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PubMed1999

An electromyogram study on mandibular movement in unilateral cleft lip and palate patients before and after orthodontic treatment.

The purpose of this study is to investigate masticatory muscle function in subjects with unilateral cleft lip and palate compared with normal occlusion and the extents of improvement before and after orthodontic treatment. Subjects were twenty pretreatment patients, thirty posttreatment patients and ten controls. Electromyograms were recorded from their masticatory muscles during masticatory movement and tapping movement. Reduction of duration/stroke ratio (D/S) was observed in electromyograms obtained during masticatory movement after orthodontic treatment. The reduction was especially notable in the masseter muscle. In spite of a significant reduction in coefficient of variation (CV) values, a significant difference between the posttreatment group and the control group indicated some persisting irregularity in masticatory movement. Electromyograms taken during tapping movement showed no change in latency in the posttreatment group, but duration of the silent period (SP) was shortened and SP appearance increased. The findings outlined above reveal electromyographically clear improvements in masticatory muscle functions and jaw reflex mechanisms after orthodontic treatment. Nevertheless, parameters for subjects with cleft lip and palate still differed from those for controls with normal occlusion. The influence of plastic surgery in subjects with the defects discussed here causes maxillary retrusion, which in turn results in skeletal malocclusion. Orthodontic treatment should be designed to compensate this dentally and alveolarly. This design and the need to improve masticatory functions would contribute to eliminate the extreme difficulty of the therapeutic process.

Adolescent↗
PubMed2005

The role of parafunctions, emotions and stress in predicting facial pain.

BACKGROUND: The authors conducted a study to examine the degree to which parafunctions and emotional states predicted jaw pain in subjects with temporomandibular disorder (TMD) and control subjects. METHODS: Ninety-six subjects diagnosed with myofascial pain, myofascial pain and arthralgia, disk displacement or no TMD symptoms participated. The authors used experience sampling methodology to collect data on pain, behaviors and emotions. They paged subjects approximately every two hours, but not during sleep. When paged, subjects completed a brief questionnaire containing rating scales of jaw pain, masticatory muscle tension, time and intensity of tooth contact, mood and stress level. RESULTS: Analyses of variance showed that groups differed significantly (P < .05) in terms of pain; masticatory muscle tension; and a composite variable measuring time and intensity of contact; mood; and stress. The two myofascial pain groups scored higher on these measures than did the group with disk displacement and the control group. The authors used masticatory muscle tension, the composite variable, mood and stress to predict jaw pain using linear regression. The model was significant and accounted for 69 percent of the variance in jaw pain. Because tension was so highly correlated with jaw pain, the authors removed this variable and re-ran the analysis. The second model also was significant and accounted for 46 percent of the variance in jaw pain. CONCLUSIONS: Parafunctional behaviors, especially those that increase muscle tension, and emotional states are good predictors of jaw pain levels in patients with TMD and healthy control subjects. CLINICAL IMPLICATIONS: Treatment that helps patients reduce parafunctions, excess masticatory muscle tension, stress and emotional distress should be effective in reducing TMD pain.

Adult↗
PubMed1984

Studies of biologic parameters for denture design. Part II: Comparison of masseter muscle activity, masticatory performance, and salivary secretion rates between denture and natural dentition groups.

Bilateral masseter muscle activities exerted during masticatory and salivary secretion rate tests of a group of 18 denture wearers were compared with a group of eight persons with 26 or more natural teeth. Denture wearers applied 22% to 39% of the muscle force applied by the ND group to chew peanuts or carrots and showed markedly lower masticatory performances. The average muscle activity was higher for chewing peanuts than carrots in the ND group but was similar for both test foods in the AD group. Motor discrimination seems to be intact in denture wearers, but their inability to tolerate high masticatory pressures may prevent them from exerting discriminatory forces comparable to those applied by persons with natural dentition when chewing relatively tough foods of varying hardness. The results indicate that the reduced muscle force applied by denture wearers is another important factor that contributes to their diminished chewing ability. Even though the denture wearers were older and applied less muscle activity during chewing, they produced slightly higher rates of stimulated parotid saliva than the ND group. This supports our previous findings and further indicates that the mucosal stimulation of dentures compensates for decreased muscle activity and absence of periodontal receptor stimulation for producing saliva in healthy denture wearers.

