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A De Laat

Publications and source records attributed to A De Laat.

At least 19 recordsLinked to original sources
PubMed2006

Reproducibility of the masseteric exteroceptive suppression period using stimulus-response curves.

The present study evaluated the reproducibility of the late exteroceptive suppression period (ES2) and of pain perception. The surface electro-myogram (EMG) was recorded from the left masseter muscle in 12 males and 12 females (22-31 year). Thirteen fixed stimulus intensities from 5 to 25 mA with 2.5 mA intervals were applied at random to the left mental area, and stimulus-response (S-R) curves were built for each subject. The first stimulation intensity at which the ES2 appeared was defined the reflex threshold, while the lowest stimulus intensity the subjects scored as painful, was called the pain threshold. Using the S-R curves, the other reflex parameters (appearance level, saturation level, slope from appearance to saturation, maximum duration of ES2, and maximum suppression degree) were also determined. Two measurement sessions were scheduled. Both the reflex and the pain sensation appeared at significantly lower stimulus intensity in females than males (P < 0.05). The reflex threshold, the reflex appearance and saturation level showed a significant decrease from the first to second session (P < 0.05), while the pain threshold was significantly higher during the second session (P < 0.01). By contrast, a good reproducibility was found for the maximum duration and suppression degree of ES2. Consequently, if S-R curves would be used to study the relation between the ES2 parameters and stimulus intensity in normal subjects for their applicability in clinical conditions, maximum duration and maximum suppression degree should be focused upon, in order to avoid session and gender effects as confounding factors.

Adult↗
PubMed2002

Hormone-dependent fluctuations of pressure pain threshold and tactile threshold of the temporalis and masseter muscle.

In order to better objectify reported pain and disturbed sensation, psychophysical parameters as pressure pain threshold (PPT) and tactile threshold (TT) have been introduced in pain research. The present study evaluated fluctuations of these parameters, obtained using an algometer (PPT) and von Frey hairs (TT), in relation to fluctuations in female reproductive hormones. Ten students not using oral contraceptives and eight students using oral contraceptives participated in the study. In addition, seven male students served as a control group. During two menstrual cycles, the PPT and TT of the masseter and temporalis muscles, as well as from the hand, were obtained twice per week. At the end of the study the values were evaluated in relation to the different phases of the menstrual cycle, by means of a linear mixed model. The TT appeared very reproducible within subjects and did not fluctuate over time. Scores on the left temporalis muscle appeared significantly higher than that on the right side. In all subjects the PPT tended to be higher on the left side, while in students using oral contraceptives, the PPT values of the temporalis muscle were significantly higher in the menstrual phase, and lower in the follicular phase. A significant correlation between the PPT of the temporalis muscle and the TT of the overlying skin was observed.

Adult↗
PubMed2001

Effects of local and remote muscle pain on human jaw reflexes evoked by fast stretches at different clenching levels.

Muscle pain imposes significant changes on natural motor tasks, but the consequences for stretch reflexes are still disputed. The present study examined the jaw reflexes to fast (10 ms) stretches of the mandible in an experimental model with local pain in the masseter muscle and remote pain in the tibialis anterior muscle. The stretch reflexes were elicited in healthy volunteers (n=13) before, during, and after periods with constant levels of experimental pain and while the subjects clenched at 0%, 15%, 30%, and 45% of the maximal voluntary contraction (MVC) levels. Surface electromyography (EMG) was used to record the reflex responses. Pain in the masseter muscle (mean +/- SEM, 3.8+/-0.4 on a 10-cm visual analogue scale), but not in the tibialis anterior muscle (3.4+/-0.3; paired t-test, P=0.318) was associated with significant changes in both prestimulus EMG activity (ANOVA, P=0.002) and in peak-to-peak amplitudes of the stretch reflex (ANOVA, P=0.022). However, when the changes in prestimulus EMG activity were taken into consideration a significant increase in the stretch reflex persisted in the painful muscle at 15% and 30% MVC. Local circuits at the trigeminal level involving the fusimotor system are proposed to mediate a significant part of this modulatory effect.

Adult↗
PubMed2001

Tactile threshold and pressure pain threshold during treatment of orofacial pain: an explorative study.

