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Biomedical subjects

C Hagberg

Publications and source records attributed to C Hagberg.

33 records · Page 2Linked to original sources
PubMed1990

Perception of cutaneous electrical stimulation in patients with craniomandibular disorders.

Perception thresholds for stimulation, discomfort, and pain were measured with electrical stimulation over the masseter area. Patients with chronic symptoms and signs of craniomandibular disorders reported significantly higher thresholds of all three variables compared with healthy controls. There were significantly negative correlations between the patients' pre-experimental discomfort and pain ratings on the Borg's scale and perception thresholds measured for discomfort and pain. The patients who presented the highest pain ratings in masticatory muscles and/or joints had the lowest threshold values when reporting discomfort and pain during gradually increased current intensity. This could be due to the cognitive effects of pain.

Adult↗
PubMed1989

Surface EMG amplitude and frequency dependence on exerted force for the upper trapezius muscle: a comparison between right and left sides.

Surface electromyographic (EMG) amplitude and mean power frequency (MPF) were used to study the isometric muscular activity of the right versus the left upper trapezius muscles in 14 healthy right-handed women. The EMG activity was recorded simultaneously with force signals during a 10-15 s gradually increasing exertion of force, up to maximal force. Only one side at a time was tested. On both sides there was a significant increase in EMG amplitude (microV) during the gradually increasing force from 0% to 100% maximal voluntary contraction (MVC). The right trapezius muscle showed significantly less steep slopes for regression of EMG amplitude versus force at low force levels (0%-40% MVC) compared intra-individually with high force levels (60%-100% MVC). This was not found for the left trapezius muscle. At 40% MVC a significantly lower MPF value was found for the right trapezius muscle intra-individually compared with the left. An increase in MPF between 5% and 40% MVC was statistically significant when both sides were included in the test. The differences in EMG activity between the two sides at low force levels could be due to more slow-twitch (type I fibres) motor unit activity in the right trapezius muscles. It is suggested that this is related to right-handed activity.

Adult↗
PubMed1989

Muscular tenderness evaluated by surface EMG frequency analysis of isometric contractions.

Myoelectric power spectrum analysis was used to compare muscular activity in the masseter and anterior temporal muscles between patients with tender masseter muscles and healthy controls. Surface EMG was recorded for 28 patients and nine controls while they were biting on a bite force transducer during a period of 10-15 s up to maximal effort (100% MVC). The mean frequency (MF) was calculated as a single estimate of the myoelectric power spectrum. Regression analyses of MF's for the masseter muscles versus the force level 0-60% MVC showed significantly less steep slopes of regression for the patients compared interindividually with the controls. As regards the anterior temporal muscles there was no significant difference between groups. One explanation for the difference in MF's for the masseter muscles between patients and controls is that the patients suffered an inhibition or difficulty in recruiting motor units. Different firing rate properties for motor units at high force levels (60-100% MVC) could be one reason for a significantly smaller decrease in MF for the patients' elevator muscles than for the controls.

Adult↗
PubMed1988

Changes in the surface electromyogram during increasing isometric shoulder forward flexions.

When using electromyographic techniques in the evaluation of muscular load it is necessary to determine the mathematical relationship between the torque and the amplitude of the electromyographic signal. Isometric gradually increasing contractions up to 100% MVC can then be used. Often more than linear increases for the amplitude (RMS)--force regression have been reported. The present study was designed to test whether changes in power spectral density function take place during a gradually increasing isometric contraction (duration 10 s). Twenty-two clinically healthy females performed an increasing isometric shoulder forward flexion for 10 s using an isokinetic dynamometer. Electromyographic activity was measured in trapezius, deltoid, infraspinatus and biceps brachii using surface electrodes. Mean torque values were determined together with mean power frequency (MPF) and root mean square values (RMS) from the EMG signals for each 256 ms period. The RMS-torque regressions showed higher regression coefficients during the 6th to 9th sec than during the first 5 s. No significant correlation existed between MPF for the four muscles and the torque. A gradual decrease in MPF was generally found from the 6th s. It is concluded that this decrease in power spectral density function might have contributed to the significantly higher regression coefficient for the RMS torque regression at the high output part of the gradually increasing isometric contraction.

Adult↗
PubMed1988

Surface EMG frequency dependence on force in the masseter and the anterior temporal muscles.

