Mandibular Rest Research Articles

Osteoarthrosis: Analyze of the Molar Bite Force, Thickness and Masticatory Efficiency.

Osteoarthrosis is a disorder of synovial joints, resulting from destruction of the cartilage and subchondral bone. The present study is aimed to investigate the molar bite force, thickness and efficiency of the masseter and temporalis muscles of subjects with osteoarthrosis. A total of forty-eight subjects participated in the study. They were distributed into two groups: with osteoarthrosis (n=24) and asymptomatic controls (n=24). Subjects were analyzed on the basis of maximal molar bite force (right and left side), thickness (mandibular rest and dental clenching in maximal voluntary contraction) and electromyographic activity of masticatory cycles through the linear envelope integral in habitual (raisins and peanuts) and non-habitual (Parafilm M) chewing of the masseter and temporalis muscles. All the data were analyzed statistically using t-test with a significance level of p≤0.05. There was no difference between groups in maximal molar bite force, muscle thickness and non-habitual chewing. Differences were found on the raisins (p=0.02) and peanuts (p=0.05) chewing for right temporal muscle, with reduced masticatory muscle efficiency in osteoarthrosis subjects. This study showed that osteoarthrosis induces negative changes in habitual chewing, highlighting the efficiency of the right temporalis muscles. The greater temporal muscle activity in subjects with osteoarthrosis may compromise chewing and consequently the nutritional status of adult subjects.

Evaluation of the impact of preoperative use of dexamethasone and cyclobenzaprine in surgical extraction of lower third molars on trismus by electromyographic analysis.

The aim of this study was to evaluate the influence of cyclobenzaprine and dexamethasone on ​the electrical activity of the masticatory muscles in patients who had undergone lower third molar surgery. Thirty bilateral impacted lower third molars with indication of extraction were randomised into three groups: the control group, the dexamethasone, and the cyclobenzaprine group. To obtain muscular electrical activity and mouth opening, an electromyographic device was used at mandibular rest and maximum voluntary contraction and compared pre- and post-operatively. During muscle contraction, no significant difference was observed in the electromyographic records on the non-operated side. On the operated side, there was a reduction in electrical activity for both drugs pre-operatively and immediately post-operatively compared to the control group. All pharmacological agents promoted a higher mouth opening compared to control group. The results suggest that dexamethasone and cyclobenzaprine may be useful as an adjuvant in the prevention of motor dysfunctions in third molar surgery.

Relationship between dentofacial morphology and mandibular movement from rest position to maximum intercuspation in Class II division 1 malocclusion patients

BACKGROUND: The objective of this study was to determine the relationship between dentofacial morphology and mandibular movement from rest position to maximum intercuspation in Class II division 1 malocclusion patients. MATERIALS AND METHODS: The sample comprised of 45 patients who were 10–14 years old and had Class II division 1 malocclusions. Eighteen cephalometric variables were evaluated to determine the dentofacial morphology using lateral cephalograms. Mandibular movements were recorded from mandibular rest position to maximum intercuspation using mandibular kinesiography. Spearman's correlation coefficient was used to analyze the relationships between mandibular movement and other dentofacial variables. RESULTS: Mandibular movement in the anteroposterior dimension was significantly negatively correlated with the curve of Spee (COS) (r = −0.45) and freeway space (r = −0.44) and positively correlated with the sella-nasion-mandibular plane (SN-MP) angle (r = 0.47) and the Frankfort-mandibular plane angle (FMA) angle (r = 0.44). Two types of mandibular movement in the anteroposterior dimension were observed. Twenty-six of 45 patients (57.8%) exhibited posterior mandibular movement from rest position to maximum intercuspation (backward group) and 19 subjects (42.2%) presented anterior movement (forward group). COS and freeway space were greater in the backward group. The SN-MP and FMA angles were higher in the forward group. CONCLUSIONS: COS, freeway space, and mandibular plane angle may relate to mandibular movement from rest position to maximum intercuspation in Class II division 1 malocclusion. Patients with deep COS combined with a large freeway space and smaller mandibular plane angle tend to present posterior mandibular movement from rest position to maximum intercuspation.

