Biomedical subjects

M Iwaku

Publications and source records attributed to M Iwaku.

At least 37 records · Page 2Linked to original sources

PubMed1996

Immunolocalization of the small proteoglycan decorin in human teeth.

The immunolocalization of decorin was studied by confocal laser scanning microscopy and transmission electron microscopy. In the apical area of developing teeth, labelling for decorin was found in the dental papilla cells, prodontoblasts and also in the Hertwig's epithelial cells. Mantle dentine and the initial predentine were negative. In circumpulpal dentine, intense reactivity extended along the calcification front and dentinal tubules. Fluorescence was also evident in odontoblast cell bodies and their processes in predentine. None was perceived, however, in the predentinal matrix. Faint staining was observed on the calcified dentinal matrix. Immunoelectron microscopy revealed staining for decorin in collagen fibrils lining the predentine-dentine junction, and where arrays of labelled filaments were noted orthogonal to the collagen fibrils. Staining extending from the calcification front was observed in the matrix adjacent to the dentinal tubule. The decorin observed at the calcification front might regulate the mineralization of dentinal matrix.

Adult↗

PubMed1996

Sterilization of infected root-canal dentine by topical application of a mixture of ciprofloxacin, metronidazole and minocycline in situ.

The aim of this study was to observe the potential of a mixture of ciprofloxacin, metronidazole and minocycline to kill bacteria in the deep layers of root canal dentine in situ. After the crowns of extracted teeth had been removed, the drug combination (0.5 mg of each drug), or sterile saline, as the control, was placed in the root canals which had been previously irrigated ultrasonically with G4M EDTA. The penetration and bactericidal efficacy were estimated by various procedures as follows. (1) A cell suspension of E. coli was placed into small cavities prepared parallel to the root canals on the cut planes of nine single-rooted teeth. The teeth were then entirely covered with blue inlay wax. At time 0, and at 5h, 24h and 48h after the drug combination had been applied, cells of E. coli were recovered from the cavities by washing the cavities several times with sterile saline solution, and were cultured on the surfaces of heart-infusion (HI) agar plates. Total colony-forming units were tuen counted. Bacterial recoveries decreased with time, and no bacteria were recovered 48 h after application of the drug combination, while bacteria survived in all cases with the controls, (2) After the drug combination or sterile saline had been placed into and sealed in the root canal with blue inlay wax, the teeth were placed into HI agar plates where cells of E. coli had been inoculated. After culturing, a clear zone caused by the inhibition of bacterial growth was observed around the teeth, but not in the control experiment. (3) After sampling infected root dentine of 12 freshly extracted teeth as positive controls, the drug combination (0.5 mg each) was placed in the root canals. No bacteria were recovered from the infected dentine of the root canal wall 24 h after application of the drug combination, except in one case in which a few bacteria were recovered. On the basis of these results, penetration through dentine and antibacterial efficacy of the drug combination can be expected against bacteria infecting the dentine of the root canal wall in situ when the drugs were placed in root canals which had been irrigated ultrasonically.

Anti-Bacterial Agents↗

PubMed1996

In-vitro antibacterial susceptibility of bacteria taken from infected root dentine to a mixture of ciprofloxacin, metronidazole and minocycline.

The aim of this study was to clarify the antibacterial effect of a mixture of ciprofloxacin, metronidazole and minocycline, with and without the addition of rifampicin, on bacteria taken from infected dentine of root canal walls. The efficacy was also determined against bacteria of carious dentine and infected pulps which may the precursory bacteria of infected root dentine. This efficacy was estimated in vitro by measuring bacterial recovery on BHI-blood agar plates in the presence or absence of the drug combination. Bacteria ranging in number from 10(2) to 10(6) occurred in samples of infected root dentine (27 cases). However, none was recovered from the samples in the presence of the drug combination at concentrations of 25 micrograms ml-1 each. The respective drug alone (10, 25, 50 and 75 micrograms ml-1) substantially decreased the bacterial recovery, but could not kill all the bacteria. Bacteria taken from carious dentine (25 cases) and infected pulps (12 cases) were also sensitive to the drug combination. These results may indicate that the bactericidal efficacy of the drug combination is sufficiently potent to eradicate bacteria from the infected dentine of root canals.