The aim of the present study was to evaluate the pressure pain threshold (PPT), tactile threshold (TT) and pain intensity as measured on a Visual Analogue Scale (VAS) in patients with pain in the orofacial region. Twenty-six patients with myogenous pain (7 ss), myogenous and capsular pain (11 ss) or neuropathic pain (8 ss) participated in the study. At baseline, the PPT was evaluated using an algometer and the TT using von Frey hairs. In addition, the pain intensity was rated on a VAS scale and the psychological profile made using the SCL-90 questionnaire. In some of the patients, the measurement procedure was conducted I week later, immediately before active treatment started. As active treatment, patients with myogenous or capsular pain received physical therapy in addition to conscious relaxation of the masticatory system, while patients with neuropathic pain were treated using tricyclic antidepressant medication. After 4 to 6 weeks, the measurements were repeated. Statistical evaluation using a linear mixed model revealed no significant changes in TT. In patients with myogenous and capsular pain, as well as in patients with neuropathic pain, the PPT increased after active treatment, while it decreased in the group with pure myogenous pain. The VAS score decreased in all groups. Regarding psychological profiles, a variety of characteristics were observed and the scale for sleeping problems was especially elevated in a majority of the patients.

Adult↗
PubMed2001

Long-term fluctuations of pressure pain thresholds in healthy men, normally menstruating women and oral contraceptive users.

The aim of this investigation was to evaluate whether the pressure pain threshold (PPT) in masticatory muscles of symptom-free subjects was influenced by fluctuations of the sex hormones. The PPT was measured with an electronic algometer for at least 10 consecutive menstrual cycles in 10 women using oral contraceptives and 10 women not using oral contraceptives, with a regular menstrual cycle (26-31 days). In addition, 10 men were measured in a regular pattern over a period of 1 year. All subjects were symptom-free with an age range between 18 and 39 years. Measurement sessions were held during three different cycle phases (follicular, luteal, perimenstrual) and each session consisted of four consecutive PPT measurements. By means of a linear mixed model (SAS), the PPTs of the masster, temporalis and thumb muscles were compared between: (1) groups, (2) sex-hormonal phases, (3) the four consecutive measurements of each muscle per session and (4) time. The PPTs of the masseter (p = 0.8419) and temporalis muscles (p = 0.2786) did not change significantly over time. There was no significant difference in variance for the masseter (p = 0.6250), temporalis (p = 0.9705) and thumb (p = 0.7446) between the three groups. The PPTs of all muscles were significantly lower during the perimenstrual phases in the two female groups. The present data showed similar patterns of PPTs for the three muscle groups. Moreover, the results have shown a very good consistency of the PPTs over a long time period, both in males and females.

Adult↗
PubMed2001

Temporomandibular disorders as a source of orofacial pain.

Since decades, the dental profession has been challenged by pain and dysfunction of the masticatory system. In recent years, a better understanding of the pathophysiological mechanisms of masticatory pain paralleled the increase of basic and clinical research focusing on pain in general. Consequently, so-called diagnostic techniques and treatment procedures, based upon hypothetical, sometimes dogmatic, etiological mechanisms, are increasingly questioned, and the ill-supported thoughts are gradually replaced by research-based insights. In addition, a better communication between basic scientists, researchers, and medical or dental practitioners focusing on musculoskeletal pain, has led to an improved quality of research on pain and dysfunction of the masticatory muscles and the temporomandibular joint (TMJ). This paper will try to review this progress, comment on the clinical implications, and give some suggestions for future research.

Facial Pain↗
PubMed2000

The way forward.

Explore the source record for details and available documents.

Dental Research↗
PubMed2000

[Bruxism: well known, but difficult to fathom].

Tooth clenching or grinding may cause serious problems for patients and dentists. Symptoms occur at the level of the teeth (wear), the periodontium and the musculoskeletal system. In the past, the definition of bruxism often was vague and controversial, and also a clinical diagnosis appeared to be difficult. More recently research in the sleep laboratory, using a combination of electromyography video- and sound recording, made it possible to distinguish between bruxism and other oral behaviour. The association between pain and dysfunction of the masticatory system with bruxism is still unclear.

Adult↗
PubMed2000

[Bruxism and overload of periodontium and implants].