Adult↗
PubMed1999

Simplified cephalometric lines for the estimation of muscular lines of action.

In the study of masticatory muscle performance, one of the biomechanical variables that can be estimated is the mechanical advantage of the masticatory muscles, namely, the ratio between the muscular moment arm and the bite force moment arm. In the present study, the position of the estimated line of action of the masseter muscle, drawn between gonion and orbitale (Go-Or) relative to dental (occlusal plane) and skeletal (Frankfort plane) references was analyzed in 431 pretreatment lateral cephalograms of orthodontic patients (195 males, 236 females) aged 6 to 50 years, and in the lateral tracings of the Bolton standards (6 to 18 years of age). The following measurements were evaluated: (1) skeletocutaneous class (soft tissue equivalent of Wits appraisal, linear distance in millimeters between the projections of points A' and B' on the occlusal plane); (2) angle between the Go-Or line and the perpendicular to the occlusal plane at the molar occlusal point; and (3) angle between the Go-Or line and the Frankfort plane. In the patients, the skeletocutaneous class ranged between--14.5 and 15.5 mm, without any sex- or age-related differences. The angle between the Go-Or line and the perpendicular to the occlusal plane was, on average, 39 degrees (range 15 to 53 degrees), and it decreased with advancing age; while the average angle between Go-Or and Frankfort plane was 42 degrees (range 30 to 54 degrees), and it increased in older patients. No effects of sex were found. The two angles were significantly correlated to each other, while no correlations were found with the sagittal jaw discrepancy. Similar results were obtained on the Bolton tracings. Overall, the present cephalometric analogue could be useful in biomechanical simulations.

Adolescent↗
PubMed1997

Muscle activity during mandibular movements in normal and mandibular retrognathic subjects.

PURPOSE: The masticatory muscles function as a unit during precise mandibular positioning movements that occur during such activities as speech, singing, or playing musical instruments. This investigation was designed to assess jaw muscle recruitment patterns during controlled mandibular movement in normal subjects and in patients with mandibular retrognathism. PATIENTS AND METHODS: A computer-integrated electromyography (EMG) and movement monitoring (Selspot) system was used to collect data over 7 seconds of a sagittal border movement (Posselt envelope) of the mandible and 4 seconds each of rest position, light tooth contact, and maximum clench. Fine wire bipolar electrodes were placed into the inferior belly of the lateral pterygoid muscles bilaterally and surface electrodes were placed bilaterally over the anterior belly of the temporalis muscles and the masseter muscles. Ten subjects with Class I occlusion, normal cephalometric values, and an absence of temporomandibular joint (TMJ) dysfunction were compared with 12 patients with mandibular retrognathism, Class II malocclusion, and an absence of clinical signs of TMJ internal derangement before and after a bilateral sagittal split and advancement of the mandible. RESULTS: There was a wide variation in standard deviations of EMG activity for the lateral pterygoid muscles in the retrognathic patients compared with normal controls before surgery (P < .05). In light tooth contact, temporalis muscle activity increased after surgery with respect to both control and the presurgical levels (P < .05, P < .005, respectively). In maximum clench, activity in all muscle groups in the retrognathic patients, both before and after surgery, were below that of control subjects (P < .005). The lateral pterygoid muscles showed late recruitment, with low EMG activity levels during the forward movement phase of the envelope, before surgery compared with controls (P < .001). After surgery, the lateral pterygoid muscle showed early recruitment in the forward movement similar to control levels. CONCLUSION: The masticatory muscles function as a unit during mandibular positioning movements. Patients with mandibular retrognathism have different muscle recruitment patterns from those of normal subjects with the mandible at rest and during mandibular movement. After orthognathic surgery, adaptation occurs in the phasic timing of jaw muscle activity.

