Eubacterium exiguum is a bacterial species of asaccharolytic anaerobic Gram-Positive rods (AAGPR) that are frequently isolated from human oral lesions. To clarify the phylogenetic relationship among oral AAGPR, we determined 16S rDNA gene sequence of E. exiguum (the type strain ATCC 700122 and 3 clinical strains) and compared with those of related oral AAGPR, including Cryptobacterium curtum, E. brachy, E. minutum, E. nodatum, E. saphenum, Mogibacterium timidum (former E. timidum). The 16S rDNA sequence of E. exgiuum was high similarity between the type strain ATCC 700122 and 3 clinical strains (>99%) but clearly distinct from those of other oral AAGPR species and some typical oral Gram-Positive bacteria. Certain regions in the 16S rDNA were found to be common among 4 strains of E. exiguum but distinct from other bacterial species, thus the regions were species-specific. In fact, 5 pairs of primers (exg 129F and exg 576R, exg 129F and exg 605R, exg 129F and exg 1263R, exg 557F and exg 1263R, exg 586F and exg 1263R), of 13 primers prepared according to the species-specific regions, were effective for PCR amplification of 16S rDNA taken from E. exiguum strains, ATCC 700122, IT-b, TU-d and ABg-f, respectively. Among these, only one combination (exg 557F+exg 1263R) was found to be species-specific, because only that combination did not show any non-specific amplification with any DNA obtained from various oral bacterial strains, and the primer pair can be used to detect E. exiguu in various clinical samples.

View full abstract

To verify the function of noggin in the hard tissue formation of embryogenesis, expressions of noggin mRNA were studied by in situ hybridization.
In the early stage of somite formation, noggin mRNA appeared in the brain membrane and myotome around the sclerotome at the stage of E 11 days. Noggin mRNA was detected in the chondrogenic condensation with the formation of Meckel's cartilage. At the stage of calcification of Meckel's cartilage, chondrocytes at the resting stage and hypertrophic stage expressed intense mRNA. In the area of mandibular bone formation, the osteoblasts and subosteoblastic cells also showed an intense expression of noggin mRNA. The cells constituting periosteum expressed noggin mRNA intensively.
The expression of noggin mRNA was obscure in the tooth germ at the cap stage except for in the mesenchymal cells of the dental follicle. In the tooth germ at postnatal 5 days, the dental papilla cells, periodontal ligament cells and osteoblasts at the bifurcation to root showed gene expression.
During the development of skeletal cartilage, noggin mRNA was detected in chondrocytes at the resting stage, and the hypertrophic stage expressed intense mRNA. With ossification, the osteoblasts and subosteoblastic cells also showed an intense expression of noggin mRNA.

View full abstract

This study evaluated a case which was unsuccessful after guided bone regeneration (GBR) operation with non-resorbable barrier membranes in the extraction socket of a beagle dog. To clarify the relationship between bone and vascular regeneration, a vascular resin cast model was observed under a scanning electron microscope (SEM).
At 30 days post-operation, vessels from the periosteum were seen migrating to the socket through the gap between the membrane and the bone wall. The regenerated bone height was no higher than that of the pre-existing alveolar crest.
At 60 days post-operation, the height of the regenerated bone was in accordance with that of the Pre-existing bone. A vascular network of granulation tissue was seen between the membrane and the upper margin of the alveolar bone. This vascular network consisted of a densely arranged vascular loop. The tracing of the circulatory pathway revealed that this network was composed of arteries from the alveolar bone marrow and veins of large diameter, which drained to the oral mucosa. The surface of a granulation tissue vessel showed a rough configuration. Resin was found to be leaking from the vascular loops.
The study of this unsuccessful case clearly showed that the membrane was neither in close contact to the surrounding bone wall nor sufficiently supported by it. This resulted in an ingrowth of vessels from the periosteum to the socket. Consequently, there was no increase in bone height growth and new bone apposition did not occur. To succeed with GBR, it is essential that vascularization of the periosteum occur and that the membrane gradually cover and seal the extraction socket.