Bruxism is responsible for occlusal tooth wear but can not induce nor aggravate gingivitis or periodontitis. Bruxism induces jiggling forces, which cause a clinical tooth hypermobility, radiologically seen as a widened periodontal space. Although there is no direct causal relation between bruxism and implant failure, implant overload may lead to fractures of the components and bone loss.

Bruxism↗
PubMed1999

Effect of clenching levels on heteronymous H-reflex in human temporalis muscle.

Selective stimulation of the masseteric nerve has been shown to elicit a heteronymous H-reflex in the ipsilateral temporalis muscle during voluntary clenching. However, the relation between the electromyographic (EMG) activity of the temporalis muscle and the amplitude of the H-reflex has not been previously described. In the present study, the hypothesis was tested that there would be a positive relationship between the level of EMG activity and the amplitude of the H-reflex. The direct motor response (M-response) in the masseter muscle and the heteronymous H-reflex in the anterior temporalis muscle were successfully elicited by electrical stimulation of the masseteric nerve in 12 of 13 subjects. A new automatic system was used to control the on-line EMG activity and to trigger the stimulus. In a random order, two series of 20 stimuli were delivered at each of four clenching levels (0, 25, 50, and 75% of maximal voluntary contraction). The analysis showed that both the masseteric M-response and the temporalis H-reflex were reproducible within and between series. The amplitude of the temporalis H-reflex increased significantly at higher clenching levels (ANOVA: P=0.003). Clenching at 50% and 75% of the maximal voluntary contraction caused significantly larger amplitudes of the H-reflex than clenching at 25% of the maximal voluntary contraction; at rest, no H-reflex could be recorded. There was a significant correlation between the background EMG activity in the ipsilateral temporalis muscle and the amplitude of the H-reflex (Pearson: r=0.313, P=0.008). These data indicate that the heteronymous H-reflex can be reliably elicited by means of an automatic system for stimulus delivery and that the amplitude of the H-reflex is dependent on the preceding activity of the motoneuron pool.

Adult↗
PubMed1998

Experimental jaw-muscle pain does not change heteronymous H-reflexes in the human temporalis muscle.

Muscle pain generally has an inhibitory effect on voluntary orofacial motor function. However, it is not known whether muscle pain causes direct or indirect changes in motoneuron excitability. In this study a monopolar needle stimulation technique was used to evoke the direct motor response (M-response) in the left masseter muscle and the heteronymous H-reflex in the left temporalis muscle as an indirect measure of motoneuron excitability. Series of 20 repeated electrical stimuli were delivered at 50% of maximal voluntary contraction (MVC) before, during, and after periods with experimental jaw-muscle pain in 11 healthy subjects. Pain was induced by standardized infusion of hypertonic (5%) saline into the mid-portion of the right masseter muscle. The mean pain intensity rating on a 100-mm visual analog scale was 42+/-5 mm. The short-latency responses (less than 6 ms) could be evoked in all subjects. Analysis of the latency and amplitude of the temporal H-reflex indicated no significant effect of jaw-muscle pain. The amplitude of the masseteric M-response was significantly smaller in the postpain condition than in the pain conditions (ANOVA, P=0.018), but no differences were found between the prepain and postpain conditions. In nine subjects, poststimulus periods (mean offset latency, 69.6+/-8.6 ms) with significantly (more than 50%) suppressed EMG activity were detected in the ipsilateral masseter muscle following the M-response (mean offset latency, 5.5+/-0.2 ms). These reflex responses did not show a systematic change during the pain conditions. In conclusion, acute contralateral jaw-muscle pain does not seem to modulate the motoneuron excitability as measured by the heteronymous H-reflex.

Adult↗
PubMed1998

Correlation between cervical spine and temporomandibular disorders.