Adaptation, Physiological↗
PubMed2005

Embryonic and postnatal development of masticatory and tongue muscles.

This review summarizes findings concerning the unique developmental characteristics of mouse head muscles (mainly the masticatory and tongue muscles) and compares their characteristics with those of other muscles. The developmental origin of the masticatory muscles is the somitomeres, whereas the tongue and other muscles, such as the trunk (deep muscles of the back, body wall muscles) and limb muscles, originate from the somites. The program controlling the early stages of masticatory myogenesis, such as the specification and migration of muscle progenitor cells, is distinctly different from those in trunk and limb myogenesis. Tongue myogenesis follows a similar regulatory program to that for limb myogenesis. Myogenesis and synaptogenesis in the masticatory muscles are delayed in comparison with other muscles and are not complete even at birth, whereas the development of tongue muscles proceeds faster than those of other muscles and ends at around birth. The regulatory programs for masticatory and tongue myogenesis seem to depend on the developmental origins of the muscles, i.e., the origin being either a somite or somitomere, whereas myogenesis and synaptogenesis seem to progress to serve the functional requirements of the masticatory and tongue muscles.

Animals↗
PubMed1988

An ultrastructural study of changes in the tendinous attachment of the deep layer of masseter muscle to the rat mandible during bite raising.

To elucidate the ultrastructural changes in the attachment of masticatory muscles during changes in the functions of masticatory muscles, rats ranging in age from 50 to 80 d, were used. 2 d after bite-raising, the fibrocartilage cells in the tendinous attachment of the deep layer of masseter muscle were characterized by ill-developed cell organelles. Undifferentiated cells around blood vessels degenerated. 4 d after bite raising, however, fibrocartilage cells exhibited well-developed cell organelles, cell division and intercellular contacts. After 10 d of bite raising, the morphologic features of the fibrocartilage cells were the same as those observed in the control. These results suggest that the mechanical stress created by the change in muscle function during bite raising caused the degeneration of the fibrocartilage cell. From 4 d after bite raising, cell proliferation and active formation of new extracellular matrix occurred in response to environmental changes. 10 d after bite raising, the remodeling of collagen fiber and the formation of bone tissue had returned to normal by the adaptation of muscle function.

Animals↗
PubMed1988

Hemifacial atrophy and temporomandibular joint pain-dysfunction syndrome.

A case is described of a patient with progressive HA who presented because of left TMJ pain, jaw locking and ipsilateral masticatory muscle spasm. Several reports exist in the literature of masticatory muscle spasm associated with HA. A diagnosis of TMJPDS was made and an occlusal splint was provided which produced resolution of the TMJ pain and jaw locking and significantly reduced the masticatory muscle spasms.

Adult↗
PubMed2000

Identification of matrix metalloproteinases and their tissue inhibitors type 1 and 2 in human masseter muscle.

Changes in masticatory muscle structure and function are either developmental, as seen in anomalies of facial form, or adaptive, as seen during procedures such as orthognathic surgery and functional-appliance orthodontic therapy. Remodelling of muscle extracellular matrix is pivotal in these processes. This turnover is mediated via members of the family of enzymes known as matrix metalloproteinases (MMP) and inhibited by the tissue inhibitors of metalloproteinases (TIMP). The aim here was to investigate the in vivo pattern of expression and distribution of MMPs and TIMPs in masseter muscle of humans with both normal and abnormal facial forms. Masseter muscle biopsies were taken from 10 patients, four with long-face syndrome and six normal controls as confirmed by cephalometry. Immunohistochemical techniques were used to show the pattern and distribution of MMPs and TIMP proteins in the muscle. Zymography of tissue extracts was used to determine the presence of MMP activity. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to detect the presence of MMP and TIMP-2 mRNA. MMP-1 was expressed around the individual muscle fibres, especially in those fibre surfaces in contact with the interstices of the connective tissue and around blood vessels. MMP-9 staining was less intense and was expressed in the interstices of the connective tissue and around blood vessels. Zymography of protein extracts confirmed that MMP-9 activity was present. MMP-2 and MMP-3 were not expressed in the samples, although MMP-2 mRNA could be detected by RT-PCR and its activity could be detected by zymography. Intense TIMP-1 staining was present around each muscle fibre, in the interstices of the connective tissue and surrounding blood vessels; TIMP-2 mRNA could be detected in all samples. These staining patterns were seen in all biopsies examined and were irrespective of the facial form of the donor. These findings provide evidence that the mechanisms required for matrix remodelling are present in the human masseter muscle.

