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Biomedical subjects

D van Steenberghe

Publications and source records attributed to D van Steenberghe.

At least 163 records · Page 9Linked to original sources
PubMed1986

Double-blind comparison of the analgesic potency of ciramadol, codeine and placebo against postsurgical pain in ambulant patients.

The efficacy and safety of ciramadol (Cir) as an analgesic in relieving moderate to severe pain after oral surgery has been studied in 79 patients randomly assigned to receive single oral doses of Cir 15, 30 or 60 mg, codeine 60 mg or placebo. During the 6-hour observation period, the three ciramadol-treated groups indicated greater pain relief than the codeine 60 mg or placebo groups. In general, Cir 60 mg was significantly more effective than codeine 60 mg, and all doses of Cir were superior to placebo. The proportion of patients in each Cir group reporting adverse experiences was significantly higher than in either the placebo or codeine groups. The experimental system proved very effective in demonstrating analgesic potency of Cir. The very high incidence of side-effects in the three ciramadol-treated groups makes it unfit for further clinical use in ambulant patients.

Adult↗
PubMed1986

The influence of jaw position and antagonistic tooth relations on the appearance of a short-latency excitatory reflex in the human masseter muscles following mechanical tooth stimulation.

Post-stimulus electromyographic complexes (PSEC) were elicited by standardized tapping of a central upper incisor in 12 subjects during isometric voluntary biting in two positions, the incisor edge-to-edge (IEE) or the maximal occlusion (MO). In IEE a short latency excitatory peak (P wave) was present in the PSEC; this was absent in MO. By superimposing the rough EMG sweeps without full-wave rectification, it appeared that this P wave was brought about by synchronous masseter motor-unit firing.

Action Potentials↗
PubMed1986

Changes in neuromuscular reflexes in the masseter muscles during functional jaw orthopedic treatment in children.

Masseteric reflexes following standardized taps on an upper incisor were recorded electromyographically (1) in children with Class II, Division 1 malocclusions at different times before and during the treatment with the Bionator functional appliance and (2) during an observation period in control subjects who were not being treated. In each experimental session, 72 taps were delivered during clenching at 10% of the maximal electromyographic output. Statistical criteria provided by a previously developed computer program allowed the objective determination of inhibitory and excitatory periods in the electromyographic output following the stimulus, which together constitute the poststimulus electromyographic complex (PSEC). The influence of the change in occlusal relations on the PSEC was determined in ten subjects by comparing pretreatment results with those obtained after 1, 3, and 6 months of treatment. Concurrent with an improvement of the sagittal jaw relation in the patients with a pronounced disharmony, a short latency excitatory peak appeared in their PSECs. It was demonstrated by averaging nonrectified electromyographic activity that this peak was brought about through synchronization of motor units. In the control group, however, the morphology of the PSEC was reproducible over time. Successful functional therapy is thus accompanied by specific transient changes in the reflex response of the masseter muscles to standardized tooth taps. The neural pathways contributing to these observations originate in periodontal and muscular receptors, and might provide a clue for the mechanism underlying successful functional treatment.

Activator Appliances↗
PubMed1986

Post-stimulus EMG complexes in the masseter muscle following gingival electrical stimulation in man.

Post-stimulus EMG complexes (PSECs) were elicited by means of electrical stimulation of the gingiva in six subjects during clenching in three biting positions, namely the maximal occlusion, the incisor edge-to-edge and the hyperpropulsive biting position. No interrelationship was found between the mechanically and electrically elicited PSECs. With electrical stimulation the PSEC morphology was not related to the biting position in contrast with the PSECs elicited with mechanical stimulation. Following gingival electrical stimulation, a P wave was not present in the PSEC.

Adolescent↗
PubMed1985

Oral pressure receptors mediate a series of inhibitory and excitatory periods in the masseteric poststimulus EMG complex following tapping of a tooth in man.

