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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.

Objective: To evaluate the effect of double jaw orthognathic surgery (OGS) on masticatory performance and electromyographic activity of the masseter and anterior temporal muscles in skeletal Class III patients., Methods: Individuals were instructed to chew standardized round tablets of silicone impression material. The cumulative weight percentage was calculated using sieve analysis. The bilateral surface electromyographic activity of the muscles was evaluated. Following the orthodontic treatment, a stabilization splint was fabricated. Patients were instructed to wear it full-time until the surgical procedure occurred. Recordings were performed before the splint application (T0), after the splint application (T1), 1 month after the OGS (T2), and 6-8 months after the OGS (T3)., Results: Median particle size of the chewed silicone material did not differ from T0 to T1 with the use of an occlusal splint (p > 0.05). However, it decreased from 9.46 to 6.92 cm from T2 to T3. From T0 to T3, a statistically significant decrease was found, following the surgical intervention (p < 0.01). A significant decrease in masticatory muscle activity was also observed during the relaxation test from T0 to T3, at which time it reached the control group value., Discussion: OGS enhanced masticatory function by improving occlusion in individuals with a dentofacial deformity.

Objectives: The aim of this study was to investigate whether the presence of a natural mediotrusive contact influences electromyographic (EMG) pattern activity in patients with temporomandibular disorders (TMDs)., Method: Bilateral surface EMG activity of the anterior temporalis (AT), masseter (MM), and sternocleidomastoid (SCM) muscles was recorded in 43 subjects during unilateral chewing and tooth grinding. Thirteen patients had TMD and a natural mediotrusive contact (Group 1), 15 had TMD without a natural mediotrusive contact (Group 2), and 15 were healthy subjects without mediotrusive contacts (Group 3). All subjects were examined according to the Research Diagnostic Criteria for TMD (RDC/TMD). All EMG values were standardized as the percentage of EMG activity recorded during maximum isometric contraction on cotton rolls., Results: EMG activity from all muscles measured showed no significant differences between groups during chewing and grinding. Overall, in all groups, the EMG activity during chewing was higher in the working side than the non-working side in AT and MM muscles. During grinding, these differences were only found in masseter muscles (mainly in eccentric grinding). SCM EMG activity did not show significant differences during chewing and grinding tasks. Symmetry, muscular balance, and absence of lateral jaw displacement were common findings in all groups., Discussion: EMG results suggest that the contribution of a natural mediotrusive occlusal contact to EMG patterns in TMD patients is minor. Therefore, the elimination of this occlusal feature for therapeutic purposes could be not indicated.

Objective and Importance: Hypoplasia of the masseter muscle is a rare condition, described as partial or total, associated with congenital malformations or pathologies. Rare cases are those with no genetic alterations in their familiar picture. The authors present a case of an idiopathic masseter muscle hypoplasia in the absence of other pathologies., Clinical Presentation: The case report involved a patient who presented to the consultant clinic complaining of facial asymmetry. The patient underwent several exams to confirm the diagnosis of masseter muscle hypoplasia, which included an X-ray, magnetic resonance of the temporomandibular articulation, and electromyography., Intervention: The patient was treated with a customized functional appliance and fixed orthodontic treatment with satisfactory functional and esthetic results., Conclusion: The case presented highlights the possibility of finding a hypoplasia of the masseter muscle even in the absence of other pathologies and without specific clinical symptoms, and how to plan an appropriate treatment with functional appliance and fixed orthodontic therapy.

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.

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.

Objective: The aim of this study was to detect sonographic predictors for the efficacy of massage treatment of masseter and temporal muscle in temporomandibular disorders (TMDs) patients with myofascial pain., Methods: Thirty-seven TMD patients with myofascial pain (6 men and 31 women, a median age of 45 years) were enrolled. An oral rehabilitation robot massaged the patient's masseter and temporal muscles with a standard massage pressure of 10 N for 16 min. The standard treatment protocol was set five sessions every 2 weeks. The median total duration of treatment was 9.5 weeks. Efficacy of treatment was evaluated based on maximum mouth opening and visual analog scale scores of muscle pain and daily life impediments. The intramuscular echogenic bands and elasticity index ratios of the masseter muscles were evaluated on sonographic or sonoelastographic images obtained before treatment and after the third and last treatment sessions., Results: The sonographic features detected different changes after the third treatment session between the therapy-effective and therapy-ineffective groups: in the therapy-effective group, the frequency of visibility of the distinct echogenic bands increased, and the elasticity index ratio decreased., Conclusion: Sonographic features after the third treatment session may be useful as predictors of therapeutic efficacy.

Aims: The masseter muscle is a common source of referred pain to the temporomandibular joint (TMJ), with a possibility of false positive diagnoses for arthralgia when diagnosed by research diagnostic criteria for temporomandibular disorders (RDC/TMD) clinical examination. The current study investigated the distribution of arthralgia diagnoses among individuals with myofascial pain, with or without pain on masseter palpation., Methodology: The study was conducted with 255 outpatients. Clinical data and questionnaires were directly entered into software that deploys algorithms based on the diagnostic criteria of the RDC/TMD, and automatically classifies and stores the diagnosis of each patient evaluated. An association between diagnostic subgroups was verified by calculating the odds ratio (OR), and the statistical significance was tested using the Chi-square test., Results: A higher frequency of concordance (about three times greater) between myofascial pain and arthralgia occurred when there was pain on palpation in the region of the ipsilateral masseter muscle, and the association was statistically significant., Conclusions: The results of this study revealed a threefold increase in the risk for the presence of temporomandibular arthralgia in cases of myofascial pain combined with pain on palpation in the region of the ipsilateral masseter muscle.

