Influence of occlusal appliances on the masticatory muscle function in individuals with sleep bruxism: A systematic review and meta-analysis.

This systematic review answers the question: "Does occlusal appliance use influence masticatory muscle function of dentate individuals with sleep bruxism?". The literature search included six databases, grey literature, and manual search for articles. Randomized and non-randomized clinical trials were included comparing muscle function of sleep bruxers before and after receiving occlusal appliances. Risk of bias was assessed with risk of bias assessment for randomized and non-randomized clinical trials tool. Twelve studies, three represent randomized clinical trials, were included. Risk of bias was considered low, moderate, or serious. Meta-analyses indicated that soft and hard appliances did not influence muscle activity and bite force of bruxers. Qualitative analysis showed that occlusal appliance use did not influence masticatory performance and muscle volume. However, it was effective in reducing tongue force. Certainty of evidence was considered very low for muscle activity when evaluated with hard appliances, and for bite force evaluated with both appliance materials. Low certainty of evidence was observed for muscle activity with soft appliances. Based on the findings of this meta-analysis, occlusal appliances do not affect masticatory muscle function of sleep bruxers. Regardless of appliance material, the activity of masseter and temporal, and bite force of sleep bruxers was not influenced.

Hemodynamic changes in the temporalis and masseter muscles during acute stress in healthy humans.

PURPOSE: Autonomic control of orofacial areas is an integral part of the stress response, controlling functions such as pupil dilatation, salivation, and skin blood flow. However, the specific control of blood flow in head muscles during stress is unknown. This study aims to investigate the hemodynamic response of temporalis and masseter muscles in response to five different stressors. METHODS: Sixteen healthy individuals were subjected to a randomized series of stressors, including cold pressor test, mental arithmetic test, apnea, isometric handgrip, and post-handgrip muscle ischemia, while in the sitting posture. Finger-pulse photoplethysmography was used to measure arterial blood pressure, heart rate, and cardiac output. Near-infrared spectroscopy was used to measure changes in tissue oxygenation and hemoglobin indices from the temporalis and masseter muscles. RESULTS: All stressors effectively and significantly increased arterial blood pressure. Tissue oxygenation index significantly increased in both investigated head muscles during mental arithmetic test (temporalis: 4.22 ± 3.52%; masseter: 3.43 ± 3.63%) and isometric handgrip (temporalis: 3.45 ± 3.09%; masseter: 3.26 ± 3.07%), suggesting increased muscle blood flow. Neither the masseter nor the temporalis muscles evidenced a vasoconstrictive response to any of the stressors tested. CONCLUSION: In the different conditions, temporalis and masseter muscles exhibited similar hemodynamic patterns of response, which do not include the marked vasoconstriction generally observed in limb muscles. The peculiar sympathetic control of head muscles is possibly related to the involvement of these muscles in aggressive/defensive reactions and/or to their unfavorable position with regard to hydrostatic blood levels.

Correlations between sleep architecture and sleep-related masseter muscle activity in children with sleep bruxism.

BACKGROUND: Sleep bruxism (SB) occurring during No-REM (nREM) sleep and increase in microarousals per hour have been described in adults, but not in children. OBJECTIVE: To assess the correlation between sleep architecture and masseter muscle activity related to sleep bruxism (SB/MMA) in children. MATERIALS AND METHODS: Forty-three children aged 7-12 years (mean age: 9.4 ± 1.3) with confirmed SB underwent a two-night polysomnographic (PSG) study in a sleep laboratory, for accommodation (first night) and data collection (second night). Data on sleep architecture (total sleep duration (TSD), sleep efficiency (SE), sleep onset latency (SOL), REM and nREM sleep duration and proportion and microarousals/hour during REM and nREM sleep) and episodes/hour of SB/MMA were recorded. Single and multiple-variable linear regression analyses were performed to assess the correlation between data on sleep architecture (predictors) and SB/MMA (dependent variable). RESULTS: Shorter TSD, REM and nREM stage 1 sleep duration, longer SOL and more microarousals/hour during REM and nREM sleep were found to be positive predictors of SB/MMA in children in the multiple-variable regression analysis (R2  = 0.511). CONCLUSION: Within the limitations of this study, it can be concluded that SB/MMA is correlated with altered sleep architecture in children (shorter total sleep duration (TSD), shorter nREM and REM sleep and higher microarousals during REM and nREM sleep). Nevertheless, the clinical significance of these findings need to be demonstrated in future studies.

