To investigate changes in the characteristics of edentulous mucosa in the alveolar ridge with aging, we applied pressure to the mucosa of the alveolar ridge in subjects of various ages and evaluated the recovery amount and time after the pressure was removed. Twenty-three subjects ranging from 23 to 79 years of age, who had lost the first mandibular molar tooth, were selected. Displacing pressure was applied to the mucosa corresponding to the mandibular first molar region. After release the pressure, we measured the recovery amount of mucosa from its displacement, which was expressed as the movement of a target which had been placed on the mucosa as measured by an indirect displacement measurement device. The levels of displacement were set at 0.1mm, 0.2 mm and 0.3 mm, and the time to achieve the selected displacement level was set at 1 second. The initial recovery of the mucosa immediately after the pressure has been released was designated as the initial recovery amount, and the time needed for recovering to 90% of the previous state was designated as the final recovery time. Then we investigated the relationships between the measures of the initial recovery amount, the final recovery time, and the subjects' ages. The initial recovery amount of mucosa was lower and the final recovery time was longer in older subjects, and this tendency was exaggerated when the displacement was increased.

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Buccal mucosa ridging and tongue indentation have been considered as one of the visible and reliable signs of bruxism. However, there have not been any reports justifying this relationship scientifically. Moreover, there have not been any studies reporting specific procedures to assess them. Thus, the purpose of the present study was to determine the clinical incidence of buccal mucosa ridging and tongue indentation and assess the possible relationship between certain factors that can influence their occurrence. A total of 244 (178 males and 66 females) dentulous adults from 20 to 59 years of age, who were employees at the Bank of Yokohama, were randomly selected. At first, the buccal mucosa ridging and tongue indentation were classified into three groups based in their intensity: none, mild, and severe. The incidence of both conditions in the different age groups, as well as the incidence by gender was evaluated. Furthermore, the possible relationships between buccal mucosa ridging and tongue indentation and age, gender, clenching awareness, grinding awareness, headache, neck stiffness, vertical dimension, temporomandibular joint (TMJ) pain to palpation, masticatory muscle tenderness to palpation, and the presence of premature contacts were evaluated using the chi-square test. A positive relationship was found between the occurrence of buccal mucosa ridging and tongue indentation and gender (p<0.01); both conditions were observed more frequently in females than in males. A positive relationship was also found to age; the group between 20-29 years old showed the highest incidence. The vertical dimension had a positive relationship with the occurrence of both buccal mucosa ridging and tongue indentation. Other factors evaluated did not show any correlation.

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We analyzed the current state of management of private dental offices in Japan using the 11th Survey of the Current Economy of Medicine and Dentistry conducted in September of 1997. The analysis was mainly performed by comparing the survey in 1997 with the survey conducted in 1989. The results show the medium-term tendencies in dental management. We also compared the data from dental offices with those from private medical offices without facilities for inpatients.
  The following are the results: the average income from dental practice for a dental office in 1997 was 4,050,000 yen, a decrease of 4.9% (about 210,000 yen) compared with the average income in 1989. The average income from treatment covered by insurance in 1997, which accounted for most of the total income, was 3,540,000 yen, a decrease of 2.8% compared with that in 1989. The average income from non-insured treatment was 490,000 yen, which was also a decrease of 17.4%. The average income from medical practice for a medical office in 1997 was 1,970,000 yen more than the average income from dental practice of the same year. The average medical practice expenses and the average balance in medicine were higher than those in dentistry by 1,360,000 yen and by 600,000 yen respectively. Although the average income from medical practice slightly increased, the average wage costs increased by as much as 42.8%, resulting in a decrease of 21.2% in the average balance.
  Dental offices attempted to weather the decreased income from dental practice by raising the average fee paid by an insured patient. The analysis in the present study suggested that a decreasing number of patients and increasing dental practice expenses diminished the balance.

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In this study, we investigated the modulation of calcium channels by vasoactive intestinal polypeptide (VIP) in hamster submandibular ganglion (SMG) cells using the whole-cell patch clamp technique. VIP (1μM) inhibited the high voltage-gated calcium channels in the SMG neurons via activation of VIP receptors and G-protein coupled to these receptors, but did not affect the low voltage-gated calcium channels. VIP at 1μM reduced the peak amplitude of the maximum high voltage-gated calcium current by 26.0±6.2% (mean±S.E., n=5) and slowed the rising phase of the calcium current. The time to peak of the maximum high voltage-gated calcium current was prolonged from 16.8 msec to 22.4 msec. In a representative cell, 1μM VIP reduced the peak amplitude of maximum high voltage-gated calcium current by 50.5% and the amplitude at the end of voltage step after 300 msec by 51.9%. The VIP-induced inhibition of the calcium current was produced in a voltage-dependent manner. Inhibition was maximal (50.5%) at the level of -20mV. Therefore, VIP inhibits both transient and sustained types of high voltage-gated calcium channels in the hamster SMG neuron.

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