Poststimulus EMG complexes (PSECs), consisting of a series of inhibitory and excitatory waves in full-wave rectified and averaged electromyogram (EMG), were elicited in the masseter muscles of 7 subjects following controlled tapping of a tooth, at a controlled clenching level. Applying local anaesthesia to this tooth decreased the total surface of the waves, on average by 89%. The excitatory and the inhibitory waves were similarly affected, indicating that mainly pressure receptors in the periodontium mediate the entire PSEC. In 4 subjects, who were exposed to acoustic noise to exclude a contribution of acoustic receptors, the recovery of the PSEC waves from local anaesthesia was tracked. In 3 subjects, one wave (the first inhibitory or the first excitatory one, respectively) recovered differently from the other waves, indicating that they are not necessarily mediated by one type of afferent axons. The evidence, nevertheless, suggests that the different PSEC waves in man reflect the projection of the periodontal afferents upon several brain structures, involved in the control of the activity of the masseteric motorneurones, as: inhibitory and excitatory control requires different groups of interneurones; and a mediation of the first inhibitory wave by slower conducting axons than the second inhibitory wave, or a mediation of both waves by axons of similar type, is not compatible with common interneurones.

Adult↗
PubMed1985

The masseteric post-stimulus electromyographic-complex in people with dysfunction of the mandibular joint.

In mandibular joint-symptom-free subjects, post-stimulus EMG complexes (PSEC) were derived by standardized mechanical stimulation of an upper central incisor during clenching at a constant level of 5 per cent of maximal masseteric EMG activity. Seventy-two sweeps per subject were processed by means of a computer program, and different morphologies of the PSEC were seen. There appears to be no correlation with the Helkimo-index as a whole or its specific components. There is a strong correlation between tooth-grinding habits and the occurrence of a single inhibitory period. Patients with myofascial pain dysfunction consistently had a single inhibitory wave. When there was one affected side, the end latency of the second inhibitory wave was significantly shorter.

Adolescent↗
PubMed1984

Spectral analysis of the surface electromyogram as a tool for studying rate modulation: a comparison between theory, simulation, and experiment.

Theoretical work suggests that if the interpulse intervals ( IPIs ) of motor unit action potential trains ( MUAPTs ) are independently and normally distributed, then spectral analysis of the electromyogram could be a useful tool for studying rate modulation by virtue of the presence of a peak in the power spectrum at the average firing frequency of all active motor units. It is shown in this paper that IPIs need not be normally distributed, specifically that the results are very much the same if the IPIs are distributed according to a Gamma probability density function ( PDF ). Simulation of the electromyogram based on this theory proved the applicability of the method. Experimental results obtained for the masseter, biceps brachii and first dorsal interosseus (FDI) muscles, however, were in disagreement with both theory and simulation except for the biceps muscle at force levels up to 20% of the maximal force and for the masseter and FDI muscles in 1 out of 5 subjects. This indicates that the models for MUAPTs hitherto used might not be generally correct. Apart from this discrepancy, our results reveal differences between masseter and FDI muscles on the one hand and the biceps brachii on the other, which indicate that motor unit synchronisation is much more pronounced in the latter muscle.

Action Potentials↗
PubMed1984

The effects of motor unit synchronization on the power spectrum of the electromyogram.

A realistic model for two synchronized motor unit action potential trains (MUAPT) is presented in which the variability of the time difference between corresponding action potentials (hereafter denoted by delay) is taken into account. Specifically, this delay is modeled as a continuous random variable that may assume both positive and negative values. Expressions are derived for the auto- and cross-power spectra of two such trains using their relations with the auto- and cross-correlation functions, respectively, with which they form Fourier transform pairs. The results show that the auto- and the cross-power spectra of two such synchronized MUAPTs differ from the auto- and the cross-spectra of two independent MUAPTs. The contribution of the statistics of the interpulse intervals to one of the auto-power spectra is smaller and the cross-power spectra no longer reduce to a Dirac sigma-function at the origin but are now determined by the other auto-power spectrum and by the Fourier transform of the density function associated with the time difference between corresponding action potentials. As a consequence of this change in the cross-power spectra synchronization leads to an absolute increase of power at low frequencies and to a relative decrease of power at high frequencies. The results are then generalized to electromyograms (EMG) composed of more than just two MUAPTs and illustrated with simulated power spectra with which the theory shows excellent agreement.

Action Potentials↗
PubMed1984

Mandibular postural tremor during relaxation and during volitional innervation of the jaw muscles.

