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Biomedical subjects

A Waltimo

Publications and source records attributed to A Waltimo.

11 recordsLinked to original sources
PubMed1999

Altered control of submaximal bite force during bruxism in humans.

The control of bite force during varying submaximal loads was examined in patients suffering from bruxism compared to healthy humans not showing these symptoms. The subjects raised a bar (preload) with their incisor teeth and held it between their upper and lower incisors using the minimal bite force required to keep the bar in a horizontal position. Further loading was added during the preload phase. A sham load was also used. Depending on the session, the teeth were loaded by the experimenter or the subject and in one session the subject did not see the load (no visual feedback). The bite force was measured continuously using a calibrated force transducer. In all the subjects, the bite force increased with increasing load. Following the addition of the load, the level of the tonic bite force was reached rapidly with no marked overshoot. The patients with bruxism used significantly higher bite forces to hold the submaximal loads compared to the control subjects. In the control subjects, the holding forces for each submaximal load were identical in the men and the women and were independent of subject maximal bite force. Sham loading evoked no marked responses in biting force. Whether the subject or the experimenter added the load or whether the subject had visual feedback or not were not significant factors in determining the level of bite force. The results indicated that the patients with bruxism used excessively large biting forces for each given submaximal load. This study showed no evidence that the inappropriate control of bite force by patients with bruxism was due to an abnormality in the higher cortical circuits that regulates the function of trigeminal motoneurons in the brainstem. This was shown by a lack of abnormality in coordination of voluntary hand movement with biting force, a lack of abnormal anticipation response to a sham load and a lack of any effect of visual feedback. The results were in line with the hypothesis that afferent input from oral (periodontal or masticatory muscle) tissues does not provide an appropriate control of motor command in bruxism.

Adult↗
PubMed1999

Masticatory force and function in patients with hemispheric brain infarction and hemiplegia.

Recent functional animal studies have reported that the motor control of masticatory muscle function is bilaterally guided by both hemispheres, which may fundamentally differ from the cortical control of limb muscle function. In this study, we investigated whether unilateral cortical brain infarction induces different impairments in masticatory and upper limb motor performance. Evidence of the importance of both hemispheres in controlling masticatory movements would be greater if the masticatory function were shown to be unimpaired in patients with severe hemiplegia. The masticatory function of 16 patients with severe hemiparesis caused by brain infarction in the region of the middle cerebral artery was studied by means of interview, clinical examination, and bite-force measurements. Finger-thumb grip-force measurements and clinical examination of the upper limbs were also performed for evaluation of the effect of infarction on upper limb motor function. Localization of the infarction was confirmed with computer tomography and magnetic resonance imaging. The Scandinavian Stroke Scale demonstrated that each patient had a major unilateral cortical infarction which had caused a marked handicap with a serious impairment of upper limb function on the contralateral side. The clinical examination revealed no major signs of temporomandibular disorders, and the masticatory muscles, when examined by palpation, contracted symmetrically. None of the patients with unilateral brain infarction showed any differences in bite forces between the healthy and paralyzed sides. These results indicate that, in hemiparetic patients, great differences may exist between the motor performances of the masticatory and upper limb muscles. The present investigation clinically illustrates the importance of both hemispheres in the control of masticatory function and movements.

Adult↗
PubMed1997

Differential effects of noxious conditioning stimulation of the cheek by capsaicin on human sensory and inhibitory masseter reflex responses evoked by tooth pulp stimulation.