Aims: The aim of this study was to evaluate the relationship between the clinical and the radiological data obtained by magnetic resonance imaging (MRI) in patients with temporomandibular disorder (TMD)., Methodology: The study group included 17 patients with symptoms of TMDs. The radiological assessments before and after therapy was evaluated by MRI; in the clinical analysis, signs and associated symptoms have been assessed., Results: With MRI before therapy, we were able to distinguish the specific type of TMD that each patient had. At the end of the treatment, a general improvement of the clinical status was noticed; MRI, however, showed the permanence of several degrees of condyle-disc incoordination in some patients., Conclusions: Certainly TMDs can be diagnosed without MRI; nevertheless, MRI gives us the possibility to obtain objective data of the patients concerned. Symptoms recorded during a clinical evaluation cannot be the only terms of diagnosis; MRI provides objective data in the diagnostic and post-therapy phases.

The study aimed to clarify the masseter muscle hardness in patients with myofascial pain, to examine their changes after massage, and to analyze whether the hardness can be an index for massage treatment. Sixteen patients with myofascial pain (12 with unilateral and 4 with bilateral masseter muscle pain) and 24 healthy volunteers were enrolled in this study. The masseter hardness between patients and the healthy volunteers was compared. The changes in the hardness in patients after massage were examined. The relation of the hardness with massage regimens and efficacies was analyzed. There was a significant right-and-left difference of the hardness in patients, although there was no difference in the healthy volunteers. The hardness decreased after massage. The pretreatment asymmetry index of the hardness showed a significant correlation with the massage pressure. It was concluded that there was a significant difference between the right and left masseter hardness in patients with myofascial pain. After massage treatment, the masseter hardness and right-and-left difference decreased. The hardness may be an index for determining the massage pressure.

In this clinical study, pre- and post-rehabilitation changes in intraborder mandible movements, chewing cycles, masticatory efficiencies, and borders of the chewing area of patients with unilateral muscular disorders (MD) (n = 20) or unilateral disc derangement disorders (DDD) (n = 20) of temporomandibular disorder (TMD) were observed and compared with healthy individuals with full dentition (n = 20) (48 female, 12 male; mean age: 28). The MD patients received stabilization splints and the DDD patients, anterior positioning splints for six weeks. Symptoms, such as muscle pain, TMJ pain, headache, chewing difficulty, and maximum mouth opening, showed significant improvements after splint therapy for both MD (p = 0.000) and DDD (p = 0.000) patients, but lateral excursion and protrusion were not significantly changed (p > 0.05). Chewing efficacy and chewing cycles improved significantly (p < 0.05) in both the MD (p < 0.05) and DDD (p < 0.05) groups, but only the MD group was comparable to the control group after treatment. Pre- and post-rehabilitation chewing cycles along the frontal plane on both sides in the MD group were similar to the control group. Considering the majority of the improvements in the diagnostic measures, patients with MD and DDD may benefit from occlusal splint therapy.

Individuals with Class III dentofacial deformities exhibit morphological changes and myofunctional adaptations, and an accurate diagnosis is essential for treatment planning. The purpose of this study was to evaluate the electrical activity of the masseter, temporal, and suprahyoid muscles in subjects with Class III dentofacial deformities, assessing electromyographic characteristics using functional tests. The research group consisted of 20 subjects with Class III dentofacial deformities and indications for surgical-orthodontic treatment. The control group consisted of 10 individuals presenting a good maxilla and mandible relationship. Electrical activities of the masseter and temporal were recorded during isometric contraction and maximal isometric contraction. The suprahyoid and masseter were assessed during maximal mouth opening and swallowing of saliva. Isometric contraction and maximal isometric contraction analysis showed less potential in the research group, with a significant difference regarding the masseter muscle in isometric contraction. In maximal isometric contraction, an increase in electrical activity in both groups was observed; it remained lower for the research group, but with no significant difference. With regard to symmetry, significant differences among the groups were observed only for the left masseter in the research group, as well as during isometric contraction. There was no significant difference found regarding maximal mouth opening. During swallowing of saliva, there was a high percentage of abnormal electromyographic tracings for both groups. This finding was not expected for the control group. The study found some changes in muscular activity in Class III dentofacial deformities, characterized by lower potential in the masseter muscle during isometric contractions. No other peculiarities were found that could contrast either group.

There are limited studies about the effects of occlusal appliance (OA) after three months of use. This study aimed to compare myofascial pain (MP) according to RDC/TMD, craniocervical relationships (CR) and masseter and temporalis bilateral electromyographic (EMG) activity, before and after three months of occlusal appliance use. Nineteen patients participated in this study. Cephalometric and RDC/TMD diagnostics were performed previously (baseline) and at the end of the study period (three months). EMG recordings at clinical mandibular rest position (MRP), during swallowing of saliva (SW) and during maximum voluntary clenching (MVC) were performed as follows: after one hour of use of an OA; after three months of using the OA for a minimum of 16 hours each day; and immediately after removal from the mouth. MP was relieved in all patients at the end of the study period. CR did not change significantly between baseline and after removal of the OA at the end of the study period. EMG activity during MRP, SW, and MVC decreased in both muscles after one hour using the OA and maintained the same level for the three-month period. When comparing baseline versus final EMG activity without OA, a significant decrease was only observed in the masseter muscle. The results observed in the present study are relevant to clinicians because they imply that the therapeutic effect of OA does not significantly affect the homeostasis of the craniocervical system.

