during mandatory dentist clinical internships. However, there are fewer opportunities for students to perform this procedure on actual patients. Hence, a tooth extraction simulator was developed based on clinical experience to evaluate the appropriate load and magnitude of the three- dimensional forces (x, y, and z axes) applied while using forceps for tooth extraction. Methods Twenty-three subjects were divided into five groups according to experience (i.e., fifth-year dental students, clinical intern dentists, early-career oral surgeons, board-certified members of the Japanese Society of Oral and Maxillofacial Surgeons [JSOMS], and JSOMS specialists and clinical instructors). The simulator was developed with Osada Electric Co. Ltd. using electromagnets and load cells. The magnitude of the three-directional load applied in actual tooth extractions was used as basis for the simulator. Results With increasing clinical experience, a consistent trend in terms of lower variation in loading, stable initial movements, and low directional variability was observed. On determination of the appropriate standards from the measurements of this study, users can not only gauge the amount of force needed to grasp the teeth and tear the periodontal ligament by dislocation but also appreciate the orientation and force required for tooth extractions. Conclusion This study demonstrated the utility of a tooth extraction simulator in evaluating the generated loads and movements during tooth extraction procedures.

Disorders of the oral mucosa are considered easy to diagnose since they can be visualized and examined directly. A change in the color of the oral mucosa reflects histopathological changes and is an important diagnostic parameter. However, the subjective perception of color varies. To determine the extent of resection for oral mucosa conditions, it is necessary to digitize the color and perform objective assessments. In recent years, fluorescence visualization devices and analysis software that measure tissue luminance G have been employed for the identification of oral mucosa diseases. Fluorescence visualization is presumably based on the decrease in epithelial flavin adenine dinucleotide content and luminance G values due to the destruction of collagen cross-links [fluorescence visualization loss (FVL)]. However, cases with differences between luminance values and histopathological presentation exist. Therefore, additional factors may affect fluorescence visualization. The present study used a portable, non-contact oral mucosa fluorescence visualization device for luminance measurements in seven patients with oral squamous cell carcinoma. Furthermore, Picro-Sirius Red and immunohistochemical staining were performed for CK13, CK17, Ki67, p53 and E-cadherin in the FVL(+) (lesion) and FVL(-) (resection stump) areas to elucidate the principle of fluorescence visualization. Fluorescence was significantly lower in the FVL(+) than in the FVL(-) areas, and the mean luminance G value was 56. The Picro-Sirius Red stain revealed collagen destruction in the FVL(+) areas but no collagen disruption in the FVL(-) areas. CK13 was negative in the FVL(+) and positive in the FVL(-) areas, whereas the opposite pattern was observed for CK17. In the FVL(+) area, p53 staining was positive. E-cadherin expression was enhanced in the FVL(-) areas and reduced in the FVL(+) areas. Furthermore, the luminance G value tended to be lower in cases with weaker E-cadherin staining. The aforementioned results suggest that decreased E-cadherin expression may be a factor that regulates fluorescence visualization.

Background With improvements in the safety and stability of surgeries, the number of orthognathic surgeries is increasing. Most patients who undergo orthognathic surgeries are younger, and the number of orthognathic surgeries for patients with comorbidities is also increasing. We report a survey and clinical investigation of patients with comorbidities who underwent orthognathic surgeries at our department to improve the safety of orthognathic surgery. Results The participants included 296 men and 712 women, with a mean age of 28 years (13–19 years, n=144; 20–29 years, n=483; 30–39 years, n=236; 40–49 years, n=102; 50–59 years, n=39; ≥60 years, n=4). In total, 347 patients underwent one-stage Le Fort type I osteotomy and sagittal split ramus osteotomy (SSRO), 243 underwent SSRO, 287 underwent plate removal, 126 underwent genioplasty and plate removal, and five underwent other surgeries. In total, 529 patients had comorbidities (52%), including allergic diseases (n=220, 33%), respiratory diseases (n=107, 16%), neurologic and psychiatric diseases (n=69, 10%), gynecologic diseases (n=28, 4%), hematologic diseases (n=27, 4%), cardiovascular diseases (n=24, 4%), digestive diseases (n=22, 3%), metabolic and endocrine diseases (n=18, 3%), spinal diseases (n=11, 2%), ophthalmologic diseases (n=11, 2%), renal and urological diseases (n=9, 1%), and other diseases (n=117, 18%). Among the patients with comorbidities, 11 with hemorrhagic diatheses (hemophilia and von Willebrand disease), arrhythmia (atrioventricular block), psychiatric disease (adjustment disorder), and metabolic disease (diabetes) required cautious perioperative management. The patient with hemophilia was managed with regular low-dose recombinant factor VIII replacement therapy, and the patient with type I diabetes mellitus was administered continuous insulin infusion and sliding-scale insulin therapy; both patients had an uneventful course. Conclusions The study findings suggest that with the increase in orthognathic surgeries, oral and maxillofacial surgeons should adequately manage cases requiring cautious perioperative control and highlight the importance of preoperative screening. Despite the well-established safety and postoperative stability of orthognathic surgeries, oral surgeons should adopt appropriate additional preventive measures for patients with comorbidities.

