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

Abstract 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.


| INTRODUC TI ON
Sleep bruxism has recently been defined as 'a masticatory muscle activity during sleep that is characterised as rhythmic (phasic) or non-rhythmic (tonic) and is not a movement disorder or a sleep disorder in otherwise healthy individuals.' 1 From this definition, it can be gathered that sleep bruxism is not a disorder, but 'just' a jawmuscle activity that does not require extensive diagnostic procedures or management, unless it is associated with negative health outcomes, like severe temporomandibular disorder (TMD) pain, extensive tooth wear and/or dental restoration fractures/failures. [2][3][4] In such cases, polysomnography (PSG; sleep recording) is considered the current gold standard diagnostic approach. 5 While PSG is costly, time-consuming, and has limited availability, a systematic review has identified several portable devices for the assessment of sleep bruxism, some of which yield promising accuracy. 6 Amongst others, BUTLER ® GrindCare ® (GrindCare; Sunstar Suisse SA, Etoy, Switzerland; Figure 1) has been developed for the easy, wireless assessment of sleep bruxism in the home environment of the individual, based on single-channel surface electromyography (EMG).
The device is able to discriminate sleep bruxism diagnosed by PSG in a selected and otherwise healthy young population, and it may thus be a valid choice in clinical practice for the assessment of sleep bruxism. 7 However, despite an increasing number of publications over the recent years, [8][9][10][11][12][13] there are as yet no evidence-based clinical diagnostic guidelines for GrindCare or any other ambulatory singlechannel EMG devices.
As indicated above, when sleep bruxism is associated with one or more negative health outcomes, not only a valid assessment but also a safe and effective management is indicated. Unfortunately, the literature on the management of sleep bruxism has long been inconclusive due to the poor study designs employed. 14 Happily, during the past decade, an increasing number of better-quality studies on the management of sleep bruxism have been published. 15 Nevertheless, there is still not enough evidence to define a standard of reference approach for the management of sleep bruxism. One of the more promising developments is the use of contingent electrical muscle stimulation, that is supposed to suppress the jaw-closing muscle activity through trigeminal reflexes. This technique is the principle behind GrindCare, which may be a safe and effective management strategy for sleep bruxism. So far, however, this has only been studied in small-scale research projects with highly selected study participants. [16][17][18][19][20] As for the use of GrindCare in the diagnosis of sleep bruxism, there are still no evidence-based clinical management guidelines for the device.
Since scientific evidence that could be used as the basis of clinical diagnostic and management guidelines is largely absent, 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. Three of the participants (FL, NNG and PS) are also members of the Academic Advisory Board for GrindCare, which is an unpaid role for two of them (FL and NNG).

| Questionnaire
Prior to the consensus meeting, the organisers (viz., Svensson and Uebersax) circulated a questionnaire amongst the participants, as to collect the participant's input on several selected GrindCare-related topics 1 : • Functionality/reliability (ie 1. does the device measure jaw-muscle activity and does it deliver contingent electrical stimuli and 2. do the GelPads provide sufficient attachment to the skin and/or do they cause skin irritation?); • Function/validity (ie 1. does the device assess jaw-muscle activity correctly and 2. does it apply the contingent stimuli correctly?); 1 Please note that the questionnaire focused on the use of BUTLER® GrindCare® (Figure 1). Depending on how the questions were formulated, they could either be answered as Yes, No or N/A, with or without a specification option.
The responses to the questionnaire were used to get the round-table discussion started. The discussion continued until full consensus was reached. The outcomes are elaborated below.

| RE SULTS
Six of the participants completed the questionnaire in advance. In Table 1, their names are indicated with a double asterisk. Below, the outcomes of the discussions are described per topic. Unless otherwise indicated, the reported issues are related to the BUTLER ® GrindCare ® (GrindCare; Figure 1).

