Journal of oral rehabilitation
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Clinical/occlusal scores and jaw-muscle EMGs were recorded in 24 TMD symptomatic (group S) and 20 normal (group N) subjects to evaluate the significance of EMG parameters and their clinical associations. Results indicated: (1) integrated EMG activity (IEMG) was larger at the rest position (RP) in anterior temporalis (Ta) but smaller at maximal voluntary clenching (MVC) in masseter (Ma) and Ta, and the ratios of IEMG at 70%MVC to the corresponding bite force (70%BF) were greater in group S; (2) mean power frequency (MPF) were almost the same in both groups but its shift was more rapid in group S; (3) silent period duration (SPD) was longer in group S; (4) asymmetry indices for SPD and silent period latency (SPL) were larger in group S; (5) muscle pain was associated negatively with IEMG at MVC and 70%BF but positively with IEMGs at RP and 70%MVC, and impaired jaw movements were associated negatively with the above EMG values; (6) muscle pain was positively associated with SPD in Ma, while joint pain and sound showed positive and negative associations with SPD, respectively; (7) associations between occlusion and EMG parameters were found more in group N. These findings verify: (1) jaw elevators in TMD may have hyper-tonic activities and a weak functional efficiency; (2) jaw muscles in TMD may become easily fatigued following a functional effort, and less relaxed following a muscle twitch; (3) the severity of pain could not be reflected in EMG activities, but impaired jaw movement may increase tonic activity and decrease functional effort; (4) TMD symptoms may alter the functional adaptation of jaw-muscle activities and occlusion.
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Seven normal male and seven normal female volunteers performed three types of biting exercises: an intermittent contraction at maximum voluntary bite force (MVBF) to pain intolerance; a ramp intermittent contraction starting at 10% MVBF and increasing 10% every 10 s; and a sustained biting at 100% MVBF to pain intolerance. The following measurements were made on the first and second days before exercise: a pre- and post-exertional overall jaw pain level; maximum pain-free jaw opening; bilateral masseter pressure pain threshold (PPT) and intolerance (PPI). The results showed that only females presented an increased overall pain level on the second day and a significant decrease in pain-free jaw opening, but no significant decrease of PPT and PPI. These results suggest that females respond differently than males to exertional jaw pain, by increasing their pain response 24 h later.
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This paper describes the modulation of human deliberately unilateral mastication by trigeminal and extra-trigeminal standardized painful stimuli. Series with 15 s of gum-chewing before induction of pain, during pain and after pain were quantitatively assessed by jaw-closing muscle electromyography (EMG) and kinematics of the lower jaw. Four different painful stimuli were used: cold stimulation of the frontal region, cold stimulation of the dominant hand, capsaicin stimulation of the hard palate, and pressure pain stimulation of the temporomandibular joint (TMJ). ⋯ Cold stimulation of the hand and palatal capsaicin stimulation caused significant increases in peak amplitudes of EMG bursts from all jaw-closing muscles and faster jaw movements whereas TMJ pressure pain produced significantly lower peak EMG amplitudes. The present results suggest that nociceptive input from different tissues and even extra-trigeminal regions may modulate trigeminal motor function in selective ways. Thus, clinical observations of changes in masticatory function may not always be due to pain in the orofacial region and therefore do not necessitate orofacial treatment.
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This study was performed to assess the prevalence of signs and symptoms related to cervical spine disorders (CSD) in subgroups of patients with temporomandibular disorders (TMD) and to compare TMD patients and CSD patients with regard to the results of orthopaedic cervical spine tests. One hundred and eleven consecutive patients with TMD and 103 consecutive patients with signs and symptoms of CSD were examined. The results indicated that there is a considerable overlap in the signs and symptoms of patients with TMD and patients with CSD. ⋯ Logistic regression analyses showed that orthopaedic tests of the cervical spine are of minor importance in discriminating between patients with TMD and patients with CSD. It is concluded that TMD with a myogenous involvement in contrast to TMD with only an arthrogenous involvement should no longer be viewed as a local disorder of the stomatognathic system. The upper quarter, including the stomatognathic system, cervical spine, and shoulder girdle, should be evaluated in patients with more complex or persistent symptoms in the head and neck region.
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Controversy exists on the aetiological importance and the effect of jaw macrotrauma (fractures excluded) on the occurrence of temporomandibular joint disorders (TMD). The purpose of this study was to assess the incidence of jaw injury in TMD patients and to compare the severity of the symptoms, the clinical characteristics and the treatment outcome in TMD patients with or without a history of trauma to the head and neck region directly linked to the onset of symptoms. The study sample included 400 consecutive TMD clinical patients. ⋯ The degree of maximal opening was similar: less than 20 mm in 3.7% and 2.2% in trauma and non-trauma patients respectively. Forty percent and 41% respectively were symptom free or had DI = 1. The results suggest that external trauma to the joint or to the jaw in general is an important initiating factor in the aetiology of TMD but also that the prognosis is favourable.