Clinical study of location and reproducibility of three mandibular positions in relation to body posture and muscle function.
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Central Nervous System↗
Biomedical subjects
G Hellsing
Publications and source records attributed to G Hellsing.
Effects of fixed anterior biteplane therapy--a radiographic study.
Orthodontic treatment of eight overbite cases with a maxillary fixed lingual arch appliance with anterior biteplane involved a reduction in overbite of 4 to 7 mm between the upper and the lower front teeth and a first molar separation of 2 to 4 mm. After a treatment period of 3.5 to 5 months, occlusal contact between the upper and the lower molars was established. The appliance was then removed, and permanent overbite reduction was secured with an edgewise appliance. With the subtraction technique, 15 temporomandibular joints were radiographically investigated in the retruded position for change of condylar position on the glenoid fossa before and directly after insertion of the appliance, as well as after achieved molar contact. All condyles changed position directly after the bite opening, indicating that pure rotation did not occur. The direction of movement varied not only between subjects but also between the two condyles of each subject. With one exception, none or very small further positional changes occurred during treatment. No imaged signs of hard structure remodeling were observed. It may be concluded that other factors than change of condylar position must be responsible for the therapeutic effect of the bite-opening appliance that has been demonstrated in an earlier study.
Adolescent↗
The hinge axis concept: a radiographic study of its relevance.
The "hinge axis concept" maintains that the mandible moves around a transverse horizontal axis through both condyles. Since it was introduced in the 1920s it has had a profound impact on clinical dental practices all over the world. By use of the radiographic subtraction technique, we demonstrated that an increase in the occlusal vertical dimension of 4 to 7 mm in the retruded position resulted in a small positional change (range 0.31 to 1.84 mm) in an unpredictable direction. Pure rotation did not occur; however, the condylar displacement is probably of minor clinical importance in prosthodontic restoration.
Adolescent↗
Increase of vertical dimension--consequences for the maxillomandibular relationship. A clinical approach.
The purpose of the present study was to compare the vertical change in the incisor and molar areas caused by insertion of a bite opening appliance and to analyse the occurrence of rotation and eruption during the following treatment period (mean 4.3 months). Eight patients between 15 and 24 years of age with vertical overlaps > or = 4 mm were treated by means of a maxillary fixed lingual arch appliance with an anterior bite plane. The retruded mandibular position was recorded with cold cure acrylic before treatment, immediately after insertion of the fixed appliance, and after removal of it. Vertical overlap and separation between the first molars was measured at each of these occasions. Finally, tooth movements during eruption were measured on the indices in the area of the second molar. The results showed that, independent of the amount of bite raise, the relation between frontal and molar area bite raise was approximately 2:1 for six and 5:3 for two patients. There was a significant difference in thickness of indices from registrations I and III in the second molar area indicating not only eruption during bite opening therapy but also buccolingual rotation.
Adolescent↗
Temporomandibular disorders: a pilot study of activation patterns and motor unit analysis of jaw muscles.
Ten patients exhibiting chronic signs and symptoms of temporomandibular dysfunction were investigated with electromyography (EMG) and compared with a group of healthy controls. A quantitative analysis of 20 individual motor units as well as single fibre recordings of the most symptomatic muscle was performed on five patients. One of these patients showed clear signs of myopathy in her right temporal muscle. Surface jaw muscle EMG of the other five patients showed co-contractions of agonists and synergists during jaw opening and closing movements. This may indicate disturbances in the integrated motor unit activity. The background of these findings may therefore be found in the function of the muscle fibre as well as in segmental and suprasegmental disturbances. Recent research has suggested a role of chemosensitive afferent endings in development of excitatory fusimotor reflexes.
Adult↗
Perception of cutaneous electrical stimulation in patients with craniomandibular disorders.
Perception thresholds for stimulation, discomfort, and pain were measured with electrical stimulation over the masseter area. Patients with chronic symptoms and signs of craniomandibular disorders reported significantly higher thresholds of all three variables compared with healthy controls. There were significantly negative correlations between the patients' pre-experimental discomfort and pain ratings on the Borg's scale and perception thresholds measured for discomfort and pain. The patients who presented the highest pain ratings in masticatory muscles and/or joints had the lowest threshold values when reporting discomfort and pain during gradually increased current intensity. This could be due to the cognitive effects of pain.