Relationship between masseter muscle activity during wakefulness and temporomandibular disorder-related symptoms.

BACKGROUND: Masseter muscle activity during wakefulness may be associated with temporomandibular disorder (TMD)-related symptoms, psychosocial status and pain-related disability; however, this relationship is unclear. OBJECTIVES: This study aimed to determine the relationship between masseter muscle electromyography (EMG) burst/duration during wakefulness and TMD-related symptoms, psychosocial status and pain-related disability. METHODS: Sixty participants were assessed masseter muscle activity during wakefulness using a data-logger-type ultraminiature EMG system and TMD-related symptoms, psychosocial status and pain-related disability through Axis I and II of the diagnostic criteria for TMD (DC/TMD). EMG bursts lasting longer than 0.25 s but less than 2.0 s and those lasting longer than 2.0 s were classified as phasic and tonic bursts, respectively. RESULTS: Participants with palpation-related pain in the temporalis and masseter muscles, as assessed through the DC/TMD examination form in Axis I, had more bursts (number/h) (p = .035 and p = .009, respectively) and longer duration (time/h) (p = .013 and p = .004, respectively) of tonic bursts of the masseter muscle during wakefulness. Participants with palpation-related pain in the masseter muscles had higher oral behaviour scores during wakefulness using Axis II (p = .001), which affected the number and duration of tonic bursts of the masseter muscle activity during wakefulness (p = .011 and p = .007, respectively). CONCLUSION: As tonic bursts mainly reflect clenching, individuals with pain in the masseter muscles by palpation may have a high frequency and longer duration of clenching, as well as a high frequency of oral behaviours during wakefulness.

Occurrence, presence and severity of bruxism and its association with altered state of consciousness in individuals with severe acquired brain injury.

BACKGROUND: Excessive jaw muscle activity is a frequent complication after acquired brain injury (ABI). OBJECTIVE: The study aimed to identify the occurrence and severity of jaw muscle activity and its association with altered state of consciousness in patients with ABI. METHODS: A total of 14 severe ABI patients with varied altered state of consciousness were recruited. A single-channel electromyographic (EMG) device was used to assess the jaw muscle activity for three consecutive nights during Week 1 and Week 4 following admission. Differences in number of EMG episodes/h between Week 1 and 4 were analysed using non-parametric tests and association between the EMG activity and altered state of consciousness were analysed using Spearman's correlation test. RESULTS: Nine of fourteen (64%) patients showed indications of bruxism (cutoff: >15 EMG episodes/h). The average EMG episodes/h at admission were 44.5 ± 13.6 with no significant changes after Week 4 of admission (43 ± 12.9; p = .917). The EMG episodes/h ranged from 2 to 184 during Week 1 and 4-154 during Week 4. There were no significant correlations between the number of EMG episodes/h during the three nights and the individuals altered state of consciousness during Week 1 and Week 4. CONCLUSION: Patients with ABI had a conspicuously high but variable level of jaw muscle activity at admission and it tend to remain high after 4 week of hospitalisation which could potentially lead to adverse effects such as excessive tooth wear, headaches and pain in jaw muscles. The lack of associations between individuals altered level of consciousness and EMG activity could be due to low sample size and further studies are clearly warranted in this patient group with special needs. Single-channel EMG devices can record jaw muscle activity early in the hospitalisation period and might be a helpful tools for early detection of bruxism in ABI patients.

Effects of age and diet consistency on the expression of myosin heavy-chain isoforms on jaw-closing and jaw-opening muscles in a rat model.

