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.

The purpose of this study was to establish a clinical method for diagnosing diurnal bruxism in denture wearers by recording masseter and anterior temporal electromyograph (EMG) activity. Seven suspected bruxists and five normal patients who wore complete dentures and/or distal extension base removable partial dentures were selected for participation. EMG activity in both the masseter and the anterior temporal muscles was recorded bilaterally during silent reading (10 min), maximal voluntary clenching (MVC), tapping in centric occlusion, lateral movements, chewing and swallowing. No significant differences of EMG activity were found between the groups during tapping, lateral movement, chewing and swallowing (P> 0.05). However, during 10 min of silent reading, a significant difference was found between the groups when comparing masseter muscle activity (P < 0.05). A threshold of 10% of MVC of at least 3-s duration was used to define an individual bruxism event. When the muscle activity recorded during silent reading was further analysed using these criteria, the control group displayed no bruxing activity while the suspected bruxist group displayed a mean frequency of six bruxism events (range 2-10). It was concluded that: (a) masseter muscle activity recorded during 10 min of silent reading showed significant difference between the groups; (b) the criteria selected in this study for the detection of sleep bruxism can also be used to assess diurnal bruxism; and (c) it is possible to diagnose diurnal bruxism in denture wearers by measuring the masseter EMG activity during 10 min of silent reading.

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 0.1 mm, 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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