An odontometric study of the maxillary molars in Australian marsupials. I. The koala (Phascolarctos cinereus).

Crown dimensions of the maxillary molars were measured in the koala (Phascolarctos cinereus). There were no significant differences in crown diameters between the first and second molars, however the fourth molars were reduced in all crown diameters. The third molar was smaller than the first or second molars in buccolingual crown diameters but there were no significant differences in mesiodistal crown diameters. It is proposed that the similar shapes of the first and second molars are associated with similar types of masticatory activity involving these teeth, The shape of the third molar, which is reduced in size buccolingually, may be linked to the koala's occlusal function which is characterized by a condylar action that leads to differences in movement between opposing anterior and posterior molar teeth during the occlusal stroke. The fourth molar, the smallest of the molar teeth in crown diameter, erupts significantly later than the other molars, and its reduction may be explained by the terminal and distal reduction theories. It is proposed that the pattern of molar morphology in the koala is associated with both masticatory activity linked to its characteristic occlusal function, as well as reflecting the sequence of tooth emergence.

Comparison of the chloride channel activator lubiprostone and the oral laxative Polyethylene Glycol 3350 on mucosal barrier repair in ischemic-injured porcine intestine.

AIM: To investigate the effects of lubiprostone and Polyethylene Glycol 3350 (PEG) on mucosal barrier repair in ischemic-injured porcine intestine. METHODS: Ileum from 6 piglets (approximately 15 kg body weight) was subjected to ischemic conditions by occluding the local mesenteric circulation for 45 min in vivo. Ileal tissues from each pig were then harvested and mounted in Ussing chambers and bathed in oxygenated Ringer's solution in vitro. Intestinal barrier function was assessed by measuring transepithelial electrical resistance (TER) and mucosal-to-serosal fluxes of (3)H-mannitol and (14)C-inulin. Statistical analyses of data collected over a 120-min time course included 2-way ANOVA for the effects of time and treatment on indices of barrier function. RESULTS: Application of 1 micromol/L lubiprostone to the mucosal surface of ischemic-injured ileum in vitro induced significant elevations in TER compared to non-treated tissue. Lubiprostone also reduced mucosal-to-serosal fluxes of (3)H-mannitol and (14)C-inulin. Alternatively, application of a polyethylene laxative (PEG, 20 mmol/L) to the mucosal surface of ischemic tissues significantly increased flux of (3)H-mannitol and (14)C-inulin. CONCLUSION: This experiment demonstrates that lubiprostone stimulates recovery of barrier function in ischemic intestinal tissues whereas the PEG laxative had deleterious effects on mucosal repair. These results suggest that, unlike osmotic laxatives, lubiprostone stimulates repair of the injured intestinal barrier.

Rare courses of the mandibular canal in the molar regions of the human mandible: a cadaveric study.

The inferior alveolar artery, vein and nerve send some branches to the molar teeth via the mandibular canal to the mental foramen. The present study attempted to define the presence and course of the mandibular canal in the mandible with the alveolar process by macroscopic cadaveric dissection and computerized tomography (CT) in order to provide information that might prevent injuries to vessels and nerves at risk during root canal treatment. We identified the position of the mandibular canal within a 30% ratio of the distance from inferior border of mandible to the apices of the root for 39 out of 131 sides (mesial root of first molar, 20%; distal root of first molar, 22.6%; mesial root of second molar, 27.8% and distal root of second molar, 47%) on panoramic X-ray observation. In one cadaver (male, 64 years old), the root apex of the second molar was in close proximity to the upper bony mandibular canal. Macroscopic dissection and computerized tomography showed that the main trunks of the inferior alveolar artery, vein, and nerve were in tight contact with the apex of the second molar. These observations of the anatomic course of the mandibular canal will be important to consider during root canal treatment of mandibular teeth.

Branch of mylohyoid and lingual nerves on submandibular and submental triangles.

The mylohyoid nerve (MN) displays several branches in the posterior, intermediate, and anterior region of the mylohyoid muscle (MM) as it courses on the internal surface of the mandibular body. Branches in the intermediate region were found in 66% of the cases (272 out of 413 sides). In the submandibular triangle, one or two large branches of the MN communicated with the lingual nerve at submandibular triangle and submental triangle in 1.45% of the cases (6 out of 413 sides). These distributions of nerve supply are an important in the operations of radical neck dissection on the submandibular triangle.

Distribution of tenascin-c and -X in rat TMJ development.

In the neonatal and postnatal development of rat TMJ, tenascin-C and -X were detected in the muscle, bone matrix, connective tissue around the bone, and blood vessel of rats at E18 (18-days old embryo), 0-, and 5-days postnatal. The reaction of tenascin-X was also found in the connective tissue around the mandibular condyle. The mRNA of tenascin-C (600 bp) and -X (588 bp) was also detected in the developmental muscle with the level of tenascin-C mRNA moderately decreased during development. Therefore, tenascin-C and -X may have different effects on the connective tissue during development of TMJ.