Use of Hyaluronic Acid in Osteoarthritis of Temporomandibular Joint in Adolescent Patient

Osteoarthritis is a type of articular origin Temporomandibular disorders, being one of the most common degenerative processes affecting the temporomandibular joint. It is characterized by remodeling of the underlying subchondral bone, deterioration and abrasion of articular tissue. Intra-arti- cular injections of hyaluronic acid are considered beneficial for treatment of pain and recovery of joint tissues properties. The aim of this article is to describe the use of hyaluronic acid in the management of osteoarthritis of temporomandibular joint in an adolescent patient. Female patient, 15 years old, presented pain with a year of progress in the bilateral preauricular region, with increased pain at maximum aperture. Considering the clinical and imaging tests the patient was diagnosed with disk displacement with reduction with bilateral osteoarthritic and inflammatory component. Mandibular rest, liquid diet, NSAIDs were indicated and the application of intra-articular hyaluronic acid (Suprahyalâ 25 mg / 2.5 ml) bilaterally. Control was quoted at 2, 3 and 16 weeks where the patient has no spontaneous pain and tenderness. The use of hyaluronic acid is one of the most commonly used therapeutic alternatives for the management of osteoarthritis of temporomandibular joint. However, further evidence of its use in intra-articular application in adolescents and children should be incorporated.

Effect of Breast Cancer Treatment on the Stomatognathic System.

Breast cancer is the most common cancer affecting women in the world and provides functional changes in the human body. Evaluate women submitted to unilateral mastectomy, through electromyographic activity (mandibular rest, right and left laterality, protrusion, maximum voluntary contraction with and without Parafilm, habitual and non-habitual mastication) and thickness (rest and maximum voluntary contraction) of the right temporal muscle (RT), left temporal (LT), right masseter (RM) and left masseter (LM), also the molar bite force (right and left) and compare the data with healthy women. Material and Methods: 32 women were divided into two groups: unilateral mastectomy group (MG), average ± standard deviation 56.50±14.50 years (n=16) and without the disease group (CG), average ± standard deviation 56.56±14.15 years (n=16). The normalized electromyographic data, muscle thickness and maximal molar bite force were tabulated and submitted to statistical analysis (SPSS 21.0; student t test, p≤0.05). Significant statistical differences between MG and CG were found in right laterality, for RM (p=0.02); left laterality, for LT (p=0.01); chewing with peanuts, for RM (p=0.04); chewing with raisins, for LM (p=0.04) and right molar bite force (p=0.03). There was no statistically significant difference between MG and CG for muscle thickness. The results of this study suggest that women undergoing unilateral mastectomy may present functional changes, with emphasis on muscular hyperactivity, lower masticatory efficiency and lower maxillary bite force.

Alterations in the stomatognathic system due to amyotrophic lateral sclerosis.

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.

Electromyographic Analysis of Masticatory Muscles in Cleft Lip and Palate Children with Pain-Related Temporomandibular Disorders.

Aim The aim of this study was to assess the electrical activity of temporalis and masseter muscles in children with cleft lip and palate (CLP) and pain-related temporomandibular disorders (TMD-P). Methods The sample consisted of 31 CLP patients with a TMD-P (mean age 9.5 ± 1.8 years) and 32 CLP subjects with no TMD (mean age 9.2 ± 1.7 years). The children were assessed for the presence of temporomandibular disorders (TMD) using Axis I of the Research Diagnostic Criteria for TMD (RDC/TMD). Electromyographical (EMG) recordings were performed using a DAB-Bluetooth Instrument (Zebris Medical GmbH, Germany) in the mandibular rest position and during maximum voluntary contraction (MVC). Results The rest activity of the temporalis and masseter muscles was significantly higher in TMD-P group compared with non-TMD children. A significant decrease in temporalis muscle activity during MVC was observed in TMD-P patients. There was a significant increase in the Asymmetry Index for temporalis and masseter muscle rest activity in the TMD-P group. Conclusion Cleft children diagnosed with TMD-P have altered masticatory muscle activity, and this can affect their muscle function.

