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PubMed2002

Immediate effect of a stabilization splint on masticatory muscle activity in temporomandibular disorder patients.

Surface electromyography (EMG) allows the quantification of the occlusal equilibrium in dysfunctional patients, for instance in those with temporomandibular disorders (TMD). Fourteen patients (ten women, four men) with internal derangement type I were selected among the TMD patients referred to a private practice in Milan. A stabilization splint with posterior contacts was made for each patient. To verify the static neuromuscular equilibrium of occlusion, EMG activity of left and right temporal and masseter muscles was recorded in all patients and the activity (ratio between the activities of the temporal and masseter muscles) index was computed over a maximum voluntary clench test of 3 s. Muscular waveforms were also analysed by computing a percentage overlapping coefficient (POC, an index of the symmetric distribution of the muscular activity determined by the occlusion). The total electrical activity was measured by calculating the area under the entire muscular waveforms. In all patients EMG was performed just before and immediately after the insertion of the splint and data were compared by paired Student's t-tests. Overall, the splint reduced the electrical activity of the analysed muscles (P < 0.005) and made it more equilibrated both between the left and right side (larger symmetry in the masseter muscle POC, P < 0.05) and between the temporal and masseter muscles (activity index, P < 0.01).

Adult↗
PubMed1994

T-cadherin expression delineates specific regions of the developing motor axon-hindlimb projection pathway.

T-cadherin is a unique member of the cadherin family anchored to the membrane by a glycosyl phosphatidylinositol moiety (Ranscht and Dours-Zimmermann, 1991). T-cadherin's distribution in the developing motor axon pathway was mapped by immunocytochemistry in the chick lumbosacral region as spinal neurons project to and innervate hindlimb muscle. On growing motor axons, T-cadherin was expressed biphasically. Initially, uniform T-cadherin expression occurred on motor neurons as they projected between the spinal cord and the base of the hindlimb (stage 21-24), and then decreased as the axons sorted to form dorsal, ventral and muscle nerve trunks (stage 25-27). Later, as motor axons entered and formed terminal axon arbors and synapses in muscle (stages 28-36), expression reoccurred heterogeneously among motor neuron pools. Thus, T-cadherin may guide the growth and fasciculation of all motor neurons during early axon extension, but only affect particular populations during the later expression period. In the mesenchyme of the motor axon pathway, T-cadherin was restricted to regions avoided by growing axons: the posterior-half sclerotome before and during the projection of motor axons through the T-cadherin-negative anterior half, and the extrasynaptic surfaces of developing muscle. The temporal and spatial expression patterns of T-cadherin and neurite outgrowth-promoting N-cadherin were complementary both in nerve and muscle tissues. Thus, in the posterior sclerotome and in maturing muscle, T-cadherin may act as a negative regulator that works in concert with neurite growth-promoting molecules to guide motor axons to their peripheral targets.

Animals↗
PubMed1986

Use of temporalis muscle flaps in complicated defects of the head and face.

Large defects in the upper two thirds of the face, skull, and skull base pose challenging reconstructive problems. There are a number of applicable reconstructive techniques, all with various advantages and disadvantages, available to otolaryngologists-head and neck surgeons. One method, originally described in the late 1800s, was evaluated by us. Applications of the technique included reconstruction of large defects of the forehead, dura, and anterior skull base, closure of orbital defects, and soft-tissue augmentation of the face. Advantages of this reconstructive technique are the flap's proximity to the defects and its simplicity of execution.

Adult↗
PubMed1994

Characteristics of muscle fatigue in patients with myofascial pain-dysfunction syndrome.

