Anatomical morphometry for Cricothyrotomy puncture and incision.

PURPOSE: Emergency surgical airway securing techniques include cricothyrotomy, puncture, and incision. While the instruments used for these methods vary in size, no index of laryngeal morphology exists to guide instrument selection. Therefore, we measured the morphology of the cricothyroid ligament in Japanese individuals and assessed its correlations with height. METHODS: This retrospective study used 61 anatomical practice specimens. The cricothyroid ligament of the laryngeal area was dissected, and a frontal image was recorded. Next, images of the midsagittal sections of the larynx and trachea were recorded. The width and height of the cricothyroid ligament were measured from the frontal images, and the depth of the larynx and the angle to the lower edge of the cricothyroid plate were measured from the mid-sagittal cross-sectional images. The height was estimated from the tibial lengths of the specimens and statistically analyzed for correlations. 　 RESULTS: The width and depth were significantly greater in males. Overall, there was a slight correlation between the results of each laryngeal measurement and estimated height for all items. CONCLUSION: The morphology of cricothyrotomy revealed that the width and depth of the laryngeal area varied according to sex. Moreover, the results also showed a correlation with the estimated height. Thus, it is important to predict the morphology of the laryngeal area and cricothyroid ligament by considering factors such as patient sex, weight, and height.

Histological observations of age-related changes in the epiglottis associated with decreased deglutition function in older adults.

Although the epiglottis plays a vital role in deglutition, histological studies of the epiglottis and surrounding ligaments associated with swallowing dysfunction are limited. Therefore, we performed histological observations to clarify age-related changes in the morphological characteristics of the epiglottis and surrounding structures. Tissue samples comprising the epiglottis and surrounding structures were collected from corpses that were both orally fed and tube-fed during their lifetimes. Following hematoxylin and eosin, Elastica Van Gieson, and immunohistochemical staining procedures, the chondrocytes, connective tissue, and glandular tissue were observed under the epiglottis epithelium, and intervening adipose tissue was observed in the surrounding area. Fatty degeneration of acinar cells was also observed in the glandular tissue, possibly because of aging. Bundles of elastic fibers were present around the vascular wall in the peri-epiglottic ligament, but some were reduced. Furthermore, large amounts of collagen fibers ran toward and through the cartilage, whereas the mesh-like elastic fibers stopped in front of the cartilage. Microfibrils considered to be oxytalan fibers, which are thinner and shorter than elastic fibers, were observed around the vascular wall and in the fiber bundles. Age-related changes included connective tissue fibrosis shown by the large amount of collagen fibers, atrophy of salivary glands, and an accompanying increase in adipose tissue. Regarding stretchability and elasticity, the elastic fibers may have an auxiliary function for laryngeal elevation during deglutition. This suggests that disuse atrophy of the laryngeal organs with or without oral intake might reduce the amount of elastic fiber in older adults.

Accuracy verification of dental cone-beam computed tomography of mandibular incisor root canals and assessment of its morphology and aging-related changes.

The root canal morphology undergoes aging-related changes, and relevant quantitative analyses have not yet been reported. We compared the cone beam computed tomography (CBCT) and micro-computed tomography (micro-CT) scans of extracted mandibular incisors to check the accuracy of morphological measurements. Thereafter, the root canal morphology and aging-related changes in the mandibular incisors of Japanese individuals were assessed using CBCT. Six extracted teeth were fixed in a phantom head and imaged using CBCT and micro-CT. The correlation between the findings of the two imaging modalities was examined. Further, CBCT reconstructed images of the mandibular incisors of 81 individuals were observed. Age-related changes of the root canals were compared between participants aged <30 years and those aged ≥30 years. The CBCT and micro-CT findings regarding the root canals of the extracted teeth coincided in 94.4% of the cases. Mandibular incisors exhibiting two root canals in either cross-section accounted for 9.9% of central incisors and 12.4% of lateral incisors. Mandibular central incisors with two root canals were observed in two (6.3%) individuals aged <30 years and six (12.2%) aged ≥30 years. Mandibular lateral incisors with two root canals were observed in one (3.1%) individual aged <30 years and nine (18.4%) aged ≥30 years. CBCT allows accurate evaluation of complex root canal morphologies and is useful for endodontic preoperative assessment. Mandibular incisors have more frequent occurrence of two root canals with aging.

