Jaw muscle soreness after tooth-clenching depends on force level.

The effects of prolonged tooth-clenching on masticatory muscle pain have not been fully elucidated. We hypothesized that late-onset soreness may develop depending on the clenching force. Ten pain-free females were asked to endure sustained clenching tasks up to exhaustion in randomized sequences of 7.5%, 10%, 15%, 25%, and 40% of maximum clenching force. Perceived pain, fatigue, and pressure-pain thresholds of masseter and temporalis muscles were assessed before, immediately after, and one day after the tasks. Endurance times differed markedly among participants and force levels, ranging from 1.2 to 245.1 min. Masseter pressure-pain threshold decreased immediately after (-13.7%; p = 0.050) and one day after (-22.0%; p = 0.006) the 7.5% task. Temporalis pressure threshold decreased one day after the 7.5 % task (-14.6%; p = 0.003). It was concluded that prolonged low-level tooth-clenching in healthy young women induces a delayed soreness in the jaw elevator muscles.

Oral lichen planus and intake of drugs metabolized by polymorphic cytochrome P450 enzymes.

OBJECTIVE: To study if patients with oral lichen planus (OLP) had a medication profile different from that of a control group without oral mucosal lesions. It was hypothesized that OLP lesions might result from poor drug metabolism (PM) because of genetic variation of the major cytochrome P450-enzymes (CYPs with a PM-risk). SUBJECTS AND METHODS: Dental records of 172 OLP patients were reviewed in this cross-sectional study and 152 sex- and age-matched subjects served as controls. The measures for the drug profiles were medicine type (ATC-code), mono- and polypharmacy, CYP-enzyme metabolism pattern, and medicine with a potential to induce lichenoid drug eruptions. RESULTS: Fifty per cent of the OLP patients consumed daily medications as compared with 59% of the controls. The OLP patients more frequently consumed medicines metabolized by CYPs with a PM-risk (P = 0.03). Furthermore, they consumed more medicine with an inhibitory effect on one or more CYPs than the controls (P = 0.01). CONCLUSION: Confounders like sex, age, systemic diseases, drug distribution into the therapeutic classes, and polypharmacy were similar in the two groups; but the OLP patients consumed more drugs metabolized by CYPs with a PM-risk. The results argue for further investigation of associations between OLP, medication intake and the CYP-enzyme metabolic pathways.

Effects of ethnicity, gender and age on clenching force and load distribution.

The aim of the study was to investigate the effect of ethnicity, gender and age on the degree of clenching force and distribution of the load over the dentition. The maximal clenching force was measured in 12 young Danish females, 12 young Japanese females, 12 young Japanese males and 10 senior Japanese males using the Dental Prescale System. The occlusal contact area, average pressure, occlusal load, antero-posterior and right-left location of the occlusal load center (i.e., a center of balance of the occlusal load distributed over the maxillary dentition: OLC) and dental arch length and width were analyzed and compared. The arch width and average pressure in young Danish females were significantly smaller/lower than in Japanese females. The arch length, arch width, contact area and total occlusal load in young Japanese males were significantly greater than those of the Japanese females. The average pressure in young Japanese males was also greater than in senior males. The location of the OLC was almost the same in all groups. The results suggest that the analysis of the OLC may be a useful method for evaluating occlusal function and prosthodontic treatment because the location of the OLC is not affected by ethnicity, gender and age.

Exploring the IBIS data library contents: tools for data visualisation, (pre-) processing and screening. Improved Monitoring for Brain Dysfunction in Intensive Care and Surgery.

During the IBIS project a high-quality data library of continuous and intermittent physiological signals and variables from patients during intensive care and surgery has been collected. To facilitate exploration of the full content of this data library a data browser was developed, which offers a flexible graphical display of the collection of multivariate data. To supplement the functionality of the display of the 'raw' data, a set of screening and pre-processing tools has been developed. A separate trend analysis tool offers a convenient overview of an entire recording focusing on the slow changes in the general state of the patient and the interaction between different physiological subsystems seen from a long-term perspective. A frequency analysis tool for processing the electroencephalography (EEG) signals has been integrated in the data browser to facilitate a quick screening of the cerebral function. The data library is the foundation of the development and validation of biosignal interpretation methods. This process can potentially be more productive using the described tool for algorithm prototyping based on a graphical network specifying the interaction between data processing primitives.

