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PubMed1987

Craniomandibular disorders in adolescents. A longitudinal study in an urban Swedish population.

The prevalence of craniomandibular disorders was studied in 285 17-year-old adolescents with the aid of a questionnaire and a functional examination of the masticatory system including evaluation of TMJs, masticatory muscles, mandibular mobility, and occlusion. The adolescents were followed up longitudinally two more subsequent years. Totally 27 subjects dropped out, leaving 258 for the longitudinal intraindividual comparisons. At the age of 17 a fifth of the subjects reported some symptoms involving the masticatory system, of which most were mild, according to the anamnestic index (Ai) used. Oral parafunctions were commonly reported of which nail-biting dominated. Grinding and clenching of teeth were reported by 8% and 11% respectively. Signs of mandibular dysfunction were found in 56% of the adolescents and were mostly mild according to the dysfunction index (Di) used. Girls more often had signs of mandibular dysfunction than boys. Morphologic malocclusion was recorded in 35%, unilateral contact in RP in 77%, lateral shift between RP and IP greater than or equal to 0.5 mm in 19% and mediotrusion interferences in 30% among the 17-year-olds. No significant difference between sexes was found. Of the sample 62% had either some sign or symptom of dysfunction and there was a positive relationship between the dysfunction indices used. Neither morphologic nor functional malocclusions were related to the Ai. TMJ sounds were related to palpation tenderness in the lateral pterygoid muscle and impaired mobility of the mandible. The number of masticatory muscles tender to palpation was related to reports of fatigue in the jaw, TMJ tenderness, and mediotrusion interferences. Recurrent headache was reported by about 18% of the girls and by almost 6% of the boys. Fatigue in the jaws and difficulties in chewing were commoner in those with frequent and more intensive headache. Tenderness to palpation of the masticatory muscles and impaired mandibular mobility were significantly commoner findings among those with recurrent headaches and those with more intense headache. Tooth-grinding and clenching were related to frequency but not to intensity of headache. Reports of TMJ sounds increased with age for girls who also more frequently reported recurrent headaches than boys. The prevalence of symptoms of mandibular dysfunction was about 20% each year, but there was no general increase of frequency and severity of symptoms during the observation period in spite of an incidence of 8%. The prevalence was, according to the Ai, significantly higher for 18- and 19-year-old girls than for boys. Most symptoms were mild and fluctuated longitudinally.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1996

Differences in capillary supply between human oro-facial, masticatory and limb muscles.

In this report we show that immunostaining of the capillary basement membrane with an antibody directed against laminin is a useful alternative in detecting the capillaries in human muscle. Using this method, the capillary supply of three embryologically, morphologically and functionally different muscle groups, oro-facial, masticatory and limb muscles, were analysed. Significant differences in capillarization between muscles and muscle groups were found. The oro-facial and masseter muscles showed significantly higher density of capillaries than the limb muscles, taken in consideration the muscle cross-sectional area, with the masseter having the highest capillary density ever reported for human sedentary skeletal muscles. Judged from the number of capillaries per muscle fibre, the limb muscles showed the best capillarization. However, since the three muscle groups investigated differed with respect to fibre diameter, our evaluation of number of capillaries per muscle fibre was related also to fibre diameter. Thus, capillary constants were created which take fibre diameter into account. Based on these new parameters, the oro-facial and masseter muscles were found to be relatively better supplied by capillaries than the limb muscles. These results suggest differences in tasks and functional activity between muscles, and reflect a relatively higher need and demand for blood supply in the masticatory and oro-facial muscles than in limb muscles.

Adolescent↗

PubMed2003

[Electromyographic changes in bruxism after auricular stimulation. A randomized controlled clinical trial].