The purpose of this study was to determine if a statistically significant reduction in muscle activity (p<0.05) occurs when prolonged disclusion time (>0.4 sec/excursion) is shortened to <0.4 sec/excursion with the Immediate Complete Anterior Guidance Development (ICAGD) enameloplasty. Forty-five symptomatic, fully informed subjects (29 female, 16 male) had their right and left disclusion times recorded with T-Scan III, while simultaneously, the bilateral masseter and anterior temporalis muscle activity was recorded electromyographically with BioEMG III (n=180 muscles). This recording was done twice, once pretreatment and again posttreatment (same day) after undergoing the ICAGD enameloplasty on the same day without changing electrodes. The Student's paired t-test was utilized to detect any significant change in the muscle activity levels between the pre- and posttreatment lateral excursive muscle contractions. Highly significant reductions were found in all four muscles' activities after shortening the pretreatment prolonged disclusion time to less than 0.4 seconds (p<0.0014); after Bonferroni correction (p<0.006). When properly performed, such that the posttreatment disclusion time is <0.4 sec/excursion, the ICAGD enameloplasty predictably reduces excursive muscle activity levels in the bilateral anterior temporalis and masseter muscles. Excursive muscle hyperactivity can be a source of lactic acid accumulation, muscular ischemia, and chronic myalgic temporomandibular joint dysfunction (TMD) symptoms. The ICAGD enameloplasty significantly reduces excursive muscle contractions after completion of the first ICAGD treatment session.

The purpose of this study was to apply Functional Anatomy Research Center (FARC) Protocol of TMD treatment, which includes the use of a specific type of mandibular occlusal splint, adjusted based on the electromyographic index, in a group of 15 patients with disc displacement, classified according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) and then analyzing the results compared with the control group. The clinical evaluations were completed both before and after the treatment. Electromyographic (EMG) data was collected and recorded on the day the splint was inserted (visit 1), after one week (visit 2) and after five weeks of treatment (visit 3). The control group consisted of 15 asymptomatic subjects, according to the same diagnostic criteria (RDC/TMD), who were submitted to the same evaluations with the same interval periods as the treatment group. Immediately after splint adjustment, masseter muscle symmetry and total muscular activity were significantly different with than without the splint (p < 0.05), showing an increased neuromuscular coordination. After treatment, significant variations (p < .05) were found in mouth opening and in pain remission. There were no significant differences among the three sessions, either with or without the splint. There were significant differences between the TMD and control groups for all analyzed indices of muscular symmetry, activity and torque, with the exception of total muscular activity. The use of the splint promoted balance of the EMG activities during its use, relieving symptoms. EMG parameters identified neuromuscular imbalance, and allowed an objective analysis of different phases of TMD treatment, differentiating individuals with TMD from the asymptomatic subjects.

A randomized controlled trial was performed to compare the short-term effectiveness of botulinum toxin injections and physiatric treatment provided by means of Fascial Manipulation techniques in the management of myofascial pain of jaw muscles. Thirty patients with a Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) diagnosis of myofascial pain were randomized to receive either single-session botulinum toxin injections (Group A) or multiple-session Fascial Manipulation (Group B). Maximum pain levels (VAS ratings) and jaw range of motion in millimeters (maximum mouth opening, protrusion, right and left laterotrusion) were assessed at baseline, at the end of treatment, and at a three-month follow-up. Both treatment protocols provided significant improvement over time for pain symptoms. The two treatments seem to be almost equally effective, Fascial Manipulation being slightly superior to reduce subjective pain perception, and botulinum toxin injections being slightly superior to increase jaw range of motion. Differences between the two treatment protocols as to changes in the outcome parameters at the three-months follow-up were not relevant clinically. Findings from the present investigation are in line with literature data supporting the effectiveness of a wide spectrum of conservative treatment approaches to myofascial pain of the jaw muscles. Future studies on larger samples over a longer follow-up span are needed on the way to identify tailored treatment strategies.

Among treatments in the literature for myofascial pain syndrome (MPS), the most reliable therapies in dentistry are spray and stretch, and, although less frequently used, anesthetic injection. Adult MPS subjects are often treated using fixed orthodontic therapy for resolution of malocclusion. There is no clarity in the literature on the prognosis of MPS during orthodontic therapy. The purpose of this study was to analyze the prognosis of MPS during orthodontic treatment of subjects with malocclusion, initially diagnosed as having MPS. The analysis covered the medical records of 91 young adult Caucasians scheduled for orthodontic treatment for various malocclusions. Thirty-seven of the patients were initially diagnosed as also having MPS (T0). Thirty patients began the orthodontic treatment and were recalled for a re-evaluation of MPS after dental alignment and dental class correction was achieved (T1). A wait-and-see strategy was applied in seven subjects who were included as the control subjects. They received no treatment for MPS. At T1, a statistically significant decrease was observed in the study group in the presence of any clicking or creaking noises from the jaw joint, a significant jaw joint and jaw muscle pain reduction, and a quality of life improvement. Among patients who were depressed at the beginning of treatment, the majority felt better at the follow-up evaluation. On muscular palpation, a statistically significant decrease was found on the visual analogic scale value of the middle fibers of the temporalis muscle, temporalis tendon, clavicular and sternal division of the sternocleidomastoid muscle, masseter muscles, and posterior cervical muscles. The temporalis and the masseter muscles showed a significant decrease in the number of subjects with trigger points (TrPs) in all areas in the study group, after treatment. The digastric and sternocleidomastoid muscles also showed a significant reduction in the number of subjects with TrPs. Subjects with MPS and malocclusion were treated using a fixed orthodontic treatment. They showed improvement, although no resolution, in the signs and symptoms of MPS, compared with the untreated control group.

In this study, the authors investigated the link between jaw clenching/bruxism and temporal bone movement associated with multiple sclerosis (MS). Twenty-one subjects participated in this study (10 patients with MS and 11 controls). To quantify the change in intracranial dimension between the endocranial surfaces of the temporal bones during jaw clenching, an ultrasonic pulsed phase locked loop (PPLL) device was used. A sustained jaw clenching force of 100 lbs was used to measure the mean change in acoustic pathlength (delta L) as the measure of intracranial distance. In the control subjects the mean delta L was 0.27 mm +/- 0.24. In subjects with MS the mean delta L was 1.71 mm +/- 1.18 (p<0.001). The increase in magnitude of bi-temporal bone intracranial expansion was approximately six times greater in subjects with MS compared to controls. Therefore, jaw clenching/bruxism is associated with more marked displacement of the temporal bones and expansion of the cranial cavity in patients with MS than in control subjects.

