Taste preference, a key component of food choice, changes with aging. However, it remains unclear how this occurs. To determine differences in taste preference between rats in different life stages, we examined the consumption of taste solutions and water using a two-bottle test. Male Sprague-Dawley rats of different ages were used: juvenile (3–6 weeks), young adult (8–11 weeks), adult (17–20 weeks), middle-aged (34–37 weeks), and old-aged (69–72 weeks). The intakes of the high and low concentration solutions presented simultaneously were measured. We observed that the old-aged group had lower preference ratios for 0.3 M sucrose and 0.1 M MSG in comparison with other groups. The preference ratio for 0.03 mM QHCl was higher in the middle-aged group than in the three younger groups and higher in the old-aged group than the juvenile group. The taste preferences for HCl and NaCl did not significantly differ among the age groups. The old-aged group tended to prefer high concentrations of sucrose, QHCl, NaCl, and MSG to low concentrations, indicating age-related decline in taste sensitivity. We also aimed to investigate differences between life stages in the electrophysiological responses of the chorda tympani nerve, one of the peripheral gustatory nerves, to taste stimuli. The electrophysiological recordings showed that aging did not alter the function of the chorda tympani nerve. This study showed that aging induced alterations in taste preference. It is likely that these alterations are a result of functional changes in other peripheral taste nerves, the gastrointestinal system, or the central nervous system.

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We concluded that the present GBR method enhanced HMS0014 cells to initiate an osteogenesis process with a direct bone-to-substratum contact on Ti discs which were subject to different surface modifications.

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To evaluate the morphology of dental arches, 53 (male: 29, female: 24) paired casts having normal dentitions and occlusion were selected from 396 (age: 18 to 26 years old; male: 257, female: 139) sets of dental study models. The mandibular dentitions were preliminarily classified as square, round-square, round and round V-shaped arches based on the conventional morphological descriptions. Midpoints of the incisor edge (I1R, I1L, I2R, & I2L), summits of the cuspids (CR & CL), buccal cusps of the premolars (P1R, P1L, P2R, & P2L), mesial buccal cusps of the first and second molars (M1R, M1L, M2R, & M2L), and the midpoint (A) of line I1R-I1L were designated as reference points. From A, let a vertical line intersected line M2R-M2L at reference point B. The line A-B intersected CR-CL at reference point E. We evaluated 1) the protrusion of the cuspids by 1. angle I2R-CR-P1R (angle R) + angle I2L-CL-P1L (angle L); 2) the curvature of the anterior teeth by 2. (A-B)/(CR-CL), 3. (180 degrees-angle(CR-A-CL), and 4. (A-E)/(CR-CL); 3) the length to width ratio of the dental arch by 5. (A-B)/(M2R-M2L); 4) the degree of roundness of the mandibular arch by estimation of 6. (rtheta5 - rtheta4)R + (rtheta5 - rtheta4)L; and 5) an item 7. for the differentiation of type I and type II round-square arches by relating the bilateral contour and position of break line P1-P2-M1-M2 (i) to line P1-M2 (ii). The data of items 1., 2., 3., 4., 5., and 6. were further standardized and summarized into three essential principal components: 1) the curvature of the anterior teeth, 2) the curvilinear contour of the dental arch, and 3) the length-to-width ratio of the dental arch. The results indicated that: 1) 36 cases (67.9%) of the mandibular dentitions were round-square arches which showed no prominent principal component. 11 cases (20.8%) were square arches and 6 cases (11.3%) were round V-shaped arches; no round arches was found in mandibular dentitions. 2) Statistical analysis indicated significant differences of items 3., 4. and 6. in various mandibular arches (Student's t-test). 3) By examination of the three principal components, significant differences of item 5. between the round V-shaped arches and square and round-square mandibular arches were evident (Student's t-test). The present study elucidated that morphology of the mandibular arch was determined by a parameters representing the curvature of anterior teeth (composed of items 2., 3. and 4., and another parameter (item 6.) representing roundness of the mandibular arch.