Myoelectric power spectrum analysis was used to study isometric contractions, 10-15 s long, of the masseter muscles and the anterior temporal muscles. Surface EMG activity was recorded from these muscles for nine females while biting on a bite force transducer up to maximal effort (100% maximal voluntary contraction; MVC). The mean frequency (MF) was calculated as a single estimate of the myoelectric power spectrum. Regression analyses were made of MF versus bite force (0-100% MVC). The mean MF values of all females' masseter muscles increased up to 55-60% MVC. For the anterior temporal muscles no increase in mean MF was found above 20-25% MVC. The increase in MF was possibly dependent on recruitment of type I fibers and low-pass tissue filtering effects. The slope of regression for the force level 0-60% MVC was intraindividually steeper for the masseter muscles than for the anterior temporal muscles. A similar decrease in mean MF was found for the masseter muscles and the anterior temporal muscles for the force level 60-100% MVC. The possibility of muscular fatigue was discussed.

Adult↗
PubMed1987

The amplitude distribution of electromyographic activity in painful masseter muscles during unilateral chewing.

The aim of this study was to investigate whether the amplitude distribution of electromyographic activity (EMG) in terms of muscular load revealed any differences between patients with painful masseter muscles and referents during the chewing of an almond and of gum. The relative masticatory forces of the masseter muscle and the anterior temporal muscle during chewing were calculated by a transformation of the muscular load levels of EMG activity (microV) to load levels of relative masticatory force (%RVC). This was done by regression in reverse of an isometric reference voluntary contraction (RVC) for EMG versus bite force biting on a bite-force sensor. The maximal bite-force values for patients and referents were similar. The relative masticatory force for chewing an almond was higher than that for gum-chewing. The peaks of the relative masticatory forces were similar for both patients and referents. During the chewing of an almond the relative masticatory forces of the masseter muscle below the peak load were higher for patients than referents. During gum-chewing the patients used higher forces than referents for 70% of the total chewing time analysed. This also applied to the anterior temporal muscle when chewing an almond. Estimates of the peak masticatory forces were calculated in newtons.

Adolescent↗
PubMed1987

EMG versus force relationship in painful masseter muscles before and after intramuscular anesthetics and saline injections.

Electromyographic (EMG) activity of masseter and anterior temporal muscles, and bite force were analyzed in 28 young, fully dentate women with painful and tender masseter muscles before and after intramuscular injection of either lidocaine or saline in superficial masseter muscle. EMG-activity of the descending part of the trapezius muscle during increased bite force was also analyzed. As regards the mandibular elevators, the intraindividual relationship between slopes for EMG-force regression at low and high contraction levels before injection were the same as for healthy women investigated previously. Intramuscular injection of lidocaine reduced postural EMG-activity of the masseter muscles and EMG-force regression curve became less steep at low contraction levels. After saline injections no changes in EMG-activity were found. The EMG-activity of the descending part of the trapezius muscle was increased significantly for the total group during the strongest bite.

Adolescent↗
PubMed1986

Discomfort and bite force in painful masseter muscles after intramuscular injections of local anesthetic and saline solution.

Thirty women with a history of daily pain in the masseter muscles were injected with either lidocaine or saline. The participants were told that they were being given an anesthetic injection to reduce their muscular discomfort. The dentist performing the injections did not know which fluid was used. The discomfort in the masseter muscle was assessed by using Borg's new rating scale before and 10 minutes after injection. The evaluation was followed up on day 1, day 3, and day 7. Bite force was registered between the first molars on the injection side. When scale values were compared individually within groups before and after injection, a significant decrease in discomfort was found in both groups, with the exception of day 1 for the lidocaine group and days 1 and 3 in the saline group. The total lidocaine and saline groups assessed the discomfort similarly except on day 3 when the lidocaine group showed significantly less discomfort. The intraindividual force values increased significantly after injection in the saline group. This effect was not found in the lidocaine group. Despite the minor tendencies for lidocaine to have a better effect, the placebo effect was considered to be high and important.

Adolescent↗
PubMed1986

The amplitude distribution of electromyographic activity of masticatory muscles during unilateral chewing.

