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PubMed2004

Muscle relaxants in the treatment of myofascial face pain. A literature review.

Among the different pharmacological approaches that could be adopted in the treatment of myofascial pain of masticatory muscles, attention has to be paid to muscle relaxants drugs, since very few studies evaluated their efficacy, despite most authors suggest their use. The present paper is a critical review of the literature on the use of the most common drugs with muscle relaxant effects (benzodiazepines, tricyclic antidepressants) and of a muscle relaxant drug (tizanidine hydrochloride) in the treatment of such condition. From literature data it emerged that these drugs had phases of alternate enthusiasm, characterized by a not constant clinical use and a fair interest in research. Nevertheless, within all the limitations that have been discussed in this paper, the use of muscle relaxants in patients with myofascial pain of masticatory muscles seems to be justifiable, even though further research is needed to verify their usefulness in terms of risk-benefit ratio.

Antidepressive Agents, Tricyclic↗
PubMed1997

Subjective pain report and the outcome of several orthopaedic tests in craniomandibular disorder patients with recent pain complaints.

A comparison between a subjective pain report and the outcome of the combined dynamic and static pain tests, and several other orthopaedic tests, was investigated in craniomandibular disorder (CMD) patients with recent pain complaints and in control subjects. Thirty-two CMD patients who clearly reported pain in the masticatory muscle region or in the temporomandibular joint region by means of a symptom report questionnaire (SRQ), participated in the study. The investigators performing the symptom report interview and the clinical tests were blinded to each other. A high correspondence was shown between the patients reporting joint or muscle pain (by means of SRQ) and the classification into arthrogenous and myogenous pain patients, based on the outcome of the dynamic and static pain tests (P = 0.0003). The outcome of four other orthopaedic tests: passive maximum mouth opening (PMMO; P = 0.0001), palpation of the temperomandibular joint (TMJ) and the masticatory muscles (P = 0.0002), TMJ-play (P = 0.0001), and TMJ-compression (P = 0.0138) demonstrated significant differences between the patients reporting joint and muscle pain.

Adult↗
PubMed1996

Motor vehicle accidents and TMDS: assessing the relationship.

Patients involved in a motor vehicle accident, or MVA, may experience signs and symptoms suggesting temporomandibular joint or masticatory muscle injury. Because there are no published clinical studies assessing the potential relationship among reported variables suggesting injury, examination findings, and crash impact and postural variables, the authors gathered data from 219 patients identifying TMD after an MVA. The results suggest that TMJ or masticatory muscle injury may be associated with varying postural characteristics and impact events, including speed, direction of impact and vehicular damage.

Acceleration↗
PubMed1990

Effect of functional appliances on jaw muscle activity.

The electromyographic (EMG) activity of masticatory muscles was monitored longitudinally with chronically implanted EMG electrodes to determine whether functional appliances produce a change in postural EMG activity of the muscles. Preappliance and postappliance EMG levels in four experimentals that had been fitted with functional appliances were compared against the background of EMG levels in controls without appliances. The insertion of two types of functional appliance to induce mandibular protrusion was associated with a decrease in postural EMG activity of the superior and inferior heads of the lateral pterygoid, superficial masseter, and anterior digastric muscles; the decrease in the first three muscles was statistically significant. This decreased postural EMG activity persisted for approximately 6 weeks, with a gradual return toward preappliance levels during a subsequent 6-week period of observation. Progressive mandibular advancement of 1.5 to 2 mm every 10 to 15 days did not prevent the decrease in postural EMG activity.

Activator Appliances↗
PubMed2006

Influence of different condylar and incisal guidance ratios to the activity of anterior and posterior temporal muscle.