The electrical activity of the masticatory muscles in children with cleft lip and palate.

Information regarding masticatory muscle function in children with cleft lip and palate (CLP) is limited. As a consequence, research on masticatory muscle activity in cleft subjects is needed. To assess masticatory muscle activity in children surgically treated for CLP as well as identify the possible factors associated with this activity. The sample comprised 82 children with mixed dentition and Class I occlusions (25 children with unilateral CLP and 57 subjects with no cleft abnormalities). A DAB-Bluetooth Instrument (Zebris Medical GmbH, Germany) was used to take electromyographical (EMG) recordings of the temporal and masseter muscles both in the mandibular rest position and during maximum voluntary contraction (MVC). Patients with clefts showed a significant increase in temporal muscle activity at rest compared with the controls. The presence of clefts and unilateral posterior crossbites are factors strongly associated with increased temporal muscle EMG potentials during rest position. Children with clefts have altered temporal muscle function. The presence of posterior crossbites affects the temporal muscle activity in cleft subjects. Early diagnosis and orthodontic treatment of malocclusions are necessary to achieve functional improvement in these patients.

Proposal of surface electromyography signal acquisition protocols for masseter and temporalis muscles

Introduction The aim of this study was to propose a method of electrodes positioning on the superficial masseter and anterior temporalis muscles for surface electromyographic (sEMG) recordings in order to overcome some known methodological constraints. Methods Fifteen volunteers with normal occlusion participated in two experimental sessions within a 7 day-period. Surface electrodes were placed on two different locations that were based on palpable and individual anatomical references. Surface EMG signals (2000 Hz per channel; A/D: 16 bits; gain: 2000 X; band-pass filter: 20-500 Hz) were recorded under three conditions: mandibular rest position, 30% and 100% of maximum voluntary bite force. Three measurements of maximal bite force were taken by using a force transducer positioned over the lower right first molar region and the highest record was taken into account. The root mean square value was considered for analysis. Intraclass correlation coefficients (ICCs), paired t test, and the Bland-Altman method comprised the statistical analyses. The level of significance was set at 0.05. Results ICC records for right and left masseter and anterior temporalis muscles at T0 (first sEMG record) and T7 (second sEMG record) intervals were significantly different (p<0.05). The results showed satisfactory to excellent reproducibility of RMS values at rest, MVBF and 30% MVBF, as well as for MVBF in kgf. Conclusion The results showed reliable reproducibility for the sEMG signal recording in masseter and anterior temporalis muscles from the protocols presented and under the three conditions investigated.

Determination of occlusal vertical dimension for complete dentures patients: an updated review.

Determination of the occlusal vertical dimension (OVD) is an integral part of complete dentures fabrication. Due to the lack of teeth, the clinician faces the challenge of how to accurately establish the OVD of the new denture. Therefore, the purpose of this review article was to present, discuss and critique the available methods used in determining the OVD for complete dentures patients. This review identified two main streams to determine the OVD: (i) pre-extraction methods and (ii) post-extraction methods. For the pre-extraction methods, the OVD of the natural dentition is transferred to the new dentures mainly by intra-oral measurements, profile tracing and cephalometric analysis. The post-extraction methods rely on mandibular rest position, facial aesthetic appearance, swallowing pattern, craniofacial landmarks measurements, cephalometric analysis, phonetics and existing dentures. In general, all the available techniques have merits and are helpful for routine clinical use. However, they are empirical in nature, controversial and lack the scientific support. Further, there is no single accurate method for OVD determination. To overcome the limitations of the techniques, the clinician will benefit from applying combination of techniques to approximate the OVD.

