Search PubMed⌕ Search

Biomedical subjects

M Iwaku

Publications and source records attributed to M Iwaku.

At least 55 records · Page 3Linked to original sources
PubMed1992

Alveolar bone remodeling in the early stage of experimental apical periodontitis in the rat mandible.

Apical periodontitis was surgically induced in the mandibular first molar of rats and chronological changes in the periapical bone tissue were observed by histochemistry and electron microscopy. On the second postoperative day (Day 2), tartrateresistant acid phosphatase (TRACPase)-positive cells emerged on the bone surface facing the inferior alveolar nerve, whereas alkaline phosphatase (ALPase)-positive cells proliferated on the bone marrow surface of the mandibular canal wall. On Day 3, the active resorption of the mandibular canal wall appeared on the surface facing the inferior alveolar nerve. The bone of the upper wall of the canal was completely resorbed. On Day 4, however, numerous ALPase-positive cells emerged over the bone surface facing the inferior alveolar nerve intermingled with TRACPase-positive cells. On Day 5, repair of the upper wall of the mandibular canal by new bone progressed. Bone formation was also observed on the bone surface facing the inferior alveolar nerve. On Day 6, the upper wall of the mandibular canal was remodeled by the new bone, whereas TRACPase-positive cells had already migrated over the bone surface in the vicinity of ALPase-positive cells. From Days 2 to 5, active trabecular bone formation continued in the bone marrow cavity close to the mandibular canal, while TRACPase-positive cells were found only on Day 6. These demonstrate that inflammatory stimuli activate bone formation coupled with bone resorption, as well as direct trabecular bone formation without a bone resorption phase. A rapid bone turnover in the early stage of apical periodontitis is also suggested. We conclude that bone defects in apical periodontitis are not the result of sole bone resorption but rather, active bone remodeling.

Acid Phosphatase↗
PubMed1992

The effects of various clinical factors on marginal enamel micro-cracks produced around composite restoration.

In this study, enamel micro-cracks produced around composite restorations were observed on surfaces and vertical sections, using a stereomicroscope and a scanning electron microscope (SEM). The effects of various clinical factors, i.e. the curing system, the marginal form and the polishing period after filling, on the incidence of marginal enamel micro-cracks were examined. Enamel micro-cracks were observed on all of the class 1 and 5 composite restorations when the cavity had no marginal bevel and the restorations were polished immediately after filling. Enamel micro-cracks distributed approximately parallel to the cavity margin and located 0.01-0.3 mm from the restored cavity margin. The occurrence of enamel micro-cracks was higher in light-cured composite resin restorations than in chemical-cured ones, for non-beveled cavities when polished 10 min or 24 hours after filling. The occurrence of micro-cracks was reduced by marginal beveling and delayed polishing.

Composite Resins↗
PubMed1990

An ultrastructural study of the process of hard tissue formation in amputated dental pulp dressed with alpha-tricalcium phosphate.

This study was undertaken to determine the reaction of amputated dental pulp to the capping agent, alpha-tricalcium phosphate (alpha TCP), and to reveal the exact nature of the processes involved in both the healing of, and new hard tissue formation in the pulp when dressed with alpha TCP. The dental pulps of the anterior teeth of Macaca fuscata were dressed with alpha TCP ceramic 4-10 microns in diameter. The teeth were fixed by perfusion, then observed with light and electron microscopes. At 10 and 14 days postoperatively, the phagocytosis of the alpha TCP layer by the many macrophages and multinucleated giant cells, both of which had emerged beneath it, was seen. The synthesis of collagenous matrix underlying the alpha TCP layer began at 14 or 21 days, the cells involved exhibiting morphologic characteristics similar to those seen in osteoblasts. By the 90th day, only a bone-like hard tissue remained. No inflammation was observed in the residual dental pulp at any time during the experimental period. At 14 days, needle-like crystals were seen to have formed on the surface of alpha TCP particles, and by the 21st day, these crystals had extended to the newly synthesized matrix, with the result that calcification of the matrix was initiated, a calcified layer being superficially produced in the matrix. In the region of the matrix adjacent to the superficial calcified layer, a number of matrix vesicles were also found to function as another mechanism of matrix mineralization. Thus, it was concluded that the bone-like hard tissue was induced in the pulp capped with alpha TCP, and its potential for clinical application to exposed dental pulp was confirmed.

Animals↗
PubMed1989

Bactericidal efficacy of metronidazole against bacteria of human carious dentin in vivo.

The bactericidal efficacy of metronidazole (MN) against bacteria of carious dentin was estimated by measuring bacterial recovery with or without application of MN to dentinal lesions in vivo. More than 10(3) colony-forming units of bacteria per milligram of sample were recovered from the samples of carious dentin. However, none were recovered from the samples of dentinal lesions which had been covered by alpha-tricalcium phosphate (TCP) cement containing MN in situ for 1 day, 1 month, 1 year and/or 2 years in vivo. Placebo experiments in which carious dentin was covered by TCP cement without MN showed that TCP itself was not bactericidal. Bactericidal efficacy of MN in situ is clearly demonstrated, indicating that MN is a valuable material in caries treatment to disinfect carious dentin.