Jaw tremor was recorded as the changes in the vertical distance between mandible and maxilla. Two states of motor performance of the jaw muscles were chosen: relaxed and actively positioning of the mandible close to toothcontact, referred to as respectively rest- and activity tremor. Rest tremor contained a strong ballistocardiac component (bc power = 50%) and was of small amplitude (9.4 micron rms). Activity tremor revealed increased amplitudes (19.2 micron rms) with a predominant neuromuscular component (nm power = 75%). Bc tremor patterns differed significantly from nm tremor patterns. A negative linear relationship, which apparently was similar for rest and for activity tremor (P greater than 0.10), existed between the estimated bc contribution and tremor amplitude. As tremor amplitude increased neuromuscular activity appeared increasingly time locked to bc activity, which should be attributed to synchronization of spindle activity, either through the stretch reflex or through vascular pulsation. The average bc contribution to tremor amplitude remained of almost constant magnitude (7.0 micron rms), with no differences between rest and activity for the group as a whole. During resting conditions, complete relaxation of the jaw muscles was not attained by the majority of the subjects. The latter revealed a heart rate arrhythmia that was strongly correlated with motor (nm) activity (P less than 0.001). During activity conditions no such correlation was present. The present results demonstrate that for the understanding and the interpretation of the underlying mechanisms of jaw tremor genesis, both the recording technique, i.e., differential jaw displacements, and the signal analysis procedure, i.e., autocorrelograms and power spectra over extended record length, were of crucial importance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

The influence of clenching level on the post-stimulus EMG complex, including silent periods, of the masseter muscles in man.

Standardized mechanical taps were delivered on an upper central incisor, while the nine subjects investigated maintained constant clenching levels of 5, 10, 20, 40 and 60 per cent of their maximal EMG outputs. Using statistical criteria, a computer program enabled an objective determination of the interaction between the clenching level and the sequence of upward and downward going waves following the stimulus in full-wave rectified and superimposed EMG, called a post-stimulus EMG complex (PSEC). The morphology of the PSEC, including one or two silent periods, was subject-specific and reproducible over one year. The surfaces of the waves were greatly influenced by the clenching level. In general, their total surface decreased as a function of the clenching level. However, the individual waves decreased selectively. The results suggest that the sequence of waves results from overlapping of inhibitory and excitatory inputs. The inhibitory waves, constituting the silent periods, are largely cancelled by the excitatory reflexes of the PSEC.

Adult↗
PubMed1983

Influence of the rate of force application on the absolute psychophysical threshold level of periodontal mechanoreceptors in man.

In seven volunteers, controlled small forces were applied in an axial direction to a maxillary central incisor. The forces were generated by a stimulating device supported by the maxillary molars. The stimuli had a symmetrical triangular shape; force-application rates were varied from 1.88 to 960 mN/s. Threshold levels of sensation were determined at the various force-application rates. The relation between force-application rate and threshold level was negative, using 1.88, 3.75 and 7.5 mN/s stimuli. This trend was interrupted as threshold levels were higher at 15 than at 7.5 mN/s. In the range of more rapidly applied forces, 15-960 mN/s, the relationship was also negative, consistently, with a slope of -0.22 of the linear regression line after logarithmic transformation. It was concluded that the periodontal mechanoreceptive unit, as far as conscious functioning is concerned, may be described as a relatively inaccurate static force-detector when small magnitude forces are applied at low rates. Some rate sensitivity appears with more rapidly-applied stimuli.

Adult↗
PubMed1982

A pendulum system to deliver reproducible taps on single teeth to elicit silent periods in the electromyograms of human jaw muscles.

To deliver taps on single teeth, an easily-constructed pendulum system was designed which delivers mechanical stimuli with a constant intensity and morphology at high tapping rates. By interchanging the tips of the hammer mounted as a pendulum, the characteristics of the mechanical pulses can be modified. An electromagnetic brake makes the system insensitive to inevitable small variations of the head position. As no sound is produced prior to and up to 400 ms after the tap on the tooth, expectation patterns or acoustic reflexes which may influence the silent period are avoided. The system can also be used in animals.

Electromyography↗