Micro-computed tomography analysis of the relationship between root canal number and root concavity in maxillary first and second molars in a Japanese population.

PURPOSE: The aim of this study was to investigate root canal configurations in maxillary first and second molars from a Japanese population, as well as the relationship between the root canal number and root concavity depth, using micro-computed tomography. METHODS: Maxillary first (N = 74) and second (N = 70) molars from a Japanese population were used. Virtual horizontal sections were created, and the number of root canals and the degree of root concavity were measured. Mesiobuccal (MB) roots were categorized into Group 1 (with a single root canal) or Group 2 (with two or more root canals). The relationship between the root canal number and root concavity depth was evaluated using the Mann-Whitney U test. RESULTS: Approximately 51% and 35% of the MB roots in the three-rooted maxillary first and second molars, respectively, had two or more root canals. The depths of the root concavities in maxillary first molars differed significantly between Groups 1 and 2 at the mesial and distal sides of the MB root, in the section 2 mm apical to the furcation area (p < 0.05). CONCLUSIONS: A significant relationship between the number of root canals and the depth of root concavity in the MB root of the maxillary first molars was observed. Close clinical monitoring is needed during the removal of calculus and cleaning of the root surfaces of maxillary first molars: specifically, excessive removal of cementum and dentin should be avoided, particularly when the molar has already undergone root canal treatment.

Age-related changes of the ultrastrucure in the parathyroid gland of the golden hamster.

We qualitatively and quantitatively investigated the parathyroid glands of golden hamsters aged 6, 12, 18, 24 and 30 months. Percent area of rER in the parathyroid gland in golden hamsters at 24 months of age was significantly higher when compared to 6 and 12 months of age, and the percent area at 30 months of age was significantly higher when compared to 12 months of age, but there were no significant differences between 24 and 30 months of age. Percent area of the Golgi apparatus at 24 and 30 months of age was significantly higher when compared to 6, 12 and 18 months of age. Ultrastructurally, we believe that in the parathyroid gland of the golden hamster, synthesis and release of parathyroid hormone increase gradually from 6 to 24months of age and are maintained from 24 to 30 months of age.

Confocal laser scanning microscopic analysis of ectopic sublingual gland-like tissue inside the hamster submandibular gland.

Based on its histochemical properties, the secretory portion of the hamster submandibular gland has been classified as seromucous cells. The presence of endogenous peroxidase (PO) reaction was shown in the nuclear envelope, cisternae of endoplasmic reticulum and Golgi apparatus. The 3,3'-diaminobenzidene, tetrahydrochloride (DAB) method revealed bipartite secretory granules containing a PO-positive dense core surrounded by a less dense halo in these cells. In the present investigation, serous and mucous-like cells were found in resin-embedded semi-thin sections of the DAB-reacted hamster submandibular gland. These sections were already on glass slides for routine light microscopic observations, therefore electron microscopic analysis could be unrealizable. We then used reflectance-mode confocal laser scanning microscopy to visualize additional sites of PO activity as detected in these sections. Using this approach, we found mucous cells with PO activity-negative secretory granules and seromucous cells with PO activity-positive spot-like secretory granules of the regular sublingual gland most frequently adjacent to the serous cells with typical electron-dense secretory granules. These cells clearly differ from the seromucous cells with bipartite secretory granules and the granular duct cells with typical electron-dense secretory granules of the hamster submandibular gland. Additionally, secretory endpieces of the ectopic sublingual gland-like tissue empty into the duct of the hamster submandibular gland lobule. Thus, our findings suggest that a mass of sublingual gland tissue extends into the hamster submandibular gland during its development, and PO may be synthesized and secreted into the same duct.

EFTEM cytochemistry and sexual dimorphism of secretory granules in male and female hamster submandibular glands.

After glutaraldehyde fixation followed by osmium tetroxide postfixing, the secretory granules of acinar cells in male hamster submandibular glands (SGs) exhibit a characteristic bipartite substructure, with an electron-lucid rim and a more electron-dense central core. In female hamsters, the reverse is seen, with the larger portion of the granules forming an electron-lucid core and an outer electron-dense crescent rim. In the present study of endogenous peroxidase (PO) activity of male and female hamster SGs, secretory granules in the acinar cells were studied by DAB cytochemical technique. Individual granules showed bipartite substructure with the PO activity in a positive center core and unreacted lucid rim in both the male and the female acinar cells. Through isolation of granular fractions, the male and the female granules exhibited the same bipartite structure. We also examined the relation between the PO activity and counterstained areas in male and female hamster SGs, and the secretory granules of acinar cells by using EFTEM. In the male SG, the secretory granules exhibited the characteristic bipartite substructure to carry out parallel-EELS, nitrogen reflecting the presence of DAB moieties and uranium from counterstaing the presence the central core but not in the rim. On the other hand, the female bipartite secretory granules of the SG, exhibit the nitrogen reflecting the presence in the central core and uranium in the rim.

Light and electron microscopic histochemistry of the peroxidase activity in the secretory granules of the developing hamster submandibular gland.

On the basis of light and electron microscopic observations of the post natal development of the hamster submandibular gland, granules in the acinar cells showed considerably variations in size and shape, as well as electron density of the peroxidase-positive reaction. The present study shows that secretory granules of the hamster submandibular gland undergo changes of area and of intensity for peroxidase activity 6 months after birth.

Cytochemical detection of endogenous peroxidase in the intralobular ducts of hamster major salivary glands.

Light and electron microscopic cytochemical investigation of endogenous peroxidase activity in the intralobular ducts of hamster major salivary glands was carried out using the diaminobenzidine-hydrogen peroxidase method. The peroxidase reaction product was localized in the nuclear envelope, the cisternae of the endoplasmic reticulum, the Golgi apparatus and secretory granules in both the intercalated duct cells and the striated duct light cells of all glands. These results suggest the ability of the intralobular duct cells to secrete peroxidase the same as that of acinar cells in hamster salivary glands.