Takashi Yosue

Measurement of Anterior Loop Length for the Mandibular Canal and Diameter of the Mandibular Incisive Canal to Avoid Nerve Damage When Installing Endosseous Implants in the Interforaminal Region: A Second Attempt Introducing Cone Beam Computed Tomography

PURPOSE To measure and compare the anterior loop length (ALL) for the mandibular canal and the mandibular incisive canal diameter (ICD) at its origin in cadavers using anatomy and cone beam computed tomography (CBCT) to safely install endosseous implants in the most distal area of the interforaminal region. MATERIALS AND METHODS The ALL and ICD were measured using CBCT in 4 cadavers, and using anatomy in 71 cadavers. RESULTS The ranges and mean +/- SD for the anatomic measurements were: ALL, 0.0 to 9.0 mm and 1.9 +/- 1.7 mm; ICD, 1.0 to 6.6 mm and 2.8 +/- 1.0 mm. The average discrepancies between CBCT and anatomic measurements were 0.06 mm or less for both the ALL and the ICD, which were less than the resolution of CBCT. CONCLUSIONS Because large variations in measurements were observed, both for ALL and ICD, no fixed distance mesially from the mental foramen should be considered safe. The ALL and the ICD can be estimated from the CBCT measurement. The preoperative CBCT measurement yields important information for each case.

Classification of the lingual foramina and their bony canals in the median region of the mandible: cone beam computed tomography observations of dry Japanese mandibles

ObjectivesWe investigated the lingual foramina and their bony canals in the median region of the mandible using cone beam computed tomography (CBCT).MethodsSixty-eight dry Japanese mandibles were studied. The mandibles were set parallel to the inferior mandibular plane, and CBCT images of the medial region were obtained. The lingual foramina in the medial region (MLFs) were classified as being on the midline superior to the mental spine (s-MLF), on the midline inferior to the mental spine (i-MLF), or beside the midline (a-MLF). The frequency, location, and angulation of each foramen and its canal were measured from the CBCT images.ResultsThe s-MLF, i-MLF, and a-MLF occurred with frequencies of 86.8%, 83.8%, and 42.6%, respectively. The respective distances from the inferior mandibular plane were 11.4, 4.4, and 5.7 mm, while the vertical angulation of the canals was 77.5°, 114°, and 114°. A significant relationship was observed between the foramen height and canal angulation. On dissecting six cadaver mandibles, the sublingual artery was identified in s-MLFs and i-MLFs, while anastomosis of the sublingual and submental arteries was found in the a-MLFs.ConclusionsMLFs were observed frequently, and we confirmed that arteries passed though their canals. Since s-MLFs were the most frequent, contained the artery, and were located superior to the other MLFs, clinicians should identify such foramina from preoperative images.

Effects of chitosan oligosaccharides on the femur trabecular structure in ovariectomized rats

ObjectivesDrugs used to treat osteoporosis are taken long-term and ideally have no adverse effects. Recent interest has focused on chitosan oligosaccharides as a bone-inducing substance for use as bone graft material. The present study was designed to investigate the effects of chitosan oligosaccharides on the femur trabecular structure in ovariectomized rats by three-dimensional imaging analysis using micro-computed tomography (CT).MethodsFemale 12-week-old Wistar rats were divided into three groups, which underwent ovariectomy (two groups) or sham surgery (one group). After 12 weeks, rats of one of the ovariectomized groups began treatment with chitosan oligosaccharides (500 mg/kg bodyweight) three times per week for 8 weeks. Then, the femurs of all rats were resected for bone analysis by micro-CT, and three-dimensional images of the femur were reconstructed from the axial CT images to evaluate the following parameters: bone volume/tissue volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.sp), trabecular bone pattern factor (TBPf), structure model index (SMI), number of nodes per unit tissue volume, number of termini per unit tissue volume, and the total strut length per unit tissue volume.ResultsThe BV/TV, Tb.Th, and Tb.N were significantly higher in the ovariectomized and treated (OVX + C) group versus the ovariectomized, untreated (OVX) group. Tb.Sp, TBPf, and SMI were significantly lower in the OVX + C group versus the OVX group.ConclusionsOur findings demonstrate that chitosan oligosaccharides prevent decreases in bone volume, trabecular number, trabecular thickness, and trabecular connectivity in the femurs of ovariectomized rats.