Bite force and occlusal load in healthy young subjects--a methodological study.

This study compares a new technique (Dental Prescale System) using pressure-sensitive foils for recording of maximal jaw closing force with a conventional clinical measurement using a miniature force transducer in 17 students. For assessment of load distribution the "pressure" image was superimposed on digitiZed images of dental casts and compared with clinical registrations of tooth contact. The bite force recorded with foil was systematically higher than that recorded by conventional measurements. Further more teeth were assessed as being loaded than having clinical occlusal contact. The new technique seems promising, although time consuming.

Digital archival and exchange of events in a simple format for polygraphic recordings with application in event related potential studies.

This paper describes a simple method of event encoding as an extension to a previously defined standard format, the European Data Format (EDF). The specification ensures full backward compatibility with the existing definition. By using this extension, the format can be used to store both continuous recordings and selected epochs of recordings. The encoding is performed in a channel of event-codes or in a pseudo-channel for annotations. Standardisation of event encoding is discussed. Decoding of events or annotations from the extended format is implemented at the application level. Existing programs that do not support the new encoding scheme still operate correctly and can simply ignore the new channels in processing 'extended' data files. The event encoding is also compatible with EDF's capability to encode channels of different sampling frequency.

[Quantitative EEG in assessment of anesthesia depth. Methods of comparison]. / Kvantitativ eeg til vurdering/af anaestesidybde. Metodesammenligning.

Methodology for assessment of depth of anaesthesia based on analysis of the electroencephalogram (eeg) is controversial. Techniques range from display of single measures, for example median value of the frequency spectrum, to dedicated pattern recognition systems based on measures of several eeg features. We have compared the performance of four techniques using tape-recorded data from 23 patients anaesthetised with either halothane or isoflurane using standardised regimens. The techniques were: median frequency, spectral edge frequency, the cerebral function analysing monitor (CFAM-1) and a depth of anaesthesia monitor based on eeg pattern recognition (ADAM). Dose-response curves are presented for stepwise increases in stable end-tidal concentrations of each agent. Results indicated considerable inter-patient variability and showed the limitations of single eeg measures, particularly with deeper anaesthesia producing burst suppression patterns in the eeg. Pattern recognition techniques reduced these difficulties and appeared to be promising over a wide range of anaesthetic levels.

Quantitative EEG in assessment of anaesthetic depth: comparative study of methodology.

Methodology for assessment of depth of anaesthesia based on analysis of the electroencephalogram (EEG) is controversial. Techniques range from display of single measures, for example median value of the frequency spectrum, to dedicated pattern recognition systems based on measures of several EEG features. We have compared the performance of four techniques using tape-recorded data from 23 patients anaesthetized with either halothane or isoflurane using standardized regimens. The techniques were: (1) median frequency, (2) spectral edge frequency, (3) the cerebral function analysing monitor (CFAM1) and (4) a depth of anaesthesia monitor based on EEG pattern recognition (ADAM). Dose-response curves are presented for stepwise increases in stable end-tidal concentrations of each agent. Results indicated considerable inter-patient variability and the limitations of single EEG measures, particularly with deeper anaesthesia producing a burst suppression pattern in the EEG. Pattern recognition techniques reduced these difficulties and appeared to be promising over a wide range of anaesthetic levels.

Ultrasonographic assessment of the swelling of the human masseter muscle after static and dynamic activity.

