Regional cerebral blood flow during experimental phobic fear

Positron emission tomographic measurements of regional cerebral blood flow (rCBF) were used to investigate central nervous system correlates of fear and anxiety. Volunteers with symptomatic snake phobia were studied while exposed to visual phobogenic, aversive, and neutral stimuli. Anxiety ratings and the number of nonspecific electrodermal fluctuations increased as a function of phobic stimulation. Phobic, compared to neutral and aversive, stimulation elevated rCBF in the visual associative cortex. The basal ganglia were not activated more by phobic than aversive or neutral stimulation. However, cortical and thalamic rCBF were always correlated during phobic but not aversive or neutral stimulation. This indicates that the thalamus could be a relay station for phobic stimulus processing and affect.     

Bite force and oral function in patients with osseointegrated oral implants

abstract – The function of the masticatory system was analyzed in 19 patients (13 women and 6 men), aged 39 to 68, randomly selected from a group of 165 patients who had been treated with osseointegrated oral implants within the last 7 years (average 3.5 years). The patients were well satisfied with the functional capacity of their implant reconstructions, especially compared with the poor function before treatment. According to the clinical examination, all but one patient had no or only mild symptoms of dysfunction of the masticatory system. Three bite-force levels were recorded. The mean value for gentle biting was 15.7 N, for biting as when chewing 50.1 N, and for maximal biting 144.4 N. The patients could thus well discriminate between the different bite-force levels, and the maximal values are much higher than those in persons with removable dentures.     

Comparative electromyographic study of bite plates and stabilization splints

Abstract – The object was to study any influence on the integrated clectromyographie activity in the masseter and temporal muscles of two types of occlusal appliances. Seventeen healthy subjects wore a bite plate with a frontal plateau and a full coverage stabilization splint at night, each for 1 wk. The EMG activity was recorded without appliances in situ, in the rest position, and during gentle and maximum biting before and after use of the different appliances. After use of the bite plate, the EMG activity was not significantly different at any tested level. After use of the splint, the activity in the rest position was significantly lower in the anterior and posterior parts of the temporal muscles. The EMG activity was significantly lower in the rest position in both parts of the temporal muscle after use of the splint than after use of the bite place. In a control group of eight subjects in whom no appliances were used, the EMG activity did not change significantly between the initial and 1- or 5-wk recordings. Thus, the occlusal design of the appliances seems to be of importance for the influence on the EMG activity in the masticatory muscles, at least in healthy subjects.     

Relationship between myoelectric activity in masticatory muscles and bite force

Myoelectric activity in the anterior and posterior temporalis and in the masseter muscle was assessed in five subjects biting unilaterally on a bite fork at 50, 100 and 200 N for 60 s. The bite fork was placed between the right first premolars and the first molars. The ipsilateral muscle activity was recorded first, and the contralateral side was evaluated 1 wk later. The relationship between exerted force and EMG-activity was expressed as ratios between EMG-activity and related bite force. EMG-activity increased with increasing force for all muscles tested. Linearity was found for the anterior temporal muscle, but not for the other muscles. Four of the subjects participated in an endurance test, exerting maximum bite force on the right side for as long as possible. The EMG activity of the right masseter muscle was closely related to bite force, in contrast to the other tested muscles. The activity of the left muscles increased at the end of the endurance test.     

Functional evaluation after TMJ surgery

summary Oral function was evaluated in 30 patients (25 women and five men) after TMJ surgery by means of bite force measurements. Twenty-seven discectomies and three condylectomies had been performed. The follow-up period was, on average, 2.5 years. The mean bite force values on the function level 'biting as when chewing' was for the whole group 125.3 N on the right side and 128.8 N on the left side. The maximal bite force was on average 362.5 N and maximal endurance time on average 32 s. All test results showed big ranges. No significant differences between right and left side or operated and non-operated side could be found on the tested function level 'biting as when chewing'. The found bite force values were high in comparison with another similar study. The results were also compared with another group of patients ( n = 6) who were examined before and 6 months after surgery. As far as bite force reflects oral function the results are indeed very encouraging.     

Endurance tests of the masticatory system on different bite force levels

Abstract — Endurance tests of the masticatory system were performed in three different groups of healthy volunteers in order to investigate the relation between bite force and endurance time on different force levels. The subjects clenched a bite fork until exhaustion. Some tests were performed with and others without visual feedback of the exerted force. It was found that the subjects could sustain the maximal bite force practically at the same level during the recording time with visual feedback. The exerted force varied during the non-feedback recordings and generally decreased on the forceful levels. The average endurance time increased at lower bite force levels and the relation between force and endurance time is described. The average integrated time-force areas did not differ between the test levels. It is concluded that endurance tests, in the clinic may be performed on submaxirnal bite force levels.     

