Taisuke Kawai

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.

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.

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.

Effects of viewing conditions on the detection of contrast details on intraoral radiographs

ObjectivesTo quantify the effects of changes in the viewing environment on the detectability of diagnostic information on intraoral radiographs.MethodsRadiographs of a dental Burger’s phantom were taken using two kinds of dental film at 60, 70, and 80 kV each. Radiographs with optical densities of 0.5, 1.0, 1.5, 2.0, and 2.5 were taken using each type of film. An observer test was performed using a viewbox with an illumination of 10 000 lx under three conditions: (1) in a lit room without viewbox masking (not blocking the light around the radiograph); (2) in a lit room with viewbox masking (blocking the light around the radiograph); and (3) in a darkened room with viewbox masking (blocking the light around the radiograph).Results and ConclusionsOptical densities of 0.5–1.0, 0.5–1.5, and 0.5–2.0 (or 0.5–2.5) were defined as underexposure, optimal exposure, and overexposure, respectively. The following results were obtained: (1) irrespective of the viewing conditions, the detectability was lowest on underexposed radiographs, while the detectability on optimally exposed and overexposed radiographs was 2.5–3.5 times higher; (2) masking the viewbox in a lit room increased the detectability on underexposed, optimally exposed, and overexposed radiographs by 8%, 14%, and 25%–47%, respectively, compared with that in the unmasked condition; and (3) with masking of the viewbox in a darkened room, the detectability on underexposed radiographs remained unchanged, while the detectability on optimally and overexposed radiographs increased by 8% and 24%–54%, respectively, compared with that in the unmasked condition in a lit room. The detectability was higher on radiographs of regions of interest taken with an optical density of at least 1.0.

A case of exceptionally large tori palatinus

A 44-year-old woman visited a general practitioner with a chief complaint of painless swelling on her palate that interfered with the functional movement of her tongue. She was referred to our university hospital. There was nothing noteworthy in her family or personal medical history. Although she had become aware of the swelling a few years earlier, she had let it go untreated because it was painless. Macroscopically, several areas of swelling were observed on the palatine and palatal surface of the alveolar bone bilaterally; these areas, which altogether occupied half of her oral cavity, were independent from each other, as they were separated by a mucosal layer. The mucosa on the surface of the swelling looked healthy, but a portion on the left side was white. Upon palpation, a bony hardness was felt. Clinically, the swelling was diagnosed as tori palatinus (Fig. 1). Postero-anterior and lateral skull radiographs showed an oval-shaped, radiopaque mass hanging from the patient’s hard palate. The images were superimposed onto the maxillary teeth and alveolar process (Fig. 2a,b). A computed tomography (CT) examination was performed to get more detailed information about the swelling, and to distinguish it from other hard tissue diseases such as osteosarcoma or fibrous dysplasia. Multiplanar reconstruc-

Multiple calcifying lesions in the maxilla and mandible of a 4-year-old girl: report of a rare case and literature review

Calcifying lesions in the jaws are usually solitary and can be diagnosed by intraoral, panoramic, and conventional extraoral radiographs. It is extremely rare for these calcifying lesions to be multiple, unless they are associated with certain systematic diseases. Herein, we report a rare case of multiple odontomas in a 4-year-old girl. The lesions were scattered throughout both jaws on the panoramic image. The reconstructed CT image showed lesions in the left maxilla that occupied the sinus and affected the floor of the left orbit. The lesions in the mandible were widespread and extended to the tooth-bearing area. Enucleations of the maxillary parts were performed, and the pathological diagnosis was a mixture of complex and compound odontomas. The 3-year postoperative follow-up by panoramic imaging was uneventful. Preoperative CT was useful for the differential diagnosis by depicting the internal calcifying lesions and revealing the extent and complex relationships among the lesions.

Morphological observation and CBCT of the bony canal structure of the groove and the location of blood vessels and nerves in the palatine of elderly human cadavers

PurposeThe greater and lesser palatine nerves and vessels supply the hard and soft palates, and the roots of these vessels and nerves run through a bony structure. However, the arrangement of blood vessels in the maxilla requires attention during clinical treatments, but detailed morphological information about changes in the greater and lesser palatine arteries and nerves during aging is unavailable. We therefore need detailed investigations of the morphology of the donor cadaver palatine using cone-beam computed tomography (CBCT) and macroscopic observations.MethodsWe investigated 72 donor cadavers using macroscopic segmentation and CBCT. The results’ analysis examined differences in skull measurement parameters and differences between dentate and edentulous cases.ResultsThe greater palatine artery and nerve showed different macroscopic arrangements in dentate and edentulous cadavers. We also classified three types of bony structures of the nerve and vessel roots in the molar regions of the palatine using CBCT images: the shallow groove, deep groove, and flat groove. The deep groove is the deepest of the three and is remarkable in edentulous elderly cadavers.ConclusionThis study of macroscopic and CBCT data provides information useful for planning dental implant surgeries and autogenous bone harvesting.

Cone-beam computed tomography and anatomical observations of normal variants in the mandible: variant dentists should recognize

Many types of cone-beam computed tomography (CBCT) have recently been developed and are being used in many dental clinics. CBCT has significantly changed imaging diagnosis in dentistry by showing detailed structures in multiple dimensions with high spatial resolution. This allows dentists to confirm what cannot be recognized with conventional two-dimensional images, such as small neurovascular canals, the buccolingual location of structures/lesions, and the three-dimensional shapes of hard tissue structures. The aim of this study was to review the normal variants of detailed anatomical structures in relation with the mandibular canal by comparing the previous reports and anatomical evaluations. These structures are likely to be observed on CBCT images by dental practitioners prior to dental procedures involving the mandibular teeth and bone. Understanding the relationship of these structures is useful for dental practitioners and oral surgeons to reduce the possibility of causing damage and patient discomfort during dental procedures.

CBCT imaging of the alveolar bone structure in maxilla of elderly donor cadavers and PCA analysis

There is an important bone matrix with remodelling between dentate and edentulous samples of the human maxilla for bone metabolism. Cone beam computed tomography (CBCT) is useful for structural analysis of bone. The objective of this study was to investigate morphological data of donor cadavers in detail using CBCT imaging and principal component analysis (PCA). We analysed 38 donor cadavers using a CBCT apparatus. The analytical results defined differences in skull measurement parameters and dentate and edentulous levels using PCA. We observed cortical bone, trabecular bone, and the distance from the bottom of the maxillary sinus to the oral mucosa at a right angle to the palatal plane of the first molar region between dentate and edentulous samples of the human maxilla using CBCT imaging. In the dentate sample of the maxilla, component 1 was defined by negative contributions from gender (-0.84) and age (-0.54) to positive contributions such as cortical bone structure (CBS, 0.68) and trabecular bone structure (TBS, 0.50). There was a difference in CBS between dentate and edentulous human maxilla samples. This study of CBCT data provides useful basal information for planning dental implant surgery using PCA.