Classifications of tunnel-like structure of human petrotympanic fissure by cone beam CT

The discomallear ligament (DML) runs through a narrow space of bony petrotympanic fissure, which joins the articular disc of the temporomandibular joint (TMJ) and the malleus in the tympanic cavity. Previous report suggest that an anatomical feature gives rise to TMJ pain and dysfunction. Recently, the movement of the malleus caused by hypertension on the discomallear ligament is important to the function of the TMJ. The purpose of this study is to define its morphological features using the cone beam CT (CBCT) and anatomical dissection of Japanese cadavers. Petrotympanic fissure and DML were observed in 14 cadavers (eight males and six females). It is revealed that a wide tunnel-like structure was found on CBCT images in the middle region of the petrotympanic fissure to the malleus in the tympanic cavity consisting of mainly three types: a wide tunnel-shaped structure (29.2%, 7/24, type 1), a tunnel-shaped structure widely open in the entrance of the petrotympanic fissure to the mandibular fossa and gradually thinning out in the tympanic cavity (20.8%, 5/24, type 2), and a tunnel-shaped structure widely open in the entrance of the mandibular fossa, middle region with flat-shaped tunnel structure and narrow exit in the tympanic cavity (41.7%, 10/24, type 3). These structures between the entrance of the petrotympanic fissure and the exit at the tympanic cavity are important to define the limited movement of the malleus. Therefore, morphological feature of the ligaments in malleus may relate to TMJ pain, dysfunction and hearing function.

Experimental study on wound healing of alveolar bone sockets in the rat maxilla after X-ray irradiation

Abstract The purpose of this study was to examine the effects of radiation on the healing process of tooth extraction wounds. X-ray doses of 10 Gy were delivered once to the maxillofacial area of Wistar strain rats, and the maxillary first molar was extracted 7 days later. Animals were killed 3, 7, and 14 days after odontectomy, and thin sections of the maxilla were prepared. The specimens were stained with hematoxylin and eosin, azan, alkaline phosphatase and tartrate-resistant acid phosphatase (TRAP) stains for microscopic observation. The ratio of the area of the bone tissue to the area of the alveolar socket (BS/TS) and the numbers of TRAP-positive cells were evaluated. Seven days after odontectomy, BS/TS was significantly lower in the irradiated group than in the nonirradiated group. Alkaline phosphatase staining was observed along the rim of the bone 7 and 14 days after odontectomy in both groups, but it was milder in the irradiated group than in the nonirradiated group. TRAP-positive cells were present on the floor of the postextraction socket and the margins of the septal alveolar bone, and, 3 days after odontectomy, the number of TRAP-positive cells was significantly greater in the irradiation group than in the nonirradiation group.

Analyzing the eye movement of dentists during their reading of CT images

Abstract In order to evaluate the eye movements of dentists when they were interpreting radiographs, ten normal computed tomography (CT) images and ten images with pathologic lesions were shown to eight dentists, and the pattern of their eye movement was qualitatively analyzed. Six fixation point parameters were calculated, including the time required to discriminate between normal and pathologic images (X1), the total fixation point count (X2), the total travel distance between fixation points (X3), the average time spent on each fixation point (X4), the total gaze fixation time (X5), and the maximum gaze fixation time spent on each image (X6). When the subjects were interpreting pathologic images, X2 and X4 were shorter; however, when they were viewing normal images, time was spent on observing multiple fixation points before the completion of the interpretive process. While pathologic images were recognized through top-down processing, there was a tendency for normal images to be recognized through bottom-up processing. The results of discriminant analysis, using a linear discriminant function, indicated that the independent variables X2 and X4 and the dependent variable X5 were the only variables that contributed significantly to differentiating between normal and pathologic images. The linear discriminant function was Z = 9.0 × 10−2 × X2 + 3.0 × X4 − 2.1 (discriminant score: Z < 0, pathologic image; Z ≧ 0, normal image). When the mean value of each individuals gaze fixation data was substituted into the discriminant formula, the hit rate for normal and pathologic images was discriminated at 94% (15 of 16).