音刺激が下顎安静位に及ぼす影響について : 閉口筋筋活動および脳波学的分析(大阪歯科大学大学院歯学研究科博士(歯学)学位論文内容要旨および論文審査結果要旨の公表)

音刺激が下顎安静位に及ぼす影響について : 閉口筋筋活動および脳波学的分析(大阪歯科大学大学院歯学研究科博士(歯学)学位論文内容要旨および論文審査結果要旨の公表)

Short-term transcutaneous electrical nerve stimulation reduces pain and improves the masticatory muscle activity in temporomandibular disorder patients: a randomized controlled trial.

Studies to assess the effects of therapies on pain and masticatory muscle function are scarce. Objective To investigate the short-term effect of transcutaneous electrical nerve stimulation (TENS) by examining pain intensity, pressure pain threshold (PPT) and electromyography (EMG) activity in patients with temporomandibular disorder (TMD).Material and Methods Forty patients with myofascial TMD were enrolled in this randomized placebo-controlled trial and were divided into two groups: active (n=20) and placebo (n=20) TENS. Outcome variables assessed at baseline (T0), immediately after (T2) and 48 hours after treatment (T1) were: pain intensity with the aid of a visual analogue scale (VAS); PPT of masticatory and cervical structures; EMG activity during mandibular rest position (MR), maximal voluntary contraction (MVC) and habitual chewing (HC). Two-way ANOVA for repeated measures was applied to the data and the significance level was set at 5%.Results There was a decrease in the VAS values at T1 and T2 when compared with T0 values in the active TENS group (p<0.050). The PPT between-group differences were significant at T1 assessment of the anterior temporalis and sternocleidomastoid (SCM) and T2 for the masseter and the SCM (p<0.050). A significant EMG activity reduction of the masseter and anterior temporalis was presented in the active TENS during MR at T1 assessment when compared with T0 (p<0.050). The EMG activity of the anterior temporalis was significantly higher in the active TENS during MVC at T1 and T2 when compared with placebo (p<0.050). The EMG activity of the masseter and anterior temporalis muscle was significantly higher in the active TENS during HC at T1 when compared with placebo (p<0.050).Conclusions The short-term therapeutic effects of TENS are superior to those of the placebo, because of reported facial pain, deep pain sensitivity and masticatory muscle EMG activity improvement.

Temporomandibular dysfunction, myofascial, craniomandibular and cervical pain: effect on masticatory activity during rest and mandibular isometry

ABSTRACT BACKGROUND AND OBJECTIVES: Craniomandibular and cervical symptoms interfere with mandibular stability. Determining whether these disorders influence muscle activation when chewing, it is possible to improve interventions for this population. The objective of this study was to verify the effect of the temporomandibular joint dysfunction, craniomandibular and cervical pain on the electromyographic activity of the masticatory muscles during rest and mandibular isometry. METHODS: Fifty-five women aged between 18 and 30 years were divided into two groups: with temporomandibular dysfunction (n=28) and without temporomandibular dysfunction (n=27). The diagnosis of temporomandibular dysfunction was established using the Research Diagnostic Criteria for Temporomandibular Disorder (RDC/TMD). The RDC was also used to determine the presence of craniomandibular pain. Cervical pain was defined by physical examination. The electromyographic activity of masseter and temporalis muscles was evaluated in the rest position and mandibular isometry. The amplitude of muscle activation was represented by the root mean square values (RMS%) and normalized by maximum voluntary contraction. The Mann-Whitney U test was used to detect differences between the groups with and without temporomandibular dysfunction; with and without myofascial craniomandibular pain; and with and without cervical myofascial pain. RESULTS: It was observed greater amplitude in the activation of masseter and right temporalis muscles in the rest position in individuals with myofascial craniomandibular pain compared to asymptomatic (p<0.05). There was no difference among individuals with and without cervical myofascial pain, and with and without temporomandibular dysfunction. CONCLUSION: The presence of myofascial craniomandibular pain did not affect the masticatory activity, with greater muscle activation in mandibular rest.