Observation of mandibular second molar roots and root canal morphology using dental cone-beam computed tomography.

The mandibular second molars show various morphological features in the roots and root canal, and a guttershaped root (GSR) caused by fusion of the mesial and distal roots is frequently encountered. In this study the number of the roots associated with mandibular second molars were observed using dental cone-beam computed tomography (CBCT). For those with a GSR, determination of root morphology and root canal classification were performed. CBCT image data from 173 Japanese mandibular second molars were obtained. Using sliced images, the number of the roots and root morphology were determined. In cases with a GSR, the ratio for the fused roots was determined and root canal morphology features were classified. A GSR was found in 61 (35.3%), with greater prevalence in females. In addition, the overall ratio of the fused part to root thickness in those with a GSR was 48.7%, with no significant difference related to sex. Furthermore, a C-shaped root canal morphology was commonly observed in both males and females with a GSR. In the present cohort examined in Japanese, most of the mandibular second molar were found to have two roots, with a GSR noted in 35.5%. While a GSR was more often observed in females, a C-shaped root canal was the most common root canal morphology in both sexs. It is considered that assessment using CBCT findings is helpful for precise determination of root canal morphology and presence of a GSR in mandibular second molars.

Cone-beam computed tomography observation of maxillary first premolar canal shapes.

A variety of shapes has been reported for the roots and root canals of maxillary first premolars. The purposes of the present study were to determine branching and shapes of the roots of maxillary first premolars, as well as age-related changes using slice images obtained with cone-beam computed tomography (CBCT) for dental use. CBCT-reconstructed images of 125 cases that included maxillary first premolars were used as subjects. Slice images at the cervical one-third, center, and apical one-third positions of the root were prepared. Root branching and number of root canals was determined at each measurement position in the images. The subjects were divided into three groups: younger than 30 years, 30 to 50 years, and over 50 years. The root canal morphology was compared among these age groups. Single-rooted premolars were the most frequent. As for number of root canals, a single-canal premolar was observed at the position of the cervical one-third in 33.6%, at the center in 35.2%, and at the apical one-third in 56.0%. Thereafter the subjects were divided into groups by age, namely, younger than 30 years, 30 to 50 years, and over 50 years old, and it was revealed that the ratio of the two-canal type increased with age. In regard to tooth morphology, it was confirmed that the two-canal type shows more frequent occurrence with aging in maxillary first premolar. Based on our findings, we consider that CBCT can be useful for determining the root canal morphology with complicated shapes.

Effect of Mesenchymal Cells on Myoblast Sheets Embedded in Collagen Gel.

The objective of this study was to investigate the effects of mesenchymal cells on myoblasts in long-term cultivation of myoblast cell sheets. Sheets of myoblasts and mesenchymal cells from Japanese rabbit oral mucosa were generated and analyzed by histochemistry, Western blot, and reverse transcription-polymerase chain reaction. The presence of desmin and type IV collagen, which is seen in normal muscle tissue, was also confirmed in all the sheets produced. Expression of desmin and type IV collagen showed a decrease under co-culture conditions. In addition, expression of genes important in maintaining the undifferentiated state (Pax7, CD34, myogenin, MyoD) in myoblasts was observed throughout the long cultivation period. Insulin-like growth factor was expressed only when the mesenchymal cells were co-cultured with myoblasts. These data suggest that the presence of mesenchymal cells in a long-term co-culture system influences myoblast differentiation.

Anatomic and Histological Study of Lingual Nerve and Its Clinical Implications.

Although the risk of injuring the lingual nerve in the mandibular molar area during dental treatment is high, it can be repaired by nerve grafting. However, from the perspective of clinical dentistry, the pathway and histomorphometric characteristics of this nerve remain to be documented in detail. The purpose of the present study was to morphologically elucidate the pathway of the lingual nerve to clarify its significance in a clinical setting. A histomorphometric analysis was also performed in consideration of nerve grafting. The vertical distance between the occlusal plane and the superior margin of the lingual nerve showed a gradual decrease from the premolar toward the distal molar area. This suggests that the risk of injuring the lingual nerve increases gradually toward the distal area. The average total fascicular area of the lingual nerve was 1.90 mm2, which was larger than that of the sural nerve. It is the first-choice donor nerve for grafting. Therefore, even though the total fascicular area of the donor nerve is a little smaller than that of the recipient nerve, nerve grafting should be successful.