Image-based diagnosis of condylar head fractures of the mandible: four case studies

This paper reports the four cases of the condylar head fractures of the mandible. The diagnostic images with panoramic radiograph and CT are presented. From 4 cases of condylar head fractures, the incidence, causes, and mechanisms are also discussed together with previous report.

Radioprotection of the murine submandibular gland by isoproterenol : autoradiography study with ^3H-leucine

Irradiation of the salivary glands results in the generation of free radicals from metal ions present in the secretory granules of acinar cells, a process that is believed to exacerbate radiation damage to the salivary glands. We therefore conducted a comparative investigation of radiation damage to the acinar cells of murine submaxillary glands in which granule secretion had been induced, and used autoradiography to visualize the pathological changes. Male BALB/c mice, at 8 weeks of age, were divided into four groups: a no-isoproterenol (IPR) and no-irradiation group (group I), a no-IPR, irradiated group (group II), an IPR, no-irradiation group (group III), and an IPR, irradiated group (group IV). Intraperitoneal injections of IPR were used, and 3 h later, the submaxillary region was irradiated with X-rays at a dose of 10 Gy. Three days after the irradiation, 3H-leucine was administered, and submaxillary glands were removed at predetermined times. Thin sections were prepared, and light- and electron-microscope autoradiography was performed. The number of reduced silver particles per unit acinar cell area was determined by light-microscopic autoradiography, and the proportion of reduced silver particles in the rough endoplasmic reticulum, the Golgi apparatus, and secretion granules was determined by electron-microscopic autoradiography. The result indicated that the effects of the radiation on the secretory potential of the submaxillary glands were diminished in acinar cells with a higher secretory granule content.

Patient dose in charge-coupled device-based full-mouth intraoral radiography

ObjectivesThis study investigated the effect of the size of the sensitive area of the charge-coupled devices (CCD) used in digital intraoral radiographic systems on the patient effective dose in full-mouth radiographic examinations.MethodsThe effective dose was assessed in full-mouth radiographic examinations using the bisecting angle technique, while assuming that CCD sensitivity is equivalent to that of E-speed film. The results were compared with the effective doses obtained using E-speed film. The tube potentials used were 70, 80, and 90 kV. The diameter of the circular field at the cone tip was 7 cm, and the length of the spacer cone was 20 cm. Twelve types of CCD devices with sensitive areas ranging from 307 to 1200 mm2 were assessed in seven digital intraoral radiographic systems.ResultsThe number of exposures and effective dose using the CCD devices were inversely proportional to the sensitive area of the CCD. Both the number of exposures and the effective dose were increased when using a CCD with a sensitive area smaller than the intraoral film size. Consequently, a reduction in the patient dose did not occur to the extent expected, based on the relative sensitivity of the CCD to film.ConclusionsIn order to fully realize the advantages of a CCD, it will be necessary both to reduce the frequency of examinations and to use a rectangular-shaped beam in CCD-based intraoral radiographic systems.

Radioprotection of the mice parotid gland by isoproterenol: study on morphometry of secretory granules and on autoradiography

ObjectivesThe aim of the present study was to investigate the effect of radiosensitivity on acinar cells in the parotid gland when the secretory granules were released.MethodsThe parotid glands of mice were exposed to 10 Gy of X-radiation when the acinar cells were degranulated with isoproterenol (IPR). Three days later, morphological images and number and area of secretory granules within the acinar cells in the parotid glands were obtained and light microscope autoradiography (LMARG) was performed using 3H-leucine.ResultsThe light microscopy images showed a disorderly arrangement and pycnosis of acinar cells and cellular atrophy in irradiated groups. The changes were milder in IPR-administered groups than in non-IPR-administered groups. The number of secretory granules in irradiated groups, which included both IPR-administered and non-IPR-administered sets, was significantly less than that in nonirradiated groups. The number of silver grains within acinar cells obtained by LMARG in the non-IPR-administered set of irradiated groups was significantly lower than that in the nonirradiated group or the IPR-administered set after 30 min of radioisotope administration, and it was significantly higher than that of the nonirradiated group after 240 min.ConclusionsWhen the secretory granules of acinar cells in mouse parotid gland were degranulated by isoproterenol, alleviation of the effects of radiation exposure on morphological change as well as the ingestion and egestion of secretory substances were indicated.