Kenichi Gotoh

Accessory mental foramen assessment using cone-beam computed tomography.

OBJECTIVE The purpose of the present study was to assess the accessory mental foramen using cone-beam computed tomography (CBCT) images. STUDY DESIGN A total of 157 patients were enrolled in this investigation. The mental and accessory mental foramina, which show continuity with the mandibular canal, were assessed using axial and cross-sectional, 2-dimensional CBCT images. The sizes of the mental and accessory mental foramina were measured and statistically analyzed. Also, the distance between the mental and accessory mental foramina was measured. RESULTS The accessory mental foramen was observed in 7% of patients. There was no significant difference regarding the sizes of the mental foramen between accessory mental foramen presence and absence. Also, the mean distance between the mental and accessory mental foramina was 6.3 mm (SD: 1.5 mm). CONCLUSION The accessory mental foramen, which shows continuity with the mandibular canal, could be observed in 7% of the subjects using CBCT.

Comparison between cone-beam and multislice computed tomography depicting mandibular neurovascular canal structures.

OBJECTIVE The most common diagnostic imaging modalities for cross-sectional imaging in dental implant planning are currently cone-beam computed tomography (CBCT) and multislice CT (MSCT). However, clinical differences between CBCT and MSCT in this task have not been fully clarified. In this investigation, the detection of fine anatomical structures in the mandible was assessed and compared between CBCT and MSCT images. STUDY DESIGN The sample consisted of 28 patients who had undergone CBCT and MSCT. The bifid mandibular canal in the mandibular ramus, accessory mental and buccal foramina, and median and lateral lingual bony canals were observed in 2-D images, and the findings were compared between CBCT and MSCT. RESULTS Four of 19 canals observed in CBCT were not observed in MSCT images. Three accessory mental foramina in 2 patients and 28 lateral lingual bony canals in 18 patients were observed consistently using the two methods. CONCLUSION Depiction of fine anatomic features in the mandible associated with neurovascular structures is consistent between CBCT and MSCT images.

Demonstration of the accessory mental foramen using rotational panoramic radiography compared with cone‐beam computed tomography

OBJECTIVE Rotational panoramic radiography is routinely used in dental practice. It has not been clarified, however, whether an accessory mental foramen can be demonstrated using this technique. The visibility of accessory mental foramina on rotational panoramic radiographs was compared with those on para-panoramic images reconstructed from cone-beam computed tomographic (CBCT) images. MATERIALS AND METHODS A total of 365 patients (130 males and 235 females) were retrospectively analyzed. Para-panoramic images were reconstructed from CBCT images with the accessory mental foramen/foramina using three-dimensional visualization and measurement software, and then the accessory mental foramen on rotational panoramic images was compared with that on para-panoramic images. RESULTS A total of 37 accessory mental foramina were observed in 28 patients on CBCT images. The rate of being able to visualize the accessory mental foramen or bony canal between the point of bifurcation from the mandibular canal and the accessory mental foramen on rotational panoramic radiographs was 48.6% (18 of 37 accessory mental foramina). CONCLUSION Approximately half of the accessory mental foramina-positive CBCT images demonstrated the accessory mental foramen, or bony canal between the point of bifurcation from the mandibular canal and accessory mental foramen on rotational panoramic radiographs.

Assessment of Maxillary Sinus Septa Using Cone-Beam Computed Tomography: Etiological Consideration