In this study, we investigated whether selective activation of nociceptive primary afferent fibers by capsaicin would induce modulations on tooth-pulp-evoked sensory or inhibitory masseter reflex responses in healthy human subjects. The contribution of central N-methyl-D-aspartate (NMDA) receptor mechanisms in capsaicin-induced effects on sensory or reflex responses was evaluated by dextromethorphan, an NMDA-receptor antagonist. The inhibitory masseter reflex was evoked by electrical stimulation (constant current, single pulses) of the upper incisor while the subject was biting at 10% of his maximal force. The sensation of the tooth pulp stimulation was evaluated by visual analogue scale (VAS). The magnitude, duration, and the the latency of the reflex were determined by bite force measurements. The inhibitor masseter reflex could be induced by non-painful tooth pulp stimulation, and the inhibition was enhanced as a function of increasing stimulus intensity. Capsaicin (1%) applied topically to the skin of the cheek produced a spontaneous burning pain sensation. During capsaicin treatment, the VAS ratings for the sensation induced by tooth pulp stimulation were significantly reduced, whereas no significant changes were found in the tooth-pulp-induced masseter reflex responses. Double-blind treatment with dextromethorphan at a dose of 100 mg (= the highest does without side-effects) had no effect on sensory or reflex responses. These data indicate that noxious stimulation of the facial skin by capsaicin induces differential effects on tooth-pulp-evoked sensory and inhibitory masseter reflex responses: Sensory responses are strongly attenuated, while masseter reflex responses are not significantly changed. Dextromethorphan at a clinically applicable dose does not influence tooth-pulp-evoked sensory or reflex responses or their modulation by capsaicin. Furthermore, the lack of modulation of the masseter reflex response by capsaicin differs from the capsaicin-induced enhancement of a nocifensive limb flexion reflex described earlier.

Administration, Cutaneous↗
PubMed1996

Does clicking in adolescence lead to painful temporomandibular joint locking?

BACKGROUND: It has been assumed that clicking of the temporomandibular joint (TMJ) may predispose to closed locking. Although jaw clicking is a common complaint, locking of the TMJ is rare. METHODS: To assess whether clicking is a reliable predictor of locking, we examined longitudinally over 9 years the variation of reported and recorded TMJ clicking in 128 young Finnish adults. Subjects were interviewed and examined at the ages of 14, 15, 18, and 23 years. FINDINGS: Reported and recorded TMJ clicking both increased significantly with age, varying from 11% to 31% and from 11% to 34%, respectively, However, clicking showed no predictable pattern, and only a few subjects consistently reported clicking (2%) or had it recorded (2%). None developed locking. INTERPRETATION: Because none of the young adults developed locking of the TMJ, we suggest treatment for clicking should be conservative.

Adolescent↗
PubMed1995

Maximal bite force and its association with signs and symptoms of craniomandibular disorders in young Finnish non-patients.

Maximal bite force values and subjective symptoms and clinical signs of craniomandibular disorders (CMD) were recorded for a non-patient sample of 129 young adults, 56 men and 73 women. The signs and symptoms of CMD were classified on the basis of Helkimo's clinical dysfunction index. The two genders reported equally frequently subjective symptoms of CMD, but women had significantly more severe clinical signs of CMD than did men. Mean maximal bite force values for men were 909 N (SD, 177) in the molar region and 382 N (SD, 133) in the incisal region and thus significantly higher than corresponding figures for women, 777 N (SD, 168) in the molar, 325 N (SD, 116) in the incisal region, suggesting that separate evaluation of the genders would be advisable in future studies involving bite force assessments. Neither subjective symptoms nor clinical signs of CMD correlated significantly with maximal bite force values. The bite force values measured were in line with theoretical calculations.

Adult↗
PubMed1994

Bite force and dentofacial morphology in men with severe dental attrition.

Patients with severely worn dentition were interviewed and clinically examined, and only those were included who had no or minimal subjective symptoms or clinical signs of craniomandibular disorder. During a 14-month screening period, only 7 patients fulfilled the inclusion criteria; all were men. Maximal bite force was measured in the molar regions and in the incisal region. Facial morphology was evaluated from lateral cephalometric radiographs, and the form of dental arches from dental casts. Average maximal bite force in the molar region was 911 N and in the incisal region 569 N. The most characteristic findings concerning bite force were the high force levels in the incisal region and an incisal/molar bite-force ratio of 63%. The facial morphology of the patients was rectangular, with an anteriorly rotated mandible, small anterior face height, and great interincisal angle. Moreover, the form of the maxillary dental arch was more rectangular than normal. The high bite forces of these patients, especially in the incisal area, can probably be explained by strong masticatory muscles and mechanically favorable skull morphology, which in its turn has been influenced by the surrounding muscles.