Mandibular position influence on pilots’ postural balance analyzed under dynamic conditions

Objective: The aim of this study is to evaluate the influence of the mandibular position on the postural stability in a sample of civilian and military pilots.Methods: Twenty military pilots (males, mean age 35.15 ± 3.14 years) and 17 civilian pilots (males, mean 34.91 ± 2.15 years) were enrolled in this study and underwent a Sensory Organization Test (SOT) using the EquiTest® (NeuroCom International Inc., Clackamas, OR, USA) computerized dynamic posturography. The composite parameter was recorded and analyzed.Results: The equilibrium score (ES) recorded in centric occlusion is slightly higher than the ES recorded in mandibular rest position; civilian pilots showed ESs slightly higher than military pilots. The two-way ANOVA analysis shows these differences are not statistically significant.Discussion: The findings of this study seem to suggest that the composite parameter of the SOT is not sensitive in analyzing the influence of the stomatognathic system on the postural balance of civilian and military pilots.

“Catch It Right”-A Case Report on Occlusal Splint

AbstractTMDs have a multifactorial etiology varying from bruxism, psychological illness and traumatic injuries from mastication, extreme mouth opening, or faulty dental restorations. The present case study highlights the importance of right diagnosis of the patients problem as this forms the foundation to formulate a comprehensive treatment plan which further ensures the right solution to the stated patient problem along with long term maintenance of healthy stomatognathic system. An hard occlusal splint has been indirectly fabricated on the semiadjustable articulator. Occlusal splint used in treatment of TMDs is designed to provide even and balanced Occlusal contacts without forcefully altering the mandibular rest position or permanently altering the dentition. One case of fabrication of mandibular occlusal splint and its therapeutic role is discussed in this case report. The splint successfully relieved the patient TMD signs and symptoms, when used over four months.

Effects of teeth clenching on the soleus H reflex during lower limb muscle fatigue

PurposeWe assessed whether the soleus H reflex was depressed or facilitated in association with voluntary teeth clenching during muscle fatigue. MethodsA total of 13 and 9 healthy adult subjects were instructed to perform right-side tiptoe standing for 5 (TS1) and 10min (TS2) to induce the soleus muscle fatigue. Electromyograms (EMGs) were recorded from the bilateral masseter as well as the right-side soleus muscles. H reflex was evoked using a surface electrode. The isometric muscle strength during plantar flexion was measured. We tested two dental occlusal conditions (1) with maximal voluntary teeth clenching (MVTC) and (2) at mandibular rest position (RP). H reflex was evoked before and after TS1 and TS2. The isometric muscle strength during plantar flexion was measured before and after TS1 and TS2. ResultsMean amplitudes of H reflex with MVTC before and after TS1 were significantly larger than that with RP before and after TS1. The mean peak torque (PT) during isometric plantar flexion was observed significant differences in all subjects. The mean amplitude of H reflex with MVTC before TS2 was significantly larger than that with RP before TS2. No significant difference between RP after TS2 and MVTC after TS2. The mean PT with MVTC before TS2 was significantly larger than that with RP before TS2. There was no significant difference between RP and MVTC after TS2. ConclusionThe present study demonstrated that teeth clenching could facilitate H reflex regardless of the degree of muscle fatigue.