BACKGROUND Septum presence in the maxillary sinus complicates sinus floor elevation surgery, and so it is important that septa are accurately diagnosed on preoperative imaging. PURPOSE Septa were observed regarding their relationship with the bony palate using cone-beam computed tomography (CT). MATERIALS AND METHODS Thirty maxillary sinuses with dentate jaws of 15 dry skulls and a cone-beam CT unit were used. A septum was defined as a pointed bone structure, and an exostosis was defined as a rounded bone structure. The occurrence and locations of maxillary sinus septa and exostoses of more than 2 mm in height were evaluated. Also, angles between the direction of septum and median palatine suture were measured on axial images. RESULTS Twelve septa of 11 maxillary sinuses (37%) and nine exostoses of nine maxillary sinuses (30%) were observed. Also, 42% of septa and 67% of exostoses were antero-posteriorly aligned according to the transverse palatine suture. Moreover, the mean septum angle was 57.9 degrees in the anterior maxillary sinus region, and 101.8 degrees in the transverse palatine suture region, and significant differences were noted between them. CONCLUSION Maxillary sinus septa and exostoses could be clarified regarding their relationship with the bony palate using cone-beam CT.

Metal artifacts from posterior mandibular implants as seen in CBCT.

Purpose:Metal artifacts from dental implants have not been clarified in cone-beam computed tomography (CBCT) images in previous studies. Hence, only mesiodistal metal artifacts from dental implants in the posterior mandibular region were assessed using CBCT. Materials and Methods:Twenty-two patients with a total of 61 dental implants in posterior mandibular sites were enrolled. The pixel values surrounding dental implants were measured using CBCT and rotational panoramic radiography, and then the means were calculated. Results:The mean pixel values between dental implants, between dental implants and neighboring teeth, and posterior to dental implants were significantly lower than between neighboring teeth in CBCT. In addition, the mean pixel value between dental implants did not significantly differ from that between neighboring teeth in rotational panoramic radiography. Conclusions:It was concluded that mesiodistal metal artifacts surrounding dental implants are demonstrated on CBCT.

Stability of voxel values in cone-beam computed tomography

ObjectiveMeasurements of jaw bone density are important for dental implants, and stable voxel values in cone-beam computed tomography (CBCT) for dental use are necessary for their evaluation. The purpose of this study was to clarify the stability of voxel values in CBCT.MethodsCylindrical phantoms composed of the same material were set at the median anterior region and left and right first molar regions of an acrylic vessel filled with water. Three kinds of cylindrical phantoms made of polyvinyl chloride, polyacetal polyoxymethylene, and polycarbonate were evaluated. CBCT images were obtained using Alphard VEGA and 3D eXam i systems. Circular regions of interest were superoinferiorly set at five levels, and the voxel values were averaged. The mean differences were calculated on the basis of the voxel values at a central level of the anterior region.ResultsThe mean voxel values for polyvinyl chloride, polyacetal polyoxymethylene, polycarbonate, and water were 1057, 293, 137, and 102 in Alphard VEGA and 554, 48, −127, and −202 in 3D eXam i, respectively. There were significant differences between sites and levels in Alphard VEGA and between sites in 3D eXam i. The mean differences for polyvinyl chloride, polyacetal polyoxymethylene, polycarbonate, and water were 73, 24, 18, and 18 in Alphard VEGA and 72, 49, 43, and 40 in 3D eXam i, respectively.ConclusionsThe mean differences for polyvinyl chloride, close to the cortical bone density, were larger than those for polyacetal polyoxymethylene, polycarbonate, and water in Alphard VEGA and 3D eXam i.

Comparative anatomy of the hyoid apparatus of carnivores

Abstract. The hyoid apparatus was described in order to examine morphological differences among eight species of carnivores. Confusion in terminology of its proximal elements is corrected at first. The tympanohyal, attached to the petrosal part of the temporal bone, is a small bone inside the stylomastoid foramen in the red fox, raccoon dog (Canidae), Asiatic black bear (Ursidae), and masked palm civet (Viverridae), in contrast, it is not visible in the Japanese weasel, Siberian weasel, Japanese marten (Mustelidae) and raccoon (Procyonidae). Inter-specific structural differences of the remainder of the hyoidean elements are not distinct. The basihyal attaches to the ceratohyal and thyrohyal. The thyrohyal is also connected with the thyroid cartilage. The anterior cornu besides the tympanohyal comprises, from distal, three bones; the ceratohyal, epihyal, and stylohyal, and a band of cartilage. The tympanohyal, if present, is connected to the stylohyal via the tympano-styloid synchondrosis. Allometry between the length of the hyoidean elements and that of the skull shows isometric growth. This reflects simply the masticatory function of the hyoid apparatus. The tympanohyal of the mustelids and procyonid is possibly covered and hidden by the tympanic bulla.

