Koh Nakajima

Assessment of the blood supply to the lingual surface of the mandible for reduction of bleeding during implant surgery

OBJECTIVES The aim of this study was to assess the frequency of the foramina and their canals on the lingual surface of the mandible using computed tomography (CT), which was carried out for dental implant planning. MATERIAL AND METHODS First, the visibility of the lingual canals of the CT image was verified by dissecting five cadavers. CT images of 200 patients, who had decided on implant treatment, were used in this study. The visibility of the foramina and their canals on the lingual surface of the mandible were assessed. RESULTS The foramina were divided into two groups by the positions of the mandible, the medial lingual foramen and the lateral lingual foramen. At least one foramen was found in all patients. In the medial group, a higher level of mental spine was seen in 190 patients, the same level of mental spine was observed in 99 patients and a lower level of mental spine was observed in 114 patients. The lateral lingual foramina were found in 160/200 patients and 88/200 patients presented bilaterally. CT can predict the position and the size of the foramina and their canals on the lingual surface of the mandible. All the patients had more than one foramen in the middle of the lingual surface of the mandible on the CT image. CONCLUSION The frequency of the lingual foramina in the medial region was 100% and that in the lateral region was 80%. It would also be useful to emphasize the significant variation in the precise location of these lingual foramina, and that these can only be visualized presurgically with volumetric imaging modalities, such as CT or Cone beam 3D systems.

Effects of tube current on cone-beam computerized tomography image quality for presurgical implant planning in vitro

OBJECTIVE The purpose of this study was to evaluate the effect of tube current reduction on the quality of cone-beam computerized tomography (CBCT) images of the maxilla and mandible for presurgical implant planning. STUDY DESIGN Six cadaver heads were imaged with a CBCT (3D Accuitomo) operated at 80 kVp and variable tube current (8, 4, 2, or 1 mA) in full-scan mode. For the posterior region of maxilla and mandible, half-scans were also performed at similar settings. The images were evaluated independently by 5 oral radiologists for 15 anatomic landmarks regarding presurgical implant planning. The quality of images were compared with their respective reference images at 8 mA and ranked on a 4-point rating scale as excellent, good, fair, or nondiagnostic. The scores of all observers were averaged for each landmark at every exposure condition, and Bonferroni test (P<.05) was performed. RESULTS The 4 mA images at full-scan mode could visualize each landmark of maxilla and mandible and were evaluated to be the same or almost equivalent in quality as the 8 mA images. Even 2 mA images in full-scan mode and 4 mA in half-scan mode could be used for implant planning. The 1 mA images were unacceptable owing to the substantial degradation in image quality. CONCLUSION Significant dose reduction can be achieved by reducing tube current without substantial loss of image quality for presurgical implant planning in CBCT.

Composition of the blood supply in the sublingual and submandibular spaces and its relationship to the lateral lingual foramen of the mandible

OBJECTIVE The purpose of this research was to contribute to minimizing arterial disruption during mandibular surgical procedures by clarifying the course of the arteries supplying the sublingual and submental regions. STUDY DESIGN Heads of 75 human cadavers were dissected to identify the arterial supply of the sublingual and submental regions. Computed tomography scans were performed to visualize the lateral lingual foramina of the mandibles. RESULTS The facial artery was found to contribute to the composition of almost half of the sublingual arteries studied. Furthermore, it was demonstrated that the arterial supply to an incisor tooth is often from the submental artery. CONCLUSIONS Our data provide important information for coping with bleeding or hematoma occurring during surgical procedures in the mandibular region.

Imaging of the mylohyoid muscle: separation of submandibular and sublingual spaces.

OBJECTIVE This article focuses on the anatomy of the mylohyoid muscle, a crucial landmark in imaging of the oral cavity and upper neck, showing dissected specimens and CT and MR images. CONCLUSION Identification of the relationship of a lesion in the sublingual space to the mylohyoid muscle using MDCT and high-resolution MRI is a key part of the imaging assessment of the oral cavity and upper neck.

Comparative anatomy of the buccinator muscle in cat (Felis domestica)

Published descriptions of the buccinator muscle of the cat (Felis domestica) differ from those for the same muscle in other mammals. Only an oral component of the muscle has been described in cats, not a buccal part. The purpose of this study was to identify the buccinator muscle in the cat and report on its anatomical features in detail. Dissections of the facial muscles were carried out on 12 specimens of adult cats (6 males and 6 females) that had been fixed with 10% formalin. We then observed the facial muscles and traced their innervations, arteries, and veins under a binocular microscope. The buccinator muscle in the cat was identified underneath an orbicularis oris, arising from the lower buccal membrane and from the molar region of the alveolar border of the mandible. It was about 3 mm wide at its origin, 4 mm wide at its insertion, and about 11 mm in length from origin to insertion. This contrasts with humans, in whom the muscle arises not only from the mandible, but also from the maxilla. Apart from this difference, this muscle in cats displays the following similarities to the buccinator muscle of other mammals: 1) it is innervated by the facial nerve; 2) it supports the buccal membrane; 3) it seems to insert into the modiolus; 4) its bundles run antero‐posteriorly; 5) the posterior part of the muscle is located medially to the masseter muscle; 6) the parotid duct, facial nerve, artery, and vein run lateral to the muscle; 7) it is located deeper than other facial muscles; and 8) the buccal nerve runs on its surface. These relationships are spatially similar to those of the buccinator muscle in mammals. This muscle may aid in mastication, including suckling, and in expelling air forcibly, like the buccinator in humans. Anat Rec 267:78–86, 2002.