The Elicitation of Viscero-motor Reflexes.

The elicitation of viscero-motor reflex especially from the small intestine has been studied on the cat under light barbituric anesthesia or after decapitation. On animals with good reflex irritability, the reflex can be elicited from the intestinal wall by mechanical, electrical, chemical and thermal stimuli without the involvement of the mesentery or of its connection with the intestine. The effect of a stimulation of the intestinal wall is stronger the nearer the stimulus is placed to the mesenterial connection. This is explained by the fact that the densityof the nerve fibres must be greater here. A cutano-motor reflex is much stronger than a viscero-motor reflex elicited by the same stimulus on an equal area of skin resp. intestinal wall. No basis has appeared for the assumption that the intestinal wall should be supplied with pain nerve end-organs, especially adapted for stretching or pulling, or which in any way should differ from the pain nerve end-organs in the somatic innervated tissues. The principle difference between the visceral and somatic innervated organs probably is a quantitative, the density of riociceptive nerve fibres with end-organs.     

Normal variation in skin surface temperature over the temporomandibular joint and masseter muscle

Abstract – The range of the temperature at the skin surface overlying the temporomandibular joint (TMJ) and the origin of the superficial belly of the masseter muscle was investigated in 35 individuals with normal TM joints and 29 individuals with normal masseter muscles. The temperature was measured by a thermistor in contact with the skin. The temperature over the TMJ varied between 32.1°C and 35.5°C (average 34.3°C). The difference in temperature between right and left sides was to an average 0.3°C. The temperature over the masseter muscle ranged from 30.9°C to 35.7°C (average 33.2°C). The difference in temperature between right and left sides was an average 0.4°C. It was concluded that there is a fairly wide range of skin temperature over the normal TMJ and origin of the masseter muscle under the experimental conditions prevailing in this study but that the differences between right and left sides are fairly small. It therefore seems possible to use this thermometric method to assess inflammatory processes and/or changed metabolic activity in the TMJ and masticatory muscles.     

Turnover in humans of β2-microglobulin: the constant chain of HLA-antigens

The turnover of beta 2-microglobulin, the common subunit of the HLA antigens, has been examined in normal subjects and in some patients with kidney disorders, multiple myeloma and rheumatoid arthritis. All patients displayed elevated serum levels of beta 2-microglobulin. The plasma disappearance curve of 125I-beta 2-microglobulin demonstrated that the protein has a rapid turnover (t 1/2 = 2.1 h; range 1.1-2.8 h) in normal persons and in patients with a normal glomerular filtration rate. In patients with kidney disorders the impaired renal filtration prolonged the turnover time and led to elevated serum levels of beta 2-microglobulin. Simultaneous measurements of 125I-beta 2-microglobulin in serum and urine allowed estimations of the beta 2-microglobulin net reabsorption in the renal tubuli. Two patients with renal disease reabsorbed 84% and 89%, respectively, of the beta 2-microglobulin filtered in the glomeruli. In normal persons the net reabsorption is close to 100%. In patients with normal kidney function increased serum levels of beta 2-microglobulin seem to be due to an increased synthetic rate of the protein as the elimination rate is normal. HLA antigen heavy chains in serum are present in smaller amounts than beta 2-microglobulin. The present data, therefore, suggest an imbalanced synthesis of the two chains.     

Inhibitory actions from low and high threshold cutaneous afferents on groups II and III muscle afferent pathways in the spinal cat

The inhibitory effects caused by volleys in cutaneous afferents on the transmission through some polysynaptic segmental pathways activated by high threshold muscle afferents were studied in chloralose anesthetized, spinal cats. Pathways studied were groups II and III to motoneurones as well as group II to primary afferents. The results suggested that two different mechanisms were involved. One mechanism, with a very slow time course (duration more than 400 ms), is suggested to be an example of presynaptic inhibition between different primary afferent systems. This mechanism required high threshold (≥ 1.6T) conditioning shocks, and appeared simultaneously with the component II dorsal root potential being evoked by the cutaneous afferent volley. The other mechanism, with a faster time course (duration always below 300 ms), was dependent upon low threshold (≥ 1.5T) cutaneous conditioning volleys. This inhibitory interaction could not be ascribed to the same presynaptic mechanism, but is suggested to be an example of postsynaptic inhibition at an interneuronal level. The presumed disynaptic excitatory pathway from group II muscle afferents to flexor motoneurones was not inhibited by cutaneous conditioning shocks, but could on the contrary be facilitated by activity in low threshold cutaneous afferents, probably at the only intemeurone involved in this group II pathway.