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Biomedical subjects

Y Akagawa

Publications and source records attributed to Y Akagawa.

103 records · Page 6Linked to original sources
PubMed1983

Changes in the pattern of SDH and PhR staining in fibres of rat masseter muscle following long-term functional stretch.

Histochemical changes in the three basic fibre types of the deep masseter muscle of the rat were studied following functional stretch due to increased vertical dimension of the occlusion. A large number of muscle fibres showed changing histochemical profiles for succinic dehydrogenase (SDH) and phosphorylase (PhR) during degeneration and subsequent regeneration of muscle fibres. On the other hand, a small number of muscle fibres with well defined sarcolemmas presented a normal pattern (i.e. low SDH and high or intermediate PhR activities) during this experiment. The ratio between the three basic fibre types remained unchanged after recovery of the muscle fibres. These results suggest that fast-twitch-oxidative-glycolytic and slow-twitch-oxidative fibres underwent degeneration and regeneration, while almost all the fast-twitch-glycolytic fibres retained normal SDH and PhR staining following functional stretch.

Animals↗
PubMed1983

Histologic changes in rat masticatory muscles subsequent to experimental increase of the occlusal vertical dimension.

Histologic changes in various masticatory muscles were studied in Wistar rats from 12 hours to 84 days after an experimental increase of the occlusal vertical dimension. The increases applied (1 to 2 mm) were based on the amount of interocclusal space (1 mm) in the rat. A sequence of tissue reaction from early acute inflammatory destruction of myofibers to healing with myofiber regeneration was most pronounced in the deep masseter muscle of the 2 mm group (12 hours to 21 days). A similar sequence was also observed to a lesser degree in the superficial masseter and anterior temporal muscles, while no changes were detectable in the posterior temporal, medial pterygoid, and anterior digastric muscles of this group. Variable severity of tissue response in different masticatory muscles might be attributable to the amount of stretching of myofibers as a result of an increased occlusal vertical dimension. On the other hand, degenerative atrophy of myofibers in the lateral pterygoid muscle occurred within 2 days with no sign of inflammation, and these condensed myofibers persisted as late as 84 days. Based on these findings, it was suggested that displacement of the mandibular condyle would exert an important influence on the prognosis after an increase in the occlusal vertical dimension. Only a transient acute inflammation occurred in the deep and superficial masseter muscles in the 1 mm group. Except for a small number of condensed myofibers in the lateral pterygoid muscle, degenerative changes of myofibers were not revealed. Therefore, increasing the occlusal vertical dimension within the extent of the interocclusal space might be regarded as appropriate for prosthodontic practices.

Animals↗
PubMedDate not supplied

Another anti-allergic mechanism: antibody IgE deglycosylation induced by a substance extracted from human urine.

Enzymically-deglycosylated antibody IgE lost its allergic activity in mouse systemic anaphylaxis, though the IgE kept its antibody activity. IgE antibody obtained from mice treated with a substance extracted from human urine was deglycosylated. This IgE also lost the allergic activity on the systemic anaphylaxis but kept its antibody activity. These findings strongly suggest that glycosylation of IgE has a close relation to the binding of the Fc receptor and that humans have another antiallergic mechanism: in vivo IgE antibody deglycosylation induced by the substance.

Allergens↗
PubMedDate not supplied

Correlation between quality of life and denture satisfaction in elderly complete denture wearers.

PURPOSE: This study was done to clarify the correlation between the quality of life (QOL), defined as overall satisfaction with daily life, and denture satisfaction in elderly complete denture wearers. MATERIALS AND METHODS: A new method for quantifying overall satisfaction with daily life (QOL) among 2,079 elderly people (age > or = 65 years) was developed by evaluating the contribution of 13 factors (eating, health problems, daily exercise, fatigue, sleep quality, smooth communication, physical comfort, aging, loneliness, job and hobbies, meaningfulness, social life, and economic problems) to overall daily life satisfaction by a multiple regression analysis. Then, correlation between the QOL and denture satisfaction was analyzed by the regression model in 84 randomly selected complete denture wearers from the above population. RESULTS: Quantification of the QOL was completed by converting category scores to integers between 0 and 100 for eight highly correlated factors (eating, smooth communication, physical comfort, loneliness, job and hobbies, meaningfulness, social life, and economic problems) to overall satisfaction with daily life (P < 0.01). Significant positive correlation was found between the QOL score and denture satisfaction score (P < 0.05). CONCLUSION: Edentulous elderly people who are well satisfied with their daily lives are also satisfied with their complete dentures.

Activities of Daily Living↗
PubMedDate not supplied

An investigation of preferable taper and thickness ratios for cast circumferential clasp arms using finite element analysis.

This study used a two-dimensional finite element method to investigate the preferred design for a cast circumferential clasp. Finite element models of the clasp arm with the constant flexibility were constructed, the stress was calculated, and the effects of taper and cross-sectional shape on stress were evaluated. The clasp arm with the taper of 0.8 showed less stress than those with other tapers, and the thinner and wider arms showed less stress than those with other cross-sectional dimensions. These results suggest that the use of the preformed clasp-pattern with a taper of 0.8 is preferable for reducing fatigue and/or permanent deformation of the clasp arm.

Chromium Alloys↗
PubMedDate not supplied

Finite element and Weibull analysis to estimate failure risk in resin-bonded retainers.

