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Background: A leaf gauge and an anterior jig may be used to assist the recording of a reproducible jaw position for restorative and prosthodontic treatment. This study investigated possible condylar displacement using an opto-electronic jaw-tracking device and a leaf gauge or anterior jig. The effect of a leaf gauge and anterior jig on jaw muscle electromyography was also examined.Methods: Five healthy adults without symptoms of temporomandibular disorders were selected. Condylar displacement during clenching were recorded simultaneously with electromyographic activity of superior and inferior heads of the lateral pterygoid, anterior and posterior temporalis, masseter, and suprahyoid muscles. Subjects were trained to bite at maximum and half-maximum bite-force using an anterior jig incorporating a force transducer.Results: No consistent condylar displacement was observed in x, y and z axes between different bite-forces although there was a trend towards superior displacement. Comparison of maximum intercuspal clench and maximum clench on a leaf gauge and an anterior jig produced significant decrease in anterior temporalis activity (p < 0.05), whilst an anterior jig with maximum clench significantly decreased posterior temporalis muscle activity.Conclusion: Within the limits of this pilot study, no consistent change in condylar position was identified with these appliances. [ABSTRACT FROM AUTHOR]

The activity of the superior head of the human lateral pterygoid muscle (SHLP) is controversial. Given the non-parallel alignment of some SHLP fibers, the SHLP may be capable of differential activation. The aims were to clarify SHLP activity patterns in relation to location within SHLP. In 18 subjects, SHLP single motor units were intramuscularly recorded at computertomography-verified sites during horizontal (e.g., protrusion) and vertical (e.g., opening) jaw tasks (recorded by a jaw-tracking device) and at resting postural jaw position. None of 92 units was active at the resting postural position. Medially located units (21) showed activity during contralateral movement, protrusion, and opening; 5 were also active on jaw closing. There was a significant association between unit location and the number of units active during vertical tasks (i.e., jaw closing and clenching). Analysis of the data suggests differential activation within SHLP and raises the possibility of functional heterogeneity within SHLP. [ABSTRACT FROM AUTHOR]

A standardized reproducible system for evoking jaw reflexes following chin tap is described. It represents an improvement over non-standardized and other standardized forms of instrumentation in that characteristics of the associated jaw displacement and parameters of the evoked jaw jerk reflexes recorded using this system have been shown to be reproducible. The need for standardized instrumentation to evoke jaw reflexes of any kind is emphasized by the influence of graded variations in tap force on the parameters of the evoked jaw jerk reflex response. Thus, higher levels of tap force correlate with an increased jaw jerk duration and amplitude and a decreased latency. [ABSTRACT FROM AUTHOR]

Occlusal form is frequently modified in clinical practice and yet we do not have detailed knowledge of the possible effects of these changes on condylar movement. The aim of this study was to quantify the effects of an alteration in the occlusion on condylar movement during a lateral excursive jaw movement. Posterior tooth guidances (i.e. metal overlays) were attached to both maxillary first molars. The movement of arbitrary condylar points on the non-working side was recorded in seven subjects duringlateral excursion under natural tooth guidance (control) and was compared with that after placement of the overlays (guidance). The guidance resulted In statistically significant changes to the displacement of the arbitrary condylar points on the non-working sides For example, at a standardized (3 nun) displacement along the mid- incisor point trajectory during the lateral excursion for both control and guidance in all subjects, the corresponding displacements of the condylar points were statistically significantly decreased under the guidance situation in comparison with the control situation. These data suggest that, for the same magnitude of mandibular displacement during lateral excursion, the introduction of a posterior tooth guidance limits condylar displacement on the non-working side. [ABSTRACT FROM AUTHOR]