Anti-Bacterial Agents↗

PubMed1996

Immunohistochemical localization of HLA-DR-positive cells in unerupted and erupted normal and carious human teeth.

Class II major histocompatibility complex (MHC) antigen-expressing cells are generally associated with the early phase of the immune response. We have studied the distribution of class II-expressing cells in developing, normal, and carious human teeth to clarify when human pulp acquires an immunologic defense potential and how this reacts to dental caries. Antigen-expressing cells were identified immunohistochemically by means of HLA-DR monoclonal antibody. In the pulp of unerupted developing teeth, numerous HLA-DR-positive cells were distributed mainly in and around the odontoblast layer. In erupted teeth, HLA-DR-positive cells were located, for the most part, just beneath the odontoblast layer, with slender cytoplasmic processes extending into the layer. Superficial caries lesions caused an aggregation of HLA-DR-positive cells in dental pulp corresponding to the lesion. In teeth with deeper caries lesions, this aggregation of cells expanded to include the odontoblast layer. Also noted were HLA-DR-positive cells lying along the pulp-dentin border, with cytoplasmic processes projecting deep into the dentinal tubules, where they co-localized with odontoblast processes. These findings suggest that: (1) human dental pulp is equipped with immunologic defense potential prior to eruption; (2) in the initial stage of caries infection, an immunoresponse mediated by class-II-expressing cells is initiated in human dental pulp; and (3) HLA-DR-positive cells trespass deep into dentinal tubules as the caries lesion advances.

Adolescent↗

PubMed1996

Immunolocalization of fibronectin during reparative dentinogenesis in human teeth after pulp capping with calcium hydroxide.

Exposed dental pulp is known to possess the ability to form a hard-tissue barrier (dentin bridge). The exact mechanisms by which pulp cells differentiate into odontoblasts in this process are unknown. Fibronectin has been demonstrated to play a crucial role in odontoblast differentiation during tooth development. This study tested the hypothesis that fibronectin is involved in the initial stages of replacement odontoblast differentiation and reparative dentin formation. We observed its immunohistochemical localization during dentin bridge formation in human teeth, after pulp was capped with calcium hydroxide [Ca(OH)2]. One day after the capping, precipitation of crystalline structures was observed at the TEM level in association with cell debris at the interface between the superficial necrotic zone and underlying pulp tissue. This layer of dystrophic calcification showed positive reaction for fibronectin, and pulp cells appeared to be closely associated with this layer, seven to ten days post-operatively. At 14 days, an alignment of cells, some of which were elongated and odontoblast-like, was observed adjacent to the fibronectin-positive irregular matrix. Between the cells, corkscrew fiber-like fluorescence was visible. At 28 days, the irregular fibrous matrix was followed by the formation of tubular dentin-like matrix lined with odontoblast-like cells. Therefore, it would seem that fibronectin associated with the initially formed calcified layer might play a mediating role in the differentiation of pulp cells into odontoblasts during reparative dentinogenesis, after pulp was capped with Ca(OH)2.

Adult↗

PubMed1995

Immunoelectron-microscopic study of the localization of fibronectin in the odontoblast layer of human teeth.

Indirect immunofluorescence-based studies have shown similarities in the distribution patterns of fibronectin-positive fibrous structures and so-called von Korff fibres. The aim of the present study was to analyse the reactivity of fibronectin in the odontoblast layer of fully developed human teeth by means of immunoelectron microscopy. Between the odontoblasts, discrete and undulatory fibrillar fascicles with peroxidase labelling were observed. They seemed to be in contact with odontoblasts in some areas, while in others they appeared to be intervening between two neighbouring odontoblasts. Higher magnifications of the fibrillar material demonstrated axial periodic staining of about 70 nm. Peroxidase reaction of fibronectin was also recognized along the cell membrane of odontoblasts facing predentine. The fibronectin in fibrillar fascicles observed between odontoblasts would be held in place by the direct molecular interaction with collagen fibrils and contribute to the pulpward migration of these cells and maintenance of their specific morphology. At the distal end of odontoblasts, a tight seal would be maintained by means of odontoblast-fibronectin adhesion.