Three-dimensional finite element analysis and Weibull analysis were used to evaluate the effect of the thickness and the rigidity of the retainers on the risk of failure of an anterior resin-bonded prosthesis. Retainer thickness ranged from 0.4 to 1.4 mm. The physical properties of metals similar to Ni-Cr and type IV gold alloys were used. A concentrated load (100 N) was applied to the incisal edge of the finite element analysis modeled pontic, and the data of other loads (150 to 500 N in 50-N increments) were calculated from the data of 100 N. Subsequent Weibull analysis revealed that failure probability diminished when there was an increase in metal thickness at loads of 300 to 350 N, particularly for the retainer made of a type IV gold alloy. The reduction in failure probability caused by increasing the thickness of the metal was greater when type IV gold alloy was used than when Ni-Cr alloy was used. This investigation suggests that the longevity of resin-bonded retainers can be prolonged by thickening the retainers, rather than using more rigid metals.

Chromium Alloys↗
PubMedDate not supplied

The effects of a stress-absorbing system involved in the superstructure supported by hydroxyapatite-coated implants in monkeys.

To evaluate the effects of a stress-absorbing superstructure on the interface of an integrated implant, the bone/hydroxyapatite-coated (HA-coated) implant interface was histologically and histomorphometrically analyzed using monkeys. A total of 12 HA-coated implants were placed in the edentulous mandible of three monkeys. Polyurethane elastomer was selected as the stress-absorbing material. A superstructure incorporating a stress-absorbing system was placed on six implants (stress-absorbed group) and a superstructure without such a system was set on the other six implants (non-stress-absorbed group). After 12 months, undecalcified ground sections were prepared and the bone/implant interface was analyzed. Clinically, all implants in both groups were immobile and mild inflammation around the peri-implant gingiva was seen. Histologically, direct bone contact was observed around all of the implants in both groups. However, histomorphometrically, the amount of bone around implants was greater in the stress-absorbed group. Bone was more highly apposed to the implant at the apical portion than at the axial portion. These different findings could be the result of stress-breaking against functional loading to the bony interface of these HA-coated implants.

Alloys↗
PubMedDate not supplied

New connective tissue attachment formation on various biomaterials implanted in roots.

To determine whether connective tissue attachment can occur on implant materials by repopulating periodontal ligament (PDL)-derived cells and whether the new connective tissue attachments formation is influenced by the type of implant materials, periodontal tissue regeneration on four materials implanted into root cavities of cat canines was observed under conditions where PDL-derived cells could populate the surface of the materials. New connective tissue attachment occurred on bioactive materials such as bioglass and hydroxyapatite, while little or no cementum deposition was seen on bioinert materials such as titanium alloy and partially stabilized zirconium. Results showed that PDL-derived cells can form new connective tissue attachments on implant materials and that the formation of new connective tissue attachment is influenced by bioactivity of the materials.

Animals↗
PubMedDate not supplied

Correlation between mucosal inflammation and marginal bone loss around hydroxyapatite-coated implants: a 3-year cross-sectional study.

In this study, a possible correlation between peri-implant mucosal inflammation and marginal bone loss in a group of patients who received two-stage hydroxyapatite-coated dental implants was evaluated 3 years after implantation. Thirty-two implants were evaluated as to their Plaque Index, Gingival Index, and crevicular fluid volume. Patients were divided into three groups: a control group with no inflammatory signs; a borderline group with moderate inflammation; and a gingivitis group with an established inflammatory process. Three dental radiographs per implant were analyzed at 2 months, 9 months, and 3 years after implantation by measuring bone height at the mesial and distal sides. Preliminary results indicated increased bone resorption in the gingivitis group compared with the control and borderline groups at both the mesial and distal surfaces (P < .05), suggesting correlation between mucosal inflammation and marginal resorption observed around these implants. Statistical analysis of correlation between the assessed mucosal parameters and bone loss indicated significance for Gingival Index and crevicular fluid volume (P < .05).

Alloys↗
PubMedDate not supplied

An in vitro study of high-strength resin posterior denture tooth wear.

This in vitro study evaluated the wear resistance of a high-strength resin posterior denture tooth against eight opposing dental materials. The tooth specimen was cusp shaped and the opposing materials were formed as a 10 x 10 x 5 mm plate. All material combinations were tested using a machine designed to produce sliding contact 20 x 10(4) times at 60 cycles per minute and a 4-mm sliding distance per stroke in the buccolingual direction under a load of 1 kg. Wear analysis was measured as the total height loss of each material combination and the volume loss of each material. Wear against human enamel was evaluated as a control. The least loss was observed opposing a gold-silver-palladium-copper alloy, and the greatest loss was observed opposing porcelain. The volume loss of high-strength resin against gold-silver-palladium-copper alloy was as small as that against human enamel. High-strength resin wear was more significant against castable ceramics and porcelain. The volume losses of high-strength resin against high-strength resin, polycarbonate, or cobalt-chromium alloy were significantly larger than those against polyethersulfone, poly(methyl methacrylate), gold-silver-palladium-copper alloy, or human enamel. These findings suggest that the were resistance of high-strength resin is influenced considerably by opposing dental materials, and that the best combination was high-strength resin-gold-silver-palladium-copper alloy, and the poorest combination was high-strength resin-porcelain.

Analysis of Variance↗