Marcelo Palinkas

Age and gender influence on maximal bite force and masticatory muscles thickness

The present study aimed investigate the age and gender influence on maximal molar bite force and at outlining the criteria for normal masticatory muscle development in a sample of 177 Brazilian Caucasian dentate individuals aged 7-80 years divided into five age groups: I (7-12 years), II (13-20 years), III (21-40 years), IV (41-60 years), and V (61-80 years). Except for Group V, which comprised nine women and eight men, all groups were equally divided in respect to gender (20 M/20 F). Bite force was recorded with a mouth-adapted 1000N dynamometer and the highest out of three records was regarded as the maximal bite force. The data were submitted to multivariate statistical analysis (SPSS 17.0 p<0.05). Effects of group and gender were found, but no interactions between them. The ANOVA showed significant differences between groups bilaterally. Bonferronis test showed that group I had significantly lower bite force means at both sides as compared to all groups, except group V. No differences were found between the left and right sides. In all the groups, gender was found to be a significant factor associated with maximal bite force. A global comparison including all the subjects and measures showed that the means of men were approximately 30% higher than those of women. Within-group comparisons yielded similar results in all groups. Muscle thickness was measured with a SonoSite Titan ultrasound tool using a high-resolution real-time 56mm/10MHz linear-array transducer. Three ultrasound images were obtained from the bilateral masseter and temporal muscles at rest and at maximal voluntary contraction. The means of the three measures in each clinical condition were analyzed with multivariate statistical analysis (SPSS 17.0 p<0.05). A gradual increase in thickness of the masseter and temporal muscles was found both at rest and maximal voluntary contraction for groups I to IV, whereas a decrease in muscle thickness was observed in group V. Multivariate analysis showed that in both conditions there was an effect of group and gender. The study of the development of the stomatognathic system in relation to age and gender can provide useful data for the identification of normal and impaired functioning patterns. The results of this study indicate that age and gender are associated with structural and functional alterations in the muscles of the stomatognathic system.

Nocturnal sleep architecture is altered by sleep bruxism

OBJECTIVE Sleep is a complex behaviour phenomenon essential for physical and mental health and for the body to restore itself. It can be affected by structural alterations caused by sleep bruxism. The aim of this study was to verify the effects of sleep bruxism on the sleep architecture parameters proposed by the American Academy of Sleep Medicine. DESIGN The sample comprised 90 individuals, between the ages of 18 and 45 years, divided into two groups: with sleep bruxism (n=45) and without sleep bruxism (n=45). The individuals were paired by age, gender and body mass index: a polysomnography was performed at night. RESULTS Statistically significant differences were found between (P≤0.05) individuals with sleep bruxism and individuals without sleep bruxism during total sleep time (P=0.00), non-rapid eye movement (NREM) total sleep time (P=0.03), NREM sleep time stage 3 (P=0.03), NREM sleep latency (P=0.05), sleep efficiency (P=0.05), and index of microarousals (P=0.04). CONCLUSIONS Sleep bruxism impairs the architecture of nocturnal sleep, interfering with total sleep time, NREM sleep latency, and sleep efficiency.

Impact of sleep bruxism on masseter and temporalis muscles and bite force.

Abstract Objectives: This study aimed to analyze the impact of sleep bruxism (SB) on electromyography (EMG) activity and the thickness of the masseter and temporal and maximal molar bite force. Method: Ninety individuals, aged between 18 and 45 years, were selected and divided into two groups: Group I (case group, 45 individuals with SB) and Group II (control group, 45 individuals without SB). A diagnosis of SB was made from polysomnography. Results: The data obtained from EMG and the muscle thickness and the maximal molar bite force were tabulated (SPSS 21.0), normalized, and subjected to statistical analysis (p ≤ 0.05). Comparisons between the groups showed significant differences regarding the habitual chewing of hard food for the left temporalis muscle (p = 0.04) and the chewing of soft food for the right masseter muscle (p = 0.04), but no significant differences for the measurements of muscle thickness and maximal molar bite force. Discussion: The present data suggest that SB negatively altered the masticatory muscles’ functions. Based on the results of this research, it can be concluded that individuals with SB showed decreased EMG activity in the masticatory muscles.

Influence of mandibular tori on stomatognathic system function

Objectives: To verify the influence of prominent mandibular tori on the functioning of the stomatognathic system. Methods: The participants included 40 individuals, divided into two groups: those with mandibular tori (GI group: 20 subjects) and those without mandibular tori (GII group: 20 subjects). The authors used the Myosystem-Br1 electromyography system to analyze electromyographic (EMG) activity. For muscle thickness, images of the masseter and temporalis muscles were captured using the NanoMaxx ultrasound. The maximal molar bite force was obtained by means of the Kratos digital dynamometer. Results: The EMG activity was higher in the masseter muscles in the GI group, compared with the GII group, in all clinical conditions assessed except for the mandibular at rest. In dynamic conditions, this higher EMG activity was also observed in the temporalis muscles. The GI group presented significantly less temporalis muscle thickness than seen in the GII group. The maximal bite force was significantly higher in the GI group. Conclusions: Mandibular tori promoted morphological and functional changes in the stomatognathic system.

