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.

No abstract

Clinical/occlusal scores and jaw-muscle EMGs were recorded in 24 TMD symptomatic (group S) and 20 normal (group N) subjects to evaluate the significance of EMG parameters and their clinical associations. Results indicated: (1) integrated EMG activity (IEMG) was larger at the rest position (RP) in anterior temporalis (Ta) but smaller at maximal voluntary clenching (MVC) in masseter (Ma) and Ta, and the ratios of IEMG at 70%MVC to the corresponding bite force (70%BF) were greater in group S; (2) mean power frequency (MPF) were almost the same in both groups but its shift was more rapid in group S; (3) silent period duration (SPD) was longer in group S; (4) asymmetry indices for SPD and silent period latency (SPL) were larger in group S; (5) muscle pain was associated negatively with IEMG at MVC and 70%BF but positively with IEMGs at RP and 70%MVC, and impaired jaw movements were associated negatively with the above EMG values; (6) muscle pain was positively associated with SPD in Ma, while joint pain and sound showed positive and negative associations with SPD, respectively; (7) associations between occlusion and EMG parameters were found more in group N. These findings verify: (1) jaw elevators in TMD may have hyper-tonic activities and a weak functional efficiency; (2) jaw muscles in TMD may become easily fatigued following a functional effort, and less relaxed following a muscle twitch; (3) the severity of pain could not be reflected in EMG activities, but impaired jaw movement may increase tonic activity and decrease functional effort; (4) TMD symptoms may alter the functional adaptation of jaw-muscle activities and occlusion.

This study evaluates the process of relapse after mandibular setback surgery by an analysis of the role of craniofacial morphology, hyoid position, pharyngeal airway and head posture. Subjects examined were 62 patients who received the sagittal split ramus osteotomies (SSRO). Changes of the craniofacial and related structures were evaluated from the serial cephalograms up to 3 years after the surgery. Results indicated that mandibular relapse represented by Pg occurred mostly within 6 months after the surgery. A net setback of the mandible was 9.1 mm and the superior move was 1.7 mm, with a reduction of 7.2 mm in mandibular length, 4.2 mm in ramus height, 3.7 mm in posterior face height, 2.6 degrees in gonial angle, an increase of 2.9 degrees in mandibular plane angle (MPA) by the last examination. Hyoid bone moved backward and downward and head posture was raised. The forward relapse of Pg was correlated with the changes of ANB, MPA, ramus height and hyoid position. Only hyoid position was predictably correlated with mandibular morphology and head posture. These findings suggest that mandibular setback alters the relationship among the hyoid position, pharyngeal airway and the head posture. It might be critical, therefore, relapse is closely monitored and controlled before the full healing of fragments and new muscular balance is established.

No abstract

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.

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.

Decreased masticatory demands due to liquid or soft diets cause a reduction in the growth of craniofacial bones and in the development of feeding musculature, but the effects on masticatory function and jaw/tongue muscle activities are unclear. The present study was undertaken to test the hypotheses that a liquid diet feeding after weaning affects the critical-period programming of mastication and the motor performances of jaw and tongue muscles. Thirty-six male Wistar rats were divided into two equals groups at weaning and fed either a solid (solid-diet group) or a liquid (liquid-diet group) diet until they reached 50 days of age. Electromyograms (EMG) of the masseter, medial pterygoid, temporalis, anterior digastric, styloglossus, and genioglossus were recorded while animals were naturally ingesting ordinary pellets, apple cubes, and a liquid diet. It was found that: (1) a more irregular chewing rhythm, a shorter chewing sequence, and a longer chewing cycle were found in the liquid-diet group, but there were no differences observed during lapping/licking between the two groups; (2) during the chewing cycles, the EMG onset of each muscle in relation to that of the masseter in the liquid-diet group was similar to that in the lapping/licking cycles in both groups; (3) the activities of jaw elevators (masseter, medial pterygoid, and temporalis) during the chewing cycles were significantly higher in the liquid-diet group; and (4) the increase in the EMG activities of jaw elevators during pellet chewing compared with apple cube chewing was significantly weaker in the liquid-diet group, whereas such an enhancement was found simultaneously in the styloglossus in the solid-diet group, and in the anterior digastric in the liquid-diet group. These findings verify that: (1) the motor output of jaw and tongue muscles may be altered in rats fed a liquid diet after being weaned; (2) the feeding of a liquid diet to rats after being weaned may obstruct the functional transition from suckling to mastication; and (3) jaw elevators that develop without motor learning of mastication are inefficiency when performing functionally.