Critical tooth number without subjective dysphagia.

AIM: To assess the critical tooth number (CTN) required for prevention of subjective dysphagia caused by oral impairments and to evaluate the relationship between this CTN and mortality. METHODS: The baseline study was performed with residents aged 40-89years (n=5,643; 2224 men and 3419 women) in Miyako Islands, Okinawa, in 1987. Dental examinations were performed by dentists, and subjective dysphagia was asked. We recorded the cause and year of death of participants who died during the next 15years. RESULTS: The average functional tooth number of participants with and without subjective dysphagia declined with age in both sexes. The CTN for each respective age group (40s, 50s, 60s, 70s and 80s) not including the denture group were 20.0, 17.5, 14.0, 11.8 and 10.1 in men and 19.0, 14.7, 12.7, 9.5 and 4.0 in women. These CTN were significant factors of 15-year mortality in both sexes (P<0.05). The hazard ratios were 0.72 (95% confidence interval=0.55-0.93) in men and 0.71 (0.51-0.99) in women. CONCLUSION: In aged people, the minimum number of functional teeth needed to avoid subjective dysphagia might not be as high as in young people.

Associations between functional tooth number and physical complaints of community-residing adults in a 15-year cohort study.

BACKGROUND: Oral function influences various general health and organ diseases. We wondered if physical complaints of unknown origin were related to oral function. METHODS: Five thousand five hundred and eighty-four community residents (2206 men and 3378 women, aged 40-89 years) on the Miyako Islands, Okinawa Prefecture, Japan, were recruited for the baseline study in 1987 and followed up for 15 years. Physical complaints and functional tooth numbers were assessed for the baseline study in 1987 by dentists and followed up for 15 years. Physical complaints of unknown origin included shoulder stiffness, lower back pain, pain of upper extremity, pain of lower extremity, neuralgia, ear ringing, difficult of hearing, dizziness and sleeping difficulties. RESULTS: Physical complaints were significantly associated with functional tooth number in the baseline study. There were no systematic differences between physical complaints and functional tooth number among different age groups. Physical complaints did not influence the survival rates in either men or women. CONCLUSION: Oral function may be related to physical complaints. Dental care may be one of the targets to treat these physical complaints of unknown origin.

Mortality rates of community-residing adults with and without dentures.

AIM: To prospectively study how dental status with and without dentures could become a predictor of overall mortality risk. METHODS: Five thousand six hundred eighty-eight community residents over 40 years old in the Miyako Islands, Okinawa Prefecture, Japan, were followed up for 15 years from 1987-2002. RESULTS: We found that female subjects with less than 10 functional teeth and without dentures showed a significantly higher mortality rate than those with dentures. There was no significant difference of mortality rates in male subjects. There were no significant differences of mortality rates between subjects with 10 or more functional teeth with and without dentures. CONCLUSION: The present study suggests that dentures are one of the factors associated with mortality rates especially in female subjects with less than 10 functional teeth.

Acceleration of orthodontic tooth movement by alveolar corticotomy in the dog.

INTRODUCTION: Tooth movement and alveolar bone reaction after corticotomies have not been thoroughly examined. In this study, the effects of corticotomies on orthodontic tooth movement and alveolar bone reaction were investigated in dogs. METHODS: Corticotomies were performed on the cortical bone of the mandibular left third premolar region in 12 male adult beagles. The third premolars on the left experimental side and on the right sham side were moved mesially with a continuous force of 0.5 N. RESULTS: Tooth movement velocities from 0 to 1 week and from 1 to 2 weeks after the corticotomies were significantly faster on the experimental side than on the sham side. Hyalinization of the periodontal ligament appeared only at 1 week after the corticotomies on the experimental sides, whereas it was observed from 1 to 4 weeks after the corticotomies on the sham sides. Tartrate-resistant-acid-phosphatase positive cells of the experimental side tended to work vigorously at an early time on the alveolar wall and in the bone marrow cavities. CONCLUSIONS: Orthodontic tooth movement increased for at least 2 weeks after the corticotomies. This might be brought about by rapid alveolar bone reaction in the bone marrow cavities, which leads to less hyalinization of the periodontal ligament on the alveolar wall.

Fatigue and damage to the masseter muscle by prolonged low-frequency stimulation in the rat.

This study aimed to examine peripheral fatigue and the resultant damage to the masseter muscle due to prolonged low-frequency stimulation. Thirty male rats were divided into S1, S2, S4, Dantr and Sham groups. The left masseters were used as experimental muscles. A pair of stimulation electrodes was placed on the left masseter. A stimulating session included rectangular electric pulses of 18 Hz (5 mA, approximately 18 V, 0.7 ms) for 2 h with a 3 min rest period between sessions. One session was given to the S1 group, two sessions to the S2 group and four sessions to the S4 group. Four sessions were given to the Dantr group with administration of dantrolene to determine any artifacts of the electrical current. No electric stimulation was given to both side masseters in the Sham group or to the control (right) masseters in the other groups. In each session, jaw-closing force increased to a peak within 1 min and attenuated to the steady force. The peak force decreased as the session advanced in each group. Both side masseters were dissected after the stimulations and examined histologically. The experimental masseter was significantly heavier than that of the controls in the S1, S2 and S4 groups, and the muscle fibres showed irregularity of size and shape with enlargement of interstitial space and infiltration of mononuclear cells into the fibres. However, no such histological change was observed in the Dantr and Sham groups. It was confirmed that fatigue and damage to muscle fibres could be induced in masticatory muscles by prolonged low-frequency stimulation.