OBJECT: Few studies quantify reactions of masticatory muscles during clenching at different occlusal positions in individuals with different anterior and posterior guidance relationship and different number of working-side occlusal contacts. The hypothesis that altered incisal guidance (IG) and a different number of working-side occlusal contacts in complete denture wearers (CDW) change a pattern of temporal muscle activity and loadings to the mandible during clenching in incisal and lateral positions was tested. DESIGN: EMG activity during clenching in incisal (IP) and left (LOP) and right lateral occlusal (ROP) positions was compared between dentate subjects (DS) with steeper IG than condylar guidance (PG) and canine or canine+first premolar guidance in laterotrusive movements with CDWs who had steeper PG than IG and group function. EMG values were expressed as percentages of maximum voluntary clenching in maximum intercuspation (ICP) in each individual. RESULTS: The CDWs exhibited significantly higher posterior temporal muscle (TP) activity in IP and during lateral biting on mediotrusive side than DSs. Their coronoid process had to be pulled backward by TP fibers to rotate condyle in a counter-clockwise direction (PG>IG); contrary DSs had to rotate condyle in a clockwise direction to compensate for vertical overlap (IG>PG). Group function allowed more working-side contacts in CDWs and significantly higher anterior temporalis (TA) activity. CONCLUSION: Alteration of IG-PG ratio and a number of occlusal contacts during lateral clenching change a pattern of TA and TP activity in CDWs and a direction of mandibular loadings, although age related changes might also be responsible.

Adult↗
PubMed1977

Constancy of clinical signs in patients with mandibular dysfunction.

Repeated clinical examinations were performed 6 weeks apart on 34 patients with mandibular dysfunction to estimate the consistancy of clinical signs. The clinical examination of the patients included the masticatory muscles, the temporomandibular joint (TMJ) and the mandibular movement capacity. The clinical dysfunction index (Di) was calculated as a measure of the degree of mandibular dysfunction. The highest agreement between examinations was found for maximal mouth opening and protrusion. The agreement for palpation tenderness of the masticatory muscles and TMJ, limited movement of the TMJ, TMJ sounds, and pain during movement was considerably lower. The lowest agreement within 6 weeks was found for the clinical dysfunction index. No statistically significant difference could be detected between the two examinations for any of the clinical signs, as a result of given information and counseling before the 6-week period. It was concluded that all clinical signs, except maximal mouth opening and maximal protrusion, showed low consistancy.

Humans↗
PubMed1994

Measurement of masseter and temporalis muscle thickness using ultrasonographic technique.

Ultrasonography was found to be a highly reliable and accurate method for imaging and measuring masticatory muscle thickness. No age and sex related variations were observed in this study on comparisons between the two groups. Similarly no changes were seen in the muscle thickness and different facial morphologies. Since no earlier studies on this type of investigation was done, it will be too premature to give a final verdict on the correlation between the masticatory muscle thickness and facial morphology for all the recorded cases. A long term follow up will provide a wealth of information for future clinical purposes. No age and sex related variations were observed in this study on comparisons between the two groups. Similarly no changes were seen in the muscle thickness and different facial morphologies.

Adolescent↗
PubMed1995

Alteration of temporomandibular joint symptoms after orthognathic surgery: comparison with healthy volunteers.

PURPOSE: The purpose was to investigate alterations in temporomandibular joint (TMJ) dysfunction after orthognathic surgery. PATIENTS AND METHODS: TMJ symptoms of preoperative patients (n = 30) were compared with those of healthy volunteers (n = 30), and changes in the symptoms were evaluated at 3- and 6-month postoperative intervals. RESULTS: There was no significant difference in the incidence of TMJ sounds, deviation of mouth opening, and tenderness of TMJ and masticatory muscles between patients and volunteers. Patients did not report TMJ symptoms significantly more often than the control subjects. At both 3 and 6 months after surgery, half or more of the patients showed no change in TMJ sounds, deviation of mouth opening, or tenderness of TMJ and masticatory muscles. At each evaluation, some patients exhibited improvement of TMJ symptoms or showed changes for the worse. Findings of TMJ sounds were observed to be associated with the postoperative reduction of mandibular mobility. CONCLUSION: These results suggest that alterations of TMJ symptoms after orthognathic surgery do not always result from the correction of malocclusion.

Adolescent↗
PubMed1996

Masseter muscle activity in bottle feeding with the chewing type bottle teat: evidence from electromyographs.