Adult↗
The temporomandibular joint: a comparison of clinical and arthroscopic findings.
Clinical signs and symptoms of temporomandibular joint arthropathy were evaluated by comparison of clinical findings with arthroscopic findings in 62 temporomandibular joints of 55 patients. The arthroscopic frequency of osteoarthritis was high and was often combined with a mild localized synovitis.
Adult↗
Occlusal adjustment and occlusal stability.
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Adolescent↗
Arthroscopy of the temporomandibular joint. A comparative study of arthroscopic and tomographic findings.
Established radiographic criteria of temporomandibular joint osteoarthrosis were evaluated by comparison of arthroscopic and tomographic findings in the superior compartment. 34 joints of 30 patients with long-standing chronic pain and/or functional impairment were investigated according to standardized techniques. Agreement was found between arthroscopy and corrected sagittal tomography regarding diagnosis of osteoarthrosis in all advanced cases. Diagnostic accuracy as regards slight changes was, however, lower. At tomographic examination, the sensitivity was slightly higher than specificity, i.e., pathological changes were more frequently identified than normality. No radiographic sign of osteoarthrosis could be specifically associated with arthroscopic features of osteoarthrosis or synovitis. Predominant location of osteoarthrosis at both arthroscopy and tomography was the posterior slope of the eminence (latero-central part). Osteoarthrosis was more widespread in the fibrocartilage than in the subchondral bone.
Adult↗
Arthroscopy of the temporomandibular joint: occurrence and location of osteoarthrosis and synovitis in a patient material.
The superior compartments of 42 temporomandibular joints of 38 patients with longstanding chronic pain and/or functional impairment were examined arthroscopically. Occurrence and location of osteoarthrosis and synovitis were investigated. Osteoarthrosis occurred in 31 joints (74%). In 17 of them more extensive changes were found. Predominant location of osteoarthrosis was the posterior slope of the eminence. The disk was less frequently affected and most commonly in the latero-central part. Synovitis occurred in 22 joints (52%) and was combined with osteoarthrosis in 17 of them. In 20 of them it was of mild and localised nature. The posterior disk attachment was affected in all of them.
Adult↗
[Disorders of the temporomandibular joint--a diagnostic challenge].
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Humans↗
Human jaw muscle motor behaviour. II. Reflex and receptor mechanisms.
The stretch reflex is much more complicated than the simple tendon jerk with a monosynaptic reflex pathway. Muscle stretch is not a necessary prerequisite to elicit the short latency EMG excitatory response. Long latency EMG responses are probably of greater functional importance. The silent period (SP) following the jaw jerk is prolonged in patients with symptoms of mandibular dysfunction. In the individual case, however, measurement of the SP may not be of diagnostic value. The Golgi tendon organs are highly sensitive tension receptors which play a much larger role in the proprioceptive regulation of muscle tension than has been believed in the past. So-called type P mechanoreceptors which like a large part of the periodontal receptors have their cells of origin in the mesencephalic nucleus V, have been found in the hard palate. The majority of periodontal mechanoreceptors are slowly adapting and thus able to respond with sustained discharge to long lasting stimulation, as during chenching or bruxing. The postural position has been assigned great clinical significance. It has been assumed that this position is constant throughout life. It has, however, been observed that the postural position rapidly adapts to changes of the vertical occlusal dimension.
Electromyography↗
Ability of edentulous human beings to adapt to changes in vertical dimension.
The ability of ten edentulous patients and one patient with a full upper removable denture and a full arch (16-26) lower fixed denture to adapt to sudden change of the interocclusal distance was tested. An upper acrylic bite splint was inserted which, on average, increased the vertical dimension of the face by approximately twice the mean interocclusal distance during relaxation. After this procedure all patients quickly acquired an unstrained new postural position of the mandible. Directly after insertion, when instructed to relax, all patients hit the lower surface of the splint. They seemed, however, to need only one such experience to adapt to the increased interocclusal distance. The second time they repeated the procedure none of them touched the splint. Instead a new postural position was established with a mean interocclusal distance of 3.3 mm. This fast re-programming of jaw muscle tonus and length is assumed to be a response to different peripheral receptor discharge converging to the cerebellum and other programming centres. The present study on edentulous patients shows that afferent discharge from periodontal receptors is not a necessary prerequisite. It also confirms that the old concept of consistency of the mandibular postural position (Thompson, 1946) is erroneous.