Background Excessive bleeding is a major intraoperative risk associated with orthognathic surgery. This study aimed to investigate the factors involved in massive bleeding during orthognathic surgeries so that safe surgeries can be performed. Patients (n=213) diagnosed with jaw deformities and treated with bimaxillary orthognathic surgery (Le Fort I osteotomy and bilateral sagittal split ramus osteotomy) in the Department of Oral and Maxillofacial Surgery at the Suidobashi Hospital, Tokyo Dental College between January 2014 and December 2016 were included. Using the patients’ medical and operative records, the number of cases according to sex, age at the time of surgery, body mass index (BMI), circulating blood volume, diagnosis of maxillary deformity, direction of maxillary movement, operative duration, incidence of bad split, injury of nasal mucosa, and blood type were analyzed. Results The results revealed that BMI, circulating blood volume, nasal mucosal injury, and operative time were associated with the risk of intraoperative massive bleeding in orthognathic surgeries. Chi-square tests and binomial logistic regression analyses showed significant differences in BMI, circulating blood volume, direction of maxillary movement, operative duration, and injury to the nasal mucosa. Operative duration emerged as the most important risk factor. Furthermore, a >4-mm upward migration of the posterior nasal spine predicted the risk of massive bleeding in orthognathic surgery. Conclusions The upward movement of the maxilla should be recognized during the preoperative planning stage as a risk factor for intraoperative bleeding, and avoiding damage to the nasal mucosa should be considered a requirement for surgeons to prevent massive bleeding during surgery.

The aim of this study was to verify the reproducibility and accuracy of preoperative planning in maxilla repositioning surgery performed with the use of computer-aided design/manufacturing technologies and mixed reality surgical navigation, using new registration markers and the HoloLens headset. Eighteen patients with a mean age of 26.0 years were included. Postoperative evaluations were conducted by comparing the preoperative virtual operation three-dimensional image (Tv) with the 1-month postoperative computed tomography image (T1). The three-dimensional surface analysis errors ranged from 79.9% to 97.1%, with an average error of 90.3%. In the point-based analysis, the errors at each point on the XYZ axes were calculated for Tv and T1 in all cases. The median signed value deviation of all calculated points on the XYZ axes was -0.03mm (range -2.93mm to 3.93mm). The median absolute value deviation of all calculated points on the XYZ axes was 0.38mm (range 0mm to 3.93mm). There were no statistically significant differences between any of the points on any of the axes. These values indicate that the method used was able to reproduce the maxilla position with high accuracy.

Developing odontoma, formerly named ameloblastic fibro-odontoma (AFO), shows similar histopathologic appearance to ameloblastic fibroma (AF) in that it is composed of epithelial and mesenchymal elements. However, unlike AF, developing odontoma contains dental hard tissues. Radiologically, developing odontoma shows well-defined, mainly unilocular radiolucency containing various sizes and shapes of radiopaque materials, whereas AF shows well-defined unilocular or multilocular radiolucency without opacities. As such, the definition between developing odontoma and AF is generally clear in intraoral or panoramic radiographs. We present a case of developing odontoma which showed atypical radiological appearance apparently similar to AF. A 9-year-old boy was referred with the chief complaints of delayed eruption of the upper left second deciduous molar and first molar. Panoramic radiography revealed the radiolucent lesion with a well-defined margin and irregular surface. Impacted teeth were involved, but radiopaque materials were not found inside the lesion. Computed tomography showed a multilocular low-density lesion with only a few punctate enamel-like high-density areas. Magnetic resonance imaging showed a heterogeneous internal structure with the same signal intensity as muscle in T1-weighted images and high signal intensity in T2-weighted images with fat suppression. Although these images were atypical, developing odontoma was suspected based on the existence of enamel-like areas. AF was diagnosed by biopsy; however, the histopathological examination revealed dental hard tissues. Subsequently, it was diagnosed as developing odontoma. Recurrence has not been seen in 23 months postoperatively. Further reading of radiographic images over comparison with histopathological specimen was suggested to distinguish between atypical developing odontoma and AF. Keywords: Developing odontoma, Radiological appearance, Ameloblastic fibro-odontoma, Ameloblastic fibroma, Mixed odontogenic tumor