BACKGROUND: Skeletal craniofacial morphology can be influenced by changes in masticatory muscle function, which may also change the functional profile of the muscles. OBJECTIVES: To investigate the effects of age and functional demands on the expression of Myosin Heavy-Chain (MyHC) isoforms in representative jaw-closing and jaw-opening muscles, namely the masseter and digastric muscles respectively. METHODS: Eighty-four male Wistar rats were divided into four age groups, namely an immature (n = 12; 4-week-old), early adult (n = 24; 16-week-old), adult (n = 24; 26-week-old) and mature adult (n = 24; 38-week-old) group. The three adult groups were divided into two subgroups each based on diet consistency; a control group fed a standard (hard) diet, and an experimental group fed a soft diet. Rats were sacrificed, and masseter and digastric muscles dissected. Real-time quantitative polymerase chain reaction was used to compare the mRNA transcripts of the MyHC isoforms-Myh7 (MyHC-I), Myh2 (MyHC-IIa), Myh4 (MyHC-IIb) and Myh1 (MyHC-IIx)-of deep masseter and digastric muscles. RESULTS: In the masseter muscle, hypofunction increases Myh1 (26, 38 weeks; p < .0001) but decreases Myh4 (26 weeks; p = .046) and Myh2 (26 weeks; p < .0001) expression in adult rats. In the digastric muscle, hypofunction increases Myh1 expression in the mature adult rats (38 weeks; p < .0001), while Myh2 expression decreases in adult rats (26 weeks; p = .021) as does Myh4 (26 weeks; p = .001). Myh7 expression is increased in the digastric muscle of mature adult rats subjected to hypofunction (38 weeks; p = <.0001), while it is very weakly expressed in the masseter. CONCLUSION: In jaw-opening and jaw-closing muscles, differences in myosin expression between hard- and soft-diet-fed rats become evident in adulthood, suggesting that long-term alteration of jaw function is associated with changes in the expression of MyHC isoforms and potential fibre remodelling. This may give insight into the role of function on masticatory muscles and the resultant craniofacial morphology.

Clinical and electromyographic signals analysis about the effect of space-adjustment splint on overerupted maxillary molars.

BACKGROUND: Overerupted maxillary molars is common in adults, which can lead to insufficient intermaxillary vertical space ,great difficulty in prosthetic reconstruction ,and cause occlusal interference in movements.To reconstruct occlusal function, it is necessary to prepare enough space for prostheses. The aim of the present study was to evaluate the effect of space-adjustment occlusal splint on overerupted maxillary molars by clinical and electromyographic signals analysis. METHODS: Eighteen patients with overerupted maxillary molars were selected to wear space-adjustment occlusal splint suppressing overerupted maxillary molars for three months. Satisfaction was assessed by 5-point Likert; intermaxillary vertical space and the teeth transportation distance were measured in models; clinical periodontal status were evaluated by periodontal probing depth (PPT) and bleeding index (BI); electromyographic recordings of the masseter and anterior temporal muscles were monitored by Cranio-Mandibular K7 Evaluation System. RESULTS: All the patients were satisfied with the treatment effect (Likert scale ≧ 4). The intermaxillary space in edentulous areas after treatment showed statistically significant increasing when compared with those before treatment. PPT and BI showed no significant difference. No statistically significant differences were found in electromyographic activity of anterior temporal muscles, while a reduction of muscle activity in masseter in the contralateral side were detected in post-treatment evaluations compared with pre-treatment at mandibular rest position. CONCLUSIONS: Space-adjustment occlusal splint is an efficient treatment option on overerupted maxillary molars by intruding the maxillary molar to obtain adequate intermaxillary space for prostheses.

Bichectomy Surgery and EMG Masticatory Muscles Function in Adult Women: A Longitudinal Study.

AIM: This longitudinal study aimed to evaluate the electromyographic activity of the masseter and temporal muscles in adult women who underwent buccal fat removal. MATERIALS AND METHODS: The sample consisted of 20 healthy adult women with no temporomandibular dysfunction and normal occlusion, who were assessed before, 30, and 60 days after the surgery. The electromyographic signal of the masseter and temporal muscles was captured through mandibular tasks including rest, protrusion, right and left laterality, and maximum voluntary contraction with and without parafilm. The results obtained were tabulated and the Shapiro-Wilk normality test was performed, which indicated a normal distribution. Statistical analysis was performed using the repeated measures test (p < 0.05). RESULTS: Significant differences were observed between time periods in maximum voluntary contraction for the left masseter muscle (p = 0.006) and in maximum voluntary contraction with parafilm for the right temporal (p = 0.03) and left temporal (p = 0.03) muscles. CONCLUSION: Bichectomy surgery did not modify the electromyographic activity of the masseter and temporal muscles during the rest task but may have influenced variations in the electromyographic signal during different mandibular tasks after 60 days of surgery, suggesting compensatory adaptations and functional recovery. CLINICAL SIGNIFICANCE: Understanding the impact of buccal fat removal surgery on the stomatognathic system function provides insights into postoperative functional recovery and potential compensatory adaptations, guiding clinical management and rehabilitation strategies for patients undergoing such procedures. How to cite this article: Cardoso AHDLS, Palinkas M, Bettiol NB, et al. Bichectomy Surgery and EMG Masticatory Muscles Function in Adult Women: A Longitudinal Study. J Contemp Dent Pract 2024;25(3):207-212.