Adult↗
PubMed1986

Organization of sensory neurons to the muscles of mastication in the cat.

The sensory neurons in the trigeminal ganglion which project to the muscles of mastication of the cat were studied using the retrograde transport of horseradish peroxidase. Horseradish peroxidase either was injected directly into the masticatory muscles or applied to the nerves supplying them. Numerous retrogradely labeled neurons were found in the ipsilateral trigeminal ganglion. All labeled neurons were sequestered within the posterolateral (mandibular) portion of the ganglion, but the ganglion cells innervating individual muscles were not organized topographically. The diameter of the labeled neurons varied greatly and included profiles considered small, medium and large. The organization of the neurons in the trigeminal mesencephalic and trigeminal motor nuclei which project to individual masticatory muscles also was noted. It is suggested that many of the ganglion cells of small and medium size may be important for the perception of muscle pain from the masticatory muscles in the cat.

Animals↗
PubMed1992

Evaluation of masticatory function before and after treatment in patients with craniomandibular disorders.

The masticatory function was evaluated in 12 patients with signs and symptoms of craniomandibular disorders of mainly muscular origin. Palpation of the masticatory muscles and measurements of occlusal force endurance, on a submaximal level with visual feedback, and of masticatory efficiency were performed before and after treatment. Significant changes occurred between the two measurements. Of a total of 10 masticatory muscles, 8 were sensitive to palpation before treatment and 2 after treatment. Occlusal force endurance increased from 92.5 seconds before treatment to 132 seconds after treatment, and masticatory efficiency increased from 54% to 65%, respectively. It is concluded that the masticatory muscle function of these patients is compromised and that treatment had a positive effect on the masticatory function.

Adult↗
PubMed2004

[Changes of mitochondrial calcium, adenosine triphosphate and adenosine diphosphate contents induced by occlusal trauma in rabbit's masseter muscles].

OBJECTIVE: To study the role of Ca2+ overload and energy metabolism in mitochondria in masticatory muscle dysfunctional induced by occlusal trauma. METHODS: Mitochondrial Ca2+ contents were measured with atomic emission spectrophotometer. Mitochondrial ATP and ADP contents were measured with high performance liquid chromatography. RESULTS: (1) Mitochondrial Ca2+ contents of masseter muscle ipsilateral to metal splint in ten and twenty days' experimental groups and that contralateral to metal splint in twenty days' experimental group increased significantly (P < 0.05). (2) Mitochondrial ATP contents of masseter muscle ipsilateral to metal splint in experimental groups were higher than that in control groups and contralateral to metal splint after twenty days. (3) Mitochondrial Ca2+ contents of masseter muscle ipsilateral to metal splint were significantly negatively correlated to the mitochondrial ATP contents (r = -0.780, P < 0.05). CONCLUSION: Ca2+ overload in mitochondria depresses ATP production, which results in energy metabolism disorder in masticatory muscle cells. It may play an important role in the mechanism that occlusal trauma results in masticatory muscle dysfunction.

Adenosine Diphosphate↗
PubMed1994

Musculotopic organization in the motor trigeminal nucleus of the reeler mutant mouse.