Adolescent↗
PubMed1989

Culture conditions for efficient recovery of bacteria from infected dental root canals.

For better bacterial recovery from endodontic lesions, several bacterial culture conditions were studied. Samples taken from endodontic lesions of 26 freshly extracted teeth, and the bacterial growth was determined in 11 kinds of growth media under aerobic (in air with or without addition of 5% CO2) or anaerobic conditions (in an anaerobic glove box). Among the media tested, bacteria of endodontic lesions were most efficiently recovered in brain heart infusion medium containing 4% sheep blood (BHI-Blood) under anaerobic conditions. For routine dental practice, serum can be substituted for blood which makes the media opaque, resulting in clear media, and thus bacterial growth can be judged more easily.

Bacteriological Techniques↗
PubMed1988

Bactericidal efficacy of metronidazole against bacteria of human carious dentin in vitro.

The bactericidal efficacy of metronidazole against bacteria in carious dentin was clarified by measuring (1) the difference between bacterial recovery from suspensions of carious dentin on metronidazole-containing BHI-Blood agar plates (10 micrograms/ml) and control plates and (2) the difference between bacterial recovery from carious lesions of freshly extracted teeth, covered by alpha-tricalcium phosphate (TCP) cement containing metronidazole (5%) for 1-3 days and that covered by TCP only. More than 10(3) bacteria per milligram sample were recovered from carious dentin. More than 99% of the bacteria were, however, not recovered when samples were inoculated on metronidazole-containing BHI-Blood agar plates or when the lesions were covered by TCP cement containing metronidazole, indicating that metronidazole effectively disinfected the carious dentin.

Bacteria↗
PubMed1983

The extent of the odontoblast process in normal and carious human dentin.

When observed by SEM, after being treated with the HCl-collagenase method, the odontoblast processes extended throughout the whole thickness of dentin in intact teeth and the whole thickness of normal and the inner carious dentin in carious teeth. Small holes and depressions were found on the processes in the transparent layer.

Adult↗
PubMed1983

Bovine teeth as possible substitutes in the adhesion test.

In order to find a substitute for human teeth in the adhesion test, the adhesive strength to bovine teeth was compared with that to human teeth using five dental cements and two composite resins. The adhesion to enamel and the superficial layer of dentin showed no statistically significant difference between human and bovine teeth, although the mean values were always slightly lower with bovine teeth. Adhesion to bovine dentin decreased considerably with the depth of dentin.

Adhesiveness↗
PubMed1982

A laboratory report on vibration etching for fissure sealants.

We have developed a vibration etching technique in which occlusal pits and fissures are simultaneously cleansed and acid-etched using a fissure needle mounted on an electromagnetic vibrator. When tested on extracted teeth, the needle completely cleansed the fissures by removing the contents and the prismless enamel layer, and widened them to from 100 to 150 micrometers to the depth reached by the needle. The sealant penetrated readily and adhered to the reduced and etched fissure walls interlocking with resin tags.

Acid Etching, Dental↗
PubMed1982

Pulpal response to a new adhesive restorative resin.

The pulpal response to a new adhesive restorative resin was histopathologically investigated using dogs, and was compared with a representative conventional resin. When filled without etching and cavity wall lining, bacterial penetration and pulpal response were less with the new resin. Lining of dentin walls and total etching of cavity walls, including dentin, caused less pulpal response under the new resin. Cavities which were totally etched and filled with the new resin showed only a slight pulpal response and no bacterial penetration.

Acid Etching, Dental↗
PubMed1981

Effectiveness of glazing composite resin restorations.

1. Microleakage was prevented when the margins of composite resin restorations were covered with a glaze. The microleakage occurred after the glaze was abraded and removed in vivo and in vitro. 2. The glaze margins gradually separated from the enamel as well as resin surfaces and fractured, creating steps which were apt to cause exogenous staining. 3. Although the glaze coated the restoration, thus producing a smooth surface, the roughness of the composite resin was exposed when the glaze was lost in the oral environment.

Composite Resins↗
PubMed1981

Tags penetrating dentin of a new adhesive resin.

The change of the dentinal tubules by acid-etching and the morphology and the adhering state of new adhesive composite resin tags penetrating the tubules were observed by SEM, comparing with the representative conventional composite resin. When the fractured surface of the unetched floor dentin were observed, all tubule entrances were closed by blocking with cutting debris up to 10 to 20 micrometers depth. Etching opened them by dissolving the debris and further widened the tubule entrances up to 10 to 20 micrometers depth by dissolving the peritubular dentin near the apertures. Resin tags penetrated 10 to 20 micrometers in vital teeth, 60 to 100 micrometers in freshly extracted teeth and several hundred micrometers in old extracted teeth. The tags of the new resin penetrating the tubules copied exactly the shape of the tubule walls, producing hollow depressions at the ends, indicating that the renin polymerized, adhering tightly to the walls, while those of the conventional resin produced highly tapered side walls with pointed ends, indicating that the resin shrank separating from the tubule walls on polymerization. The new resin did not produce any gap at the resin-dentin interface unlike the conventional resin.

Acid Etching, Dental↗