Effect of surgical treatment of mandibular fracture: electromyographic analysis, bite force, and mandibular mobility.

Abstract This study aimed to examine individuals undergoing surgery for the treatment of the fractured mandibular angle, using bite force, mandibular mobility, and electromyographic (EMG) analysis in many different clinical conditions, after 2 months postoperatively. Bite force was recorded with a digital dynamometer, model IDDK. The EMG activity (Myosystem-Br1) included the analysis of the masseter and temporal muscles. Mandibular mobility was measured using a digital pachymeter. The subjects were divided into 3 groups: G1, mandibular angle fracture (n = 7); G2, condylar process fracture (n = 5); and G3, control (n = 12). Data were tabulated and submitted to statistical analysis using the repeated-measure test carried out over time and the Student’s t-test (P < 0.05), using the Statistical Package for the Social Sciences software, version 19 (SPSS Inc, Chicago, IL). G1 and G2 had an increase in bite force. In G1, there was a regular decrease in the EMG activity in the second postoperative month. G2 presented an irregular pattern in EMG data during the period tested. Regarding the mandibular mobility, both groups obtained amplitude of all mandibular movements with a high percentage, when compared with control. A good functional recovery was achieved by the individuals who had a mandible angle fracture or condylar process fracture, after 2 postoperative months.

The effect of a Lucia jig for 30 minutes on neuromuscular re-programming, in normal subjects

The Lucia jig is a technique that promotes neuromuscular reprogramming of the masticatory system and allows the stabilization of the mandible without the interference of dental contacts, maintaining the mandible position in harmonic condition with the musculature in normal subjects or in patients with temporomandibular dysfunction (TMD). This study aimed to electromyographically analyze the activity (RMS) of the masseter and temporal muscles in normal subjects (control group) during the use of an anterior programming device, the Lucia jig, in place for 0, 5, 10, 20 and 30 minutes to demonstrate its effect on the stomatognathic system. Forty-two healthy dentate individuals (aged 21 to 40 years) with normal occlusion and without parafunctional habits or temporomandibular dysfunction (RDC/TMD) were evaluated on the basis of the electromyographic activity of the masseter and temporal muscles before placement of a neuromuscular re-programming device, the Lucia jig, on the upper central incisors. There were no statistically significant differences (p < 0.05) in the electromyographic activity of the masticatory muscles in the different time periods. The Lucia jig changed the electromyographic activity by promoting a neuromuscular reprogramming. In most of the time periods, it decreased the activation of the masticatory muscles, showing that this device has wide applicability in dentistry. The use of a Lucia jig over 0, 5, 10, 15, 20 and 30 minutes did not promote any statistically significant increase in muscle activity despite differences in the data, thus showing that this intra-oral device can be used in dentistry.

Influence of age on the electromyographic fatigue threshold of the masseter and temporal muscles of healthy individuals.

During human aging, the process of decreasing organic and functional activity triggers uncertainties as to how this natural biological process, unlike one that is pathological and characterized by morphophysiological changes, acts in the stomatognathic system (Cecílio et al., 2010; Glowacka et al., 2016; Santos, Fraga, & Cardoso, 2014). Among evaluations of the muscular activities of the stomatognathic system, the analysis of physiological neuromuscular fatigue induced by sustained contractions determines the functional performance of the skeletal striated musculature in humans (Schodrowski, Seipelt, AdibiSedeh, Eienbröker, & Tackenberg, 2016). Through specific and internationally recognized methodologies such as surface electromyography, the muscle fatigue threshold can be assessed using the median frequency spectrum, in order to detect the susceptibility of the muscle to an induced physiological fatigue condition; i.e., the moment at which desired force production can no longer be maintained and contractile fatigue is observed (Halvorsen et al., 2016; Pitta, Nitsch, Machado, & de Oliveira, 2015; Svensson, Burgaard, & Schlosser, 2001; Youn, Lee, & Lee, 2016) During constant force contraction, the muscle fibers reduce shortening at a specific point, as an act of organic defense, so that functional damage does not occur in the musculature, at the point at which continuous and sustained isometric contractions occur, leading to possible changes in muscular activity, which can be detected by monitoring the median frequency spectrum change of the EMG signal (Alam et al., 2015; Politti et al., 2016). The reproduction of the spectral parameters of the electromyographic signal in the masticatory muscle can provide important information about which variables change according to established situations (González-Izal et al., 2010), but have not yet determined the developmental trajectory of normal parameters in the fatigue threshold of the masseter and temporalis muscles of healthy individuals. Therefore, the primary objective of this study was to determine the fatigue threshold of the masseter and temporalis muscles by mean median frequency of the electromyographic signal during development and aging. A secondary objective was to analyze intergroup differences in the fatigue threshold by electromyographic signal of the masseter and temporalis muscles. Establishing these parameters in individuals aged between 7 and 80 years is of great scientific value, because it provides health professionals who work with movements of the human body comparisons between the healthy organism and one in which there are pathological changes, such as muscular myopathies and atrophies, and generates further advancement in the research on muscle fatigue thresholds.