[Evaluation of the efficiency of the method of biological feedback in complex therapy of patients with hypertonus of the chewing muscles]. / Metod biologicheskoi obratnoi svyazi v kompleksnoi terapii patsientov s gipertonusom zhevatel'nykh myshts.

The aim the study. Evaluate the effectiveness of biofeedback therapy in the complex rehabilitation of masticatory muscle hypertonicity in patients with a high level of anxiety. MATERIAL AND METHODS: The study included 40 patients aged 20 to 32 years with complaints of fatigue and discomfort in the area of chewing muscles, teeth compression during the day, nocturnal bruxism, crowding of teeth. Two groups were formed: the study group, whose patients underwent splint therapy in combination with biofeedback therapy trainings; in the control group, patients received treatment with splint therapy without the use of biofeedback therapy. Electromyography of the masticatory muscles at rest and during compression were used to diagnose hypertonicity of the masticatory muscles. To assess the psycho-emotional state, a medical and social questionnaire was conducted using questionnaires: «Health Questionnaire¼, Beck Depression Inventory, Spielberger-Khanin Anxiety Scale, SF-16 Quality of Life Scale. RESULTS: A decrease in the level of depression, anxiety was revealed with the stabilization of emotional sensitivity in relation to other people, emotional involvement in everyday life, and an increase in the quality of life. When comparing electromyographic data at rest and during clenching of teeth in patients of the study group the indicators were lower than in the control group. CONCLUSIONS: The effectiveness of biofeedback therapy at the stages of orthodontic treatment using splint therapy was established in the form of a decrease in the activity of masticatory muscles in patients of the study group. In the control group, the index of masticatory muscle activity decreased to a lesser extent. Biofeedback methods have shown a high level of effectiveness in reducing the symptoms of anxiety and depression, improving the quality of life.

The mechanism for regulating the isometric contraction of masseter muscles is involved in determining the vertical dimension of occlusion.

We previously demonstrated that accurate regulation of isometric contraction (IC) of jaw-closing muscles to counteract the ramp load applied to the jaw in the jaw-opening direction is achieved through the calibration between the two sensations arising from muscle spindles (MSs) and periodontal mechanoreceptors (PMRs). However, it remains unclear whether this calibration mechanism accurately works at any jaw positions, i.e., any vertical dimensions of occlusion (VDO). In the present study, we examined the effects of altering VDO on the IC of the masseter muscles in complete dentulous and edentulous subjects. At a VDO higher than the original VDO (O-VDO), the root mean square (RMS) of masseter EMG activity increased more steeply with a load increase, resulting in an over-counteraction. The regression coefficient of the load-RMS relationship significantly increased as the VDO was increased, suggesting that the overestimation became more pronounced with the VDO increases. Consistently also in the edentulous subjects, at a higher VDO than the O-VDO, a steeper increase in the RMS emerged with a delay in response to the same ramp load whereas a similar steeper increase was seen surprisingly even at a lower VDO. Thus, the edentulous subjects displayed a delayed overestimation of the ramp load presumably due to less and slowly sensitive mucous membrane mechanoreceptor (MMR) in alveolar ridge compared with the PMR. Taken together, the accurate calibration between the two sensations arising from MSs and PMRs/MMRs can be done only at the O-VDO, suggesting that the O-VDO is the best calibration point for performing accurate IC.NEW & NOTEWORTHY Since 1934, the vertical dimension of occlusion (VDO) in edentulous individuals has been anatomically determined mostly by referring to the resting jaw position. However, such a static method is not always accurate. Considering the dynamic nature of clenching/mastication, it is desirable to determine VDO dynamically. We demonstrate that VDO can be accurately determined by measuring masseter EMG during the voluntary isometric contraction of jaw-closing muscles exerted against the ramp load in the jaw-opening direction.

Correlation of masticatory muscle activity and occlusal function with craniofacial morphology: a prospective cohort study.