The present study was comprised of 43 patients (16 men) with cervicogenic headaches for over three months, diagnosed according to the International Classification of Diagnostic Criteria of Headaches (ICDH-II). The patients were randomly assigned to receive either manual therapy for the cervical region (usual care group) or additional manual therapy techniques to the temporomandibular region to additionally influence temporomandibular disorders (TMD). All patients were assessed prior to treatment, after six sessions of treatment, and at a six-month follow-up. The outcome criteria were: intensity of headaches measured on a colored analog scale, the Neck Disability Index (Dutch version), the Conti Anamnestic Questionnaire, noise registration at the mandibular joint using a stethoscope, the Graded Chronic Pain Status (Dutch version), mandibular deviation, range of mouth opening, and pressure/pain threshold of the masticatory muscles. The results indicate in the studied sample of cervicogenic headache patients, 44.1% had TMD. The group that received additional temporomandibular manual therapy techniques showed significantly decreased headache intensities and increased neck function after the treatment period. These improvements persisted during the treatment-free period (follow-up) and were not observed in the usual care group. This trend was also reflected on the questionnaires and the clinical temporomandibular signs. Based on these observations, we strongly believe that treatment of the temporomandibular region has beneficial effects for patients with cervicogenic headaches, even in the long-term.

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.

Bifid mandibular condyle is a rare anomaly; there are several theories about its etiology, and it has been studied in both prehistoric and historic skulls, as well as in living human beings. It is a frequent, although unexpected, finding in asymptomatic individuals during radiological treatment. Presented here is a review of the literature over the past 10 years and two new cases of unilateral bifid condyle. Computerized tomography is usually considered the test of choice for establishing the differential diagnosis, although in certain cases, its use seems questionable. The distinction between bifid condyle and condylar notch or cleft has been described in the literature, it is proposed a criteria for defining bifid condyle depending on the level of the two heads. It is suggested that further testing such as MRI or CT be carried out only in cases where the therapeutic approach involves an active treatment. It is proposed that bifid condyle is described as that which presents two condylar heads emerging from the neck of the condyle or further down.

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.

The masseter muscle is an integral part of the oral facial complex and one of the muscles of mastication. It functions with the other masticatory muscles in moving and posturing the mandible and in verbalizing, eating and swallowing. When a patient has temporomandibular dysfunction (TMD) or a myogenic disorder, the integrity of the masseter muscle can be compromised resulting in pain, malfunction, inflammation and/or swelling. A careful evaluation of the masseter muscles is necessary in facial pain patients since the pain can originate from a distant site and be referred to this area. One of the little known disorders involving the masseter and its tendinous origin is tenomyositis, in which an inflammation of the muscle and its tendon occurs. In this retrospective study, the charts of 114 consecutive patients (N = 114) were evaluated to determine the prevalence of this disorder and the reported etiology.

This is a case of unilateral masseter muscle hypertrophy (MMH) treated with botulinum toxin (NHAI-normalised hemi-facial asymmetry index improvement from 5.48 to 3.04). After 19 months the treatment was repeated because of hypertrophy relapse (NHAI increase up to 6.82). The volume variations in the masseter area were monitored during 25 months using a laser scanner to compute facial volume. In order to relate the cause of hypertrophy and relapse to the presence of parafunctional activities, a nocturnal electromyography (EMG) study was conducted with positive results (nocturnal parafunctions of patients 4074.99 microV to be compared with a control group value of 1644.63 microV). The lack of the left inferior molars and the consequent right occlusal support seemed to justify the hypertrophy of right masseter (MMRight-POC [percent overlapping coefficient] 91.9%). However, the prosthetic rehabilitation did not prevent relapse in the same muscle. The EMG analysis of both the muscular activation (MMRight-POC 66.0% after relapse) and inhibition activity in Maximum Voluntary Clench (MVC) resulted in contradictory conclusions. At present, the available knowledge regarding MMH physiopathology is very limited and does not support a therapeutic rationale for relapse prevention.

This study assessed the interexaminer reliability and validity of palpation (PA) and pressure pain threshold (PPT) of the temporomandibular joint (TMJ) and the masseter and temporalis muscles in patients with temporomandibular disorders (TMD) and asymptomatic controls. Eighty (80) subjects were distributed into two groups: Group 1 consisted of 40 TMD patients with muscular and joint pain selected by RDC/TMD Axis I; and Group 2 (control) with 40 asymptomatic individuals. Training and calibration of examiners was undertaken prior to testing. Mean reliability values were 0.64 and 0.78 (PPT), and 0.59 and 0.75 (PA), for patients and controls, respectively. Results showed statistically significant differences (p<0.001), for PA and PPT among TMD patients compared with the control. The results also showed acceptable specificity values (above 0.90), although sensitivity had low values. The tests had low diagnostic validity to discriminate between patients and controls, with low positive predictive values (PPV).

The aim of this study was to investigate the frequency of otologic symptoms and their relationship to orofacial signs and symptoms of temporomandibular disorder (TMD), and the effect of orofacial myofunctional therapy. The study was conducted on eight asymptomatic subjects (Group C) and 20 subjects with articular TMD, randomly distributed over two groups: one treated using orofacial myofunctional therapy (OMT Group) and a control group with TMD (Group CTMD). Patient selection was based upon the Research Diagnostic Criteria for TMD (RDC/TMD). All subjects submitted to a clinical examination with self-reporting of symptom severity, and to orofacial myofunctional and electromyographic evaluation at diagnosis and again, at the end of the study. Correlations were calculated using the Pearson test and inter- and intragroup comparisons were made (p < 0.05). In the diagnosis phase, subjects with TMD reported earache (65%), tinnitus (60%), ear fullness (90%), and 25% of the asymptomatic subjects reported tinnitus. The otologic symptoms were correlated with tenderness to palpation of the temporomandibular muscles and joints and with orofacial symptoms. Only the OMT group showed a reduction of otologic and orofacial symptoms, of tenderness to palpation and of the asymmetric index between muscles. OMT may help with muscle coordination and a remission of TMD symptoms.