Neuroanatomical interconnections and neurophysiological relationships between the orofacial area and the cervical spine have been documented earlier. The present single-blind study was aimed at screening possible correlations between clinical signs of temporomandibular disorders (TMD) and cervical spine disorders. Thirty-one consecutive patients with symptoms of TMD and 30 controls underwent a standardised clinical examination of the masticatory system, evaluating range of motion of the mandible, temporomandibular joint (TMJ) function and pain of the TMJ and masticatory muscles. Afterwards subjects were referred for clinical examination of the cervical spine, evaluating segmental limitations, tender points upon palpation of the muscles, hyperalgesia and hypermobility. The results indicated that segmental limitations (especially at the C0-C3 levels) and tender points (especially in the m. sternocleidomastoideus and m. trapezius) are significantly more present in patients than in controls. Hyperalgesia was present only in the patient group (12-16%).

Adolescent↗
PubMed1998

Heteronymous H-reflex in temporal muscle motor units.

An electric stimulation of the masseteric nerve elicits a heteronymous H-reflex in the temporal muscle. The characteristics of this reflex response were investigated by analysis of the firing probability changes of single motor units. Eleven healthy subjects participated in the experiments. The heteronymous H-reflex of the temporal muscle was electrically elicited by stimulation of the masseteric nerve at 120% of the intensity needed for the maximal masseteric M-wave. From 8 to 24 motor units were sampled from the temporal muscle of each subject. Peri-stimulus time histograms of motor unit recordings were built with a 0.5-ms bin width. The mean firing probability was calculated for the 20 ms preceding the stimulus. The firing probability was considered increased when it exceeded the mean by 3 standard deviations. Of 104 sampled motor units, 40 motor units showed a significant increase of the firing probability, which lasted 1 ms or less in 29 of them. In 12 out of 16 motor units, a significant increase of firing probability also persisted at a lower stimulation intensity (120% of the threshold needed to elicit a masseteric M wave). These data indicate that: (1) some temporal muscle motor units are modulated by afferents from the masseter muscle, (2) the heteronymous H-reflex has a monosynaptic component, and (3) there might be a more complex than just monosynaptic organization serving the heteronymous temporal H-reflex. For the latter conclusion regarding synaptic wiring, however, PSTH studies like the present one can offer only indirect evidence, and this question could be better studied in animals.

Adult↗
PubMed1998

Are jaw and facial reflexes modulated during clinical or experimental orofacial pain?

A variety of jaw and facial reflexes can be evoked by orofacial mechanical or electrical stimuli. Because of its possible diagnostic utility in the management of pain and dysfunction of the masticatory system, the exteroceptive suppression that can be evoked in the masseter and temporalis muscles has been particularly investigated. A review of the different studies emphasizes the crucial importance of the area stimulated and the type of stimulation used to evoke the reflex. More recent studies have applied the necessary standardization of stimulus intensity, clenching levels, recording procedures, and unbiased interpretation of the reflex components in muscle electromyographic (EMG) activity. Controversial results have been reported regarding the differences in these inhibitory (and excitatory) reflex responses between temporomandibular disorder or headache patients and controls. Even if the absence of a second inhibitory phase in the masseteric EMG activity of the patients is a frequent finding, its sensitivity and specificity as a diagnostic tool for myogenous pain or bruxism remain to be tested. Controlled studies on the duration of the second exteroceptive suppression period in tension-type headache patients could not confirm the initially reported difference between patients and asymptomatic subjects. Studies that involve experimentally induced muscle pain could provide better insight into the characteristics of the afferent fibers and synaptic circuitry that are involved in the jaw and facial reflexes.

Arthralgia↗
PubMed1998

Short-term reproducibility of pressure pain thresholds in masticatory muscles measured with a new algometer.

The purpose of this project was to test the within-day and between-days reproducibility of a new and inexpensive algometer. Twelve symptom-free men and nine women participated. Pressure pain thresholds (PPTs) of the bilateral masseter and temporalis muscles were assessed during four sessions (mornings and afternoons of days 1 and 3). During each session, each palpation point of the masticatory muscles was measured four times. There was an interval of only a few seconds between measurements 1 and 2, and between measurements 3 and 4, respectively, while at least 5 minutes of rest were allowed between measurements 2 and 3. The PPT values between the morning and afternoon sessions and between days 1 and 3 were not significantly different. When the within-session reproducibility for all muscles was considered, only the PPT values between measurements 2 and 4 were not significantly different. Analysis of variance showed that the interindividual variability of PPT was 1.4 to 6.8 times higher than the variability observed within or between sessions and days. No gender difference was found.

Adult↗