AIM: The aim of this study was to verify in bruxism patients the possible efficacy of auricular stimulation in reducing the hypertonicity of some masticatory muscles. METHODS: Forty-three bruxism patients were randomly allocated to 3 groups: acupuncture, needle contact for 10 seconds, no treatment (control). Helkimo's clinical dysfunction index (CDI) and anamnestic dysfunction index (ADI) were used to assess the functional state of the masticatory system. The resting electrical activity of the anterior temporalis (AT), masseter (MM), digastric (DA) and sternocleidomastoid (SCM) muscles was measured, according to Jankelson, with surface electrodes at baseline, after stimulation and continually for 30 minutes (120 measurements in total). The electromyographical variations in the 3 groups were studied with t test for independent samples. RESULTS: Acupuncture and needle contact were superior to control in reducing the muscle hypertonicity of all muscles except SCM. In the comparison between acupuncture and needle contact the former showed better results only for the right TA and left DA (p = 0.000). CONCLUSION: In this study it was possible to measure the efficacy of the stimulation of only one point or area, which is an ideal model for research in acupuncture. The auricular area we chose for stimulation was never used before for the purpose of relaxing masticatory muscles. Acupuncture and needle contact for 10 seconds showed similar effects.

Acupuncture, Ear↗

PubMed1994

Masticatory function in normal and crowded occlusion using Hellman's dental stages.

As a consequence of this study, the following conclusions were obtained by means of an estimate of the interocclusal point number of the integrated value of the electromyographs, of the masticatory rhythm with 40 subjects in each group (the normal groups: IIA 10. IIIA 10, IIIC 10, IVA 10; the crowding groups: IIA 10, IIIA 10, III C 10, IVA 10). 1. From the view of the integrated value of the electromyographs. In the normal groups with a normal occlusion. TA% to the total active potentials turned out to be less in proportion to the advancement of the dental stages, while TP% remained as the same. M% should an increase, whose ratio turned out to be high enough to take TA's place. 2. In the crowding groups, in spite of the indication of TA's decrease, M's increase, a comparison with the normal groups' that even after the stage IIIC TA-M-type masticatory pattern had to be maintained. 3. Regarding the interocclusal point number, in IIIC, IVA, the total amount and number at the molar segments indicated a significantly smaller value in the crowding groups. 4. Concerned with the integrated value of the masticatory muscle, the most related factor to yield the characteristic masticatory pattern observed in the crowding groups could be considered the number of the interocclusal points, which proved that great importance should be paid to the maintenance of the well harmonized status of the upper and lower occlusion.

Case-Control Studies↗

PubMed2005

The deep belly of the temporalis muscle: an anatomical, histological and MRI study.

In order to achieve a better functional and clinical knowledge of a masticatory muscle called the sphenomandibularis that is suspected to be responsible for headaches by compressing the maxillary nerve, bilateral dissections of the infratemporal fossa were performed on ten human cadavers and completed by histological and radiological studies of the same areas. Both macroscopic and microscopic observations obviously showed that the so-called sphenomandibularis muscle corresponds to the deep portion of the temporalis muscle, since there is no epimysial septum between these two structures, which previously have been described as being completely independent from each other. In spite of the close topographic relationship between the deep belly of the temporalis and the lateral pterygoid muscle, as well as their similar innervation pattern, the sphenomandibularis in fact has to be considered functionally as an original but non-isolated positional fascicle of the temporalis muscle itself. Our observations, correlated with MR images, suggest indeed that the deep belly of the temporalis muscle is of functional importance in the masticatory movements, but is not involved by its neurovascular vicinity in the genesis of specific headaches. Its surgical release, however, should be discussed in the case of a temporal myoplasty.

Aged↗

PubMed1995

Muscle-specific enzyme activity patterns of the capillary bed of human oro-facial, masticatory and limb muscles.

