Assessment of neuromuscular fatigue through frequency analysis of the electromyographic signal of control participants and those with temporomandibular dysfunction treated with resilient or hard occlusal devices.

STATEMENT OF PROBLEM: Muscle hyperactivity that leads to neuromuscular fatigue can be evaluated by electromyography. Whether treatment with occlusal devices can restore neuromuscular balance to patients with temporomandibular disorders (TMDs) is unclear. PURPOSE: The purpose of this clinical study was to evaluate neuromuscular fatigue by analyzing the frequency of the electromyographic signal of the masseter and anterior temporalis muscles on both sides in healthy participants and those with TMD treated with a resilient or hard occlusal device. MATERIAL AND METHODS: One hundred asymptomatic participants and 30 with TMD were divided into 2 groups: treated with a hard device or treated with a resilient device. All underwent electromyographic examination before and after treatment with the occlusal devices. RESULTS: In both groups, the results showed statistically significant differences (P<.01) when the fatigue rate before and after treatment with an occlusal device was compared. CONCLUSIONS: Treatment with both types of occlusal device was efficient in reducing the rate of neuromuscular fatigue in patients with TMDs.

Can a spontaneous smile invalidate facial identification by photo-anthropometry?

PURPOSE: Using images in the facial image comparison process poses a challenge for forensic experts due to limitations such as the presence of facial expressions. The aims of this study were to analyze how morphometric changes in the face during a spontaneous smile influence the facial image comparison process and to evaluate the reproducibility of measurements obtained by digital stereophotogrammetry in these situations. MATERIALS AND METHODS: Three examiners used digital stereophotogrammetry to obtain 3-dimensional images of the faces of 10 female participants (aged between 23 and 45 years). Photographs of the participants' faces were captured with their faces at rest (group 1) and with a spontaneous smile (group 2), resulting in a total of 60 3-dimensional images. The digital stereophotogrammetry device obtained the images with a 3.5-ms capture time, which prevented undesirable movements of the participants. Linear measurements between facial landmarks were made, in units of millimeters, and the data were subjected to multivariate and univariate statistical analyses using Pirouette® version 4.5 (InfoMetrix Inc., Woodinville, WA, USA) and Microsoft Excel® (Microsoft Corp., Redmond, WA, USA), respectively. RESULTS: The measurements that most strongly influenced the separation of the groups were related to the labial/buccal region. In general, the data showed low standard deviations, which differed by less than 10% from the measured mean values, demonstrating that the digital stereophotogrammetry technique was reproducible. CONCLUSION: The impact of spontaneous smiles on the facial image comparison process should be considered, and digital stereophotogrammetry provided good reproducibility.

Influence of tongue exercise and orofacial myofunctional status on the electromyographic activity and pain of chronic painful TMD.

Objective: To analyze the influence of tongue exercise and myofunctional status on the electromyographic activity (EMG) and pain perception in individuals with chronic painful TMDs.Methods: Twenty-four subjects diagnosed according to the DC/TMD (18-52 years old) were assessed: EMG on the masseter and anterior temporalis; myofunctional orofacial conditions underwent clinical assessment (OMES); and questionnaire for self-perception of TMD signs and symptoms (ProTMDMulti). The 50th percentile was calculated to establish a cutoff value based on OMES scores related to the functional variables of the tongue.Results: The compared groups showed no differences (p > 0.05) in self-perception of their TMD signs and symptoms or in the EMG activity during tongue exercises.Discussion: The myofunctional status of the tongue showed no impact on the painful TMD or on the activity of the masticatory muscles (captured during tongue exercise). The indication of tongue exercises in TMD cases is a safe and adequate possibility.

Are the bite force and electromyographic activity altered in muscle TMD patients with abfraction lesions?

OBJECTIVE: To verify if the maximal molar bite force (BF) and the electromyographic activity (EMG) are altered in TMD patients with abfraction lesions (AL) when compared to those without AL. METHODS: The sample was composed of 45 patients (18-60 years old), 30 diagnosed with TMD (RDC/TMD) (15 with AL and 15 without AL) and 15 controls. The BF and the EMG of the masticatory muscles (maximal voluntary contraction (MVC) and chewing gum) were measured. RESULTS: TMD patients showed decreased BF (p < 0.001), without differences between patients with and without AL. The electromyographic activity during MVC was similar among all groups (p > 0.05), although there was a greater trend of muscular balance for the control group (percentage overlapping coefficient and electromyographic indexes). The TMD group without AL showed a lower number of cycles and masticatory frequency. DISCUSSION: TMD patients with and without AL exhibited similar results in the analysis of the BF and EMG, without differences.