The objective of this investigation was to test the hypothesis that alteration of the occlusions of patients suffering from temporomandibular disorders (TMD) to one that is neuromuscularly, rather than anatomically based, would result in reduction or resolution of symptoms that characterize the TMD condition. This hypothesis was proven correct in the present study, where 313 patients with TMD symptoms were examined for neuromuscular dysfunction, using several electronic instruments before and after treatment intervention. Such instrumentation enabled electromyographic (EMG) measurement of the activities of the masticatory muscles during rest and in function, tracking and assessment of various movements of the mandible, and listening for noises made by the TMJ during movement of the mandible. Ultra low frequency and low amplitude, transcutaneous electrical neural stimulation (TENS) of the mandibular division of the trigeminal nerve (V) was used to relax the masticatory muscles and to facilitate location of a physiological rest position for the mandible. TENS also made it possible to select positions of the mandible that were most relaxed above and anterior to the rest position when the mandible was moved in an arc that began at rest position. Once identified, the neuromuscular occlusal position was recorded in the form of a bite registration, which was subsequently used to fabricate a removable mandibular orthotic appliance that could be worn continuously by the patient. Such a device facilitated retention and stabilization of the mandible in its new-found physiological position, which was confirmed by follow up testing. Three months of full-time appliance usage showed that the new therapeutic positions achieved remained intact and were associated with improved resting and functioning activities of the masticatory muscles. Patients reported overwhelming symptom relief, including reduction of headaches and other pain symptoms. Experts consider relief of symptoms as the gold standard for assessment of effectiveness of TMD treatment. It is evident that this outcome has been achieved in this study and that taking patients from a less to a more physiological state is an effective means for reducing or eliminating TMD symptoms, especially those related to pain, most notably, headaches.

The aim of this study was to analyze the symmetry of the electromyographic (EMG) activity of the temporalis, masseter, and sternocleidomastoid (SCM) muscles in volunteers divided into a control group and a temporomandibular disorder (TMD) group. The surface EMG recordings were made during mandibular rest position, maximal intercuspal position, and during the chewing cycle. Normalized EMG waves of paired muscles were compared by computing a percentage overlapping coefficient (POC). The difference between the groups and between the static and dynamic clenching tests was analyzed through repeated measures, ANOVA. Symmetry of the temporalis, masseter, and SCM muscles activity was smaller in the TMD group compared to the control group. The mandibular postures were also significantly different among themselves. The asymmetric activation of jaw and neck muscles was interpreted as a compensatory strategy to achieve stability for the mandibular and cervical systems during masticatory function.

Simultaneous recording of excursive function and muscle activity on 62 MPDS patients demonstrated that reducing prolonged disclusion time (1.4 seconds per excursion) to short disclusion time (0.41 seconds per excursion) created a therapeutic effect such that within one month's time following treatment, there was an observed increase in the maximal clenching capacity of the masseter and temporalis muscles. This clinical treatment effect appears to be the result of decreased ischemia in these same muscles resultant from minimizing the time posterior teeth compress their periodontal ligament mechanoreceptors as these teeth are engaged and disengaged during excursive function.

The aim of this study was to test the hypothesis that strengthening masticatory muscles using a controlled chewing exercise protocol improves muscle function, as evaluated quantitatively by electromyogram, and reduces pain at rest and during function. The study included 20 patients diagnosed with myofascial pain according to the Research Diagnostic Criteria for Temporomandibular Disorders with low masseter volume increase during maximal clench. The exercise group (ten patients) was subjected to a controlled gum chewing exercise protocol for eight weeks: the control group (ten patients) received only support and encouragement. Patients were examined at the beginning and at the end of the experiment which included an electromyogram (EMG) to assess muscle performance, masticatory muscle tenderness to palpation, mouth opening range, subjective anamnestic indices to evaluate pain perception and pain relief, and chewing tests. The EMG showed that the masticatory muscle exercise did produce objective physiologic results. In the exercise group, a significant increase was found in the electric muscle activity of the masseters during maximal voluntary clench (p=0.007). The exercise group showed significant reduction in pain during rest, pain during the chewing test, and a disability score. At the end of the study, a difference between the two groups was shown in the Pain Relief Scale: significantly greater pain relief was found in the exercise group as compared to the control group (p=0.019). For all other clinical parameters, there was no difference between the two groups or interaction between time and treatment. The results of this study seem to be equivocal. Additional experiments on larger population groups with extended chewing protocols are necessary before a more substantial conclusion can be reached.

The aim of this study was to evaluate the efficiency of the Pró-Fono Facial Exerciser (Pró-Fono Productos Especializados para Fonoaudiologia Ltda., Barueri/SP, Brazil) to decrease bruxism, as well as the correlation between the masseter and the buccinator muscles using electromyography (EMG). In this study, 39 individuals ranging from 23 to 48 years of age were selected from a dental school and then underwent surface EMG at three different periods of time: 0, 10, and 70 days. They were divided into a normal control group, a bruxer control group (without device), and an experimental bruxer group who used the device. The bruxer group showed a greater masseter EMG amplitude when compared to the normal group, while the experimental group had deceased activity with a reduction in symptoms. The buccinator EMG spectral analysis of the experimental bruxist group showed asynchronous contractions of the masseter muscle (during jaw opening) after using the Pró-Fono Facial Exerciser. The normal group also showed asynchronous contractions. Upon correlation of the data between these muscles, the inference is that there is a reduction in bruxism when activating the buccinator muscle.