It was reported that the activity of the masticatory muscles is reduced in bottle fed babies. The effects of chewing type bottle teats distributed in Japan on masticatory muscle activity were evaluated. Myoelectric activities of the masseter muscles of 12 babies bottle fed with chewing type bottle teats were recorded and analyzed by the same method as in the previous study. The electromyographic records of 12 breast fed babies and 12 babies bottle fed with regular sucking type bottle teats, which were reported in a previous study, were used as controls. The results show that the masseter muscle activity of babies bottle fed with chewing type bottle teats was similar to that of breast fed babies qualitatively as well as quantitatively. However, activity was visibly different from that of babies bottle fed with sucking type bottle teats, showing significant difference by ANOVA. These data suggest that babies who are ingesting milk from chewing type bottle teats do so with a chewing action similar to that of breast feeding, but very different from that of bottle feeding with sucking type bottle teats. The conclusion was that the chewing type bottle teat is useful for establishing masseter muscle activity.

Bottle Feeding↗
PubMed1989

Electromyographic studies of craniomandibular disorders: a review of the literature.

Craniomandibular disorders have been investigated from many points of view, structurally and functionally. To evaluate the behaviour of the masticatory muscles, electromyography (EMG) has been widely used and the studies have emanated from many different paradigms. The purpose of this paper is to review articles in which EMG has been used to study symptomatic subjects. Findings from sleep studies and basic laboratory studies seem to support the hypothesis of a correlation between masticatory muscle hyperactivity and symptoms. Experimentally induced stress studies consistently show an increased activity in symptomatic subjects. Investigations of motor pauses, the often lengthened silent period, are summarized and discussed. Several different treatment strategies, particularly splints and biofeedback, have been evaluated using EMG, indicating a normalization, but controlled outcome studies are sparse. The use of EMG has thus substantially increased our knowledge of dysfunction of the masticatory system.

Biofeedback, Psychology↗
PubMed1979

The functional significance of primate mandibular form.

A stress analysis of the primate mandible suggests that vertically deep jaws in the molar region are usually an adaptation to counter increased sagittal bending stress about the balancing-side mandibular corpus during unilateral mastication. This increased bending stress about the balancing side is caused by an increase in the amount of balancing-side muscle force. Furthermore, this increased muscle force will also cause an increase in dorso-ventral shear stress along the mandibular symphysis. Since increased symphyseal stress can be countered by symphyseal fusion and as increased bending stress can be countered by a deeper jaw, deep jaws and symphyseal fusion are often part of the same functional pattern. In some primates (e.g., Cercocebus albigena), deep jaws are an adaptation to counter bending in the sagittal plane during powerful incisor biting, rather than during unilateral mastication. The stress analysis of the primate mandible also suggests that jaws which are transversely thick in the molar region are an adaptation to counter increased torsion about the long axis of the working-side mandibular corpus during unilateral mastication. Increased torsion of the mandibular corpus can be caused by an increase in masticatory muscle force, an increase in the transverse component of the postcanine bite force and/or an increase in premolar use during mastication. Patterns of masticatory muscle force were estimated for galagos and macaques, demonstrating that the ratio of working-side muscle force to balancing-side muscle force is approximately 1.5:1 in macaques and 3.5:1 in galagos during unilateral isometric molar biting. These data support the hypothesis that mandibular symphyseal fusion is an adaptative response to maximize unilateral molar bite force by utilizing a greater percentage of balancing-side muscle force.

Adaptation, Physiological↗
PubMed2003

Neurobiological mechanisms involved in sleep bruxism.

Sleep bruxism (SB) is reported by 8% of the adult population and is mainly associated with rhythmic masticatory muscle activity (RMMA) characterized by repetitive jaw muscle contractions (3 bursts or more at a frequency of 1 Hz). The consequences of SB may include tooth destruction, jaw pain, headaches, or the limitation of mandibular movement, as well as tooth-grinding sounds that disrupt the sleep of bed partners. SB is probably an extreme manifestation of a masticatory muscle activity occurring during the sleep of most normal subjects, since RMMA is observed in 60% of normal sleepers in the absence of grinding sounds. The pathophysiology of SB is becoming clearer, and there is an abundance of evidence outlining the neurophysiology and neurochemistry of rhythmic jaw movements (RJM) in relation to chewing, swallowing, and breathing. The sleep literature provides much evidence describing the mechanisms involved in the reduction of muscle tone, from sleep onset to the atonia that characterizes rapid eye movement (REM) sleep. Several brainstem structures (e.g., reticular pontis oralis, pontis caudalis, parvocellularis) and neurochemicals (e.g., serotonin, dopamine, gamma aminobutyric acid [GABA], noradrenaline) are involved in both the genesis of RJM and the modulation of muscle tone during sleep. It remains unknown why a high percentage of normal subjects present RMMA during sleep and why this activity is three times more frequent and higher in amplitude in SB patients. It is also unclear why RMMA during sleep is characterized by co-activation of both jaw-opening and jaw-closing muscles instead of the alternating jaw-opening and jaw-closing muscle activity pattern typical of chewing. The final section of this review proposes that RMMA during sleep has a role in lubricating the upper alimentary tract and increasing airway patency. The review concludes with an outline of questions for future research.