Statement of Problem: During lateral excursive and protrusive jaw movements, condylar points are distant from any instantaneous rotational center. Therefore, it is likely that different condylar points would follow similar trajectories during these movements., Purpose: This study evaluated the effect of changes in condylar point location on trajectories of condylar points on the nonworking side and during a protrusive jaw movement and compared these changes with the effects described for open-close and working-side condylar movements in the same group of subjects., Methods: The movements of 5 clinically determined condylar points were recorded in 44 subjects during a contralateral excursion and during protrusion (7 radiographically determined condylar points in 2 subjects)., Results: During any single jaw movement, the trajectory of each condylar point was similar in form and dimension to the other condylar points within that subject., Conclusion: Changes in condylar point location had little effect on the trajectories of condylar points on the nonworking side and during protrusive jaw movement.

Objective: Functional heterogeneity, i.e. regional or selective activation of subpopulations of fibres within a muscle, has been described in some jaw and limb muscles. Each head of the lateral pterygoid muscle may also be functionally heterogeneous. The aims of this investigation were to develop a technique to test this hypothesis, and to use this technique to determine whether there is any multi-unit electromyographic (EMG) evidence for functional heterogeneity within the inferior head of the lateral pterygoid (IHLP)., Methods: In 3 human subjects without craniomandibular disorders, recordings were made of condylar movement and multi-unit EMG activity from two sites in the IHLP during repeated trials of a contralateral (n = 21) and a protrusive (n = 26) jaw movement. The recording sites within IHLP were approached extraorally (labelled IHLP-extra) and were verified by computer tomography (CT); the other (IHLP-intra) were from sites in IHLP approached intraorally., Results: In each subject, the time of occurrence of the peak filtered signal from IHLP-extra was significantly different (P<0.05) from IHLP-intra for all protrusion trials but not for contralateral trials., Conclusions: The data suggest a task-dependent change in motor unit recruitment order within IHLP and that IHLP is functionally heterogeneous.

Statement of Problem: Trajectories of different condylar points provide different interpretations of condylar movement during open-close jaw movements. Movement of the working-side condyle is often assessed clinically by recording the trajectory of a single arbitrary condylar point., Purpose: This study examined the effect of the differences in condylar point location on condylar point movement trajectories during a working-side movement., Methods: Different points exhibited different trajectories during a single working-side movement in each of 44 subjects., Results: Up to 40% of a point's displacement could be attributed simply to the location of the point., Conclusions: Interpretation of condylar movement on the working side within a subject depends on the point chosen.

Previous studies have shown the ability for bone to grow under occlusive membranes. This study was undertaken to determine the time required for bone to form in the space created under the membrane and to determine the amount of bone that may be grown under the membrane. Thirty-two New Zealand white rabbits were divided into three groups. A Brånemark implant, having a diameter of 3.75 mm with a length of 7 mm, was placed in each tibia and Gore-Tex membrane was draped over the implant on the experimental side and tethered to the wound margin. Sixteen rabbits were sacrificed at six weeks, eight at twelve weeks, and eight at eighteen weeks. At six weeks the available space under the membrane was filled to 68 per cent, at twelve weeks it was 45 per cent, and at eighteen weeks 54 per cent. A comparison of bone height measurements on test and control sides showed a significant difference (p = 0.0001) at the three time intervals. A comparison of grown bone volumes (test vs control) was also statistically significant (p = 0.0001). The ability to grow bone under an occlusive membrane was confirmed but the long-term survival rate and ability to support load needs to be investigated.

Statement of Problem: Clinical assessments of condylar movement often rely on the movement of a single clinically determined or average value condylar point., Purpose: The aim of this investigation was to study the effect of differences in condylar point location on recorded movement trajectories with an open-close jaw movement., Methods: Recordings were made of the movements of various condylar points in 44 subjects. The points were identified clinically (average value points) and radiographically., Results: The trajectory of each condylar point, whether average value or radiographically determined, was different in form and dimension from any other condylar point within a subject for the same open-close jaw movement., Conclusions: Depending on the point chosen in the vicinity of the condyle, quite different interpretations of condylar movement within a subject could be made. The data underscore the caution that must be exercised when interpreting condylar movement from the movement of a single condylar point.