Enzyme-histochemical methods were used to analyse the activities of alkaline phosphatase (AP), dipeptidylpeptidase IV (DPP IV) and adenosine triphosphatase (ATPase) in capillaries of four different human oro-facial muscles, the major and minor zygomatic, the orbicularis oris and buccinator, one masticatory, the masseter and two limb muscles, the biceps brachii and first dorsal interosseus muscles. In all muscles, except for the orbicularis oris, the majority of the capillaries lacked enzyme activity. Therefore, none of these enzymes seems to be reliable as a general marker for human muscle capillaries. In general, the capillaries of the limb muscles and the major and minor zygomatic and the buccinator, were similar in their staining pattern for AP and ATPase, but differed in DPP IV staining. The orbicularis oris muscle differed from the other muscles by showing the largest proportion of capillaries with AP and ATPase activity. The masseter muscle had the largest proportion of capillaries stained for DPP IV. The muscle specific differences in enzyme activity of the capillaries are in agreement with our previous findings of specific differences between limb, oro-facial and masticatory muscles with respect to capillary supply and composition of fibre types and myosins. The results reflect functional specialization of the capillary bed of human muscles.

Adenosine Triphosphatases↗

PubMed1989

[Bilateral chronic luxation of the mandible. Clinical case].

The pathogenesis and treatment of the long standing dislocation of the mandible is showed by the Authors. A case of four months duration in a young man is presented. The reduction was accomplished manually under intravenous anaesthesia and relaxant drug. By the means of a digital electromyography a survey of the masticatory muscle before and after reduction was done. The normalisation of masticatory function was closed followed by improvement of electromyographic results.

Adolescent↗

PubMed1979

Muscle function during chewing and swallowing in patients with osseointegrated oral implant bridges. An electromyographic study.

The activity of the anterior and posterior portions of the temporal muscle, the masseter and the upper lip has been studied with electromyography in 13 women with osseointegrated oral implant bridges and compared with that in 10 subjects with natural teeth. The functions examined were chewing and swallowing of apple, bread and peanuts. There was no difference between implant and control subjects in the number of chewing cycles nor in duration of the act of chewing or in the amplitude of the muscle activity during chewing and swallowing. However, the duration of the activity during chewing was longer in the implant than in the control subjects. The number of years of wearing a maxillary implant bridge was found to be of importance for the number of chewing cycles during an act of chewing and for the muscle activity during chewing. Other factors influencing the muscle activity were age, number of occluding tooth units and the extension of the lower implant bridge. It was concluded that patients with osseointegrated oral implant bridges have a masticatory muscle function equal to or approaching that in patients with natural teeth or with bridges supported on natural teeth with the same extension of the dentition.

Adult↗

PubMed1988

Craniofacial sequelae of lesions to facial and trigeminal motor nuclei in growing rats.

Unilateral electrolytic lesions were made in the left-side facial motor nucleus (FMNu) of six Sprague-Dawley rats at 35 days of age in order to correlate craniofacial sequelae with changed motoneuron function. Experimental and control rats were killed at 22, 32, 42, and 52 days postoperatively to provide muscle weight, brain histology, and dry skull preparations for analyses. Dissection, muscle weight, motoneuron count, and osteometric data revealed that lesion-side facial and masticatory muscles were affected by the lesions. Paired t-tests indicated that significant differences existed between weights of experimental lesion- and nonlesion-side anterior digastric, temporalis, masseteric complex, and medial pterygoid muscles, numbers of facial and trigeminal motoneurons, and several skeletal dimensions of the skull. Basi-cranial dimensions of experimental animals were least affected by the lesion, whereas zygomatic arch, dorsal facial region, and mandibular condyle dimensions were most affected. Statistical analyses also detected significant differences between experimental and control groups for several skeletal dimensions of the skull. Data indicated that damage to the trigeminal motor nucleus (TMNu) was secondary to the primary lesion in the FMNu. Motoneurons within the facial and trigeminal neuromuscular complexes (FNC and TNC) play an important role in craniofacial growth and development.

Animals↗

PubMed1989

[A study on the reliability of EMG examination using EM2].