Effects of dose reduction on multi-detector computed tomographic images in evaluating the maxilla and mandible for pre-surgical implant planning: a cadaveric study

OBJECTIVE To assess effects of dose reduction on image quality in evaluating maxilla and mandible for pre-surgical implant planning using cadavers. MATERIALS AND METHODS Six cadavers were used for the study using multi-detector computed tomography (CT) operated at 120 kV and the variable tube current of 80, 40, 20 and 10 mA. A slice thickness of 0.625 mm and pitch 1 were used. Multi-planar images perpendicular and parallel to dentitions were created. The images were evaluated by five oral radiologists in terms of visibility of the anatomical landmarks including alveolar crest, mandibular canal, floors of the maxillary sinus and nasal cavity, contours/cortical layer of jaw bones and the details of trabecular bone. Observers were asked to determine the quality of the images in comparison with 80 mA images based on the criteria: excellent, good, fair or non-diagnostic. The average scores of all observers were calculated for each specimen in all exposure conditions. RESULTS The 40 mA images could visualize such landmarks and were evaluated to be same or almost equivalent in quality to the 80 mA images. Even the 20 mA images could be accepted just for diagnostic purpose for implant with substantial deterioration of the image quality. The 10 mA images may not be accepted because of the obscured contour caused by image noise. CONCLUSION Significant dose reduction by lowering mA can be utilized for pre-surgical implant planning in multi-detector CT.

The Co-existence of the Gastrocnemius Tertius and Accessory Soleus Muscles

A bilateral gastrocnemius tertius muscle and a unilateral accessory soleus muscle were encountered during the routine educational dissection studies. The right gastrocnemius tertius muscle consisted of one belly, but the left one of two bellies. On the left side, the superficial belly of the gastrocnemius tertius muscle had its origin from an area just above the tendon of the plantaris muscle, the deep belly from the tendon of the plantaris muscle. The accessory soleus muscle originated from the posteromedial aspect of the tibia and soleal line of the tibia and inserted to the medial surface of the calcaneus. On the right side, the gastrocnemius tertius muscle had its origin from the lateral condyle of the femur, and inserted to the medial head of the gastrocnemius muscle. The co-existence of both gastrocnemius tertius and accessory soleus muscle has not, to our knowledge, been previously reported.

The Pterygoideus Proprius Muscle Revisited

The pterygoideus proprius muscle is an anomaly in the infratemporal fossa that has immovable attachments to the infratemporal crest and the lateral pterygoid plate of the sphenoid bone. We report the identification of three cases of this anomaly, suggest its embryological origin, and speculate about its function. Clin. Anat. 11:332–337, 1998.

Mylohyoid muscle defects: comparison of CT findings and dissected specimens

ObjectivesTo investigate whether CT images reflect the anatomical condition of mylohyoid muscle defects by confirmation with subsequent dissection of cadavers, and to evaluate whether CT images are useful for detecting such defects.MethodsCT scans of the head and upper neck were performed in six cadavers. Multiplanar reconstruction was carried out to obtain 2-mm-thick axial and coronal images of the mylohyoid muscle. The number of defects was determined. All the cadavers were subsequently dissected for comparison with the CT findings. The contents of the defects were also identified.ResultsCT demonstrated the presence of one or more mylohyoid defects in four of the six cadavers. Defects were seen bilaterally in three of the four cadavers. Five of eight defects were observed on both axial and coronal images, whereas two were not observed on coronal images and one was not observed on axial images. The defects contained part of the sublingual gland bilaterally in one cadaver and unilaterally in another. In one cadaver, the submental artery passed through the defect bilaterally. In the other cadaver, there were bilateral defects without any substantial contents.ConclusionsOur results indicate that mylohyoid defects are commonly seen anatomically, and that some of them show herniation of the sublingual gland. CT images can demonstrate mylohyoid defects on multiplanar reconstructed images.

Rare case of myloglossus in Japanese cadaver: anatomical and developmental considerations.

The styloglossus is one of the three extrinsic muscles of the tongue; it enters the tongue from behind. During human dissection practice for dental students at the Showa University School of Dentistry in 2006, the authors observed anomalous muscle arising from the inner surface of the mandibular angle and inserting into the tongue bilaterally. This muscle was termed myloglossus by Wood. On the right side, the myloglossus was accompanied by a weak rudimentary styloglossus, but the styloglossus was absent on the left side. The hypoglossal nerve innervated the myloglossus bilaterally, and a small branch of mandibular nerve also entered the muscle on the left side. The styloglossus develops from the styloid process and the mandibular angle as a bicipital muscle, but the segment attached to the mandibular angle generally atrophies during development. The present anomalous muscle was thought to represent persistence of this muscle bundle arising from the inner surface of the mandibular angle. The innervation of the innermost part of the left myloglossus by the mandibular nerve was explained by persistence of a vestigial nerve supplying a small muscle bundle originating from the tensor veli palatini, which had fused to the myloglossus.