We examined the musculotopic organization in the motor trigeminal nucleus and the somatotopical arrangement in the trigeminal ganglion of the normal and reeler mice. To determine whether or not masticatory motoneurons are malpositioned in the reeler mouse, we injected horseradish peroxidase (HRP) into the masticatory muscles of normal and reeler mice. Injections of HRP into the jaw-closing muscles, i.e., the masseter and temporalis muscles, labeled large multipolar neurons in the dorsolateral division of the motor trigeminal nucleus of both normal and reeler mice. Similar injections into the jaw-opening muscles, i.e., the anterior belly of the digastric muscle and mylohyoid muscle, labeled large multipolar neurons in the ventromedial division of the motor trigeminal nucleus of both mouse strains. Thus, the normal myotopical arrangement of the masticatory muscles on the motor trigeminal nucleus is preserved in the reeler mouse. However, detailed analysis revealed that jaw-opening motoneurons were more widely scattered in the reeler mouse than in the normal control. To examine the somatotopical arrangement of the first-order sensory neurons in the trigeminal ganglion of the normal and reeler mice, we subcutaneously injected Fast blue (FB) into the mental region and Diamidino yellow (DY) into the vibrissal region of the same animals. No differences in distribution patterns of FB-labeled and DY-labeled neurons in the whole-mounted trigeminal ganglion could been seen between these two strains, suggesting that migration of trigeminal ganglion cells, which are derived from the neural crest and placode, is not deranged by the reeler genetic locus.

Animals↗
PubMed1998

A pilot study comparing the efficacy of hard and soft stabilizing appliances in treating patients with temporomandibular disorders.

STATEMENT OF PROBLEM: Soft and hard stabilizing appliances have been used to treat temporomandibular disorders. No data exist to suggest whether a hard or soft appliance is beneficial. PURPOSE: This study compared soft and hard acrylic resin stabilizing appliances in the reduction of masticatory muscle pain in patients with temporomandibular disorders. MATERIALS AND METHODS: Twenty-three patients with at least one clinical sign from the list of diagnostic subgroups of temporomandibular disorders were alternately assigned a hard or soft appliance for temporomandibular disorder treatment. No other temporomandibular disorder treatment (self-care, physical therapy, biofeedback, or muscle or joint injections) was rendered. Each patient was seen by two dentists at each visit. One dentist initially fabricated the appliance and adjusted the appliance on each visit and an examining dentist examined the patient each visit and recorded signs of temporomandibular disorders. The appliance material (soft or hard) was not disclosed to the examining dentist, only to the dentist who fabricated and adjusted the appliance. Patients were examined and appliances were adjusted every 2 to 3 weeks for a minimum of 10 weeks. Masticatory muscles were palpated and charted on each visit. Data were analyzed and subjected to nonparametric Mann-Whitney test. RESULTS: Eighteen of the initial 23 patients, 7 in the hard appliance group and 11 in the soft appliance group finished the study over 10- to 15-week period. Soft and hard appliances performed the same in reduction of masticatory muscle pain. CONCLUSION: This study suggests, based on the limited number of participants, that soft and hard stabilizing appliances may be equally useful in reducing masticatory muscle pain in short-term appliance therapy.

Acrylic Resins↗
PubMed1979

Effects of the interpolated vibratory stimulation on the interdental dimension discrimination in normal and joint defect subjects.

No significant differences in the interdental dimension discrimination (IDD) ability were found between normal and joint defect subjects. Furthermore, vibration onto the mandible gave similar effects on the nature of IDD in both subject groups. Thus, the muscle spindles of masticatory muscles may contribute to IDD, but temporomandibular receptors may not.

Adolescent↗
PubMed2003

[Dysfunctions of the stomatognathic system in tinnitus patients compared to controls].