The use of a custom-made mouthguard stabilizes the electromyographic activity of the masticatory muscles among Karate-Dō athletes

To analyze and compare the electromyographic activity of the temporal (anterior portion) and masseter muscles among Karate-Dō athletes before and after training, with and without the use of a mouthguard. Twenty athletes (14 males and 6 females) with a mean age of 23.7±7.5 years participated. They had surface electromyography recordings taken of their bilateral temporal and masseter muscles before and after training under the following conditions: no mouthguard, with a ready-made mouthguard, and with a custom-made mouthguard. Activity was examined at mandibular rest, while clenching, and at maximum voluntary contraction. The data were normalized using the mean maximum voluntary contraction. The right (p=0.005) and left (p=0.015) temporal muscles showed significantly lower electromyographic activity with a custom-made mouthguard compared with no mouthguard after training while clenching. The electromyographic activity of the temporal and masseter muscles did not show significant differences when tested at mandibular rest and while clenching before or after training with a custom-made mouthguard (p>0.05). The use of a custom-made mouthguard preserved participants' electromyographic profiles before and after training; thus, they allow for stable muscle activity during the training of Karate-Dō athletes.

The effect of denture installation at mandibular rest position on unsteady motion of the centre of pressure in postural sway

Wearing dentures has been believed to decrease the instability of the postural sway using the total length of centre of pressure (CoP) trajectory or the magnitude of its variability. However, the physical aspects of the postural sway have not been taken into account while evaluating the CoP in patients who wear dentures. The CoP fluctuations are found to show a random walk process. Therefore, changes in the random movement of CoP caused by wearing dentures should be examined by nonlinear dynamics that enables analysis of the characteristics found in the random movement. We evaluated the effect of complete denture installation on CoP sway for twenty-six edentulous patients by performing the following steps. First, we excluded subjects who did not show crossover in spectral analyses. Then, we evaluated the spectral characteristics and phase shifts of the velocities of CoP sway for the subjects who showed crossover. We found that wearing complete dentures decreased the fluctuations in the high-frequency part of the power spectral density (PSD) and the phase shift in the mediolateral direction. On the other hand, we also found that the use of complete dentures decreased the fluctuations of PSD amplitude in the anteroposterior direction. From the point of view of the kinetic energy of the musculoskeletal system, we suggested that the use of complete dentures could reduce the energy consumption for the standing posture.

Tonic activity of the human temporalis muscle at mandibular rest position

ObjectiveThere are two theories on the control of the human mandibular rest position; the visco-elastic theory and the muscular theory. In this study, we have searched for evidence for the muscular theory. DesignWe have investigated the activity of the anterior temporalis muscle during various positions of the mandible using intramuscular electrodes. ResultsIn nine out of ten subjects tonic activity in the anterior temporalis muscle during the mandibular rest position was observed. Most of these units ceased firing under the jaw dropped condition of the mandible. ConclusionsCurrent findings support the muscular theory since single motor unit activity during the rest position of the mandible is observed in the anterior temporalis. We do not however have any evidence against the visco-elastic theory which may contribute in part to maintain the rest position of the mandible.

Electromyography and asymmetry index of masticatory muscles in undergraduate students with temporomandibular disorders

Aim: To compare the electromyographic activity and the asymmetry index among degrees of severity of temporomandibular disorders (TMD). Methods: Surface electromyography (EMG) of the right and left masseter and temporalis muscles was performed in 126 undergraduate students at rest and at maximal voluntary contraction. Three measurements were performed for five seconds of maximal contraction and mandibular rest. The degree of temporomandibular dysfunction was identified according to the Fonseca anamnestic index. The analysis of the asymmetry index for two pairs of muscles during maximal voluntary contraction was based on the asymmetry index proposed by Naeije, McCarrol and Weijs (1989). Results: 48.41% of the sample had mild TMD, followed by volunteers without TMD (26.98%), moderate TMD (19.05%) and severe (5.56%). The survey results show absence of correlation between the Fonseca anamnestic index and electromyographic activity at rest and at maximal voluntary contraction in undergraduate students in both muscles (p>0.05) and the asymmetry index did not differ between the analyzed groups. Conclusions: For the population of undergraduate students, there is no evidence that the presence and severity of TMD influence the EMG activity of masseter and temporalis muscles and the muscle asymmetry index at rest and maximal voluntary contraction.