This study was performed to investigate the reliability of EM2 (Myotronics research Inc.). Two dentists as examiners took part in the study and examined 21 dental students, Seoul National University, respectively and repeatedly. Strong correlations could be found between the results of examinations. Conclusively, it is believed that the use of EM2 could be an electrodiagnostic modality for diagnosis and evaluation for the activity of masticatory muscles.

Adult↗

PubMed1999

Effects of controllable stress on masticatory behaviour and muscle structure: partial protective effect of clomipramine.

The influence of controllable painless stress and clomipramine treatment was evaluated on masticatory behaviour and myosin heavy chain expression in masticatory rat muscles: anterior digastric, anterior temporalis and masseter superficialis. The adult fast isoforms of myosin heavy chains detected were myosin heavy chains 2A, 2X and 2B. The myosin heavy chains composition of anterior temporalis muscle was unchanged by stress or by treatment. In anterior digastric and masseter superficialis muscles, stress induced an increase in 2B and a decrease in 2X and 2A. Under stress, whereas the myosin heavy chains composition of anterior temporalis and anterior digastric muscles was unaffected by clomipramine, this drug modified significantly the myosin heavy chains composition of masseter superficialis muscle which became comparable to that of control muscle. Stress-induced myosin heavy chains transformations led to an increased velocity of anterior digastric and masseter superficialis muscles but not anterior temporalis muscle. Gnawing and mastication were increased by stress and incisor grinding was reduced. Stress shortened the duration of gnawing and increased the fatigability of anterior digastric and masseter superficialis muscles, whereas clomipramine increased the duration of mastication and reduced the fatigability of masseter superficialis muscle. Stress produces selective changes in masticatory muscles and behaviour. This study demonstrates the muscle type-specific protective effect of clomipramine against stress-induced structural transformations of masseter superficialis muscle and the specific concomitant behavioural modifications.

Animals↗

PubMed1990

[Importance of masseter insertion surface in different mammal groups].

The objective of this study is to compare the strength of the masseter muscle in various mammals by calculating the ratio between insertion area of the masseter and total mandibular surface. We will also determine the factors capable of modifying the insertion area of this masticatory muscle.

Anatomy, Comparative↗

PubMed1989

Sensory components facilitating jaw-closing muscle activities in the rabbit.

The role of oral and facial sensory receptors in the control of masticatory muscle activities was assessed from the effect of acute deafferentiation on cortically induced rhythmic jaw movements (CRJMs) in anesthetized rabbits. When a thin polyurethane-foam strip (1.5, 2.5 or 3.5 mm thick) was placed between opposing molars during CRJMs, masseteric activities were facilitated in association with an increase in the medial excursion of the mandible during the power phase. The effects varied with the pattern of CRJMs, and the rate of facilitation was greater for small circular movements than for the crescent-shaped movements. Furthermore, the response of the masseter muscle was greater in the anterior half of the muscle, where muscle spindles are most dense, than in its posterior half. It was also demonstrated that the response increased with an increase in the thickness of the test strip. In contrast, the activities of the jaw-opening muscle were not affected significantly. The duration of masseteric bursts increased during application of the test strip and the chewing rhythm tended to slow down. However, the latter effect was not significant. After locally anesthetizing the maxillary and inferior alveolar nerves, the facilitative responses of the masseter muscle to the test strip was greatly reduced but not completely abolished. Lesioning of the mesencephalic trigeminal nucleus (Mes V) where the primary ganglion cells of muscle spindle afferents from jaw-closing muscles and some periodontal afferents are located, also reduced the facilitative effects. Similar results were obtained in the animals with the kainic acid injections into the Mes V 1 week before electrical lesioning of this nucleus. In these animals the effects of electrical lesioning of the Mes V could be attributed to the loss of muscle receptor afferents since the neurons in the vicinity of the Mes V were destroyed and replaced by glial cells, whereas the Mes V neurons are resistant to kainic acid. When electrical lesioning of the Mes V and sectioning of the maxillary and inferior alveolar nerves were combined in animals with a kainic acid injection into the Mes V, the response of the masseter muscle to application of the strip was almost completely abolished. From these findings, we conclude that both periodontal receptors and muscle spindles are primarily responsible for the facilitation of jaw-closing muscle activities.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1999

Jaw-muscle spindle afferent feedback to the cervical spinal cord in the rat.