OBJECTIVES: Masticatory function, including masticatory muscle activity and occlusal function, can be affected by craniofacial morphology. This study aimed to investigate the relationship between craniofacial morphology and masticatory function in participants who had completed orthodontic treatment at least two years before and had stable occlusion. MATERIALS AND METHODS: Fourty-two healthy participants were prospectively enrolled and divided into three vertical cephalometric groups according to the mandibular plane angle. Masticatory muscle activity (MMA) in the masseter and anterior temporalis muscles was assessed using surface electromyography. The occlusal contact area (OCA) and occlusal force (OF), defined as occlusal function in this study, were evaluated using occlusal pressure mapping system. Masticatory muscle efficiency (MME) was calculated by dividing MMA by OF. The craniofacial morphology was analyzed using a lateral cephalogram. The masticatory function was compared using one-way analysis of variance. Pearson correlations were used to assess relationships between craniofacial morphology and masticatory function. RESULTS: The hypodivergent group had the lowest MMAand the highest MME in the masseter (167.32 ± 74.92 µV and 0.14 ± 0.06 µV/N, respectively) and anterior temporalis muscles (0.18 ± 0.08 µV/N, p < 0.05). MMA in the masseter showed a positive relationship with mandibular plane angle (r = 0.358), whereas OCA (r = -0.422) and OF (r = -0.383) demonstrated a negative relationship (p < 0.05). The anterior temporalis muscle activity negatively correlated with ramus height (r = -0.364, p < 0.05). CONCLUSIONS: Vertical craniofacial morphology was related to masticatory function. Hypodivergent individuals may have low MMA and high occlusal function, resulting in good masticatory muscle efficiency. CLINICAL RELEVANCE: Hypodivergent individuals require careful consideration in orthodontic diagnosis and prosthetic treatment planning.

The association between forward head posture and masticatory muscle pressure pain thresholds in patients with temporomandibular joint dissorders: a cross-sectional observational study.

OBJECTIVES: Forward head posture (FHP) is common in patients with temporomandibular joint disorders (TMDs); however, whether it contributes to TMD symptoms remains unclear. The aim of this study was to investigate the association between (1) FHP and masticatory muscle pressure pain thresholds (PPTs) and (2) neck muscle and masticatory muscle PPTs. MATERIALS AND METHODS: A total of 145 patients diagnosed with TMD were recruited between December 2020 and April 2021. Data regarding FHP and neck and masticatory muscle PPTs were collected. FHP was characterized by the craniocervical angle (CVA) measured between the horizontal line through C7 and the line between the tragus of the ear and C7. Patients were divided into either the FHP group (CVA ≤ 51°) or the non-FHP group. Differences in the masseter and temporalis muscle PPTs between the two groups were analyzed using the Mann-Whitney U test. The correlation between the CVA, neck, and masticatory muscle PPTs in all patients was determined by Spearman's correlation analysis. RESULTS: There were 70 patients in the FHP group and 75 patients in the non-FHP group. No significant difference in masseter and temporalis muscle PPTs was found between the two groups (p > 0.05). No correlation was found between FHP and masticatory muscle PPTs (p > 0.05). A significant association was found between the neck muscle and masticatory muscle PPTs (p < 0.05). The C5-C6 pillar and masticatory PPTs were either moderately (r = 0.435, masseter muscle) or strongly (r = 0.608, temporalis muscle) correlated, while the correlation between the trapezius and masticatory muscles was moderate (r = 0.378, masseter muscle and r = 0.461, temporalis muscle). CONCLUSION: FHP was not directly associated with masticatory muscle PPTs. Masticatory muscle PPTs were strongly or moderately associated with neck muscle PPTs. Therefore, the presence of neck pain, not the degree of FHP, in patients with TMD is of significance. CLINICAL RELEVANCE: In TMD treatment, we should pay attention to and actively relieve neck pain.

Repeatability of Teethan® indexes analysis of the masseter and anterior temporalis muscles during maximum clenching: a pilot study.

OBJECTIVES: The aim of this study is to assess the repeatability of a surface electromyographic (EMG) device (Teethan®, Teethan S.p.A., Milan, Italy), designed for the analysis of the masseter and anterior temporalis muscles. MATERIALS AND METHODS: Tests were performed on a sample of 30 healthy fully dentate TMD-free individuals randomly selected. Each test consisted of two distinct recordings performed at 5-min intervals: (i) the patient is asked to clench with maximum voluntary contraction (MVC), with two cotton rolls interposed between the dental arches; (ii) the patient is asked to repeat the same clenching activity without the cotton rolls. The outcomes of the study were the EMG indices conceptualized by the manufacturing company, based on the differences between the two test conditions (i.e., clenching on cotton rolls and on dentition). Pairwise correlation analysis and ANOVA test were performed to assess the strength of correlation and the significance of differences between the results of the three trials. RESULTS: Thirty TMD-free healthy individuals (20 females and 10 males; mean age 44 years, range 16-60 years) took part in the study. ANOVA test did not show any statistically significant difference between the three trials. The Global Index, which is the mean of the other EMG indices, showed the highest correlation values between the three trials, while some other indices showed a weak-to-medium correlation level. One out of five participants showed a coefficient of variation higher than 10%. CONCLUSIONS: The statistical analysis showed that the indices provided by the device are quite repeatable. However, this does not necessarily imply a specific clinical application of the device, which was here used in fully controlled experimental conditions. CLINICAL RELEVANCE: The clinical usefulness of the applied protocol remains questionable. Further studies should test the repeatability of EMG findings gathered with this device under various circumstances, in a more heterogeneous population.

