Kazunari Shiozaki

Characteristics of Accessory Mental Foramina Observed on Limited Cone-beam Computed Tomography Images

In this retrospective study with limited cone-beam computed tomography (limited CBCT), we investigated the anatomic characteristics of the accessory mental foramina and accessory branches of the mandibular canal. The CBCT records of approximately 150 patients were evaluated, and 17 accessory mental foramina were found in 16 patients. The anatomic peculiarities of the mandibular canal that might be relevant to endodontic treatment were observed. Accessory mental foramina tended to exist in the apical area of the first molar and posterior or inferior area of the mental foramen. The accessory branches of the mandibular canal showed common characteristics in the course of gently sloping posterosuperior direction in the buccal surface area. Verification of the existence of accessory mental foramina would prevent accessory nerve injury during periapical surgery. In root canal treatment, the possibility of accessory mental foramina-related nerve paresthesia seems low unless the mental foramen and mandibular canal are injured. Limited CBCT is effective for presurgical 3-dimensional assessment of the neurovascular structures in dentoalveolar treatment.

Accuracy of oral mucosal thickness measurements using spiral computed tomography.

BACKGROUND Assessment of oral mucosal thickness is important in implant surgery; however, examining the soft tissue three dimensionally is difficult. A reamer method is invasive, and a non-invasive ultrasonic method produces only low-resolution images depending on anatomic variations. The emerging technology of spiral computed tomography (CT) is an alternative to the conventional methods. Spiral CT has been a useful diagnostic tool in implant surgery. Although it delivers high radiation doses, spiral CT provides three-dimensional imaging of low-contrast structures. The purpose of the present study is to assess the accuracy of oral mucosal measurements using spiral CT. METHODS Thickness of maxillary oral mucosa was measured in five cadavers. The measurement sites were set up in buccal, palatal, and middle of the crest in the missing tooth area in the incisor, canine, premolar, and molar regions. Each cadaver was exposed to spiral CT after installing the measurement guide. After that, each site was physically measured by reamer. Linear regression and correlation analysis were performed to describe the association between radiographic and physical measurements. RESULTS A total of 114 measurements were performed with statistical analyses. Mean values and standard deviations of physical and radiographic measurements were 3.12 ± 1.43 and 2.83 ± 1.70 mm, respectively. The radiographic and physical measurements demonstrate strong correlation (r = 0.90; P <0.01). Measurement error was 0.52 ± 0.36 mm. According to the regions, the measurements in buccal, palatal, and missing tooth region depicted a significant correlation (r = 0.92, r = 0.85, and r = 0.91, respectively). The boundary of the bone and mucosa was indistinguishable at 23 buccal sites. Twenty-three measurements that could not be distinguished with CT had a mean of 0.69 and standard deviation ± 0.13 mm. CONCLUSIONS The correlation between spiral CT and physical measurement was high except in sites of very thin mucosa. Spiral CT can be considered an alternative method for the measurement of oral mucosal thickness. Because of the higher radiation exposure, caution should be exercised and radiation dosage versus clinical benefit assessment is required.

Anatomical variations in the tendon sheath of the first compartment

Using Hiranuma’s classification, we carefully examined anatomical variations in the first compartments of 246 human wrist joints from 124 cadavers. Morphological examinations were conducted to determine the number of accessory tendons and the existence of dissepiments for the extensor pollicis brevis (EPB) and abductor pollicis longus (APL) tendons. Anatomical variations of EPBs and APLs were grouped together by type, and appearance ratios were calculated based on Hiranuma’s classification. Of the 246 wrist joints, 156 were categorized as normal type (63.4%), 57 as complete dissepiment type (23.2%), 22 as incomplete dissepiment type (8.9%), and 11 as EPB-lacking type (4.5%). Accessory tendons were identified in both the EPB and the APL tendons of most cadavers, and the incidence of dissepiment in tendon sheaths was approximately 33%. Sixty-six of the 193 wrist joints (34.2%) showed equal numbers of right and left accessory tendons. However, the number of EPB accessory tendons was higher than in previous studies, and in all cases some kind of dissepiment was observed in the APL and EPB. The number of EPB and APL accessory tendons showed no clear differences by gender, age, or right and left specificity.