View full abstract

This is a morphological investigation of the influence of xylitol on remineralization in experimentally demineralized dental enamel. Materials were human third molars, the dental surfaces of which had been demineralized. The samples were immersed at 37°C for 2, 4, and 8 weeks in either a remineralizing solution (Ca: 1mM, P: 2mM, F: 0.2PPm) containing 10% xylitol or a remineralizing solution without xylitol. Specimens were then prepared as ground sections (100μm) and contact-microradiograms were obtained. Degrees of mineralization were measured by Multipurpose Image Processor. Results showed that, in the no-xylitol group, remineralization had occurred in the surface layer but not in the intermediate and deep layers. In the xylitol group, remineralization in the surface and deep layers after 2 weeks' immersion, was greater than that in the no-xylitol group. After 8 weeks' immersion, mineralization had decreased in the surface layer but had increased in the intermediate layers. Remineralization near the surface layer advanced because of crystal formation resulting from fluoride action. Xylitol additives working as calcium-ion carriers Possibly promoted remineralization in the intermediate and deep layers. The lowering of surface-layer remineralization after 8 weeks' immersion may indicate both inhibition of the crystal nucleation and the occurrence of demineralization in the outermost surface layer by xylitol.

View full abstract

The objective of the present study was to investigate the beneficial effects of xylitol chewing gum containing Gloiopeltis furcata extract and calcium hydrogenphosphate on remineralization of initial carieslike enamel lesions. Initial caries-like enamel lesions were artificially prepared by demineralizing human enamel blocks with a 0.01M acetate buffer (pH 4.0) at 50°C. We investigated sucrose gum (control), xylitol gum, and xylitol gum containing G. furcata extract and calcium hydrogenphosphate. In the in vitro intvestigation, the enamel blocks having initial caries-like enamel lesions were immersed in a remineralizing solution containing the extract of each chewing gum at 37°C for 2 weeks, and then evaluated for degrees of remineralization by contact microradiography. The remineralizing potential of each chewing gum in vivo was also evaluated by an oral device fixed with artificially demineralized human enamel block. Each subject was fixed on this device on the lingual surface of the mandibular molar for one week, and was given chewing gum samples 7 times a day. This in vivo study was carried out by the double-blind method.
It was found that xylitol gum enhanced the remineralization of initial caries-like enamel lesions, and that xylitol gum containing G. furcata extract and calcium hydrogenphosphate promoted the action of xylitol gum on remineralization. These findings suggest that adding G. furcata extract and calcium hydrogenphosphate to xylitol gum can amplify the remineralization effect of xylitol and can be expected to be effective in reducing dental caries.

View full abstract

The effects of dequalinium chloride (DC) and domiphen bromide (DB), which have an inhibitory action on water-insoluble glucan synthesis and an antibacterial action, on caries development were examined in male SD rats (ca. 50g) orally inoculated with S. sobrinus 6715. 0.02% DC solution, 0.02% DB solution or tap water (control) was administered ad libitum to the rats as drinking water for 54 days. The number of S. sobrinus cells adhering to molar surfaces was markedly less in the 0.02% DC and 0.02% DB groups than in the control group in the middle and latter test periods. The caries scores of smooth surface and sulcal lesions were lower in the 0.02% DC and 0.02% DB groups than in the control group, whereas those of proximal lesions were as follows, in decreasing order: 0.02% DB group>control group>0.02% DC group. When evaluated by the sum of the caries scores of the three lesions, the 0.02% DC- and 0.02% DB-induced suppression of caries development was 68% and 34%, respectively. There was no toxic effect of DC or DB on rats under the present experimental conditions. From these results, it can be considered that DC and DB inhibited caries development by decreasing the number of bacterial cells adhering to the teeth.

View full abstract