A visual analog pain scale and scalar responses to 13 pain/symptom indicator Symptom Checklist-90-Revised (SCL-90-R) questions were used to assess symptom prevalence and pain severity in 43 chronic orofacial muscle pain patients and 40 control subjects. The orofacial muscle pain group reported pain in an axial skeletal distribution; neurocognitive, gastrogenitourinary, and musculoskeletal symptoms; infectious events at or preceding onset; similar symptoms in sexual partners; and low prevalence of trauma. Sudden onset was reported by 30.2% of pain patients. Strong associations were found between chronic orofacial muscle pain and (1) onset-related infectious-like events (67.4%); (2) a higher prevalence of history of respiratory and gastrogenitourinary infectious events; and (3) high prevalences of similar pain symptoms in long-term sexual partners. The SCL-90-R somatization scores (> 62) had a higher prevalence in the chronic pain group. No prevalence differences or associations with pain/symptom indicators were found for depression or anxiety dimension scores. These data suggest that patients with recurrent systemic infectious events have a higher prevalence of reporting of chronic orofacial muscle pain compared with control subjects, and these infectious events are associated with the onset of chronic orofacial muscle pain in 67% of patients.

Chronic fatigue syndrome (CFS) patients have a urinary metabolite labeled CFSUM1 with increased incidence (P < 0.004) and relative abundance (P < 0.00003). The relative abundances of urinary CFSUM1 and beta-alanine were associated with alterations in metabolite excretion and symptom incidence. In 20 CFS patients and 45 non-CFS subjects, symptom/metabolite associations were investigated by assessing symptom sensitivity and specificity, and symptom indices of total symptom incidence, CFS core symptoms, cognitive, neurological, musculoskeletal, gastrointestinal, infection-related and genitourinary symptom indices, as well as a visual analogue pain scale of average pain intensity. Thirty-three symptoms had significant (P < 0.005) sensitivity and specificity in the CFS patients compared to that in the non-CFS controls. Severe fatigue was the only symptom with 100% sensitivity and specificity and CFSUM1 excretion was the primary metabolite for expression of this symptom. All nine symptom indices had elevated responses in the CFS patients (all P < 0.0000001). Multiple regression analyses indicated that all the symptom indices had significant correlations (R) with changes in the urinary excretion of metabolites (P < 0.0001). CFSUM1 and beta-alanine were the first and second metabolites correlated with the CFS core symptom index and CFSUM1 was primarily associated with infection-related and musculoskeletal indices whereas beta-alanine was primarily associated with gastrointestinal and genitourinary indices. The strong associations of CFSUM1 and beta-alanine with CFS symptom expression provide a molecular basis for developing an objective test for CFS.

Chronic fatigue syndrome (CFS/ME) is a debilitating fatigue illness that has an unknown etiology. We studied 20 chronic fatigue syndrome (CFS) patients, who complied with the Oxford and American CDC definitions, and 45 non-CFS subjects. Participants completed questionnaires, were clinically examined, and had first morning urine specimens collected, which were screened by gas chromatography-mass spectrometry for changes in metabolite excretion. Multivariate analysis of the urinary metabolite profiles differed significantly in the CFS patients compared to the non-CFS patients (P < 0.004). The CFS patients had increases in aminohydroxy-N-methylpyrrolidine (P < 0.00003, referred to as chronic fatigue symptom urinary marker 1, or CFSUM1), tyrosine (P < 0.02), beta-alanine (P < 0.02), aconitic acid (P < 0.05), and succinic acid (P < 0.05) and reductions in an unidentified urinary metabolite, CFSUM2 (P < 0.0007), alanine (P < 0.005), and glutamic acid (P < 0.02). CFSUM1, beta-alanine, and CFSUM2 were found by discriminant function analysis to be the first, second, and third most important metabolites, respectively for discriminating between CFS and non-CFS subjects. The abundances of CFSUM1 and beta-alanine were positively correlated with symptom incidence (P < 0.01 and P < 0.001, respectively), symptom severity, core CFS symptoms, and SCL-90-R somatization (P < 0.00001), suggesting a molecular basis for CFS.