Comparison of dynamic electromyographic analysis of masticatory capsules with materials of different textures.

OBJECTIVES: The aim of this study was to compare the mastication electromyographic indexes of capsules used for the masticatory efficiency evaluation "ME-mastig" and of materials of different textures (gum, raisins, and peanuts). METHODS: Thirty young, healthy, adult subjects, with an average age of 23.46 years old, with no symptoms of temporomandibular dysfunction (TMD), confirmed by the clinical exam, RDC/TMD, and the static test of electromyography (EMG) were chosen. Afterward, dynamic tests were performed (bilateral mastication of the compounds) to determine number of chewing cycles (CYCLES); masticatory frequency (FREQ); SMI (symmetrical masticatory index - corresponding to the value of neuromuscular coordination during mastication); and IMPACT (corresponding to impact - total electromyographic activity performed by the system during chewing). RESULTS: Cycle and frequency were similar. Regarding SMI and IMPACT, the raisin, the capsule, and the peanut were similar between each other, and different from the gum. CONCLUSIONS: Masticatory capsules and the natural foods with different textures had similar results regarding EMG indexes.

Low level laser therapy as an adjunctive technique in the management of temporomandibular disorders.

The purpose of this study was to assess the effect of low level laser therapy on subjects with intra-articular temporomandibular disorders (IA-TMD), and to quantify and compare severity of signs and symptoms before, during, and after the laser applications. The sample consisted of 45 subjects randomly divided into three groups (G) of 15 subjects each: G-I: 15 individuals with IA-TMD submitted to an energy dose of 52.5 J/cm2; G-II: dose of 105.0 J/cm2; and G-III: placebo group (0 J/cm2). In all groups, the applications were performed on condylar points on the masseter and anterior temporalis muscles. Two weekly sessions were held for five weeks, totaling 10 applications. The assessed variables were: mandibular movements and painful symptoms evoked by muscle palpation. These variables were measured before starting the study, then immediately after the first, fifth, and tenth laser application, and finally, 32 days after completing the applications. The results showed that there were statistically significant differences for G-I and G-II at the level of 1% between the doses, as well as between assessments. Therefore, it was concluded that the use of low level laser increased the mean mandibular range of motion and reduced painful symptoms in the groups that received effective treatment, which did not occur in the placebo group.

Standardization of the electromyographic signal through the maximum isometric voluntary contraction.

The objective of this study was to analyze the electromyographic (EMG) data, before and after normalization. One hundred (100) normal subjects (with no signs and symptoms of temporomandibular disorders) participated in this study. A surface EMG of the masticatory muscles was performed. Two different tests were performed: maximum voluntary clench (MVC) on cotton rolls and MVC in intercuspal position. The normalization was done using the mean value of the EMG signal of the first examination. The coefficient of variation CV showed lower values for the standardized data. The standardization was effective in reducing the differences between records from the same subject and in different subjects.

Effects of orofacial myofunctional therapy on temporomandibular disorders.

The objectives of the current study were to analyze the effects of orofacial myofunctional therapy (OMT) on the treatment of subjects with associated articular and muscular temporomandibular disorders (TMD). Thirty subjects with associated articular and muscular TMD, according to the Research Diagnostic Criteria (RDC/TMD), were randomly divided into groups: 10 were treated with OMT (T group), 10 with an occlusal splint (OS group), and 10 untreated control group with TMD (SC). Ten subjects without TMD represented the asymptomatic group (AC). All subjects had a clinical examination and were interviewed to determine Helkimo's Indexes (Di and Ai), the frequency and severity of signs and symptoms, and orofacial myofunctional evaluation. During the diagnostic phase, there were significant differences between groups T and AC. There were no significant differences between group T and OC and SC groups. During the final phase, groups T and OS presented significant improvement, however, the group T presented better results and differed significantly from group OS regarding the number of subjects classified as Aill; the severity of muscular pain and TMJ pain; the frequency of headache and the muscles and stomatognathic functions. The group T differed significantly from the SC group but no longer differed significantly from the AC group. OMT favored a significant reduction of pain sensitivity to palpation of all muscles studied but not for the TMJs; an increased measure of mandibular range of motion; reduced Helkimo's Di and Ai scores; reduced frequency and severity of signs and symptoms; and increased scores for orofacial myofunctional conditions.

Immediate effect of the resilient splint evaluated using surface electromyography in patients with TMD.