Adult↗
PubMed2005

Temporomandibular disorders in association with scuba diving.

OBJECTIVE: To determine the prevalence of temporomandibular disorders (TMD) in scuba divers and to identify the risk factors for the development of pain in the stomatognathic system before and after diving by the use of a questionnaire. DESIGN: : Retrospective cohort study based on questionnaires. PARTICIPANTS: A total of 296 active divers, aged 18 to 65 years, participating in scuba diving meetings in Heidelberg, Germany. INTERVENTIONS: Each diver answered a questionnaire containing 29 questions, predominantly on symptoms of TMD. MAIN OUTCOME MEASURES: The data collected from the divers were calculated by the use of logistic regression tests. Risk factors for the development of TMD were evaluated. RESULTS: Clenching seemed to be the greatest risk factor for pain while holding the mouthpiece and for pain in the masticatory muscle system after diving. Limited mouth opening and clenching were responsible for the development of pain in the temporomandibular joint after the dive. The prevalence of TMD-related symptoms was higher in women before, during, and after the dive. CONCLUSIONS: Individuals exhibiting TMD-related symptoms seem to be at the greatest risk of developing pain in the masticatory muscle system and/or the temporomandibular joint during or after the dive.

Adolescent↗
PubMed1996

Quantitative evaluation of the tonic vibration reflex (TVR) in the masseter muscle.

PURPOSE: This study evaluated the efficacy of the tonic vibration reflex (TVR) elicited by high-frequency vibration in evaluating masticatory muscle excitability. SUBJECTS AND METHODS: The experiment was performed on 16 male adult volunteers, 20 to 45 years of age, without spontaneous pain or tenderness in the masticatory muscles. The subjects were seated in a chair in a fixed head position with the mouth kept open with a bite block. TVR was elicited by vibratory stimulation applied to the mandible (approximately 15 m/s2, 160 Hz). An electromyogram (EMG) was recorded bilaterally from the masseter muscles and analyzed quantitatively using an arbitrary index (TVR index) calculated from the response. Bite force was measured during clenching using a pressure-sensitive foil. RESULTS: Wide variations in the TVR index (maximum, 22.7%; minimum, 0.9%, average, 7.7%) were observed among individuals. The mean index for five subjects with a clenching habit was significantly higher than that for 11 subjects without a history of clenching. Tolperisone HCl (100 mg taken orally), a gamma-drive depressant, was found to reduce the response for 2 hours. There was a negative correlation (r = -.504, P < .05) between bite force and TVR index when the values on both sides were compared. CONCLUSIONS: The TVR may be of use in evaluating masseter muscle excitability.

Adult↗
PubMed1990

[The effects of solid or liquified diet on the submandibular glands of mice with age].

The influence of properties of the diets on the retardation of growth of the jaw bones and masticatory muscles has been established. As the intake of liquid foodstuffs increases in the human diet, it is considered possible that these liquid diets may retard the growth of human salivary glands. 180 newborn C3H/He strain male mice were divided into solid and liquid diet groups and then the development and aging of the submandibular glands were observed both in function and morphologically until 60 weeks of age. The following results were obtained: 1. No differences could be detected in body length and body weight of the mice between solid and liquid diet groups. The wet weight of the liver in the liquid diet group was significantly larger than the solid diet group, which suggested that the liquid diet may have accelerated metabolic functions. Additionally, masticatory muscles of the liquid diet group were significantly smaller than the solid diet group which suggested growth retardation of the masticatory organ. 2. The submandibular gland wet weight and its DNA content in the liquid diet group were lower than in the solid diet group during the experimental period. This suggested that the number of cells and their ability to divide was diminished. The wet weight of glands per unit DNA content showed an increase in cell size during the adult period. 3. The alpha-amylase activity and total protein content of the submandibular glands in the liquid diet group were lower than in the solid diet group. This suggested that the saliva secretory function and protein synthesis were depressed, in agreement with the low number of cells detected. 4. The differentiation of the acinar cells and convoluted tubule cells of the liquid diet group was retarded and the 60 weeks subgroup showed hypertrophy of the convoluted tubule cells, disappearance of the secretory granules and a decrease in the number of acinar cells. 5. Slight stromal fibrosis was observed with increasing age (60 weeks) with no difference between the two groups. 6. This suggested that when mice were fed a liquid diet, the development of salivary glands was retarded and also aging changes occurred more rapidly.