Adult↗
PubMed1994

Bite force on single as opposed to all maxillary front teeth.

The relation of number of teeth to maximal clenching force was tested in 10 healthy female dental students. The maximal force in the interincisal position was tested by spreading the load with individual acrylic splints over a varying number of teeth in the anterior region. In the maxilla, one splint covered teeth 13-23; another covered tooth 11. In the mandible, one splint covered teeth 33-43 in all experiments. The maximal force in the incisal position was measured 10 times, five times with each splint. The maxillary splints were changed in random order. The tactile sensibility of tooth 11 and its antagonists was tested before and immediately after interincisal force measurements. A highly significant difference between maximal forces was seen in comparing biting between a single tooth and multiple teeth. In addition, bite force also showed a significant increase in both single tooth and multiple teeth successive biting trials during the experiments. Tactile sensibility between d 11 and its antagonist was not altered by the maximal bite force trials.

Acrylic Resins↗
PubMed1993

Effects of jaw clenching, jaw movement and static jaw position on facial skin sensitivity to non-painful electrical stimulation in man.

The effects of isometric jaw clenching, static jaw position and jaw movement on electrically evoked perception thresholds of the facial skin of the mental region were studied in healthy human subjects. Exercise consisted of brief (1 s) isometric contractions of jaw-closing muscles against a static load (30% of the maximum force), or continuous jaw movements at two different frequencies (1 and 3 Hz). A visual cue was used to indicate the start and end of the isometric exercise (duration 1 s.). Isometric jaw clenching induced a significant elevation of perception thresholds in the skin of the lower jaw just before and during the early electromyographic response of the jaw-closing muscles. This elevation was attenuated before the end of the exercise. Corresponding thresholds evoked by electrical stimulation applied to the dorsum of the hand were not changed by isometric jaw clenching. Changes in static jaw position did not have any effect on detection thresholds. Continuous 'masticatory-like' jaw movements produced a velocity-dependent reduction of sensitivity in the facial skin. The suppression was significantly stronger than that produced by isometric jaw exercise. An imagined isometric biting exercise, which presumably activated the supplementary motor cortex, did not cause any threshold elevations. The results indicate that isometric jaw clenching as well as cyclical jaw movements produce segmentally a phasic, rapidly attenuating masking of facial skin sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Maximal contraction force and endurance of human jaw-closing muscles in isometric clenching.

Maximal unilateral bite force and endurance times from maximal bite force to the 75% and 50% levels of maximal values were recorded for 13 men and 15 women with bite openings of 10 and 14 mm. Measurements were made both from right and left molar regions and from the incisal region. Bite force values were significantly higher than previously measured in endurance tests by devices with unilateral housings. Men achieved greater bite force than women in the molar region in every trial. The general assumption that women's muscles are superior to those of men in static endurance when both are working at the same percentage of maximal voluntary contraction was not supported by this work for jaw-closing muscles. The endurance times to 75% and 50% levels of maximal bite force were shorter than could be expected from previous reports, and endurance times to the 50% level were even shorter than those reported for muscles of limbs.

Adult↗
PubMed1993

A novel bite force recorder and maximal isometric bite force values for healthy young adults.

Human bite forces have been studied with several types of equipment, and the maximal values reported have varied greatly. In the present study, a new bite force recorder was developed to measure human bite forces. When measuring maximal bite force, the mandible is, laterally and sagittally, almost in the intercuspal position, while the vertical opening of the jaws in the molar region is about 14 mm. Several teeth bite upon the housing. A quartz force transducer serves as a sensory unit. A microprocessor produces a numeric result, shown on a liquid crystal display (LCD). In order to adapt the sensor to be a part of a bite force recorder, we designed a unilateral housing of nonhardened tool steel. In laboratory calibration tests, a series of loads from 112.8 to 1691.5 N was used. The maximal bite forces of healthy undergraduate dental students, 15 men and 15 women, were investigated. The results for both genders remarkably exceeded the values previously reported for unilateral housings. The mean maximal bite force value in the molar region was 847 N for men and 597 N for women. The finding that pain or lack of muscular strength most often limited the clenching suggests that the actual masticatory potential was registered.

Adult↗