Putative synaptic contacts between masticatory-muscle spindle afferents and brainstem neurons which project to the cervical spinal cord were studied in rats by combining retrograde and intracellular neuronal labeling. Spinal cord projecting neurons were retrogradely labeled via injection of horseradish peroxidase unilaterally or bilaterally into cervical spinal cord segments C2 through C5. Twenty-four hours after the injection of horseradish peroxidase, one to five jaw-muscle spindle afferent axons were physiologically identified and intracellularly stained with biotinamide on each side of the brainstem. Horseradish-peroxidase-labeled neurons were found bilaterally in the supratrigeminal region, trigeminal principal sensory nucleus, parvicellular reticular nucleus including its alpha division, spinal trigeminal subnuclei oralis and interpolaris and the medullary reticular formation. Retrogradely labeled neurons were most numerous in the spinal trigeminal subnucleus oralis, parvicellular reticular formation and the ventral part of the spinal trigeminal subnucleus interpolaris. A small number of horseradish-peroxidase-labeled neurons were also present in the trigeminal mesencephalic nucleus and spinal trigeminal subnucleus caudalis. Appositions between jaw-muscle spindle afferent boutons and spinal projecting neurons were found in the supratrigeminal region, dorsomedial portions of the trigeminal principal sensory nucleus and spinal trigeminal subnuclei oralis and interpolaris, and the parvicellular reticular formation including its alpha division. Putative synaptic contacts were most frequent in the parvicellular reticular formation and the dorsomedial portion of the trigeminal subnucleus oralis. These results indicate that some orofacial proprioceptive feedback transmitted via the mesencephalic trigeminal nucleus reaches the cervical spinal cord directly and suggests that jaw-muscle spindle afferent feedback reaches the cervical spinal cord predominately via relays in the dorsomedial part of the spinal trigeminal subnucleus oralis and the parvicellular reticular formation. It is hypothesized that these pathways are primarily involved in the coordination of jaw and neck movement during mastication and biting.

Afferent Pathways↗

PubMed1976

Taenia saginata cysticerci in muscles of beef cattle.

Minute dissection of carcasses infected with Taenia saginata cysts revealed that heart and masticatory muscles were more heavily and more frequently infected with Taenia saginata cysts than were any other muscle groups. Increasing the number of inspection cuts in the heart and masseter muscles, while omitting cuts in such sites as the diaphragm, during meat inspection would increase the efficiency in detecting beef cysticercosis. Complete dissection of cattle found to have a single viable or dead cyst by routine inspection revealed dead or viable cysts in portions of the carcass not routinely examined. These findings justify the recent change in routine meat inspection procedures whereby all carcasses with a single cyst (whether viable or dead) are now cooked or refrigerated, instead of having the offending cysts excised.

Animals↗

PubMed2000

Dynamic simulation of muscle and articular properties during human wide jaw opening.

