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ABSTRACT: Masticatory performance of denture wearers was compared with that of the normal subjects by analyzing the behavior of the mechanical properties of the bolus. The index of the ability to comminute bolus was described as the total number of masticatory strokes until swallowing and therefore this was chosen as the first index. Principal Component Analysis (PCA) on the data of six parameters; 80% energy, elasticity, viscosity, hardness, adhesiveness, and cohesiveness, indicated that the cohesiveness was independent of the other parameters and should be evaluated as the second index of the ability to dilute bolus with saliva. Two factor scores of the other parameters were calculated using the standardized scoring coefficient obtained from PCA and factor analysis on the data of the normal subjects, which realized to compare two groups on the same plane of factor scores. The movement of factor scores on the factor plane would indicate the total behavior of mechanical properties of bolus and was chosen as the third index of the ability to knead bolus. Triangle Diagram (TD) was completed by using these three indices. On the TD, all the subjects were lower level at least in one index than the normal subjects in all the foods.
Journal of medical and dental sciences 10/2008; 55(3-4):227-46.
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ABSTRACT: The aim of this study was to investigate changing mechanical properties of the bolus during mastication and to quantify mechanical properties of the final bolus at swallowing. Changing mechanical properties of the bolus of three different types of foods (rice cracker, cheese and peanuts) by twelve normal dentitions were investigated by principal component analysis (PCA) on six mechanical properties (rupture energy, elasticity, viscosity, hardness, cohesiveness and adhesiveness). The raw data of cohesiveness immediately before swallowing was always constant. In all three food samples, the results by PCA on six parameters indicated that cohesiveness was independent from the remaining five parameters, and two factors were extracted on these five parameters by PCA. Furthermore, factor structure of bolus at swallowing showed no difference between the three food samples in spite of the variations in the raw data. The mechanical properties of swallowable bolus were clarified for the first time.
Journal of medical and dental sciences 07/2008; 55(2):197-206.
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ABSTRACT: The effect of different polishing materials on the surface texture and the color change of indirect prosthetic resin composite materials exposed to a staining agent was studied. Six different resin composites were polished using the same procedures and were measured for the gloss. After exposed to a coffee solution, the changes were measured on the color properties. The six different types of resin composites were further divided into four groups of eight specimens each for the different surface polishing procedure. The gloss was measured by a gloss meter (TC-108D, Tokyo-Densyoku, Tokyo, Japan) with an angle of 45 degrees and expressed in gloss units (GU). Before and after exposure to the staining agent, the color measurements of all specimens were recorded with a colorimeter (TC-1800MKII, Tokyo-Densyoku, Tokyo, Japan) using CIE L* a* b*. All specimens were stored in the coffee solution for 5 weeks at 37 degrees C. Most of the resin composites showed the highest gloss and staining resistances when the fine silicone diamond polishing point was used. The results of this study suggested that there are differences in the gloss and the color changes depending on the filler type and the composition of the polishing materials.
Journal of medical and dental sciences 03/2008; 55(1):1-6.
