Trigeminal brainstem modulation of persistent orbicularis oculi muscle activity in a rat model of dry eye.

Altered corneal reflex activity is a common feature of dry eye disease (DE). Trigeminal sensory nerves supply the ocular surface and terminate at the trigeminal interpolaris/caudalis (ViVc) transition and spinomedullary (VcC1) regions. Although both regions contribute to corneal reflexes, their role under dry eye conditions is not well defined. This study assessed the influence of local inhibitory and excitatory amino acid neurotransmission at the ViVc transition and VcC1 regions on hypertonic saline (HS) evoked orbicularis oculi muscle activity (OOemg) in urethane-anesthetized male rats after exorbital gland removal (DE). HS increased the magnitude of long-duration OOemg activity (OOemgL, >200ms) in DE compared to sham rats, while short-duration OOemg activity (OOemgS, <200ms) was similar for both groups. Inhibition of the ViVc transition by muscimol, a GABAA receptor agonist, greatly reduced HS-evoked OOemgL activity in DE rats, whereas injections at the VcC1 region had only minor effects in both groups. Blockade of GABAA receptors by bicuculline methiodide at the ViVc transition or VcC1 region increased HS-evoked OOemgL activity in DE rats. Blockade of N-methyl-D-aspartate (NMDA) receptors at either region reduced HS-evoked OOemgL activity in DE and sham rats. GABAαß3 receptor density was reduced at the ViVc transition, while NMDA receptor density was increased at both regions in DE rats. Loss of GABAergic inhibition at the ViVc transition coupled with enhanced NMDA excitatory amino acid neurotransmission at the ViVc transition and the VcC1 region likely contribute to altered corneal reflexes under dry eye conditions.

Mandibular lingual canals distribute to the dental crypts in prenatal stage.

PURPOSE: To 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 METHODS: Nine 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. RESULTS: In 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. CONCLUSIONS: It was suggested human dentition could be developed by plural mandibular and lingual canals.

A comparative study of myostatin, follistatin and decorin expression in muscle of different origin.

Muscle regeneration supports muscle function in aging, and plays a role in the functional impairment caused by progressive neuromuscular diseases. Major substances controlling this process are growth factors and the extracellular matrix (ECM). Thus, follistatin is known to antagonize the function of several members of the TGF-ß family of secreted signaling factors, including myostatin-the most powerful inhibitor of muscle growth characterized to date. Decorin-a small leucine-rich proteoglycan-traps myostatin and modulates its activity towards myogenic cells in the ECM. In addition, there are few reports concerning the regenerative muscle process of masseter muscles, which are of branchial arch origin, in mdx mice. Thus, in order to clarify the muscle regenerative process of masseter muscle, gene and protein expression of myostatin, follistatin and decorin were examined using the tibialis anterior (TA)muscle as a positive control. In both muscles, a gradual increase in mRNA myostatin, follistatin and decorin expression was detected, with the increase being greater in TA muscle than in masseter muscle. At 2 weeks, both muscles exhibited normal skeletal muscle cells. At 3 weeks, masseter muscle demonstrated scant areas of necrosis, whereas large necrotic zones were seen in TA muscle. At 4 weeks, the formation of necrotic tissue and presence of follistatin protein was observed clearly in masseter muscle. This result indicates that follistatin production is stimulated in the presence of necrosis. Interestingly, both muscles showed the same process of muscular formation, but with different time frames, which could be related to muscle origin.

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.

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.

Macroscopic anatomy of the sphenomandibular ligament related to the inferior alveolar nerve block.

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.

Anatomical study of accessory nerve innervation relating to functional neck dissection.

PURPOSE: The present study sought to clarify correlations of accessory nerve innervation in the neck region and innervation of the sternocleidomastoid and trapezius muscles with postoperative dysfunction after functional neck dissection by macroscopic observation. MATERIALS AND METHODS: The materials used in this study were 35 cadavers provided for anatomical practice to the Department of Anatomy, Tokyo Dental College. The accessory nerve was identified at the anterior margin of the trapezius muscle, and its innervation in the posterior triangle of the neck was examined in detail. RESULTS: The superficial cervical vein vascularizes the anterior margin of the trapezius muscle near an area where the main trunk of the accessory nerve innervates the trapezius muscle. The results showed 3 types of accessory nerve innervation of the sternocleidomastoid muscle: Type A, the not penetrating type; Type B, the partially penetrating type; and Type C, the completely penetrating type. In addition, 5 types of innervation of the trapezius muscle by the main trunk and branches of the accessory nerve were apparent, with the number of branches innervating the muscle ranging from 0 to 4. CONCLUSIONS: Dysfunction after functional neck dissection can thus be avoided by paying attention to not only the main trunk of the accessory nerve, but also the branches. Moreover, when identifying accessory nerve innervation of the trapezius muscle, the superficial cervical vein may offer a useful surgical landmark.

Relationship between large tubules and dentin caries in human deciduous tooth.

The purpose of this study was to elucidate the relationship between large tubules and dentin caries by using human deciduous incisors that showed various levels of attrition but no macroscopical lesions resulting from caries. The teeth were cut longitudinally in the mesio-distal direction and the exposed surfaces observed with a high-resolution field emission scanning electron microscope. The inside of each large tubule showed dense collagen fibers running parallel to its long axis and small spherical bodies of aggregated crystals, but no marked attrition. In teeth where attrition had exposed dentin at the incisal edge, oral bacteria had infiltrated the large tubules. Furthermore, in teeth with advanced attrition, it was difficult to distinguish between the large tubules and the surrounding dentin matrix, and numerous bacteria were observed in both areas. These findings support the hypothesis that large tubules play a role in the pathway of caries formation in coronal dentin when incisal dentin is exposed by attrition. This suggests that early treatment of exposed dentin surfaces might be effective in preventing dental caries.