Actin Cytoskeleton↗

PubMed1995

Effects of antibacterial capping agents on dental pulps of monkeys mechanically exposed to oral microflora.

The effects of antibacterial drugs on bacterially contaminated dental pulps were investigated in monkeys. Class V buccal cavities with pulpal exposures were prepared and then left open to the oral environment for 24 h. The exposed pulps were capped with alpha-tricalcium phosphate (alpha-TCP) containing a mixture of antibacterial drugs. Either alpha-TCP or Ca(OH)2 was used as a control. Pulpal responses were histologically evaluated after 4 wk. Those teeth capped with alpha-TCP alone showed total pulp necrosis and bacterial growth within the pulp chamber. By contrast, the pulps capped with alpha-TCP containing mixed antibacterial drugs remained almost normal without any necrotic layer, but showed persistent absorbing response to capping materials and no signs of hard tissue barrier formation. In teeth capped with Ca(OH)2, a hard tissue barrier was formed below the exposure site, with a wide loss of pulp tissue. No inflammation was seen under the barrier. These results indicate that mixed antibacterial drugs added to alpha-TCP effectively disinfected pulpal lesions, without destroying any of the sound pulp tissue. However, hard tissue barrier formation was delayed by this mixture as compared with Ca(OH)2.

Animals↗

PubMed1994

The metabolism of phenylalanine and leucine by a cell suspension of Eubacterium brachy and the effects of metronidazole on metabolism.

Degradation of phenylalanine and leucine by resting cells of Eubacterium brachy ATCC 33089 were studied under strict anaerobic conditions. The effects of metronidazole and air on the metabolism were also studied. The organism principally produced phenylpropionate and isocaproate from phenylalanine and leucine, respectively. Other products were cinnamate and phenylacetate from phenylalanine, and alpha-ketoisocaproate and isovalerate from leucine. The organism also produced hydroxylated end-products, i.e. phenyllactate from phenylalanine and hydroxyisocaproate from leucine. When metronidazole was added to the reaction mixture, the production of phenylpropionate, cinnamate, phenylacetate, isocaproate, alpha-ketoisocaproate and isovalerate was inhibited, while that of hydroxylated products was not, suggesting that the organism has metronidazole-sensitive and -tolerant pathways of metabolism. A similar inhibitory effect was also found when the reaction was done aerobically, suggesting that the inhibitory mode of metronidazole is similar to that of oxygen.

Aerobiosis↗

PubMed1994

A confocal laser scanning microscopic study of the immunofluorescent localization of fibronectin in the odontoblast layer of human teeth.

The distribution of fibronectin in dental pulp was studied in developing and developed human teeth by indirect immunofluorescence using a confocal laser scanning microscope. In the apical region of developing teeth, intense fluorescence was found along the basement membrane facing the mesenchyme of Hertwig's epithelial sheath and first-formed (mantle) predentine. With further elongation of odontoblasts, fibronectin was observed between the cells, appearing as corkscrew fibres passing from the pulp into predentine parallel to the long axis of the odontoblasts. In the coronal region of developing and developed teeth a similar distribution of fibronectin was observed in the odontoblast layer. At the border zone between odontoblasts and predentine the reaction was intense, but was weak in the predentine itself. In the calcified dentinal matrix it had disappeared completely, except for the area along the dentinal tubules. The results demonstrate that fibronectin is present in the odontoblast layer during all stages of dentinogenesis. Fibronectin-positive fibrous structures between odontoblasts probably correspond to von Korff fibres, and are closely related to odontoblast differentiation and dentinogenesis.

Adult↗

PubMed1994

Bacteria invading periapical cementum.