Adaptation, Physiological↗
Human jaw muscle motor behaviour. I. Motor drive.
Jaw muscle motor behaviour, however complicated, has important implications for the every day dental practice. In recent years the understanding of jaw and other skeletal muscle function has increased considerably. Direct recording of primary afferent discharge in conscious human beings and animals during normal function has caused radical changes of the concepts of muscle receptor function. Central pattern generators at segmental levels and suprasegmental programming centres are important mechanisms behind voluntary and automatic movements of different kinds. The most important proprioceptive function is probably to provide reassurance of correct movement pattern, to adjust the central programming to environmental changes and to directly influence slow movements requiring precision. Muscle spindle receptors contribute to mandibular kinesthesia. Muscle spindles are rarely present in jaw opening muscles. Despite this fact an excitatory reflex similar to the stretch reflex but with longer latency has been demonstrated. Further on a reciprocal organisation with antagonist inhibition has been shown to exist between jaw openers and closers. Motor behaviour of jaw and limb muscles thus seem to have many characteristics in common.
Humans↗
Arthrotic changes and deviation in form of the temporomandibular joint--an autopsy study.
An autopsy study was performed on 84 left human temporomandibular joints. Frequency and location of osteoarthrosis and deviation in form were registered in each joint component. Locations of disc perforations were registered with special emphasis on involvement of the bilaminar zone. The anatomical relationship between the deep masseter muscle and the TMJ capsule was investigated in part of the material. Deviation in form was most frequent in condyles (53%) compared with temporal components (40%) and discs (15%). The relative frequencies of the three joint components were opposite for osteoarthrosis; discs (32%), temporal components (26%) and condyles (21%). Higher frequency of arthrotic changes was found in edentulous specimens than in dentulous ones. Disc perforations were located within disc tissue except for one joint where it also included part of the bilaminar zone. No correlation between sex and arthrosis and/or deviation in form was found. Insertion of the posterior fibres of the deep masseter muscle into the anterior capsule was macroscopically observed in six of ten joints.
Adaptation, Physiological↗
Temporomandibular joint disorders: a diagnostic challenge.
During the past decade much interest has been focused on disorders of the TMJ. The etiology appears to be multifactorial, with signs and symptoms difficult to evaluate and radiologic investigations insufficient. This review attempted to analyze current diagnostic tools. The recent introduction of various techniques promises optimism for this diagnostic and therapeutic challenge.
Arthroscopy↗
Arthroscopy of the temporomandibular joint. A clinical study.
Temporomandibular joint (TMJ) arthroscopy on 30 joints of 26 patients with different signs and symptoms of TMJ arthropathy was evaluated. Local anaesthesia was used and proved efficient. In 27 cases, the superior, and in 3 cases both, compartments were punctured. Successful examination was performed in 26 superior and 3 attempted inferior compartments. Functional impairment following arthroscopy was minor and rarely lasted more than one week. No postoperative bleeding, nerve damage, or infection was observed. Of the 2 systems tested, the rod-lens arthroscope showed superior optical quality.
Anesthesia, Local↗
Arthroscopy of the rabbit temporomandibular joint.
Arthroscopy of the rabbit temporomandibular joint was evaluated experimentally on 22 rabbits. A small arthroscope with so-called "Selfoc"-system was employed. The reaction to arthroscopy was analyzed clinically. Macroscopic dissection and histology were then employed to detect possible pathological changes in the joints at periodic intervals. The established criteria for evaluation of postoperative reactions were erythema, suppuration, weight changes and chewing capacity. The results of this study indicate that the rabbit temporomandibular joint may be arthroscoped with subsequent minor reversible changes. It also seems feasible to assume that temporomandibular joint arthroscopy in humans runs a low risk for postoperative complications.
Animals↗