| Functionality/reliability
The discussion on the functionality/reliability topic mainly focused on possible detachment of the GelPads that has been observed and that could be a possible cause for unreliable functioning. Half of the respondents reported loss of stickiness, even after thorough skin cleansing. Consequently, the GrindCare device itself does not function properly, which was also reported in the questionnaire. Assuming that patients always apply fresh GelPads every time, the loss of stickiness is possibly, at least in part, skin temperature-related or associated with a slight warming up of the device over time. As the stickiness cannot be further increased due to the concurrently increased risk of skin damage, the only available measure is to store the GelPads in a cool place prior to their application. In addition to the detachment issue, some cases of skin allergy have been encountered. This cannot be prevented other than by a thorough oral history and adequate user instructions.

| Function/validity
The discussion on the function/validity topic zoomed in on the contradictory respondents' reports and published research findings.

| Patient benefit
All respondents agreed that patients increase their awareness of bruxism when using the GrindCare. Four out of six respondents reported that their patients benefit from the GrindCare in terms of lifestyle adaptation as well as of the assessment and reduction in jaw-muscle activities. In the free text option, respondents indicated that their patients especially report reductions in oro-facial pain, headache, neck pain, jaw tension, teeth sensitivity, disturbed sleep and hypertrophic jaw musculature. As per the discussion on the patient benefit topic, it should be noted that scientific evidence for such reductions is largely lacking. Recently, however, Shimada et al 20 reported GrindCare-related reductions in jaw-muscle symptoms like soreness, tiredness and unpleasantness, but not in jaw-muscle pain.

| GrindCare indication
Especially, developing high bite forces while bruxing was frequently reported as an indication for GrindCare (4/6 respondents). To a much lesser extent, many negative health outcomes were considered an indication (2/6 respondents). While this latter outcome seems surprising, the discussion learned that all respondents were aware of the fact that scientific evidence for such indication is largely lacking and that at the same time all respondents expressed the desire to work as much as possible according to the principles of evidencebased dentistry. It should be noted that the paper by Shimada et al 20 was not available to the respondents at the time of the round-table discussions.

| Management protocol
The main part of the round-table discussions dealt with the management protocol for GrindCare usage. In Table 2, the respective questions and the respondents' answers are summarised. The outcomes of the discussion on this topic are summarised below.
Regarding the first question of this topic, all participants to the discussion agree that while differences in the positioning of the GrindCare between nights influence the measurements, they seem unimportant for the diagnostic and management functions of the device.
Questions 2-6 of this topic are related to the timing of the diagnostic and management phases of the GrindCare usage. Consensus on this important issue was reached as described in Table 3. For a schematic representation, see Figure 2. Apart from the proposed clinical guidelines, the participants agree that there is a large TA B L E 2 Questions and answers of the respondents (n = 6) related to the management protocol topic of the questionnaire that was filled in before the round-table consensus meeting, and the consensus that was reached during the meeting  Active phase (with contingent electrical stimulation; to reduce the number of jaw-muscle activities; the average number of jaw-muscle activities in the last 2 wk of this phase should be lower than the activity measured at baseline) 4 Inactive phase (without contingent electrical stimulation; to avoid commonly reported reduction in sensitivity to stimuli) 2

| D ISCUSS I ON
Repetition of active and inactive phases until a lasting reduction in the number of jaw-muscle activities and/or associated complaints has been achieved 4 resp. 2 TA B L E 3 Consensus-based clinical guidelines for BUTLER® GrindCare® usage: timing of the diagnostic and management phases F I G U R E 2 Schematic representation of the consensus-based clinical guidelines for BUTLER® GrindCare® usage: timing of the diagnostic and management phases yield unsatisfactory outcomes, pharmacological strategies are added to the management protocol. Clearly, at least at ACTA and Aarhus University, GrindCare is part of a larger management protocol, and more research is needed to establish the validity of this protocol. A large-scale study with that aim will be started shortly. Of course, the proposed clinical guidelines as described in the current paper will be implemented in that study's protocol. Other centres and clinics are encouraged to do that as well.
In conclusion, the consensus meeting that was organised with GrindCare developers, researchers, and academic and non-aca-