Objectives The shape of the anterior region of the maxilla is critical when planning implant treatment. The purpose of the present study was to assess the typical morphology of the incisive canal and surrounding bone. Methods In total, 70 maxillae of Japanese dry skulls were used after being divided into dentate and edentulous groups. Cone-beam computed tomography (CBCT) images of the maxilla were acquired by using standardized methods. Using the anterior nasal spine as a reference point, the change in position was measured and analyzed statistically. Also, three-dimensional (3-D) images of the incisive canal were classified into five subsets: cylinder, groove, penetration, bifurcation at the superior portion, and bifurcation at the inferior portion. Results The quantity of alveolar bone in the incisor region was greatly reduced from the alveolar ridge and labial surface. Moreover, the vertical position of the incisive foramen was significantly (P \ 0.05) superior in the edentulous groups. Regarding the classification of maxillae by the 3-D shape of the incisive canal, many canals were cylindrical. Conclusions Horizontal bone reduction from the labial side and vertical bone reduction from the alveolar crest were conspicuous; thus, the angle of the anterior alveolar bone changed after the loss of teeth. The incisive canal diameter in the edentulous group was larger than in the dentate group. The nondestructive assessment of the incisive canals and surrounding bone with CBCT showed two typical shapes for the presence or absence of the incisors. These findings indicate the importance of image diagnosis before esthetic restoration.
The width and morphology of the mandible with impacted teeth and the location of the mandibular canal at the third molar region could be clearly determined using cross-sectional CBCT images.
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.
Classifi cation of the lingual foramina and their bony canals in the median region of the mandible: cone beam computed tomography observations of dry Japanese mandibles Abstract Objectives. We investigated the lingual foramina and their bony canals in the median region of the mandible using cone beam computed tomography (CBCT). Methods. Sixty-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 classifi ed 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. Results. The 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 signifi cant relationship was observed between the foramen height and canal angulation. On dissecting six cadaver mandibles, the sublingual artery was identifi ed in s-MLFs and i-MLFs, while anastomosis of the sublingual and submental arteries was found in the a-MLFs. Conclusions. MLFs were observed frequently, and we confi rmed 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.
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