Work-related fatigue, pain and disorders in skeletal muscles have been related to prolonged static and dynamic activity. Such contractions have been shown to impair blood flow and increase muscle thickness and fluid. In the present study the effect of static and dynamic activity was evaluated from changes in masseter thickness as a measure of oedema, simultaneously with assessment of perceived pain/discomfort and cardiovascular responses. As static activity, fourteen young healthy women bit at 15% maximal voluntary contraction on bite-force transducers in the molar regions until exhaustion or 20 min at maximum (median endurance time 7.1 min). For dynamic activity, the same individuals chewed gum unilaterally until exhaustion or 40 min at maximum (all endured 40 min) with a cycle time of 725 ms, an average load of 9.3% of maximal electromyographic activity (maxEMG) and a peak mean voltage of 54.3% of maxEMG. Muscle thickness was measured by ultrasonography at the mid-portion of the ipsilateral masseter. Immediately after exercise, muscle thickness was significantly increased, more after static (14.0%) than dynamic (8.6%), and returned to pre-exercise values after 20-min recovery. Visual analogue scales (VAS) revealed the concomitant occurrence of pain (static 11.9 VAS%; dynamic 5.9 VAS%), and discomfort (static 8.1 VAS%; dynamic 5.9 VAS%), and both sensations decreased to pre-exercise values after 20-min recovery. Systolic blood pressure increased significantly, more during static (12.5%) than dynamic activity (4.3%), whereas heart rate rose significantly only during dynamic exercise (13.3%). Hence, activity was associated with muscular swelling and pain, and, despite the relatively small size of the masticatory muscles, also with general cardiovascular responses.

The value to the anaesthetist of monitoring cerebral activity.

The administration rate of general anaesthetic drugs is at present guided by clinical experience, and indirect indicators such as haemodynamic parameters. In the presence of muscle relaxants most of the clinical signs of inadequate anaesthesia are lost and accidental awareness may occur. A number of monitoring modalities, primarily based on analysis of the electroencephalogram (EEG), have been proposed for measurement of the anaesthetic depth. Moreover intraoperative cerebral monitoring may also provide the anaesthetist with early warning of cerebral ischaemia, or information on specific neurological pathways. To facilitate this, it is essential to combine analysis of the spontaneous EEG with recording of evoked potentials, to assess both cortical and subcortical activity/events. None of the reviewed methods, however promising, can alone meet all of the requirements for intraoperative monitoring of cerebral function. We suggest that the future direction should be to integrate several modalities in a single device, to provide valuable new information, upon which to base clinical management decisions.

Sleep disturbances in IDDM patients with nocturnal hypoglycemia.

Eight insulin-dependent diabetic patients were studied to evaluate sleep patterns during normoglycemia and spontaneous and insulin-induced hypoglycemia. Two channels of electroencephalogram (EEG), electromyogram and actooculogram were recorded. The signals were analyzed off-line, using a polygraphic sleep analysis system. The scoring was mainly based on the color density spectral array of the EEG. Blood glucose and growth hormone were measured serially. Asymptomatic, spontaneous nocturnal hypoglycemia occurred in 38% of the nights. Conventional sleep analysis showed a tendency toward prolongation of the two first rapid eye movement cycles on hypoglycemic nights, although it was insufficient to explain the activities seen during hypoglycemia. Blood glucose values below 2.0 mmol/l were observed in some of the patients accompanied by EEG changes with increased theta and delta activity.

Nocturnal electroencephalogram registrations in type 1 (insulin-dependent) diabetic patients with hypoglycaemia.

Eight Type 1 (insulin-dependent) diabetic patients with no diabetic complications were studied overnight for two consecutive and one subsequent night with continuous monitoring of electroencephalogram and serial hormone measurements. The aims were: 1) to evaluate the influence of spontaneous and insulin-induced hypoglycaemia on nocturnal electroencephalogram sleep-patterns and, 2) to evaluate counter-regulatory hormone responses. Spontaneous hypoglycaemia occurred on six nights (38%) with blood glucose concentrations less than 3.0 mmol/l and on four nights less than 2.0 mmol/l. All the patients experienced insulin-induced hypoglycaemia with a blood glucose nadir of 1.6 (range 1.4-1.9) mmol/l. The electroencephalogram was analysed by a new method developed for this purpose in contrast to the traditional definition of delta-, theta-, alpha- and beta-activity. The blood glucose concentration could be correlated to the rank of individual electroencephalogram-patterns during the whole night, and specific hypoglycaemic amplitude-frequency patterns could be assigned. Three of the eight patients showed electroencephalogram changes at blood glucose levels below 2.0 (1.6-2.0) mmol/l. The electroencephalogram classes representing hypoglycaemic activity had peak frequencies at 4 and 6 Hz, respectively, clearly different from the patients' delta- and theta-activity. The changes were not identical in each patient, however, they were reproducible in each patient. The changes were found equally in all regions of the brain. The three patients with electroencephalogram changes during nocturnal hypoglycaemia could only be separated from the other five patients by their impaired glucagon responses. Against this background the possibility of protection by glucagon, against neurophysiologic changes in the brain during hypoglycaemia may be considered.