Comprehensive evaluation of mandibular function requires a broader assessment of the head, neck, and jaws than is normally performed. Examining only the teeth and periodontium will fail to assess problems in muscles and joints, which should be considered in the management plan. Recognition of function-related symptoms is important in the prediction of treatment outcomes. Stress-induced muscle tension and traumatic oral habits may be linked with reported symptoms of headache, earache, and temporomandibular joint problems, and the significance of these symptoms should be assessed through detailed clinical examination.

Whereas other radiographs may be adequate for assessment of mandibular anterior implant sites, the use of computerised tomography is recommended for evaluating potential implant sites in the maxillae. A complete denture replica with appropriate radiopaque markers aids in the assessment. Hounsfield densitometric measurements provide additional information on the quality of available bone.

A craniocervical dysfunction index has been developed (based on the Helkimo Dysfunction Index) to comprehensively assess craniocervical dysfunction and to objectively monitor the management of patients who present with these clinical problems. The close functional interrelationship of temporomandibular joints, jaw muscles, and cervical joints and muscles is reviewed, and a mechanism is proposed to explain dysfunctional relationships between these structures. This is the first of three papers stemming from a clinical study that investigated craniomandibular disorders and assessed the effect of routine dental management on craniomandibular and craniocervical dysfunction.

Temporomandibular joint clicking is frequently a sign of craniomandibular disorders, and the etiologic predisposing, initiating, and perpetuating factors must be considered in its management. The present study assesses the usefulness of isokinetic exercises in the treatment of temporomandibular joint clicking. At the end of a 6-month test period, 18 of 22 subjects (approximately 82%) with clicks no longer had clicking, but four subjects (approximately 18%) with bilateral reciprocal clicking did not lose their clicks. A number of proposals have been suggested in the past as an explanation of the cause of temporomandibular joint clicking, but the present study has shown that clicking in young adults is predominantly neuromuscular in origin and may be a reversible condition that can be treated successfully with a conservative exercise regimen.

A device for imparting reproducible chin taps was employed to evoke monosynaptic jaw-closing reflexes in subjects without (group A) and with (group B) overt muscle-joint pain dysfunction. Latency, duration and amplitude values obtained were consistent within an individual at constant tap force at a single-recording session but varied among subjects. Latency differences between sides were greater in subjects exhibiting mild to moderate dysfunction (group B) than in group A, but there were not corresponding differences in duration and amplitude. Stimuli were delivered in 5 subjects whilst the jaw was firmly held at postural jaw position with the aid of acrylic resin indices secured with adhesive to the maxillary and mandibular teeth. Recordable reflex responses were evoked in the masseter muscles of one subject only, indicating that vibration alone was not an adequate stimulus consistently to evoke a jaw-closing reflex at postural jaw position. Spindle stretch is needed, unless postural motoneurone excitability is at a sufficiently high level. Reproducible jaw-closing reflexes were evoked following standardized stimuli; subtle variations in motoneurone excitability, such as reflected by differences in jaw-jerk latency between sides, may then become apparent.

Latency-inhibition behavior was always produced in contracting anterior temporal muscles following the application of various stimuli to the teeth and jaws of 31 subjects. Statistically significant differences in duration were generally observed with different procedures. In half of the subjects, the first one or two closures in a sequence of repetitive tapping evoked a longer period of inhibition than subsequent closures. No reflex or latency-inhibition behavior could be produced in contracting digastric muscles. Comparisons of means for individual subjects did not follow the pattern suggested by comparisons of total sample means in almost half of the subjects.