The purpose of this study was to compare the properties of muscle fatigue in the masseter and temporalis muscles of normal individuals and those with myofascial pain-dysfunction syndrome (MPD). The MPD muscle is presumed to have different characteristics of fatigue than its healthy counterpart; these characteristics can be quantitated using standard electromyogram (EMG) signal-processing techniques. A total of 18 patients diagnosed as having MPD comprised the experimental group and 15 adults with no history or present symptoms of temporomandibular joint pain and dysfunction served as controls. Surface EMG recordings were made for both the masseter and anterior temporalis muscles while the subject held an incisal bite force level of 10 N for as long as possible. The EMG data were transferred to a microcomputer where the power-density spectrum of the signals were calculated for 2-s samples at 10-s intervals. The mean power frequency (MPF) and power (root mean square, r.m.s.) of the signals were calculated from the power-density spectra. Results showed: (1) the endurance times were significantly shorter for the MPD patients; (2) the masseter was not active in three of 17 MPD patients; (3) decreases in MPF over time were significantly greater for the MPD patients than normal subjects; (4) increases in r.m.s. power were significantly greater over time for the MPD patients; (5) bandwidths of the power-density spectra were similar for the two groups. The implication of these results is the MPD muscle is not in a state of constant fatigue, as is currently believed, but rather demonstrates accelerated fatigue.

Adolescent↗
PubMed2004

Management of forehead and brow deformities.

The subcutaneous trichophytic forehead browlift allows rejuvenation of the forehead with precise, stable brow positioning, excellent visualization, and direct treatment of the brow and forehead musculature. This method avoids lengthening the forehead and, with meticulous closure, can produce an imperceptible scar and natural-appearing hairline.

Endoscopy↗
PubMed1997

Comparison of habitual masticatory patterns in men and women using a custom computer program.

STATEMENT OF PROBLEM: Though computer-based systems for recording three-dimensional jaw motion and muscle activity during mastication are common, few computer programs are available to analyze the resultant data. Few studies have discussed the variability over time of the many parameters of the masticatory cycle now measurable by computer systems. PURPOSE: The purposes of this study were to (1) use a custom computer program, (MAS), for analysis of long-term repeated measurements of mandibular motion and muscle activity; (2) determine sex differences for mandibular movements and activity of the muscles involved during mastication; and (3) determine the variability over time and the statistical power of these methods. MATERIALS AND METHODS: Masticatory cycles of 20 normal men and 17 normal women were examined during mastication of a constant bolus at a sampling rate of 500 fps. Measurements included duration of chewing cycle and its component phases, mandibular displacement in three dimensions, and electromyographic activity in the temporalis and masseter muscles. The MAS custom computer program was used for analysis. Two-way repeated measures analysis of variance was used to compare the men with the women over three trials at 0, 6, and 12 months. The variability over time associated with each measurement was also estimated. RESULTS: Timing of the phases of the chewing cycle were most repeatable between trials, whereas lateral excursions and muscle force magnitudes were the least repeatable measures. Durations of total cycle, its slow-open and fast-close phases, were significantly longer for the female group, and their bursts of muscle activity tended to be longer. The amount of vertical mandibular excursion tended to be greater for men. There were no gender-related differences in the amplitude of muscle activity. CONCLUSIONS: This study demonstrated that men have significantly shorter chewing cycles with faster velocities than women. Men used significantly greater chewing force than women, although their electromyographic activity levels were equivalent. The masticatory measurements made by the MAS program had differing amounts of variation over time. Total duration of the chewing cycle and amount of opening varied the least, whereas amount of lateral excursion and jaw muscle electromyographic magnitudes exhibited the greatest variation.

Adult↗
PubMed2003

Electromyographic responses to prescribed mastication.