The aim of this study was to determine whether microorganisms invade periapical cementum of human teeth from the adjacent periapical lesions. We therefore attempted to isolate microorganisms from periapical cementum through the adoption of standard anaerobic procedures for obligate anaerobes. Samples of cementum were taken from 10 amputated tooth roots at the time of apicoectomy. From two of these samples, bacteria were recovered after anaerobic incubation, but no bacteria were recovered after aerobic incubation of the same samples. Of a total of eight isolates from the cementum, seven were obligate anaerobes and one was aerotolerant. The obligate anaerobes isolated were assigned to the genera Prevotella, Peptostreptococcus, Eubacterium, and Fusobacterium. The aerotolerant anaerobe was Campylobacter. From this, we conclude that bacteria can successfully invade cementum via periapical periodontal tissue, and that such bacteria may play a significant role in chronic periapical pathosis.

Actinomyces↗

PubMed1994

Histological observations of hard tissue barrier formation in amputated dental pulp capped with alpha-tricalcium phosphate containing calcium hydroxide.

This study was performed to evaluate the pulpal response to alpha-tricalcium phosphate (alpha TCP) containing calcium hydroxide (Ca(OH)2). The dental pulps of monkeys were amputated and dressed with four agents: alpha TCP, alpha TCP containing 1% Ca(OH)2, alpha TCP containing 5% Ca(OH)2, and Ca(OH)2 being used as a control. The pulpal responses were histologically evaluated after 4 and 8 weeks. The pulp tissue treated with alpha TCP proliferated above the level of the original wound surface, and a thin layer of hard tissue barrier was formed directly against the capping agent. The barrier demonstrated atubular matrix lined with flattened or cuboidal cells, but occasionally appeared irregular in form. Ca(OH)2 dressing resulted in destruction of pulp tissue, with a thick hard tissue barrier being formed below the level of the exposure site. The barrier consisted coronally of osteodentin and pulpally of tubular dentin lined with odontoblast-like cells. By contrast, 1% Ca(OH)2 added to alpha TCP produced a slight proliferation of pulp tissue. An atubular matrix barrier, pulpally lined with cuboidal cells, formed above the exposure site. It was later followed by the formation of tubular matrix lined with columnar cells. Teeth treated with 5% Ca(OH)2 showed a thin necrotic layer and a thick barrier formation. The barrier was composed of tubular dentin-like tissue lined with odontoblast-like cells. It would appear that alpha TCP containing a small amount of Ca(OH)2 may be clinically useful as a capping agent, as it induced consistent hard tissue formation, without excessive destruction of underlying pulp tissue.

Animals↗

PubMed1994

In vivo wear pattern of experimental composite resins containing different filler components.

Using a scanning electron microscope (SEM) and an electron probe surface roughness analyzer (ERA), we conducted the in vivo study of the effect of various filler components on the wear of composite resins. Experimental light-cured composite resins were prepared employing three different filler components; -(1) Silica type, (2) Strontium type, and (3) Barium type. The filler content for all three types was 80 wt%, with the mean particlesize being 2.6 microns in diameter. The resin monomers consisted of 40 wt% Bis-GMA, 40 wt% TEGDMA and 20 wt% UTMA. These materials were placed in 2 mm diameter cylindrical cavities located in the OCA (occlusal contact area) or the CFA (contact free area) of cast crowns temporarily set in a volunteer patient's mouth. The crowns were removed at monthly intervals for longitudinal SEM observation. After two months, worn surfaces were also analyzed by ERA. The result showed that the wear patterns of the composites were characterized by the filler components, especially in the OCA.

Adult↗

PubMed1993

Pulpal response to a new light-activated fluoride releasing liner.

The purpose of this study was to investigate the degree of pulp irritation of a newly developed light-activated fluoride-releasing adhesive resin liner using canine teeth compared to the amount caused by a negative control, zinc oxide eugenol cement (ZOE), and a positive control, silicate cement (silicate). In the cases of unexposed pulp, this experimental liner showed none, slight or moderate pulpal changes at 3 d postoperatively. At 30 and 90 d, no pulpal response to the experimental liner was detected in almost all cases. These findings were similar to the ZOE and better than the silicate. There was less evidence of pulpal irritation produced by the experimental liner. This material seems to be safe to the pulp under the conditions of this study.

Analysis of Variance↗

PubMed1993

In vivo wear pattern of experimental composite resins based on different resin monomers.