Mandibular lingual canals distribute to the dental crypts in prenatal stage

PurposeTo describe configurations of human prenatal mandibular, lingual canals using a limited-field cone beam computed tomography (CBCT) to examine their origin and anatomical significance.Materials and methodsNine fetal mandibles were examined using a CBCT. Mandibular maturity was assessed according to the mandibular size measured directly and image findings on development of dental crypts. Mandibular, lingual canals and the related foramina (mandibular, mental, and lingual foramina) were observed on axial, sagittal, and cross-sectional images. The horizontal position of mental and lingual foramina was assessed by direct observation using a loupe.ResultsIn all nine mandibles, CBCT images depicted three separate mandibular canals, which individually occurred at the ramus area. One was a short canal directly connecting to the permanent molar crypt. The other two showed a parallel course, following the mandibular corpus toward the frontal area; the upper one connected to the mental foramen, and the lower one distributed anterior area of canine and incisor crypts. Lingual foramina were observed bilaterally in eight of nine mandibles, whose horizontal position was lingual against the crypt of deciduous canine. The lingual canals occurred from lingual foramina, and connected to the close deciduous tooth crypt or the mandibular canal distributing in the frontal area.ConclusionsIt was suggested human dentition could be developed by plural mandibular and lingual canals.

Macroscopic Anatomy of the Sphenomandibular Ligament Related to the Inferior Alveolar Nerve Block

Abstract We performed macroscopic observations of the sphenomandibular ligaments, and measured the space that is surrounded by the mandibular ramus and the ligament by using computed tomography. The materials used in this study were 40 heads of 40 adult cadavers. The cadaver head was cut on the mid sagittal plane. The medial pterygoid muscles of the cadavers were removed to observe the ligaments. The attaching style of the sphenomandibular ligament to the mandibular ramus was classified into three types: Type I (5 in 40 samples; attached only to the mandibular lingula), Type II (12 in 40 samples; attached to the mandibular lingula and extended toward the rear part of the internal surface of the mandibular ramus), and Type III (23 in 40 samples; attached to the mandibular lingula and toward the posterior border of the mandibular ramus). There was no statistical difference in the length of the ligament among the three types. However, Type III showed the largest width, and the space was approximately eight and three times as large as those of Type I and II, respectively. This indicated that the Type III ligament covered a larger area over the mandibular foramen than Type I. These results suggest that the three-dimensional morphology of the sphenomandibular ligament, as represented by Type III, may affect the effectiveness of anesthesia.

A method for the staining of intraosseous nerve fibers using Sihler’s staining technique

Abstract Understanding nerve fiber distribution in the jaw bone is important when performing invasive surgical treatments. Both microscopic and macroscopic anatomical techniques have been developed to study innervation. Conventional methods of removing and staining these structures, however, often alter structure and lack reproducibility of the resulting specimens. We sought to optimize Sihler’s staining technique to stain intraosseous nerves in mandibles. Four cadaver specimens were used. The best staining of intraosseous nerve fibers was achieved by using the Plank-Rychlo solution. When the Styrene monomer was used, the resulting transparency was better than that obtained with glycerin under the same conditions. No significant differences were found between Sihlers staining procedure performed according to the conventional method and the procedure in which the second decalcification step was omitted. Our results demonstrate that applying Sihler’s staining technique to bones makes them transparent and allows observation of nerves while preserving the external shape of the bone and maintaining the position of intraosseous nerve fibers. Our findings suggest our Sihler staining method for intraosseous nerve fibers can provide an intermediate resolution between macroscopic and microscopic techniques.