Effect of experimental jaw muscle pain on EMG activity and bite force distribution at different level of clenching

Bite force at different levels of clenching and the corresponding electromyographic (EMG) activity in jaw‐closing muscles were recorded in 16 healthy women before, during and after painful stimulation of the left masseter muscle. Experimental pain was induced by infusion of 5·8% hypertonic saline (HS), and 0·9% isotonic saline (IS) was infused as a control. EMG activity was recorded bilaterally from the masseter and temporalis muscles, and static bite force was assessed by pressure‐sensitive films (Dental Pre‐scale) at 5, 50 and 100% of maximal voluntary contraction (MVC) during each session. Visual feedback was applied by showing EMG activity to help the subject perform clenching at 5, 50 and 100% MVC, respectively. EMG activity at 100% MVC in left and right masseter decreased significantly during painful HS infusion (1·7–44·6%; P < 0·05). EMG activity at 5% and 50% MVC was decreased during HS infusion in the painful masseter muscle (4·8–18·6%; P < 0·05); however, EMG activity in the other muscles increased significantly (18·5–128·3%; P < 0·05). There was a significant increase in bite force in the molar regions at 50% MVC during HS infusion and in the post‐infusion condition (P < 0·05). However, there were no significant differences in the distribution of forces at 100% MVC. In conclusion, experimental pain in the masseter muscle has an inhibitory effect on jaw muscle activity at maximal voluntary contraction, and compensatory mechanisms may influence the recruitment pattern at submaximal efforts.     

Effect of transcranial direct current stimulation on neuroplasticity in corticomotor pathways of the tongue muscles

The aim of this study is to investigate effects of transcranial direct current stimulation (tDCS) on neuroplasticity in corticomotor pathways related to tongue muscles evoked by a training task using the tongue drive system (TDS). Using a crossover design, 13 healthy participants completed two sessions of tDCS while performing 30 min of TDS training. Sessions were spaced at least 2 weeks apart and participants randomly received anodal and sham tDCS stimulation in the first session and the other condition in the second session. Single and paired pulse transcranial magnetic stimulation was used to elicit motor evoked potentials (MEPs) of the tongue at three time‐points: before, immediately after and 30 min after training. Participant‐based reports of fun, pain, fatigue and motivation, level of difficulty and effort were evaluated on numerical rating scales. There was no consistent significant effect of anodal and sham stimulation on single or paired pulse stimulation MEP amplitude immediately or 30 min after TDS training. Irrespective of tDCS type, training with TDS induced cortical plasticity in terms of increased MEP amplitudes for higher stimulus intensities after 30 min compared with before and immediately after training. Participant‐based reports revealed no significant difference between tDCS conditions for level of fun, fatigue, motivation, difficulty and level of effort but a significant increase in pain in the anodal condition, although pain level was low for both conditions. In conclusion, tongue MEP amplitudes appear to be sensitive to training with the tongue using TDS; however, anodal tDCS does not have an impact on training‐evoked neuroplasticity of tongue corticomotor pathways.     

Bite or brain: Implication of sensorimotor regulation and neuroplasticity in oral rehabilitation procedures

Tooth loss, decreased mass and strength of the masticatory muscles leading to difficulty in chewing have been suggested as important determinants of eating and nutrition in the elderly. To compensate for the loss of teeth, in particular, a majority of the elderly rely on dental prosthesis for chewing. Chewing function is indeed an important aspect of oral health, and therefore, oral rehabilitation procedures should aim to restore or maintain adequate function. However, even if the possibilities to anatomically restore lost teeth and occlusion have never been better; conventional rehabilitation procedures may still fail to optimally restore oral functions. Perhaps this is due to the lack of focus on the importance of the brain in the rehabilitation procedures. Therefore, the aim of this narrative review was to discuss the importance of maintaining or restoring optimum chewing function in the superageing population and to summarise the emerging studies on oral motor task performance and measures of cortical neuroplasticity induced by systematic training paradigms in healthy participants. Further, brain imaging studies in patients undergoing or undergone oral rehabilitation procedures will be discussed. Overall, this information is believed to enhance the understanding and develop better rehabilitative strategies to exploit training‐induced cortical neuroplasticity in individuals affected by impaired oral motor coordination and function. Training or relearning of oral motor tasks could be important to optimise masticatory performance in dental prosthesis users and may represent a much‐needed paradigm shift in the approach to oral rehabilitation procedures.     