Electromyographic activities of the jaw and facial muscles in subjects with different vertical skeletal patterns and breathing modes.

BACKGROUND: Mouth breathing (MB) can affect morphological changes in the craniofacial structures, electromyography is widely used for quantitative analysis of muscle function. OBJECTIVE: The aim was to evaluate the electromyographic (EMG) activities of the anterior temporalis (TA), masseter muscle (MM), orbicularis oris superior (OOS) and mentalis muscle (MT) in children with different vertical skeletal patterns and breathing modes during rest and various functional mandibular movements. METHODS: BioEMG III was used to measure the variations in EMG activities of TA, MM, OOS, and MT in 185 subjects aged 6-12 years during continuous clenching, rest, maximal intercuspation, lips closed lightly and swallowing. RESULTS: The results of logistic regression analysis showed that the model with vertical skeletal patterns as the dependent variable was ineffective (p = .106), while the model with breathing modes as the dependent variable was effective (p = .000). When considering both vertical skeletal patterns and breathing modes, the following significant differences were found. (1) In the normal-angle group, the EMG ratio in OOS with lips closed lightly of MB was significantly higher than NB (p = .005). (2) In the low-angle group, EMG ratios in TA and MM during the swallowing of MB were significantly lower than NB (p = .020, p = .040, respectively). (3) In the high-angle group, EMG ratios of MB were significantly higher in MT during continuous clenching, rest, lips closed lightly and swallowing (p = .038, p = .036, p = .005, p = .028, respectively), and OOS with lips closed lightly compared to NB (p = .005). CONCLUSION: Breathing modes and vertical skeletal patterns interacted to alter maxillofacial EMG activities, with breathing modes having a greater effect.

Diagnostic accuracy of a portable device (Bruxoff®) to measure sleep bruxism.

BACKGROUND: Diagnosis of sleep bruxism (SB) challenges clinicians every day due to multiple forms of assessment tools available, including self-reported questionnaires, clinical examinations, portable devices and laboratory polysomnography (PSG). PSG has become the gold standard for evaluating SB, but it can be limited due to cost and restricted accessibility which often is characterised by long waiting times. Hence, there is a need for the development of a reliable method that can assess SB in a simple and portable manner, which would offer acceptable sensitivity and specificity to evaluate SB. OBJECTIVE: The objective of this study was to investigate reliability and validity of the Bruxoff® device for the diagnosis of SB compared to the PSG. METHODS: Forty-nine subjects underwent one night of polysomnographic study with simultaneous recording with the Bruxoff® device. Rhythmic masticatory muscle activity (RMMA) index was scored according to published criteria. Pearson correlation, Bland-Altman plot and receiver operating characteristic (ROC) curve outcomes were used to quantify the agreement between both methods. RESULTS: Receiver operating characteristic analysis showed an acceptable accuracy for the Bruxoff® with sensitivity of 83.3% and specificity of 72% when the cut-off was set at two events per hour. Pearson correlation analysis showed a nearly significant correlation between PSG and Bruxoff® for RMMA index (r = .282 p = .071) and for total SB episodes per night (r = .295 p = .058). Additionally, the Bland-Altman plot revealed a consistent and systematic difference in the measurement of events between devices. CONCLUSION: The Bruxoff® device appears to be a promising diagnostic method for clinical use, but further study is needed.

Bilateral treatment of the masseter with botulinum toxin: Consequences for mastication, muscle force and the mandibular condyle.