The amplitude probability distribution function (APDF) of electromyographic activity was used to describe the variation in relative masticatory force in the superficial masseter muscle and the anterior temporal muscle during unilateral chewing. The masticatory force, predicted from an isometric reference contraction, increased significantly in both muscles when chewing an almond compared to chewing half a stick of gum. Analysis of the distribution levels of contraction showed that the significant differences in relative masticatory forces were found for high levels of contraction. The individual variations were large when masticatory force between the muscles was compared. Maximal loading of the masseter muscle and the anterior temporal muscle exceeded 100% of the reference voluntary contraction in six females out of nine, mainly during chewing of an almond. The results indicated that APDF can be useful for analysing chewing when estimations of relative masticatory force and a measure of the distribution of different levels of contractions are desirable.

Adult↗
PubMed1986

Electromyography and bite force studies of muscular function and dysfunction in masticatory muscles.

Electromyographic (EMG) activity versus bite force was studied during a gradually increased isometric contraction up to maximal effort for patients with painful masseter muscles and referents. The masseter muscle, the anterior temporal muscle and the descending part of the trapezius muscle were chosen for the recordings. Bite force was registered with a bite force sensor placed between the first molars. The effects of double blind intramuscular injections of lidocaine and saline in the patients' masseter muscle were evaluated by EMG versus bite force and by assessment of discomfort. EMG activity during unilateral chewing was compared in terms of relative masticatory force between referents and patients by amplitude probability distribution analysis. Regression analyses showed intra-individually steeper slopes for high force levels than for low force levels for the masseter muscle. This was not observed for the anterior temporal muscle. These differences in slopes of the EMG versus force regressions for the masseter muscle and the anterior temporal muscle could be due to differences in recruitment pattern. The same intra-individual relationship between low and high force levels was found for referents and patients. An increased activity, especially among the patients, was found for the descending part of the trapezius muscle during stronger activity of the mandibular elevators. The EMG versus force relationship for low force levels of the masseter muscle was less steep after an intramuscular injection of lidocaine but not after saline. Both solutions for injection had a positive effect on the patients' assessments of discomfort one week after the injection. Three days after injection the patients who received lidocaine experienced a reduction in muscular discomfort. This reduction was not found among patients receiving saline. The amplitude probability distribution analysis revealed that the patients used greater relative masticatory forces than the referents during the chewing of an almond for all probability levels analysed below the peak load of the masseter muscles. Rough estimates of the peak masticatory forces in Newton (N) were for chewing an almond 364 N (referents); 373 N (patients) and for gum-chewing 239 N (referents); 238 N (patients) as regards the masseter muscle. The values were similar for the anterior temporal muscle.

Bite Force↗
PubMed1985

Regression analysis of electromyographic activity of masticatory muscles versus bite force.

Electromyographic (EMG) activity of the superficial masseter and the anterior temporal muscles versus the bite force was studied in 10 young women. They were fully dentate and had no dysfunction of the stomatognathic system. The descending part of the trapezius muscle was also chosen for EMG registration. The average bite force between the first molars was 396 N (Newton). Steeper slopes for the EMG versus force regression curve at high contraction levels than at low contraction levels for the superficial masseter muscle may indicate that this muscle has a recruitment pattern that differs from that of the anterior temporal muscle. In the case of the anterior temporal muscle there was no difference between the slopes for the EMG-force regression at low and high contraction levels. There was significantly increased activity in the descending part of the trapezius muscle mainly during high bite force levels in half the subjects.

Adult↗
PubMed1984

Role of brushing technique and toothbrush design in plaque removal.

Twenty-four adults participated in an intraindividual crossover experimental study to compare the plaque removing ability of straight multitufted and V-shaped brushes. Twelve of the participants had loss of periodontal tissue resulting in open but healthy interdental areas while the other 12 displayed no periodontal breakdown. In part 1 the participants were asked to brush their teeth using their own brushing technique and length over two 12-day periods during which time they, at random, used one brush for the first and the other brush for the second period. In part 2 the participants were professionally brushed by two dental assistants using four brushing techniques (The Bass, The Roll, The Circular Scrub and The Horizontal Scrub) randomly assigned to the four quadrants of the mouth. Cleaning was performed once a day for two 5-day periods, during which time the participants refrained from brushing and interdental cleaning. Initial toothbrush assignment was randomized. At the beginning of the study and each test period no plaque or gingival inflammation was visible. At the end of each period the accumulated plaque was registered. The results showed that there was no difference between the two brushes tested in the unsupervised part. The plaque removing ability when using either of the brushes varied between participants. When professionally used the straight multitufted and V-shaped toothbrushes did not show any difference in plaque removal on buccal and lingual surfaces. Interproximally the V-shaped toothbrush was better at plaque removal than the straight one.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