Histological study of the developing pterygoid process of the fetal mouse sphenoid.

The pterygoid process undergoes ossification of both the cartilage and membrane. However, few studies have attempted to explore the sequential development of the pterygoid process. Using histological examination, we performed morphological observations of the pterygoid process and surrounding tissue. ICR mice at embryonic days 13.5-18.0 and postnatal day 0 were used for morphological observations of the pterygoid process. By embryonic day 14.5, a mesenchymal cell condensation forming the anlage of the future medial pterygoid process differentiated into osteoid-like tissue and cartilage. At embryonic days 15.5-16.5, cartilage cells were clearly evident in the medial pterygoid process. In the medial pterygoid process, a bone collar was evident and calcified bone tissue surrounded the cartilage. At this point, a mesenchymal cell condensation formed the anlage of the pterygoid hamulus. At embryonic days 17.0-18.0, the cartilages were located along the lower and posterior border of the medial pterygoid process. A metachromatically stained matrix first became detectable around cells located in the pterygoid hamulus. On the other hand, at embryonic day 13.5, a metachromatically stained matrix was already evident in the space between the flattened cells in the lateral pterygoid process. At embryonic day 17.0, a hypertrophic cell zone had clearly formed in the diaphysis. On the basis of our present investigation, the lateral pterygoid process can be classified as primary cartilage, whereas the medial pterygoid process can be classified as secondary cartilage. Furthermore, it was found that the pterygoid hamulus is formed latest in the medial pterygoid process.

Engineered three-dimensional rabbit oral epithelial-mesenchymal-muscular hybrid sheets.

Regenerative muscles are required for swallowing and mastication, and are important for functional recovery from diseases involving oral muscular defects. Therefore, we generated three-layer hybrid sheets, similar to oral mucosal structures containing submucosal muscles, using rabbit oral mucosa epithelial, mesenchymal, and myoblastic progenitor cells, and examined the structural proteins. Each cell type was obtained from rabbit oral mucosa using enzymatic digestion. Isolated mesenchymal and myoblastic cells were multi-differentiated into osteoblasts, adipocytes, and chondrocytes or myotubes. Isolated epithelial cells were cultured on collagen gels containing isolated mesenchymal cells for 2 weeks, and these epithelial-mesenchymal cell sheets were laminated onto myoblastic cell sheets. The engineered hybrid sheets were multi-stratified in the epithelial and myoblastic layers in a time-dependent manner, expressing intermediate cytoskeletal filament proteins of epithelium and muscle. Hybrid sheets also expressed extracellular matrix basement membrane proteins. Immature cell markers for epithelial and myoblastic cells were observed continuously in hybrid sheet cultures. We established engineered three-dimensional rabbit oral mucosa hybrid sheets containing each immature cell type in vitro.

Proliferative activity of skeletal myoblast sheet by paracrine effects of mesenchymal stem cells.

OBJECTIVES: The purpose of this study was to examine the proliferative activity enhancement of skeletal myoblasts in the presence and absence of mesenchymal stem cells (MSC). METHODS: We artificially fabricated two types of cell sheets by co-culturing rabbit skeletal myoblast sheets with rabbit MSCs using type IA collagen gel (MC+), and cell sheets without rabbit MSCs (MC-). RESULTS: The results of hematoxylin and eosin staining revealed that MC+ was thicker than MC- on day 7. Immunohistochemical staining revealed a low level of desmin expression in both sheets on day 2. Desmin expression increased at days 7 and 12, and desmin localization was consistent with the stratified area. Reverse transcription PCR revealed the presence of MyoD and PAX7 in both sheets on days 2, 7, and 12. The presence of myogenin was confirmed in both sheets on days 7 and 12. Hepatocyte growth factor expression was evident in MC+ on day 2, and in both sheets on day 7. Measurement of cell proliferative activity based on DNA cell cycle analysis indicated that MC+ had significantly higher cell proliferative activity than MC- on day 7. There were no significant differences in cell proliferative activity between MC+ and MC- on day 12. CONCLUSIONS: This study demonstrated that the presence of MSCs could transiently enhance the proliferative activity of myoblasts, but that this enhancement is ultimately diminished due to contact inhibition.