This study investigated the effects of various monomer systems on composite resin wear in vivo. Experimental light-cured composite resins were prepared employing four different monomer systems: (1) Bis-GMA type, (2) D-2. 6E type, (3) UDMA type, (4) UTMA type. The resin monomers consisted of 70wt% main monomer and 30wt% TEGDMA. These composites contained 80wt% fine quartz. The resins were placed in 2 mm diameter cylindrical cavities located in the occlusal contact area or the contact free area in cast crowns, temporarily set in a mouth. The crowns were removed at monthly intervals, for longitudinal SEM observation. Two months after setting, wear was analyzed, using an electron probe surface roughness analyzer. Microabrasion of the resin matrix and loss of filler particles were observed for all types of monomer systems. The effect of matrix resin systems on occlusal wear was smaller than that of filler systems.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1993

In vivo wear pattern of experimental light-cured hybrid composite resins.

This study evaluated the effect of various types of microfiller on the in vivo wear resistance of composite resins. Experimental light-cured composites with two different microfiller systems were prepared: (1) 56 wt % fine quartz filler, 21 wt% organic filler and 3 wt% colloidal silica filler (Hybrid type 1), and (2) 64 wt% fine quartz filler and 21 wt% colloidal silica filler (Hybrid type 2). The resin monomer consisted of 50 wt % Bis-GMA and 50 wt% TEGDMA. These materials were placed in 2 mm diameter cylindrical cavities located in the OCA (occlusal contact area) or the CFA (contact free area) in cast gold-silver-palladium alloy full coverage crowns, which were temporarily set in a volunteer patient's mouth. The crowns were removed at monthly intervals for SEM observation. Hybrid type 1, which contained organic fillers, showed bulk fractures in the OCA, by the second month of the experiment. However, reinforcement of the resin matrix by dispersion of microfiller provided Hybrid type 2 with superior wear resistance for up to two months.

Adult↗

PubMed1993

Direct observation of in vivo wear of composite resins.

This study developed a simple method for in vivo evaluation of wear on composite resins and examined the role of filler particles in this process. Experimental light-cured composite resins with two different filler systems were prepared: (1) 81 wt% fine quartz filler (Conventional type) and (2) 73 wt% organic filler (Microfilled type). The resin monomer consisted of 50 wt% Bis-GMA and 50 wt% TEGMA. These materials were placed in cylindrical cavities 2 mm in diameter located in the OCA (occlusal contact area) or the CFA (contact free area) in Au-Pd crowns, temporarily set in a volunteer's mouth. The crowns were removed at monthly intervals for longitudinal SEM observation. Results showed that the newly developed method was useful for observing the in vivo wear-patterns of composite resins. The two experimental composite resins with different filler systems showed quite different wear-patterns.

Adult↗

PubMed1992

A new light-activated adhesive composite: shear bond strength and microleakage.

A new light-activated adhesive composite has been formulated. Its shear bond strength and marginal microleakage were compared with glass ionomer cements: Fuji Ionomer Type II, Ketac-Fil and Ketac-Bond. The new material showed significantly (p < 0.05) higher bond strength to non-etched enamel (7.9 MPa) and dentin (7.3 MPa) than commercially available materials. It also performed significantly better (p < 0.05) in the microleakage test. Ease of use and the excellent marginal sealing ability of the new material are expected to allow considerable innovation in restorations of root caries, cervical erosion and other conditions where the marginal seal of the gingival cavosurface is difficult.

Aluminum Silicates↗

PubMed1992

A new light-activated adhesive cavity liner: an in vitro bond strength and microleakage study.

A new formulation of a light-activated calcium hydroxide-based cavity liner was developed for this study. Its shear bond strength and marginal microleakage in a Class V cavity preparation were compared to those of commercially available light-activated liners and conventional glass ionomer liners: GC Lining Cement (GC), Ketac-Bond (ESPE), Time Line (Caulk), Vitrabond (3M), XR lonomer (Kerr), and Zionomer (DenMat). The new formulation had significantly higher shear bond strength to dentin than the commercially available materials. Its microleakage along gingival (cemento-dentin) walls was statistically equivalent to one of the other materials and significantly better than all the others.

Analysis of Variance↗