Both experimental and retrospective studies suggest a link between parafunctions and pain in temporomandibular disorder (TMD) patients. To investigate the role of parafunctions in TMD, experience sampling methodology was used as a prospective test of the hypothesis that patients with TMD have higher levels of tooth contact and tension than non-TMD controls. Three groups of TMD patients and a group of normal controls carried pagers for one week, were contacted approximately every two hours by an automated calling system, and completed questionnaires assessing tooth contact, tension, and pain at each contact. Results showed that tooth contact was much more frequent among normal controls than is commonly presumed. Patients with myofascial pain with/without arthralgia reported more frequent contact, higher intensity contact, and more tension than patients with disk displacement or normal controls. Increased masticatory muscle activity responsible for tooth contact and tension may be an important mechanism in the etiology and maintenance of the myofascial pain and arthralgia of TMD.

The purpose of this study was to evaluate the effectiveness of the therapy with a centric relation stabilization appliance (CRSA) in patients with temporomandibular disorders of myogenous origin by electromyography and compare the results with two asymptomatic control groups. Three groups of 20 patients each were selected for the study. Electromyography (EMG) of masseter and anterior temporalis muscles was performed during mandibular rest position. In the treated group, the occlusal appliance reduced the electrical activity of the analyzed muscles at right and left sides (p<0.0001), and equilibrated muscular activity between right and left sides (p<0.0001), reaching values close to the control groups. Although there was not a statistically significant difference, the normal control group presented lower EMG values than control group II and presented the lowest asymmetry index of all subjects. More than 85% of all subjects, including the controls, demonstrated a statistically significant temporal anterior activity prevalence (p<0.0001). Treatment with the CRSA reduced the activity index, although the prevalence of the temporal muscle over the masseter was maintained. The significant laterodeviating (torque) effect found in the temporomandibular disorder patients was reduced after treatment. No side prevalence was found in the control groups.

The aim of this study was to investigate the reliability between different examiners when using the axis I of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). The hypothesis was that the standardized RDC/TMD examination protocol enables calibrated examiners to evaluate all examination items reliably. After calibration training by the RDC/TMD calibration team including the calibration of palpation pressure and the performance of the standardized examination protocol, four examiners, blinded to the patients' medical histories examined 24 subjects in a randomized sequence. One experienced examiner was the standard (hierarchical calibration). The recorded measurements strictly followed the RDC/TMD. Intraclass correlation coefficients (ICC), bias and precision were calculated to estimate interrater reliability. Acceptable (0.75 > or = CC > 0.4) to excellent (ICC > 0.75) reliability was found for 20 of the 23 (87%) examinations. Only sub-retromandibular muscle palpation and joint sound vibration recordings on lateral excursion showed poor-results (ICC < or = 0.4). The RDC/TMD examination protocol enables calibrated examiners to perform most (87%) examination items with satisfactory reliability. Therefore multi-site studies based on the RDC/TMD examination protocol may become feasible, keeping in mind the unsatisfactory reliability of 13% of the items (clicking during laterotrusion to the ipsilateral side, palpation of the posterior and submandibular region).

This study tested the reproducibility of visual analog scale (VAS) pain scores to measure changes in masseter muscle pain evoked by maximally tolerable mechanical stimulation over a short time period in healthy subjects. This study also evaluated gender differences in reproducibility of VAS scores to mechanical stimulation. Ten healthy female and eight healthy male individuals participated in this study. The recordings of VAS pain scores to an identical mechanical pressure on the masseter muscle were performed at three different sessions (T1, T2, and T3). The subjects rated their pain on a VAS to a maximally tolerable stimulus that was recorded on an algometer at the first session. The algometer pressure reading was recorded for each subject and then used to duplicate the same identical mechanical stimulus at each of the three sessions. This identical pressure was repeated in the same marked spot at six minutes and after 30 minutes. The subjects rated the pain on a VAS to this identical stimulus at each session. There was no significant difference in VAS pain scores of all subjects at T1, T2, and T3. There was no significant difference in reproducibility of VAS pain scores in females compared to males. Intraclass correlation coefficients were 0.811 on the right masseter and 0.844 on the left masseter. VAS pain scores to mechanical stimulation were reproducible over a short time period. Gender did not affect the reproducibility. This previously unreported method of measuring pain to repeated identical mechanical stimulation appears to have potential for both clinical and research application.

Sleep-related phenomena or disorders, including snoring and tooth grinding, can be investigated using polysomnography. This method, however, generates large amounts of synchronically recorded data that are often analyzed visually with subjective interpretation. The purpose of this study was to minimize the need for subjective evaluation by developing a computer program for analysis of EMG data linked with polysomnographic recordings in a standardized and semi-automatic way. The selected algorithm differs from the Root Mean Square (RMS) method by being based on the theory of "differentiated EMG" (DIFEMG), which relies on two principles. The first says that the activation of a larger number of motor units results in a greater force production. The second principle says that the force production will continue for some time after the muscle is no longer stimulated. After a visual check for artifacts in the basic EMG recordings, the computer program is used to analyze the corrected basic EMG signal. The results were that both methods yield identical results as far as the detected number of events is concerned. There is, however, a significant difference when the duration of the events is considered, because the start and end of an event can be more accurately determined with the new method presented here. The computer program described will make comparison of data from different studies easier.