BACKGROUND: Clinical use of botulinum neurotoxins (BoNTs) in masticatory muscles is usually bilateral, but most studies on the functional consequences of BoNT treatment have used unilaterally treated animals. OBJECTIVES: To test the hypothesis that bilateral BoNT treatment of the rabbit masseter hampers mastication and to assess its effects on bone density of the mandibular condyles. METHODS: Ten 5-month-old female rabbits received injections of BoNT into both masseter muscles and nine sham animals received saline. Body weight, incisor bite force during masseter tetany, and surface and fine-wire electromyography (EMG) of the masseter and medial pterygoid muscles were assessed at regular intervals. Half the sample was terminated after 4 weeks and the remainder after 12 weeks. Muscles were weighed and mandibular condyles were scanned with microCT to analyse bone density. RESULTS: BoNT rabbits lost weight and required a soft-food diet. Incisor occlusal force plummeted after BoNT injection and remained lower than the shams. The duration of masticatory cycles was increased in the BoNT rabbits for 5 weeks, with most of the increase due to the adductor burst. Masseteric EMG amplitude began to improve at Week 5, but remained low on the working side throughout the experiment. At the 12-week endpoint, masseter muscles were smaller in the BoNT rabbits. Medial pterygoid muscles did not compensate. Condylar bone density was reduced. CONCLUSION: Bilateral treatment of the rabbit masseter by BoNT severely affected chewing performance. Even after a 3-month recovery period, deficits remained in bite force, muscle size and condylar bone density.

Unilateral Hypofunction of the Masseter Leads to Molecular and 3D Morphometric Signs of Atrophy in Ipsilateral Agonist Masticatory Muscles in Adult Mice.

Mice are commonly used to study mandibular dynamics due to their similarity in chewing cycle patterns with humans. Adult mice treated unilaterally with botulinum toxin type A (BoNTA) in the masseter exhibit atrophy of this muscle characterized by an increase in the gene expression of atrophy-related molecular markers, and a reduction in both muscle fiber diameter and muscle mass at 14d. However, the impact of this muscle imbalance on the non-treated masticatory muscles remains unexplored. Here, we hypothesize that the unilateral masseter hypofunction leads to molecular and 3D morphometric signs of atrophy of the masseter and its agonist masticatory muscles in adult mice. Twenty-three 8-week-old male BALB/c mice received a single injection of BoNTA in the right masseter, whereas the left masseter received the same volume of saline solution (control side). Animals were euthanized at 2d, 7d, and 14d, and the masticatory muscles were analyzed for mRNA expression. Five heads were harvested at 14d, fixed, stained with a contrast-enhanced agent, and scanned using X-ray microtomography. The three-dimensional morphometric parameters (the volume and thickness) from muscles in situ were obtained. Atrogin-1/MAFbx, MuRF-1, and Myogenin mRNA gene expression were significantly increased at 2 and 7d for both the masseter and temporalis from the BoNTA side. For medial pterygoid, increased mRNA gene expression was found at 7d for Atrogin-1/MAFbx and at 2d-7d for Myogenin. Both the volume and thickness of the masseter, temporalis, and medial pterygoid muscles from the BoNTA side were significantly reduced at 14d. In contrast, the lateral pterygoid from the BoNTA side showed a significant increase in volume at 14d. Therefore, the unilateral hypofunction of the masseter leads to molecular and morphological signs of atrophy in both the BoNTA-injected muscle and its agonistic non-injected masticatory muscles. The generalized effect on the mouse masticatory apparatus when one of its components is intervened suggests the need for more clinical studies to determine the safety of BoNTA usage in clinical dentistry.

Effect of rehabilitation by using the shortened dental arch concept on the thickness of the masseter muscle and occlusal force: A pilot study.