The Cost-Effectiveness of the Kiva Antibullying Program: Results from a Decision-Analytic Model

Bullying causes substantial suffering for children and adolescents. A number of bullying prevention programs have been advocated as effective methods for counteracting school bullying. However, there is a lack of economic evaluations of bullying prevention programs assessing the “value for money.” The aim of this study was to assess the cost-effectiveness of the Finnish bullying prevention program KiVa in comparison to “status quo” (treatment as usual) in a Swedish elementary school setting (grades 1 to 9). The cost-effectiveness analysis was carried out using a payer perspective based on a Markov cohort model. The costs of the program were measured in Swedish kronor and Euros, and the benefits were measured using two different metrics: (1) the number of victim-free years and (2) the number of quality adjusted life years (QALYs). Data on costs, probability transitions, and health-related quality of life measures were retrieved from published literature. Deterministic and probabilistic sensitivity analyses were carried out to establish the uncertainty of the cost-effectiveness results. The base-case analysis indicated that KiVa leads to an increased cost of €829 for a gain of 0.47 victim-free years per student. In terms of the cost per gained QALY, the results indicated a base-case estimate of €13,823, which may be seen as cost-effective given that it is lower than the typically accepted threshold value in Swedish health policy of around €50,000. Further research is needed to confirm the conclusions of this study, especially regarding the treatment effects of KiVa in different school contexts.     

The bruxism construct: From cut‐off points to a continuum spectrum

This commentary discusses the need to move on from the adoption of cut‐off points for the definition of the presence/absence of bruxism and justifies the need to embrace an evaluation based on the continuum of jaw motor behaviours. Currently, the number of events per hour, as identified by polysomnography (PSG), is used to define the presence of sleep bruxism (SB). Whilst PSG still remains the indispensable equipment to study the neurophysiological correlates of SB, the scoring criteria based on a cut‐off point are of questionable clinical usefulness for the study of oral health outcomes. For awake bruxism (AB), criteria for a definite diagnosis have never been proposed. Some goal‐oriented strategies are proposed to identify bruxism behaviours that increase the risk of negative oral health outcomes (eg, tooth wear, muscle and/or temporomandibular joint [TMJ] pain, restorative complications). One possible strategy would embrace an improved knowledge on the epidemiology and natural variability of bruxism, even including study of the amount of PSG/SB and electromyography masticatory muscle activity (EMG/MMA) during sleep and the frequency/prevalence of bruxism behaviours during wakefulness that are needed to represent a risk factor for clinical consequences, if any. There should not be any preclusion about the diagnostic strategies to pursue that goal, and a combination of instrumental and non‐instrumental approaches may even emerge as the best available option. Once data are available, large‐scale, non‐selected population samples representing the entire continuum of EMG/MMA activities are also needed, in the attempt to estimate untreated health risks in the population.     

EFFECT OF TRANSCUTANEOUS NERVE STIMULATION ON MICROCIRCULATION IN INTACT SKIN AND BLISTER WOUNDS IN HEALTHY VOLUNTEERS

Healthy non-smoking volunteers participated in two experimental studies in which the circulatory changes induced by transcutaneous nerve stimulation (TENS) were quantified by two different methods. In experimental series 1 (intact skin), nine volunteers were given TENS on the left lower leg for 60 minutes on three occasions at different frequencies each time (2 Hz, 100 Hz, and sham). Changes in blood flow were assessed by laser Doppler imaging technique every five minutes. The mean blood flow increased by 40% during low frequency TENS and by 12% during high frequency TENS. There was no change in mean blood flow during sham stimulation. In experimental series 2 (blister wound), the circulatory changes induced by TENS were studied by intravital video microscopy and computerised image analysis in standard blister wounds on the lower leg. The microcirculatory blood flow, measured as red blood cell velocity (RBC-V) in 5-14 individual capillaries in each wound, was assessed before and during 45 minutes of TENS (2 Hz and 100 Hz). Mean RBC-V increased by 23% during low frequency TENS (n = 6) and by 17% during high frequency TENS (n = 8). The results show that: laser Doppler imaging and intravital video microscopy techniques can be used to study events at the microcirculatory level; the blister wound is an interesting new standard wound for use in clinical studies; and TENS stimulates the peripheral cirulation.     

Experiences of returning to work after acquired brain injury

The purpose of this qualitative study was to explore experiences of returning to work after rehabilitation, from the viewpoint of people with acquired brain injury. A purposive sampling of eight informants was made, and data were collected through personal interviews with open questions. The data were then analysed through qualitative content analyses in five steps, resulting in four main categories of experiences: “A new person”, “Stimulants and fellowship”, “Understanding and support”, and “To reach insight” with appurtenant sub-categories. The overarching theme was “Returning to work after acquired brain injury is a long process”. The conclusion of this study is that returning to work after acquired brain injury requires motivated individuals, flexible work, accommodating labour management, and prolonged environmental support. This study also shows that the informants need support for a long period of time to reach a balance and to obtain a functional working role. In order to achieve this, client-centred rehabilitation, professional teamwork, and longer follow-up periods than those of today are required.