Human mandibular function is determined in part by masticatory muscle tensions and morphological restraints within the craniomandibular system. As only limited information about their interactions can be obtained in vivo, mathematical modeling is a useful alternative. It allows simulation of causal relations between structure and function and the demonstration of hypothetical events in functional or dysfunctional systems. Here, the external force required to reach maximum jaw gape was determined in five relaxed participants, and this information used, with other musculoskeletal data, to construct a dynamic, muscle-driven, three-dimensional mathematical model of the craniomandibular system. The model was programmed to express relations between muscle tensions and articular morphology during wide jaw opening. It was found that a downward force of 5 N could produce wide gape in vivo. When the model's passive jaw-closing muscle tensions were adjusted to permit this, the jaw's resting posture was lower than that normally observed in alert individuals, and low-level active tone was needed in the closer muscles to maintain a typical rest position. Plausible jaw opening to wide gape was possible when activity in the opener muscles increased incrementally over time. When the model was altered structurally by decreasing its angles of condylar guidance, jaw opening required less activity in these muscles. Plausible asymmetrical jaw opening occurred with deactivation of the ipsilateral lateral pterygoid actuator. The model's lateral deviation was limited by passive tensions in the ipsilateral medial pterygoid, which forced the jaw to return towards the midline as opening continued. For all motions, the temporomandibular joint (TMJ) components were maintained in continual apposition and displayed stable pathways despite the absence of constraining ligaments. Compressive TMJ forces were presented in all the cases and increased to maximum at wide gape. Dynamic mathematical modeling appears a useful way to study such events, which as yet are unrecordable in the human craniomandibular system.

Adult↗

PubMed1994

The efficacy of oral splints in the treatment of myofascial pain of the jaw muscles: a controlled clinical trial.

Oral splints are widely used in the treatment of myofascial pain of masticatory muscles, even though their mechanism of action is unknown. The present study evaluated the therapeutic efficacy of splints using a parallel, randomized, controlled and blind design. Following a sample size estimation, 63 subjects were recruited and assigned to 3 groups: (1) passive control: full occlusal splint worn only 30 min at each appointment; (2) active control: palatal splint worn 24 h/day; and (3) treatment: full occlusal splint worn 24 h/day. On each of 7 visits over 10 weeks, subjects rated on 100 mm visual analogue scales their pain intensity and unpleasantness at rest and after experimental mastication. The effect of pain on the quality of life was also rated on category scales. All pain ratings decreased significantly with time, and quality of life improved for all 3 groups. However, there were no significant differences between groups in any of the variables. These data suggest that the gradual reduction in the intensity and unpleasantness of myofascial pain, as well as the improvement of quality of life during the trial, was non-specific and not related to the type of treatment.

Adolescent↗

PubMed2003

Maximum bite force, muscle efficiency and mechanical advantage in children with vertical growth patterns.

This study correlated maximum bite force and masticatory muscle electromyography (EMG) activity with craniofacial morphology and mechanical advantage of children with vertical growth patterns. From lateral cephalograms of 30 females and 17 males (9.3 +/- 3.6 years of age), 13 morphological and eight biomechanical measurements were recorded. Two maximum bite forces and 12 submaximal bite forces along with their associated EMG muscle activity were recorded at the right mandibular first molar. Muscle efficiency was evaluated using the relationship between bite forces and EMG activity levels. There were no significant sex differences (P > 0.05) for any of the morphological, functional or biomechanical variables. Factor analyses reduced: (1) the 13 morphological variables to four factors explaining 82.8 per cent of the morphological variance; (2) six functional variables to two factors explaining 68.8 per cent of the functional variance; and (3) 11 biomechanical variables to three factors explaining 90.9 per cent of the biomechanical variance. The vertical size factor was negatively correlated with the muscle efficiency factor (r = -0.39; P = 0.006) and positively correlated with the moment arm factor (r = 0.67; P < 0.001). The morphological divergence factor was negatively correlated with the bite force factor (r = -0.34; P = 0.019) and the mechanical advantage factor (r = -0.32; P = 0.028). The muscle efficiency factor (functional) was negatively correlated with the moment arm factor (r = -0.33; P = 0.023). It is concluded that: (1) independent of chronological age, children with larger faces have larger moment arms and require less muscle activity to attain any given force, and (2) greater hyperdivergence is related to poorer mechanical advantage and lower maximum bite force. These data support the relationships between bite force, muscle strength and morphology in children, similar to those reported for adults.

Adolescent↗