Aging↗
PubMed2006

Change of mRNA amount of myosin heavy chain in masseter muscle after orthognathic surgery of patients with malocclusion.

INTRODUCTION: Surgical correction of malocclusion changes the force to moment ratio of masticatory muscles inserting at the mandible caused by shortening, lengthening and rotation of the bone following osteotomy. During muscle adaptation the expression of mRNA for the myosin heavy chain (MyHC) of type I and type II fibres may be changed. MATERIAL AND METHODS: The adaptation of the masseter muscle was investigated at the mRNA level in 10 patients 6 months after orthognathic surgery in the mandible. The competitive polymerase chain reaction (cPCR) is a suitable method for quantification of MyHC mRNA. For application of this minimal invasive method an amount of 35 mg muscle tissue was sufficient. RESULTS: 6 month postoperatively there was a deficiency of about 87% of MyHC mRNA for fibre type I and II in both groups of patients. The deficiency in patients with mesial position of the mandible was higher but not significant different to patients with distal malocclusion. CONCLUSION: Patients should use the postoperative interval for training their masticatory muscles. This improves the stability of treatment result and prevents relapse.

Adult↗
PubMed1975

Reflex control of the jaw muscles by stimuli from receptors in the periodontal membrane.

In the opinion of a number of investigators, the only function of the mechano-receptors in the periodontal membrane is to inhibit closure of the jaws via a reflex pathway when a predetermined pressure on the teeth has been exceeded. In our opinion, the receptor system in the periodontal membrane may also play a role in a complex regulatory system which controls the movements of the lower jaw during chewing. In order to test this hypothesis a study was made of the changes occurring in the contraction pattern of three masticatory muscles of the cat, when the cuspids in the upper jaw were displaced in various directions. In all the experimental animals used, electromyographic changes in the three muscles investigated, could be recorded as a result of displacement of the cuspids. The results obtained suggest, at least in the case of the temporal and pterygoid muscles, that there are specific reflexogenic zones in the periodontal membrane, These results support the previously suggested hypothesis that a number of the pressure-sensitive receptors in the periodontal membrane play a role in a regulatory system which controls the movements of the lower jaw--as during chewing--by exerting a reflex influence on the degree of contraction of the masticatory muscles. In the discussion this hypothesis is worked out in more detail and the extent to which the results fit the chewing pattern of the cat is examined. In the conclusion, the author asks whether the finding of a regulatory system in the cat may also be applied to man.

Animals↗
PubMed2006

The development of mastication in rodents: from neurons to behaviors.

The development of suckling behavior is a fundamental characteristic of mammalian development. The occurrence of this behavior across mammals allows us to extrapolate information from animal models to better understand normal and abnormal masticatory development in infants. This review focuses on prenatal cell, molecular, and morphological changes in rat and/or mouse masticatory muscles, trigeminal motoneurons (Mo5) and mesencephalic trigeminal neurons (Me5) that accompany the development of suckling behavior. A special emphasis is placed on N-methyl-d-aspartate (NMDA) receptor subunit expression because of the important role that NMDA receptors play in the production of rhythmical jaw movements and neuronal development. Prenatally the timing of NMDA subunit changes follows neuromuscular junction formation in masticatory muscles, and is coincident with the emergence of rhythmical jaw movements and in vitro rhythmical trigeminal activity. Our data suggest that NMDA receptor subunit changes in Mo5 and Me5 are synchronized with the emergence of rhythmical jaw movements and trigeminal motor activity.

Animals↗