This study was aimed at evaluating the effects of a novel physiotherapy machine called MAGMA (AntiGravitary Modification of the Myotensions of Asset) on postural and masticatory muscles of subjects with myogenic cranio-cervical-mandibular dysfunction (CMD), by using surface electromyography (sEMG). Fifteen subjects, nine males and six females (mean age 27.6 years), with CMD were included in the study. The bilaterally monitored muscles were: masseter, anterior and posterior temporalis, digastric, posterior cervical, sternocleidomastoid, and upper and lower trapezius. All muscles were monitored at rest, with a second record of maximal voluntary clenching (MVC) for both the masseter and anterior temporalis. Patients were subjected to MAGMA therapy for one session/week of 30 min over ten weeks. The surface EMG activity was recorded twice, at the baseline and at the end of the therapy. After MAGMA therapy, the sEMG activity at rest of the monitored muscles was significantly better when compared to the baseline; the only exception was the anterior and posterior temporalis muscles which did not improve. On the contrary, with the MVC, all the monitored muscles (masseter and anterior temporalis) significantly improved their sEMG activity. Although more investigations are needed, these results indicate that the use of such antigravitary therapy can provide a tool for resolving myogenic CMD.

In the prognathic (P) patient group clenching at maximal intercuspal position (MIP), we found that the Ar-Go-Me angle is greater than in the control group (C = 120.9 degrees +/- 7 degrees vs. P = 134.4 degrees +/- 5.2 degrees): the same as the masseter fibers angle (alpha). The average EMG voltage class was similar in both groups (C = 1488.5 +/- 303.4 microvolt vs. P = 1317.6 +/- 293.4 microvolt). The mean total number of contact points in tooth arches was greater in the control group than in the patient group (C = 5.77 +/- 0.43 vs. P = 3.07 +/- 0.29), and there was a greater number of contact points between both premolar and molar areas. Both the control group and the patient group showed balanced occlusion in the premolar and molar areas. Therefore the finding of a similar mean EMG value between the control group and the patients emphasizes the importance of balanced contact points in the posterior areas.

Contracture of the jaw-closing muscles is one of the causes of limitation of jaw opening. This study examined whether there is any difference between the EMG activities of jaw-closing muscles during jaw opening in healthy people and in patients with masseter muscle contracture (MMC), who do not have a history of trauma or infection. The patient group consisted of eleven females, 18 to 62 years old with no history of trauma or infections, with limited mouth opening due to MMC. The control group included eleven healthy females, 23 to 50 years old. The EMG activity was recorded bilaterally in the central portion of masseter muscles (Mm), the anterior portion of temporal muscles (Tm), and the anterior belly of digastric muscles (Dm). Nine out of the patient group showed obvious EMG activity in Mm during jaw opening which was different from typical EMG patterns during jaw opening of up to 40 mm in the control group. Among the nine patients, eight showed antagonistic contraction in Tm as well as Mm. The mean integral value of Mm and Tm during jaw opening in the patient group was significantly higher than in the control group (P<0.01). These results suggest that EMG activity during jaw opening in MMC patients with no history of trauma or infections is different from that in healthy people.

Hyperwork of the masseter muscles due to habitual parafunction is thought to induce masseteric hypertrophy (so called work hypertrophy). However, the causes underlying this disease are not yet fully understood. Recently, we had a patient with bilateral masseteric hypertrophy, and we performed a partial excision of the masseter muscles. In this patient's case, we examined muscular activity, energy metabolism, and fiber type composition of the masseter muscles using electromyograms (EMG), 31P-magnetic resonance spectroscopy (MRS), and enzyme-histochemistry. The EMG showed no hyperactivity, and the 31P-MRS showed normal energy spectral patterns and PCr contents of the masseter muscles. The fiber type composition, however, in the muscles in this case was very different from that in muscles with "work hypertrophy" and also that in normal masseter muscles: 1. Loss of type IIB fibers; 2. Increases in type IIA and in type IM & IIC fibers; and 3. Decrease in type I fibers. The findings suggest that this is not a case of work hypertrophy but a case of compensatory hypertrophy possibly due to a lack of high-tetanus-tension type IIB fibers.

Because the concept of whiplash as a causative factor for temporomandibular disorders (TMD) is highly controversial, we decided to do a retrospective analysis of patients treated in our office who had sustained whiplash injuries and were treated for cervical and temporomandibular disorders. The records of 300 patients with TMD preceded by a motor vehicle accident were examined retrospectively. The most common presenting symptoms, in order, were: jaw pain, neck pain, post-traumatic headache, jaw fatigue, and severe temporomandibular joint (TMJ) clicking. The most common TMD diagnoses were: masseter trigger points, closing jaw muscle hyperactivity, TMJ synovitis, opening jaw muscle hyperactivity, and advanced TMJ disk derangement. Based primarily on the physical examination, we concluded that the TMJ and surrounding musculature should be examined similarly to other joints, with no preconceived notion that TMD pathology after whiplash is unlikely.

This study tested the hypothesis that parafunctional clenching increases pain, can lead to a diagnosis of temporomandibular disorder (TMD) pain, and can produce reductions in proprioceptive awareness. Twenty individuals participated in EMG biofeedback training sessions on the left and right temporalis and masseter muscles. No subjects had TMD prior to training. Subjects were randomly assigned to either a Decrease group, who were instructed to maintain EMG activity below 2 microV during training, or an increase group, who were instructed to maintain EMG activity above 10 microV. To test the impact of parafunctional clenching on proprioceptive awareness, all subjects were instructed to barely touch their teeth together while EMG activity was recorded pre- and post-training. Three subjects assigned to the Increase group and no subjects assigned to the Decrease group were diagnosed with TMD pain following training. Self-reported pain post-training was significantly higher for the Increase group. Parafunctional clenching did not affect performance in the proprioceptive test.