Use of tungsten sheet as an alternative for reducing the radiation dose behind the digital imaging plate during intra-oral radiography

OBJECTIVES To verify the use of tungsten sheet as an alternative to lead foil for reducing the radiation dose behind storage phosphor plates (SPPs). METHODS At six sites (incisor, canine, and molar sites in both the maxilla and mandible) in a head phantom, radiation doses were initially measured behind conventional film packets containing two films and a lead foil. At the same sites, radiation doses were also measured behind packets containing only SPPs. Thereafter, the same dose measurements were performed with shielding materials (lead foil or tungsten sheet) within the packets. These doses were defined as behind doses. RESULTS There were no differences in the mean behind doses between the conventional film packets and the SPP packets without shielding materials for any of the six sites examined. The behind doses were reduced by both lead foil and tungsten sheet, with significant differences in all sites when compared with no shielding. Lead foil reduced the behind dose of the SPP packet to 37.6% on average, while tungsten sheet reduced the behind dose to less than 20% in all of the sites examined, with an average of 14.7%. CONCLUSIONS Tungsten sheet appeared to be effective as an alternative shielding material, sufficiently reducing the doses behind the SPP packets to less than 20% when compared with sheetless packets in all of the six sites examined.

Longitudinal observation of maxillary sinus bony bridges and septa in childhood

The rate of septum presence in the maxillary sinus has been reported to be over 30%. It was considered that a bony bridge might change to a maxillary sinus septum with growth in a previous study using dry child skulls. In the present investigation, maxillary sinus bony bridges and septa were longitudinally observed using computed tomography (CT). Multislice CT was performed in three patients. A bony bridge was defined as a bony structure between the maxillary sinus wall and dental germ. Also, a septum was defined as a pointed bony structure in the inferior wall of the maxillary sinus. The height and angle of the bony bridge/septum and the distance between the base of the bony bridge/septum and bony palate were measured. In three patients, the bony bridge in the maxillary sinus floor was observed in the second molar on the first CT, and the maxillary sinus septum was observed on the second CT at the same site. In conclusion, it was longitudinally observed that a bony bridge changed to a maxillary sinus septum with growth, such as root formation and tooth eruption.

Optimizing the reconstruction filter in cone-beam CT to improve periodontal ligament space visualization: An in vitro study

Purpose Evaluation of alveolar bone is important in the diagnosis of dental diseases. The periodontal ligament space is difficult to clearly depict in cone-beam computed tomography images because the reconstruction filter conditions during image processing cause image blurring, resulting in decreased spatial resolution. We examined different reconstruction filters to assess their ability to improve spatial resolution and allow for a clearer visualization of the periodontal ligament space. Materials and Methods Cone-beam computed tomography projections of 2 skull phantoms were reconstructed using 6 reconstruction conditions and then compared using the Thurstone paired comparison method. Physical evaluations, including the modulation transfer function and the Wiener spectrum, as well as an assessment of space visibility, were undertaken using experimental phantoms. Results Image reconstruction using a modified Shepp-Logan filter resulted in better sensory, physical, and quantitative evaluations. The reconstruction conditions substantially improved the spatial resolution and visualization of the periodontal ligament space. The difference in sensitivity was obtained by altering the reconstruction filter. Conclusion Modifying the characteristics of a reconstruction filter can generate significant improvement in assessments of the periodontal ligament space. A high-frequency enhancement filter improves the visualization of thin structures and will be useful when accurate assessment of the periodontal ligament space is necessary.