STATEMENT OF PROBLEM: Knowledge of the effect of a shortened dental arch on masseter muscle thickness and occlusal force is sparse but could help clinicians understand how a shortened dental arch might affect the stomatognathic system. PURPOSE: The purpose of this pilot clinical study was to evaluate and compare the masseter muscle thickness and occlusal force of participants rehabilitated by using a shortened dental arch with matched completely dentate individuals. MATERIAL AND METHODS: Twelve partially edentulous participants with a minimum of 1 posterior occluding pair on each side of the arch were enrolled in the study. The mandibular arch of these participants was rehabilitated by using a single posterior mandibular implant crown (group S). The maxillary arch of all participants in group S was intact. Masseter muscle thickness (cm) and occlusal force (N) were recorded before (T1) and 6 months after implant rehabilitation (T2) for each participant. Twelve participants were selected as controls (group C). They were matched for age, sex, height, and weight with group S and evaluated for masseter muscle thickness and occlusal force. Masseter muscle thickness was evaluated by using ultrasonography during the rest position and maximum volumetric clenching. Occlusal force was measured with an occlusal force measuring appliance. All recordings were done for the left and right sides of the arch. Descriptive analysis was followed by comparison between groups and within group S by using the paired t test (α=.05). RESULTS: Higher masseter muscle thickness and higher occlusal force were observed in group C than in group S before and after rehabilitation. An increase in masseter muscle thickness in the rest position and in maximum volumetric clenching was observed within group S after rehabilitation. Before rehabilitation, a difference in the masseter muscle thickness between group S and group C was statistically significant for the left side at the rest position (P=.017) and during maximum volumetric clenching (P=.016). After rehabilitation, the difference between group S and group C was not statistically significant for masseter muscle thickness at the rest position (P=.890 for right side and P=.555 for left side) and during maximum volumetric clenching (P=.109 for right side and P=.755 for left side). The difference in occlusal force between group S and group C was statistically significant for the right side and left side (P<.001) before rehabilitation and statistically not significant after rehabilitation (P=.161 for the right side and P=.134 for the left side). CONCLUSIONS: Rehabilitation following the concept of a shortened dental arch increased masseter muscle thickness and occlusal force in partially edentulous individuals, making the masseter muscle thickness and occlusal force comparable with those of a completely dentate arch.

Uptight responses between clenching and forearm raising with factors of visual feedback and maintenance effort in healthy young women: An experimental study on factorial design.

BACKGROUND: To achieve different central preset force levels requires various fine-tuning efforts and may elicit different uptight responses. The mandibular lever system has a distinct regularity in the fine-tuning function of the upper limbs. The purpose of the present study was to detect whether the uptight responses elicited from motivating clenching differ from those induced by motivating forearm raising at different force levels. METHODS: Twenty-five healthy females were enrolled in this study. The target was low, medium, and maximum force levels with or without visual feedback and/or maintenance effort. Surface electromyographic (SEMG) activity was recorded from the bilateral anterior temporalis and masseter or left biceps brachii muscle (BicL), and the T-Scan III System synchronously recorded the sensitive force values. The uptight responses and task difficulties were recorded for occlusal and left forearm lifting tasks using a unique visual analogue scale. RESULTS: The highest uptight response value was achieved at a low clenching force level with visual feedback requiring no maintenance effort but at a maximum forearm-raising force level with visual feedback and maintenance effort. The SEMG activities of both jaw-closing muscles and BicL were associated with the central preset force level (P < 0.001). However, the maintenance effort only increased the jaw-closing muscles' SEMG activity at the maximal force level (P < 0.001). CONCLUSIONS: Clenching at the central preset lower force level with visual feedback is prone to elicit a higher degree of uptight response. The constant need for a low-intensity bite can have a negative effect on an individual's mood.

Neuromuscular and occlusion analysis to evaluate the efficacy of three splints on patients with bruxism.

OBJECTIVE: Occlusal splints are always applied on individuals with bruxism to reduce tooth wear and relieve orofacial symptoms such as myofascial pain. The stomatognathic system is mainly composed of tooth, occlusion, masticatory muscles, and temporomandibular joint. The occlusion and masticatory muscles function are regarded as the important parameters for evaluating the stomatognathic system state objectively. However, the effects of occlusal splints on individuals with bruxism is rarely elucidated from accurate neuromuscular analysis and occlusion evaluation. The aim of the present study was to estimate the effects of three different splints (two clinically common full coverage occlusal splint and an modified anterior splint) on subjects with bruxism using K7-J5 neuromuscular analysis system and Dental Prescale II (DP2) to evaluate occlusion. METHODS: Sixteen subjects claimed to be suffering from nocturnal bruxism,with complete dentition and stable occlusal relationship, were selected for study.The intermaxillary space and the baselines of EMG-activity of the anterior temporalis and masseter were recorded for all the subjects. The participants was treated with three different splints, and outcomes were estimated by comfort index, occlusion and surface electromyography of anterior temporalis and masseter. RESULTS: At teeth clenched position, EMG data were significantly lower in the participants with use of modified anterior splint than with hard, soft occlusal splint or without splint (p < 0.05). The maximum bite force and bite area occur in subjects without use of splint, while the minimal occur in subjects with use of modified anterior splint. Intermaxillary space increased and masticatory muscles presented significant reduction of EMG data at rest position as a result of J5 (p < 0.05). CONCLUSION: Modified anterior splint seems to be more comfortable and effective in reducing occlusion force and electromyographic activity of anterior temporalis and masseter for subjects with bruxism.