Biomedical subjects

Shigezo Hirano

Publications and source records attributed to Shigezo Hirano.

4 recordsLinked to original sources

PubMed2003

A new polyisoprene-based light-curing denture soft lining material.

OBJECTIVES: The purpose of this study was to investigate some clinically relevant properties of Clearfit LC, a newly developed polyisoprene-based light-curing lining material. Its properties were compared with those of other four commercial products. MATERIALS AND METHODS: Five soft lining materials, Clearfit LC, two plasticised acrylics (Super-soft, Soften) and two silicones (Molloplast B, Sofreliner) were used to determine water sorption, solubility, staining resistance, Shore A hardness and shear bond strength to denture base. Five specimens for each test were fabricated. The results of each test among the five materials were compared by one-way ANOVA and Scheffe's post-hoc test at alpha=0.05. RESULTS: One-way ANOVA of each test showed that the differences among five materials were significant (P<0.05). Clearfit LC showed the intermediate water sorption and solubility (10.07; 1.72 microg/mm(3)). It also showed the lowest color change in beta-carotene/olive oil solution and instant coffee solution (DeltaE=1.19, 5.48, respectively). The shear bond strength of Clearfit LC was 1.56MPa, and no adhesive failure was found. Its Shore A hardness value (56.2) was located between two acrylics and silicones. It was also found that the softer materials tend to failure cohesively. CONCLUSIONS: The polyisoprene-based lining material showed low water sorption and solubility, moderate softness, high staining resistance and satisfactory shear bond strength to denture base resin. It also provides clinicians sufficient working time due to its light-curing property. It would be an attractive alternative as a relining material.

Absorption↗

PubMed2002

[In vitro study on accuracy and repeatability of the T-Scan II system].

The T-Scan system has been used to analyze the distribution of occlusal loading forces, and occlusal contact variability. An enhanced version, the T-Scan II system, has been developed with clinical significance of its center of force. The T-Scan II system was also found to be clinically useful for measuring simultaneous occlusal contacts bilaterally. However, its improvement in accuracy and repeatability is still unknown. In the present study, the accuracy of time recordings, the liner relation between loaded forces and force recordings, the pressure sensitivity, and the variability of force recordings for repeated loadings, were investigated. The conclusions were as follows: 1. By regression analysis between the time and the time recording, the following equation was obtained: Y = 0.00357 + 0.9889 X R2 = 0.9964. The time recordings were proportion to the real time. 2. The force recordings were acceptably precise, especially for the moderately high level and default level, where a linear relation was observed. 3. The pressure sensitivity showed 6-61 g/cm2 for the high-4 level, 25-581 g/cm2 for the moderate-3 level, 56-1814 g/cm2 for the default level, and 146-3821 g/cm2 for the low-2 level. 4. The stability of force recordings for the repeated loadings was acceptable. A significant influence of repeated loading was found for the low-2 level; however, no significant difference was found between the repeated loadings, by post hoc analysis. On the contrary, the repetition of continuous loadings raised force recordings gradually, up to 120% at the fourth loading. The level of the force recordings stayed at the same level with no significant influence by repetition.

Bite Force↗

PubMed2002

[A clinical application of the T-Scan II system--usefulness for evaluating occlusal contacts of complete denture wearers].

The purpose of this study was to assess the reproducibility of the T-Scan II system and its clinical usefulness for evaluating occlusal contacts of complete denture wearers. The occlusal contacts of 13 dentate subjects, and 14 complete denture wearers, were recorded using a T-Scan II system during maximum voluntary clenching. The recordings for complete denture wearers were taken after each treatment for the new denture, and continued until the completion of all corrections. The recordings for complete denture wearers were analyzed using repeated measured ANOVA. In addition, the variables obtained with the system, the delta of the occlusal area and load, and the maximum-load time (MLT), which represented the time length taken to reach the occlusal load at the maximum level, were then compared between dentate subjects and complete denture wearers, using a t-test. The conclusions were as follows: 1. The standard errors values for both occlusal area and the load recordings for the dentate subjects were limited to within 10% of the means. 2. The values of the occlusal area and load significantly increased, and delta of the occlusal area and load significantly decreased, as the denture corrections were repeated. 3. The means of the MLT were about 0.3 seconds for dentate subjects, and 0.8 seconds for complete denture subjects. It was revealed that the T-Scan II showed acceptable reproducibility, and it was useful to evaluate occlusal contacts of complete denture wearers.

Adult↗

PubMed2002

Effects of a denture adhesive on masticatory functions for complete denture wearers--consideration for the condition of denture-bearing tissues--.

The purpose of this study was to examine effects of a denture adhesive on masticatory functions for complete denture wearers considering the condition of denture-bearing tissues. Sixteen edentulous subjects wearing well-fitting complete dentures volunteered to participate in this study. According to the condition of denture-bearing tissues, subjects were divided into two groups; "good group" and "poor group". Maximum biting forces, masticatory performance, and electromyography of the masseter muscle during mastication were recorded with and without a denture adhesive. Durations of chewing burst and cycle, and coefficients of variation for these variables were calculated using electromyography recordings. Data were analyzed by using two-way repeated-measured ANOVA and paired t-test in order to assess the effect of the use of a denture adhesive. The use of the denture adhesive increased maximum biting force and provided rhythmic masseter muscle activity during mastication for both groups. Masticatory performance was improved and duration of chewing burst was decreased only for "poor group". It was concluded that the effects of the denture adhesive on masticatory functions were observed overall for both groups, and more significant for denture wearers with poor denture-bearing tissues than with good denture-bearing tissues.

Adhesives↗