The aim of this study was to analyze the immediate effect of resilient splints through surface electromyography testing and to compare the findings with the electromyographic profiles of asymptomatic subjects. The participants were 30 subjects, 15 patients with TMD (TMD Group) and 15 healthy subjects (Control Group), classified according to Research Diagnostic Criteria (RDC/TMD) Axis I. A resilient occlusal splint was made for each patient in the TMD Group from two mm thick silicon to cover all teeth. The EMG examination was performed before and immediately after installing the splint. Three tests were performed as follows: 1. Maximum Voluntary Contraction (MVC) using cotton rolls (standards test); 2. MVC in maximal intercuspation position; and 3. MVC with the splint in position. The EMG signal was recorded for five seconds. EMG indices were calculated to assess muscle symmetry, jaw torque, and impact. There was a statistically significant difference when comparing the results among the study groups. The symmetry index values in the Control Group were higher than the TMD Initial Group and similar to the TMD Group after the installation of the splint. The index values of torque were higher in TMD Initial Group when compared with the Controls. Impact values were lower than normal values in the TMD Initial Group and restored upon installation of the splint. The resilient occlusal splints may be used as complementary or adjunctive treatment of temporomandibular disorders.

Low level laser effects on pain to palpation and electromyographic activity in TMD patients: a double-blind, randomized, placebo-controlled study.

The purpose of this study was to evaluate the effect of diode laser (GaAIAs - 780 nm) on pain to palpation and electromyographic (EMG) activity of the masseter and anterior temporalis muscles. The laser was applied on the temporalis and masseter muscles twice a week (four weeks). Forty-eight (48) patients with myofascial pain were randomly assigned between actual and placebo treatments and between the energetic doses of 25 J/cm2 and 60 J/cm2, and were evaluated using VAS before, immediately after the final application, and 30 days after the laser treatment. Surface electromyography was performed with maximum dental clenching before and after laser therapy. The results show there were no significant statistical differences in the EMG activity between the groups before and after laser treatment. With regard to the pain at palpation, although both groups presented a significant difference in the symptoms before and after the treatment, only the active doses showed statistically significant reductions in pain level in all the regions of the palpated muscles. However, there was no significant statistical difference between groups (experimental and placebo). In conclusion, low level laser did not promote any changes in EMG activity. The treatment did, however, lessen the pain symptoms in the experimental groups.

Electromyographic evaluation of neuromuscular coordination of subject after orthodontic intervention.

The aim of this work was to investigate the neuromuscular changes associated with the orthodontic post-treatment using surface electromyography. One hundred (100) young, healthy adults without signs and symptoms of temporomandibular dysfunction (TMD) were divided into two groups: 60 subjects who were undergoing orthodontic intervention (Ortho Group) and 40 subjects who had no orthodontic intervention (Control Group), aged 18-25 years. EMG activity of masseter and temporalis anterior muscle was recorded during two different tests: 1. maximum voluntary clench (MVC) with cotton rolls; and 2. MVC in intercuspal position. In all subjects, both tests were performed with symmetric muscular patterns (more than 85%) and with insignificant latero-deviating of the mandible (lower than 10%). There are no statistically significant differences between the subjects of both groups evaluated. Both groups showed medium index values calculated according to the normal standards established previously.

Photoelastic study of the support structures of distal-extension removable partial dentures.

PURPOSE: The double system of support, in which the distal-extension removable partial denture adapts, causes inadequate stress around abutment teeth, increasing the possibility of unequal bone resorption. Several ways to reduce or more adequately distribute the stress between abutment teeth and residual ridges have been reported; however, there are no definitive answers to the problem. The purpose of this study was to analyze, by means of photoelasticity, the most favorable stress distribution using three retainers: T bar, rest, proximal plate, I bar (RPI), and circumferential with mesialized rest. MATERIALS AND METHODS: Three photoelastic models were made simulating a Kennedy Class II inferior arch. Fifteen dentures with long saddles, five of each design, were adjusted to the photoelastic patterns and submitted first to uniformly distributed load, and then to a load localized on the last artificial tooth. The saddles were then shortened and the tests repeated. The quantitative and qualitative analyses of stress intensity were done manually and by photography, respectively. For intragroup analyses the Wilcoxon test for paired samples was used, while for intergroup analyses Friedman and Wilcoxon tests were used to better identify the differences (p < 0.05). RESULTS: The RPI retainer, followed by the T bar, demonstrated the best distribution of load between teeth and residual ridge. The circumferential retainer caused greater concentration of stress between dental apexes. Stress distribution was influenced by the type of retainer, the length of the saddle, and the manner of load application. CONCLUSIONS: The long saddles and the uniformly distributed loads demonstrated better distribution of stress on support structures.