Bruxism is mainly regulated centrally, not peripherally

Bruxism is a controversial phenomenon. Both its definition and the diagnostic procedure contribute to the fact that the literature about the aetiology of this disorder is difficult to interpret. There is, however, consensus about the multifactorial nature of the aetiology. Besides peripheral (morphological) factors, central (pathophysiological and psychological) factors can be distinguished. In the past, morphological factors, like occlusal discrepancies and the anatomy of the bony structures of the orofacial region, have been considered the main causative factors for bruxism. Nowadays, these factors play only a small role, if any. Recent focus is more on the pathophysiological factors. For example, bruxism has been suggested to be part of a sleep arousal response. In addition, bruxism appears to be modulated by various neurotransmitters in the central nervous system. More specifically, disturbances in the central dopaminergic system have been linked to bruxism. Further, factors like smoking, alcohol, drugs, diseases and trauma may be involved in the bruxism aetiology. Psychological factors like stress and personality are frequently mentioned in relation to bruxism as well. However, research to these factors comes to equivocal results and needs further attention. Taken all evidence together, bruxism appears to be mainly regulated centrally, not peripherally.     

Clinical tests in distinguishing between persons with or without craniomandibular or cervical spinal pain complaints

The recognition of a craniomandibular or cervical spinal pain is usually based upon the pain complaint of the patient, reported during an oral history, and the pain responses provoked in a clinical examination. Often used clinical tests are palpation, and function tests like dynamic/static tests or active movements. The relative importance of these tests for the recognition of the musculoskeletal pain is important. Therefore, it was the aim of the present study to determine which test, or combination of tests, best discriminates between persons with or without craniomandibular and/or cervical spinal pain complaints. Two hundred and fifty persons participated. From each person, a standardized oral history was taken. Then, in a randomized order and using a blind design, physical examinations of the craniomandibular system and of the neck were performed. Forward stepwise logistic regression analyses showed that the dynamic/static tests discriminated better between persons with and without pain complaints than the other tests did. In conclusion, in studies to the coexistence of craniomandibular and cervical spinal pain, it may be a good choice to base the recognition of these disorders on the pain complaints reported in the oral history which are verified by the pain response of the dynamic/static tests.     

Consensus-based clinical guidelines for ambulatory electromyography and contingent electrical stimulation in sleep bruxism

As yet, there are still no evidence-based clinical diagnostic and management guidelines for ambulatory single-channel EMG devices, like the BUTLER^® GrindCare^® (GrindCare), that are used in patients with sleep bruxism. Therefore, a consensus meeting was organised with GrindCare developers, researchers, and academic and non-academic clinicians experienced with the use of ambulatory EMG devices. The aim of the meeting was to discuss and develop recommendations for clinical guidelines for GrindCare usage, based on the existing clinical and research experience of the consensus meeting's participants. As an important outcome of the consensus meeting, clinical guidelines were proposed in which an initial 2-week baseline phase with the device in its inactive (non-stimulus) mode for habituation and assessment of the number of jaw-muscle activities is followed by a 4-week active phase with contingent electrical stimuli suppressing the jaw-muscle activities. As to avoid the commonly reported reduction in sensitivity to the stimuli, a 2-week inactive phase is subsequently installed, followed by a repetition of active and inactive phases until a lasting reduction in the number of jaw-muscle activities and/or associated complaints has been achieved. This proposal has the characteristics of a single-patient clinical trial. From a research point of view, adoption of this approach by large numbers of GrindCare users creates a great opportunity to recruit relatively large numbers of study participants that follow the same protocol.     

Comprehension of pictograms for pain quality and pain affect in adults with Down syndrome

Background Adults with Down syndrome (DS) are at risk for age-related painful physical conditions, but also for under-reporting pain. Pictograms may facilitate self-report of pain, because they seem suitable for the global visual processing in DS and for iconic representation of abstract concepts.

Method Participants (N?=?39, M age?=?41.2) assigned pain qualities to pictograms, rated pain affect levels in facial scales (pictograms vs. drawn faces), and performed cognitive tests.

Results Recognition of all intended pain qualities was above chance level. Pain affect levels of both facial scales were ordered equally well. Both facial scales were preferred equally well. Comprehension of the 3 scales was positively associated with mental age, receptive language ability, and verbal memory. Most participants (74%) had pictograms in their direct environment, mainly to communicate activities or objects.

Conclusion Using pictograms may optimise communication about pain for a subgroup of cognitively higher functioning adults with DS.     

Mandibular movements in response to electrical stimulation of superficial and deep parts of the human masseter muscle at different jaw positions.

Anatomical and electromyographical evidence suggests a compartmentalized function of the human jaw-closing muscles during both static and dynamic motor tasks. However, the voluntary nature of these tasks hampers unequivocal interpretation of this evidence, because it is impossible to activate voluntarily a single part of a muscle exclusively. Activation of discrete, localized regions can be accomplished with electrical stimulation. A previous study confirmed a functional subdivision of the temporalis muscle into at least three parts. Here, differences in the direction of the lower incisal-point (IP) movement in response to electrical stimulation of four different parts of the masseter muscle were examined in five healthy men. The deep masseter muscle and the anterior, middle, and posterior parts of the superficial masseter muscle were stimulated with monopolar wire electrodes in four different jaw positions (resting position; 50% maximum mouth opening; and 10-mm right and left lateral excursions, both with respect to resting position). Electrode-insertion depth was measured from magnetic resonance images. Movement responses to stimulation were recorded with the OKAS-3D jaw-movement analysis system. The variation in the direction of the IP movement in response to stimulation of parts of the masseter was partly explained by the effects of stimulus location and jaw position. The response to stimulation of the deep masseter was mainly laterovertically directed, whereas the response to stimulation of each of the superficial parts had a mainly anterovertical direction, the responses being most pronounced with the mandible in its resting position. These results provide further evidence for a functional subdivision of the masseter into a superficial part and a deep part, but not for a further subdivision of the superficial part into an anterior, middle, and posterior part.