The aim was to understand between-volunteer differences in Electromyography (EMG) behaviour during chewing. EMG was used to record the electrical activity of the temporal and masseter muscles of volunteers, who carried out mastication movements by operating calibrated springs held between their incisors. The volunteers coordinated their jaw movements with the signal produced by a metronome, at four rates: 30, 60, 90 and 120 beats per minute (bpm). Raw data were analyzed to examine the distributions of the intervals between chews. For the highest prescribed chew rates, the volunteers' distributions were very similar. The distributions varied most for the 30 bpm data, suggesting that volunteers differed in their ability to carry out and maintain this prescribed chewing pattern. The data were Fourier transformed to give power spectra in the frequency domain. The low frequency (<10 Hz) region contained spectral features related to the prescribed chew rate. Principal component analysis of the power spectra revealed that readings from each volunteer clustered together, and the clusters could be largely separated. Such grouping was found irrespective of whether data from each chew rate were analyzed separately or simultaneously. This indicated that within-volunteer variance, arising from the different chew rates as well as between-session variance, is lower than between-volunteer variance; even when individuals are asked to make jaw movements in the same prescribed manner, they can nevertheless be uniquely distinguished by their muscle activity as recorded by EMG.

Adult↗
PubMed2001

Controlled study of EMG activity of the jaw closers and openers during mastication in patients with myasthenia gravis.

Mastication was evaluated in patients with bulbar myasthenia gravis and compared with that of patients with ocular myasthenia gravis, patients in remission who previously suffered from bulbar symptoms, and healthy controls. Bulbar myasthenia gravis may impair mastication due to weakness of the masticatory muscles. The aim of the study was to objectively evaluate the influence of myasthenia gravis on mastication. The subjects chewed a piece of breakfast cake and chewed 1 min on a piece of chewing gum. Surface EMG of the masseter muscle, temporalis muscle and jaw opener muscles was recorded. Statistical analysis revealed that bulbar patients produced significantly less EMG activity in the closing phase of a chewing cycle in both experiments. The EMG of the masseter muscle expressed as percentage of the maximum EMG during maximal clenching showed significantly higher values in the bulbar group than in the other groups. This was not found for the temporalis muscle. It was suggested that bulbar patients use a strategy of limited effort to produce a bolus that can be swallowed. The ocular patients and the patients in remission showed no subclinical impairments in muscle function during chewing.

Adult↗
PubMed2002

Task-related electromyographic spectral changes in the human masseter and temporalis muscles.

The masticatory muscles differ in their fiber type composition. It can therefore be expected that their electromyographic (EMG) power spectra will differ during the performance of different bite force tasks. In the present study, surface EMG activity was picked up from the masseter and from the anterior and posterior temporalis muscles of nine adult subjects. At a bite force level as low as 25 N, the mean power frequency (MPF) values of the posterior temporalis were significantly lower than those of the masseter and anterior temporalis. The MPF values of the masseter muscles decreased with an increase of bite force magnitude, whereas the MPF values of the anterior and posterior temporalis did not change significantly. The MPF values were significantly influenced by the direction of bite force. The observed changes of MPF are possibly related to the recruitment of different fiber types, and support the concept that the masticatory muscles behave heterogeneously.

Adult↗
PubMed2001

Modulation of the stretch reflex of jaw-closing muscles in different modes and phases of respiration.

The objective of this study was to investigate whether and how changes in the mode of respiration affect the electromyographic activity of human jaw-closing muscles. Fifteen men were examined in this study. A pair of surface electrodes was attached bilaterally to the masseter and anterior and posterior temporalis muscles for electromyographic recording. Respiratory movements of the chest wall and nasal airflow were recorded simultaneously. Recordings were performed with subjects in the sitting position during quiet nasal and oral respiration. The stretch reflex of jaw-closing muscles was elicited by randomly tapping the chin with an impulse hammer. In 11 subjects, we measured nasal resistance with a rhinomanometer. The amplitude of electromyographic activities of the masseter and anterior temporalis muscles during oral respiration was significantly less than that during nasal respiration, whereas that of the posterior temporalis muscle showed no significant difference between the different modes of respiration. Furthermore, the reduction in the amplitude of the electromyographic activity was more evident in the inspiratory phase during oral respiration. There was a significant positive correlation between the ratio of the reflex amplitude during inspiration in the 2 respiratory modes and nasal resistance for the masseter muscle, but not for the anterior temporalis muscle. These results suggest that the reflexive electromyographic activity of some human jaw-closing muscles is modulated during oral respiration.

