Prevalence of oromandibular dysfunction in a general population.

The prevalence of oromandibular dysfunction was studied in 735 subjects from a random sample population of 1,000 subjects aged 25 to 64 years. A diagnosis of oromandibular dysfunction was based on criteria established by the International Headache Society, as a subgroup to tension-type headache. Tenderness in pericranial or jaw muscles was not included. The most common symptoms were clenching (22%) and grinding of teeth (15%). The most common sign was irregular jaw movements on opening and closing (29%). The ratio of men to women for most symptoms and signs ranged from 2:3 to 1:3. This study serves as a base in evaluating the importance of oromandibular dysfunction as a causative factor for tension-type headache.

[Occurrence of muscle contraction headache in children with abnormal incisor occlusion]. / Forekomst af muskel-spaendingshovedpine hos born med afvigende fortandsokklusion.

The principal result of the investigation indicates that children with abnormal incisor occlusion must be regarded as a risk group concerning muscle contraction headache (MCH). The need for orthodontic treatment of children with abnormal incisor occlusion is usually by layman regarded as being based upon psychosocial considerations. These considerations shall not be underestimated. For children as well as for grown up persons an appearance dominated by a visible abnormal incisor occlusion will be loading in contact with other people. From a professional point of view need for orthodontic treatment of children with abnormal incisor occlusion has usually been defined from the demand for stability. Grown up people with abnormal incisor relations are frequently referred to orthodontic specialists because of problems, such as migration of the incisors, extreme attrition or functional disturbances in the masticatory system. These problems are closely related to the abnormal incisor occlusion. With our present knowledge of the importance of the incisor relation for the function of the masticatory system, this condition must have high priority in the evaluation of need for orthodontic treatment of children. The treatment will, by improving the functional condition of the masticatory system and normalizing the function, have importance as prophylaxis and/or early treatment of a risk group concerning muscle contraction headache.

Response of elevator activity during mastication to treatment of functional disorders.

The pattern of elevator activity during mastication in temporal and masseter muscles of 37 patients with functional disorders and pain in the masticatory system was studied before and after conventional treatment and compared with a control group of 43 subjects. As compared to controls, patients before treatment chewed with greater relative strength (percent of maximal elevator activity), longer relative contraction times (percent of total duration of chewing cycle) and stronger intermediary activity between strokes. These parameters of muscle coordination are proposed as quantitative estimates of "hyperactivity". Conventional treatment abolished pain, tenderness and other symptoms and signs completely in 18 patients in whom the most significant findings in the muscles under study were reductions in absolute and relative contraction times ascribed to increased stability produced by occlusal adjustment. It is suggested that relatively shorter pauses before treatment impaired blood flow and that their prolongation following treatment improved circulation. During the strong, dynamic contractions of mastication, masseter muscles tended to be more susceptible to hyperactivity than the temporal muscles.

Postural and maximal activity in elevators of mandible before and after treatment of functional disorders.

In a longitudinal study we compared clinical data on pain and tenderness and electromyographic recordings of postural and maximal activity from 37 patients before and after treatment of functional disorders of the masticatory system. Forty-three dental students served as controls. Treatment was followed by a concomitant decrease of pain, tenderness and postural activity. Muscle strength in terms of the activity during maximal bite in the intercuspal position was not altered by treatment, but activation of the right and left anterior temporal muscles became more uniform. The relative postural loading of the elevators was assessed as their activity in percent of full effort. Following treatment, loading in patients decreased significantly and became more symmetrical in the anterior temporal muscles. Loading also tended to decrease in the posterior temporal and masseter muscles. However, it still significantly exceeded postural activity in percent of full effort in the controls. Since treatment involved correction of the occlusion we conclude that the intermaxillary conditions of tooth contact during function play a role in the etiology of functional disorders and that the reduction of the relative postural loading of the elevators of the patients due to this treatment contributed to their relief. The relatively high percentage of full effort displayed as postural activity by the patients even after treatment may explain fluctuation of symptoms and signs of functional disorders of the masticatory system. It also emphasizes the need for improved methods of treatment to reduce the probability of recurrence.

Pain, tenderness and strength of human mandibular elevators.

In terms of the mean voltage during maximal bite in the intercuspal position we compared the strength of the temporal and masseter muscles of 39 patients with functional disorders of the chewing apparatus and 45 controls. Maximal electrical activity was significantly stronger in the controls than in the patients. Differences between the two samples with respect to sex, age, number of opposing teeth in contact and the presence of pain and tenderness tended to favor stronger activity in the controls. However, the different levels of electrical activity, especially in the case of the masseter muscles, could only be accounted for on the basis of a difference in maximal strength. We suggest that the weaker elevator muscles of the patients was a predisposing factor making these muscles less fit to endure hyperactivity induced psychologically or as a reflex response to occlusal interferences and functional disorders of the temporomandibular joints or other elements of the oral neuromuscular system. The sample of controls had much stronger elevators, less susceptible to such hyperactivity.

The need-demand problem in patients with oro-mandibular functional disorders.

General conditions and facts concerning need-demand will be discussed and applied to oro-mandibular functional disorders. The balance between demand for treatment and offer of treatment will be considered and with this the importance of prevention, attention to the risk groups and early treatment will be shown.