Previous studies have identified various factors related to masticatory performance. This study was aimed to investigate variations and impacts of factors related to masticatory performance among different occlusal support areas in general urban population in Japan. A total of 1875 Japanese subjects (mean age: 66·7 years) were included in the Suita study. Periodontal status was evaluated using the Community Periodontal Index (CPI). The number of functional teeth and occlusal support areas (OSA) were recorded, and the latter divided into three categories of perfect, decreased and lost OSA based on the Eichner Index. Masticatory performance was determined by means of test gummy jelly. For denture wearers, masticatory performance was measured with the dentures in place. The multiple linear regression analysis showed that, when controlling for other variables, masticatory performance was significantly associated with sex, number of functional teeth, maximum bite force and periodontal status in perfect OSA. Masticatory performance was significantly associated with number of functional teeth, maximum bite force and periodontal status in decreased OSA. In lost OSA, masticatory performance was significantly associated with maximum bite force. Maximum bite force was a factor significantly influencing masticatory performance that was common to all OSA groups. After controlling for possible confounding factors, the number of functional teeth and periodontal status were common factors in the perfect and decreased OSA groups, and only sex was significant in the perfect OSA group. These findings may help in providing dietary guidance to elderly people with tooth loss or periodontal disease.

Hong-Ou-Mandel (HOM) interference[1] unveils a distinct behavior of identical particles which cannot be distinguished from each other. Especially for bosons, two separated identical particles passing through a beamsplitter always go together into one of the output ports, but that is not the case with other particles including fermions or classical ones. So far many elemental properties of quantum physics and information [2] have been discovered through the concatenated HOM effects, which has been demonstrated in photons [1,3,4,5,6,7,8] and recently in plasmons [9,10], atoms [11] and phonons [12]. However, all demonstrations in optical region employed two particles in different spatial modes. Here we first report the HOM interference between two photons in a single spatial mode with different frequencies (energies) by using a partial frequency conversion. The demonstrated frequency-domain interferometer allows us to replace spatial optical paths by optical frequency multiplexing, which opens up a distinct architecture of the quantum interferometry.In the past three decades since the HOM interference has been proposed and demonstrated with two photons from spontaneous parametric down-conversion (SPDC) process [1], a huge varieties of experiments based on the HOM interference revealed fundamental properties in quantum physics, especially in quantum optics [2], and its applications are widely spreading over quantum information processing, such as quantum computation [13,14,15,16], quantum key distribution [17,18], quantum repeater [19,20,21] and quantumoptical coherence tomography [22]. HOM interference has been observed with photons generated not only from nonlinear optical phenomenon but also from quantum dots [3,4], trapped neutral atoms[5], trapped ions[6], NV centers[7] and SiV centers[8] in diamond. Furthermore not only photons but also other bosonic particles, e.g., surface plasmons [9,10], Helium 4 atoms[11] and phonons [12] show the HOM interference. In spite of such demonstrations using various kinds of physical systems, to the best of our knowledge, all of them essentially used the spatial or polarization degree of freedom for the HOM interference, including the use of polarization modes of photons that are easily converted to and from spatial modes. The demonstrations use the beamsplitter (BS) which mixes the two particles in different spatial/polarization modes.In this letter, we report the first observation of the HOM interference between two photons with different frequencies in optical region. In contrast to the spatial interferometer, the frequency-domain HOM interferometer is implemented in a single spatial mode with a nonlinear optical frequency conversion [23,24,25]. In the experiment, we input a 780 nm photon and a 1522 nm photon to the frequency converter that partially converts the wavelengths of the photons between 780 nm and 1522 nm as shown in Fig. 1a. We measured coincidence counts between the output photons at 780 nm and those at 1522 nm from the frequency converter. The observed HOM inter...

These results indicated that the visual scoring method was valid and reliable for evaluation of masticatory performance.

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Despite the importance of masticatory performance in health promotion, assessment of masticatory performance has not been widely conducted to date because the methods are labour intensive. The purpose of this study is to investigate the accuracy of a novel system for automatically measuring masticatory performance that uses β-carotene-containing gummy jelly. To investigate the influence of rinsing time on comminuted jelly pieces expectorated from the oral cavity, divided jelly pieces were treated with two types of dye solution and then rinsed for various durations. Changes in photodiode (light receiver) voltages from light emitted through a solution of dissolved β-carotene from jelly pieces under each condition were compared with those of unstained jelly. To investigate the influence of dissolving time, changes in light receiver voltage resulting from an increase in division number were compared between three dissolving times. For all forms of divided test jelly and rinsing times, no significant differences in light receiver voltage were observed between any of the stain groups and the control group. Voltages decreased in a similar manner for all forms of divided jelly as dissolving time increased. The highest coefficient of determination (R(2)  = 0·979) between the obtained voltage and the increased surface area of each divided jelly was seen at the 10 s dissolving time. These results suggested that our fully automatic system can estimate the increased surface area of comminuted gummy jelly as a parameter of masticatory performance with high accuracy after rinsing and dissolving operations of 10 s each.