Unilateral advancement of the maxillary minor segment by distraction osteogenesis in patients with repaired unilateral cleft lip and palate: report of two cases.

OBJECTIVE: Collapse of the maxillary minor segment with lateral crossbite is a common feature in patients with repaired unilateral cleft lip/palate because of maxillary alveolar bony defect and palatal scar tissue. Distraction osteogenesis (DOG) is an effective technique of lengthening and augmentation for bone and gingiva. This case report describes the effects of unilateral advancement of the maxillary minor segment by DOG in two patients with the repaired unilateral cleft lip/palate.

Nitric oxide mediates the effects of pulsed electromagnetic field stimulation on the osteoblast proliferation and differentiation.

The purpose of this research was to investigate whether the effects of pulsed electromagnetic field (PEMF) stimulation on the osteoblast proliferation and differentiation are mediated by the increase in the nitric oxide (NO, nitrogen monoxide) synthesis. The osteoblasts (MC3T3-E1 cell line) were cultured in the absence (-NMMA group) or in the presence (+NMMA group) of the NO synthase inhibitor L-NMMA. First, osteoblasts were subjected to PEMF stimulation (15 Hz and 0.6 mT) up to 15 days. The DNA content and the NO concentration in the conditioned medium were determined on the 3rd, 7th, and 15th days of culture. Following, osteoblasts were stimulated in the proliferation (P-NMMA and P+NMMA groups) or in the differentiation (D-NMMA and D+NMMA groups) stages of maturation, and the alkaline phosphatase (AlPase) activity was determined on the 15th day of culture for all groups. PEMF stimulation increased significantly the nitrite concentration in the -NMMA group on the 3rd, 7th, and 15th days of culture. However, this effect was partially blocked in the +NMMA group. The DNA content in the -NMMA group, but not in the +NMMA group, increased significantly on the 3rd and 7th days of culture. The AlPase activity in the P-NMMA and D-NMMA groups, but not in the P+NMMA and D+NMMA groups, also increased significantly. In conclusion, the PEMF stimulatory effects on the osteoblasts proliferation and differentiation were mediated by the increase in the NO synthesis.

Effects of pulsed electromagnetic field (PEMF) stimulation on bone tissue like formation are dependent on the maturation stages of the osteoblasts.

The effects of pulsed electromagnetic field (PEMF, 15 Hz pulse burst, 7 mT peak) stimulation on bone tissue-like formation on osteoblasts (MC3T3-E1 cell line) in different stages of maturation were assessed to determine whether the PEMF stimulatory effect on bone tissue-like formation was associated with the increase in the number of cells and/or with the enhancement of the cellular differentiation. The cellular proliferation (DNA content), differentiation (alkaline phosphatase activity), and bone tissue-like formation (area of mineralized matrix) were determined at different time points. PEMF treatment of osteoblasts in the active proliferation stage accelerated cellular proliferation, enhanced cellular differentiation, and increased bone tissue-like formation. PEMF treatment of osteoblasts in the differentiation stage enhanced cellular differentiation and increased bone tissue-like formation. PEMF treatment of osteoblasts in the mineralization stage decreased bone tissue-like formation. In conclusion, PEMF had a stimulatory effect on the osteoblasts in the early stages of culture, which increased bone tissue-like formation. This stimulatory effect was most likely associated with enhancement of the cellular differentiation, but not with the increase in the number of cells.

Emotional stress and brux-like activity of the masseter muscle in rats.

The aim of this study was to further clarify the relationship between emotional stress and bruxism. In experiment 1, 60 male 9-week-old Wistar rats were divided into four groups: the emotionally stressed (ES), the emotionally non-stressed (NS), the electrically foot-shocked (FSd), and the non-foot-shocked (NSd). ES rats were confined in a communication box for one hour a day to observe the emotional responses of neighbouring FSd rats. On days 0, 1, 4, 8, and 12, the electromyographic activity of the ES and NS rats' left masseter muscles was recorded for one hour, three hours after confinement in the communication box. Brux-like activity appeared in the masseter muscle of the ES group on days 1, 4, 8, and 12, but not in the NS group. In experiment 2, 36 male Wistar rats, 9 weeks old, were divided into three groups: emotionally stressed rats treated with an anti-anxiety drug (DES), emotionally stressed rats treated with saline as a vehicle (VES), and 24 FSd rats. Stress and EMG procedures were the same as those in experiment 1. Brux-like episodes decreased in DES rats from day 1 and significant differences were found on days 4 (P < 0.01), 8 (P < 0.05), and 12 (P < 0.05), when compared with the VES group. These findings suggest that emotional stress induces brux-like activity in the masseter muscle of rats, which was reduced with anti-anxiety drugs.