The Real Role of Sensitivity, Specificity and Predictive Values in the Clinical Assessment.

Journal of Clinical Sleep Medicine, Vol. 12, No. 2, 2016 We would like to thank Dr. Raphael, because her letter 1 published in this issue of the Journal of Clinical Sleep Medicine provides us with an opportunity to emphasize points already highlighted in our article. The main goal of our study was to evaluate the diagnostic ability of signs and symptoms of sleep bruxism (SB) according to the criteria of the American Academy of Sleep Medicine (AASM) and a diagnostic classification system proposed by international experts to assess SB. The validity of a diagnostic test is determined as the ability of a test to tell who have the disease from who do not. For this purpose, two components are calculated: sensitivity and specificity. Sensitivity is the ability to correctly identify those who have the disease, while specificity is the ability to correctly identify those who do not have the disease.2 In order to calculate sensitivity and specificity, it is required that patients be identified by another test which provides a more permanent result, is often more sophisticated, more invasive, and more expensive, named gold standard.2 In our study, the polysomnography (PSG) was considered the gold standard for SB assessment. The evaluation of the validity of a diagnostic test is usually performed on selected contexts as well, with two equally-numbered groups of patients—one with the disease, one without it—as this is an efficient way of describing sensitivity and specificity.3 Having that in mind, we selected a control group with the same number of patients as the group of patients with the disease for the sample, then we calculated the sensitivity and the specificity of each tested diagnostic criteria. We know that sensitivity and specificity are characteristics of the diagnostic test, although the predictive value is also influenced by the prevalence.3 That is why when we want to evaluate the discriminatory capacity of a particular diagnostic test, we calculate sensitivity and specificity, even though the predictive values are clinically more useful.2 In our study, besides the main measures to determine accuracy, we chose to present additional analyses reporting predictive values of each test, which were calculated based on the prevalence of our sample LETTERS TO THE EDITOR

Alterations in the stomatognathic system due to amyotrophic lateral sclerosis

Abstract Objectives: To compare the molar bite force, electromyographic activity, chewing efficiency and thickness of the masseter and temporalis muscles in individuals with amyotrophic lateral sclerosis (ALS) and healthy individuals. Material and Methods: Thirty individuals enrolled in the study were divided into the study group (with ALS, n=15) and control group (healthy individuals, n=15). Data regarding molar bite force (right and left), electromyographic activity (mandibular rest, right and left laterality, protrusion, and maximum voluntary contraction), chewing efficiency (habitual and non-habitual), and masticatory muscle thickness (rest and maximum voluntary contraction) were tabulated and subjected to statistical analysis (Student’s t-test, p≤0.05). Results: Comparisons between the groups demonstrated a statistically significant increase in the electromyographic activity of the right masseter (p=0.03) and left masseter (p=0.03) muscles during mandibular rest; left masseter (p=0.00), right temporalis (p=0.00), and left temporalis (p=0.03) muscles during protrusion; and right masseter (p=0.00), left masseter (p=0.00), and left temporalis (p=0.00) muscles during left laterality, in individuals with ALS as compared with healthy individuals. A statistically significant decrease was observed in the habitual chewing efficiency of the right masseter (p=0.00) and right temporalis (p=0.04) muscles in individuals with ALS. No statistically significant difference between the groups was found the masticatory muscle thickness and maximal molar bite force. Conclusions: ALS may lead to modifications in the activities of the stomatognathic system, including muscular hyperactivity and reduction in chewing efficiency; however, no change has been observed in the masticatory muscle thickness and molar bite force.

Evaluation of the electromyographic fatigue of the masseter and temporalis muscles in individuals with osteoporosis

Abstract Objectives The objective of this study was to evaluate the electromyographic fatigue of the masseter and temporalis muscles in individuals with and without osteoporosis. Methods Median frequency of the initial, mid, and final periods of the electromyographic signal in the 33 subjects with osteoporosis (OG) and 33 subjects without osteoporosis [control (CG)] was analyzed. Results OG showed a decrease in median frequency along the electromyographic signal, with a significant difference for the right masseter: initial vs. mid periods, initial vs. final periods; left masseter: initial vs. final periods; temporal (right and left): initial vs. mid periods, initial vs. final periods, and mid vs. final periods. Percentage comparison of median frequency between the initial and mid periods and between initial and final periods in the OG showed a significant difference in the masticatory muscles. Discussion The findings suggest that osteoporosis is associated with changes in the function of masticatory muscles, especially when measured by electromyographic fatigue.