Assessment of anaesthetic depth by clustering analysis and autoregressive modelling of electroencephalograms.

The brain activity electroencephalogram (EEG) was recorded from 30 healthy women scheduled for hysterectomy. The patients were anaesthetized with isoflurane, halothane or etomidate/fentanyl. A multiparametric method was used for extraction of amplitude and frequency information from the EEG. The method applied autoregressive modelling of the signal, segmented in 2 s fixed intervals. The features from the EEG segments were used for learning and for classification. The learning process was unsupervised and hierarchical clustering analysis was used to construct a learning set of EEG amplitude-frequency patterns for each of the three anaesthetic drugs. These EEG patterns were assigned to a colour code corresponding to similar clinical states. A common learning set could be used for all patients anaesthetized with the same drug. The classification process could be performed on-line and the results were displayed in a class probability histogram. This histogram reflected in all patients the depth of anaesthesia, when the concentration of the anaesthetic agent was adjusted either based on clinical signs or according to the protocol. This uniform display, where colours in a class probability histogram indicate the depth of anaesthesia, may in the future serve as on-line advice for the administration of anaesthetics. A comparison of multiparametric with single parametric methods, based on calculation of median, spectral edge and peak frequencies, questions the reliability of the single parametric methods in monitoring anaesthetic depth.

Computerized monitoring of depth of anaesthesia with isoflurane.

Changes in brain activity were studied at different depths of isoflurane anaesthesia. Ten healthy women (ASA group I) were investigated during non-critical surgery. Two channels of the EEG were stored on tape simultaneously with alveolar concentration of carbon dioxide, inspired oxygen concentration, mean arterial pressure, ECG and temperature. Signal processing was made offline. Spectral information from 2-s EEG segments was extracted using autoregressive modelling. Repetitive hierarchical clustering was used to define a common learning set of basic patterns. With this learning set, the EEG was classified, and the results presented in a class probability histogram. The basic patterns were related to the clinical depth of anaesthesia in all patients and assigned specific colours. Using this colour code, the class probability histogram showed a high degree of simplicity. Decreasing or increasing the isoflurane concentration caused the same trend in the class profile in all patients. This indicates that the EEG pattern might be a sensitive tool for decision making during administration of general anaesthetics.

Risk indicators for low back trouble.

A general population of 928 men and women aged 30, 40, 50 and 60 years participated in a health survey with emphasis on low back trouble (LBT). In all 135 variables were analysed to identify possible indicators for first-time experience and recurrence or persistence of LBT during a one-year follow-up. Stepwise logistic regression analyses were carried out to identify the most informative combinations of indicators for prediction of LBT. For men, a high risk for recurrence or persistence of LBT was associated with frequent LBT in the past, worsening of the LBT since its onset, sciatica and living alone. For women corresponding risk indicators were: recency of the last LBT episode, waking up during night because of LBT, aggravation of LBT when standing, rumbling of "the stomach" and smoking. The strongest risk indicators for first-time experience of LBT were epigastric pain, daily smoking and low isometric endurance of the back muscles. In addition, hospitalisations for whatever cause and a long distance from home to work showed predictive power for first-time LBT among gainfully employed participants. The results indicate that persons with either recurring or first-time LBT had more health problems and probably lived under a higher psycho-social pressure than those without LBT in the follow-up year.