AIMS OF THE STUDY: The high prevalence of ear, nose and throat symptoms in patients with temporomandibular disorders seems to depend on anatomical, functional, neuromuscular, or psychosomatic connections between both phenomena. The present study evaluates the prevalence of temporomandibular dysfunctions in tinnitus patients compared to controls. PATIENTS AND METHODS: A total of 40 patients and 35 controls were clinically examined. The case history as well as the quality of tinnitus and its influence on the patient's life were evaluated, and psychosocial data collected by a questionnaire dealing with stress factors. RESULTS: Tinnitus patients showed muscle tenderness in masticatory muscles as well as in other muscle groups significantly more frequently than controls. The prevalence of arthrogenous dysfunctions was not significantly different between the groups. Occlusal parameters such as instability of intercuspidation, presence of dysgnathia, and signs of parafunctions were significantly more frequent in patients than in controls. The psychosocial assessment showed some trend towards the tinnitus patients feeling more stress in society, daily life, their partnerships and at work. CONCLUSIONS: Tinnitus correlates significantly with myogenous disorders but not with arthrogenous disorders of the temporomandibular joint (TMJ). This result supports the concept of neuromuscular and functional relationships between tinnitus and the stomatognathic system.

Adult↗
PubMed1994

Differences in myosin composition between human oro-facial, masticatory and limb muscles: enzyme-, immunohisto- and biochemical studies.

Immunohistochemistry was used to determine the myosin composition of defined fibre types of three embryologically different adult muscles, the oro-facial, masseter and limb muscles. In addition, the myosin composition in whole muscle specimens was analysed with biochemical methods. Both similarities and differences between muscles in the content of myosin heavy chains and myosin light chains were found. Nevertheless, each muscle had its own distinct identity. Our results indicated the presence of a previously undetected fast myosin heavy chain isoform in the oro-facial type II fibre population, tentatively termed 'fast F'. The masseter contained aberrant myosin isoforms, such as foetal myosin heavy chain and alpha-cardiac myosin heavy chain and unique combinations of myosin heavy chain isoforms which were not found in the limb or oro-facial muscles. The type IM and IIC fibres coexpressed slow and fast A myosin heavy chains in the oro-facial and limb muscles but slow and a fast B like myosin heavy chain in the masseter. While single oro-facial and limb muscle fibres contained one or two myosin heavy chain types, single masseter fibres coexpressed up to four different myosin heavy chain isoforms. Describing the fibres according to their expression of myosin heavy chain isozymes, up to five fibre types could be distinguished in the oro-facial and limb muscles and eight in the masseter. Oro-facial and limb muscles expressed five myosin light chains, MLC1S, MLC2S, MLC1F, MLC2F and MLC3F, and the masseter four, MLC1S, MLC2S, MLC1F, and, in addition, an embryonic myosin light chain, MLC1emb, which is usually not present in normal adult skeletal muscle. These results probably reflect the way the muscles have evolved to meet the specialized functional requirements imposed upon them and are in agreement with the previously proposed concept that jaw and limb muscles belong to two distinct allotypes.

Adult↗
PubMed1990

Occlusal force and craniofacial biomechanics during growth in rhesus monkeys.

The masticatory muscles in 132 anesthetized male and female rhesus monkeys ranging in age from juvenile to adult were unilaterally stimulated. Muscle forces and speeds were measured with a bite force transducer positioned at the incisors, premolars, and molars during twitch and tetanic contractions. Lateral cephalographs of all animals were used to estimate the orientation and mechanical advantage of the masticatory muscles. Results showed that maximal occlusal forces increased at a greater rate than body weight during growth. However, maximal occlusal forces increased isometrically relative to mandibular length. Mean forces at the incisors ranged from 70.3 newtons (n) in juveniles up to 139.9 n in adult males. Forces at the molars were 2-2.5 times greater than at the incisors. Time-to-peak tension decreased with increasing body size from 44.1 msec in juveniles to 37.4 msec in adult females to 31.0 msec in adult males. Regression analysis showed that adult males have faster muscles than adult females or juveniles even when corrected for body size. Temporalis and masseter orientation was found to change little throughout growth. The mechanical advantage of the masseter and temporalis muscles for producing occlusal forces on the distal molars improved between juveniles and adults, which is contrary to findings of Oyen et al. (Growth 43:174-187, 1979). Among adults, females had a greater mechanical advantage of the masseter muscles than males.

Analysis of Variance↗