Adult↗
PubMed2002

Treatment of condylar hypoplasia with distraction osteogenesis: a case report.

This report describes the surgical-orthodontic treatment procedures of a patient with condylar hypoplasia. Condylar hypoplasia is a major factor in any facial abnormality in a growing child. This case report describes a patient with a facial anomaly with an acquired unilateral condylar hypoplasia. His asymmetry was corrected by using functional therapy for the correction of muscle tonus and distraction osteogenesis for lengthening the mandibular ramal height. Fixed orthodontic appliances were used for conventional orthodontic therapy and final occlusal adjustment.

Bite Force↗
PubMed2005

Influence of bitter taste on mastication pattern.

Mastication is a rhythmic activity that can be modified by peripheral information generated in the mouth. To study whether taste cognition could influence the way in which a food is broken down in the mouth, subjects masticated firm, sugar-based gelatine gels with differing concentrations of quinine, up to 1500 micromol/kg, while electromyography (EMG) of masticatory muscles was recorded. Taste intensity and composition of saliva were measured. With increasing quinine concentration, the average number of chews for nine subjects decreased from 30 to 22, and their average clearance time increased from 7 to 14 sec. Quinine concentration had no effect on chewing frequency (1.3 Hz) or on the rate of salivation (5.5 g/min). Bitterness increased, while acceptability and sweetness decreased, with increasing concentration of quinine in the gel and in saliva. Taste cognition could therefore modify food breakdown in the mouth.

Adult↗
PubMed1992

[Evaluation of a histochemical method specific for myosin ATPase activity in the masticatory muscles of the rat].

A biological study of masticatory muscle behaviour (Divry and Westphal, 1991) suggested the analysis of physiologic correlates (biologic parameters related to a behavioural event) such as histochemical reactions of muscular fibres studied by M-ATPase and SDH activities. For such investigations, routine methods are needed. In the present study, a modification of the original method of Tunell and Hart (1977) was used, in which three features of the original alkaline preincubation method (composition, incubation time and pH) were modified. These allowed a single step differentiation of the various fibre types found in rat masticatory muscles, for which the classical technics gave only a weak contrast, not suitable for image analysis. Acid preincubation was also tested but failed to give new information. By combining this modified technic with SDH staining (Nachlas, 1957) a classification of fibres into 12 theoretical types was proposed.

Alkalies↗
PubMedDate not supplied

The effect of different transplanted soft tissues on bone resorption around loaded endosseous implants in patients after oral tumor surgery.

One hundred eighty-five dental implants loaded for at least 1 year in 49 patients treated with ablative tumor and reconstructive surgery in the oral cavity were examined to ascertain peri-implant bone resorption. While 96 implants penetrated local mucosa and served as the control group, 27 implants were associated with split-thickness skin grafts, 9 in mucosal grafts, 18 in myocutaneous flaps, 30 in jejunal grafts, and 5 in a vastus lateralis and a temporalis muscle flap. Restoration type was similar in all groups (overdentures) except for implants placed in the jejunal grafts (fixed implant-supported prostheses). Regular follow-up was done over an observation period of 3 to 5 years after implant placement. Overall survival rate of the 89 implants surrounded by transplanted soft tissues was 94.1%. Bone loss under the various transplanted soft tissues was similar to or less than that under local mucosa. Over time, only horizontal bone resorption under jejunal grafts and vertical bone resorption under mucosal grafts showed higher values. Mean values of all measurements for split-thickness skin grafts were higher than for local mucosa for the horizontal as well as for the vertical resorption pattern. It can be concluded that transplanted tissues foreign to the oral cavity have no detrimental effect on bone resorption around loaded dental implants and do not endanger their long-term stability. Of all the transplants used, split-thickness skin grafts are least recommended as peri-implant soft tissue.

Bone Resorption↗