The purpose of this research was to employ a double-blind placebo control design of iontophoretically administered lidocaine to assess the test-retest reliability and validity of a magnitude matching procedure using a pressure algometer. In studies in the literature on assessment of pain in temporomandibular disorders (TMD), the pressure algometer has been found to be a reliable means of measuring pressure-pain threshold and a sensitive measure of treatment-response in the laboratory. However, previous research with this apparatus has not employed more sophisticated psychophysics. This study employs a magnitude matching psychophysical protocol to obtain a multidimensional pain report. Test-retest reliability over two occasions, 3-8 days apart, was found to be moderate for discriminability (r = .71, p < .01) but poor for response bias (r = .44). The validity study used iontophoresis as an anesthetic in a double-blind placebo and no-treatment control design. Although it was hypothesized that subjects in the anesthesia group would demonstrate reduced discriminability as compared with the control groups, no differences were found among the three groups on this measure. However, differences in response bias were found, with both the placebo control and no-treatment control groups differing from the experimental group but not from each other. Possible explanations and the implications of these findings are discussed.

In 13 healthy subjects (eight men and five women, mean age, 22 years), an aluminum intercuspal interference (height, 0.25 mm) was placed on the maxillary right first premolar to study its effect on the contractile symmetry of the right and left masseter and anterior temporalis muscles when measured through a Percentage Overlapping Coefficient (POC), derived from surface electromyographic recordings of maximum voluntary teeth clenching. Additionally, and to estimate the potential of the experimental intercuspal interference to induce lateral displacement of the mandible, a Torque Coefficient (TC) was derived from surface electromyographic recordings. The conclusion was that the experimental occlusal interference gave rise to asymmetric contractile activity in the studied mandibular elevator muscles as well as a potential to displace the mandible in a lateral direction.

There have been few reports analyzing the activity of the jaw-closing muscles after coronoidectomy performed on a patient with coronoid hyperplasia. This paper presents a case study using electromyograms (EMGs) to evaluate the effects of unilateral coronoidectomy on the activity of masseter and temporal muscles. The patient was a 25-year-old male whose maximal range of jaw opening was 24 mm. After coronoidectomy of the left region, the range improved to 43 mm. EMGs were recorded in the center of the masseter muscles and the anterior part of the temporal muscles during gum chewing. Preoperatively, no abnormal EMG activity was observed. Eight months after surgery, increase in the ratio of the bilateral temporal muscle activity and a decrease in the ratio of the right masseter muscle activity were observed, and the proportion of activity of jaw closing muscles was out of the normal range. Eighteen months after surgery, there was slight return to the preoperative EMG activity. It was concluded that unilateral coronoidectomy could result in EMG changes of masseter and temporal muscles with a gradual return.

This study was conducted in order to determine the input visual effect on electromyographic (EMG) activity of the sternocleidomastoid and masseter muscles in the supine and lateral decubitus positions. The study was performed on 22 patients with myogenic cranio-cervical-mandibular dysfunction (CMD) and 18 healthy subjects. EMG activity at rest and during swallowing of saliva and maximal voluntary clenching was recorded in the supine and lateral decubitus positions in the following conditions: 1. with eyes open; and 2. with eyes closed after 5 minutes in a dark room. A significant decrease of EMG activity at rest with closed eyes in both groups was observed in the sternocleidomastoid (lateral decubitus position) and in the masseter muscle (supine position). During swallowing of saliva a significant decrease of EMG activity with closed eyes was observed only in the sternocleidomastoid muscle (lateral decubitus position) in healthy subjects. During maximal voluntary clenching any significant differences were observed upon variation in the visual input. The significant change in EMG activity, mainly observed at rest, suggests that the visual input effect is weak. The absence of a significant change in EMG activity during maximal voluntary clenching upon variation in the visual input could be clinically relevant in patients with myogenic CMD who habitually brux.

To test the hypothesis that the pain-producing effect of parafunctional clenching is mediated by oral contraceptive use and estrogen levels, eight premenopausal women participated in daily (five days/week) 20-minute-long EMG biofeedback training sessions (on the left and right temporalis and masseter muscles) structured as a two-phase cross-over study. Four subjects used oral contraceptives, and four did not. Subjects were instructed to maintain temporalis and masseter activity below 2 microV during decrease training and above 10 microV during increase training. All subjects began their participation at the start of menses. The initial week of training was followed by a week of rest and then a second week of training at mid-cycle. Preliminary screening examinations showed that none of the subjects had TMD. One subject was diagnosed with TMD pain during increase training, and no subjects were diagnosed with TMD during decrease training. Self-reported pain following training increased significantly during increase training. No effects on pain were observed for oral contraceptive status. We conclude that chronic, low-level parafunctional clenching may be a factor producing temporomandibular disorder pain and that oral contraceptive status does not play a role in the TMD pain produced by the experimental protocol.

The effect of anterior repositioning (AR) splint therapy on masticatory muscle activity was investigated in seventeen patients with internal derangement; disk displacement with reduction in particular. Integrated electromyography (EMG) recordings from the masseter and anterior temporalis muscles were analyzed quantitatively during maximal biting in intercuspal position before and after eight week treatment period, EMG recordings were taken for each subject prior to the beginning of clinical therapy and final EMG recordings were made without AR splint to provide a standard for comparison. The results of the investigation revealed the following: 1. AR splint therapy did not cause any significant modification of the EMG activity in the recorded muscles during maximal biting in intercuspal position; 2. Before and after treatment the EMG activity from the masseter muscle was less than from the temporal muscle; 3. AR splint therapy resulted in reduction of the pain (88.2%) and jaw joint sounds (64.7%) and mean vertical opening which was 42.17 mm before treatment increased to 45.06 mm.

A physiotherapeutic approach, with manual maneuvers and/or distraction appliances, is indicated in the treatment of temporomandibular joint disorders (TMDs) to prevent the progressive fibrosis of the muscle fibers. In this article, the authors report preliminary results of experimental and clinical studies conducted to assess the real effect of distraction in temporomandibular joint disorders. The experimental invivo studies confirmed the structural alteration due to compression and distraction on the capsular and condylar tissues. Clinical cases are reported to show the increase of the intraarticular vertical dimension, with a forward and downward movement of the condyles in a more physiologic condition.