Biomedical subjects
Publications and source records attributed to B Ingervall.
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The effect of treatment with an oral screen was studied in sixteen children with incompetent lips who were compared with a control group of sixteen children who also had incompetent lips. The period of observation was 1 year. The treatment brought about retroclination of proclined maxillary incisors with a resulting decrease in overjet, in the diastema between the incisors, and in arch length. The mandibular incisors proclined somewhat. No change in general intermaxillary relation or in arch width was observed with the treatment. Neither lip morphology nor the electromyographically recorded function of the lips was affected by the treatment. The maximum force that the lips could exert to resist an external force was increased substantially by the treatment. Whether this is of value for the stability of the orthodontic treatment result is not known.
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The influence of dental status, occlusal interference, occlusal anomalies, and general background variables on bruxism and subjective symptoms and clinical signs of mandibular dysfunction has been studied in children. Three samples of children, aged 7, 11, and 15 years, were included. The interrelations were analyzed by rank-correlation and stepwise multiple regression. In the rank-correlation analyses, dental wear and age were significantly correlated to all of the dysfunction variables. Bruxism (reported by the subjects) was not found to be significantly correlated to any of the independent variables in the regression analysis. Subjective symptoms of dysfunction could be explained to a small extent by the independent variables, of which dental wear and sucking habits were found to be the most important. Recurrent headache was, to a certain extent, dependent upon age and sex. TMJ clicking was positively correlated with dental wear and unilateral contact in the retruded contact position but was most influenced by age and sex; TMJ clicking increased with age and was more common in girls than in boys. The clinical dysfunction index of Helkimo and tenderness of the masticatory muscles on palpation were explainable, although to a minor degree, by the influence of a combination of age, occlusal interference, motor activity, and psychological factors. Functional malocclusion (occlusal interference) is more important than morphologic malocclusion in explaining the existence of mandibular dysfunction. Nevertheless, morphologic malocclusion such as Class II and Class III occlusion, frontal open-bite, and cross-bite, when associated with functional malocclusion, may create a predisposition to mandibular dysfunction. The study confirms the multifactorial etiology of mandibular dysfunction.
The effect of lip training was studied in 15 children with incompetent lips, who were compared with a control group of 10 children who also had incompetent lips. Lip function was evaluated by electromyography of the activity of the lips in resting posture and during swallowing and chewing. The morphology of the dentition, facial skeleton and lips were studied on dental casts and profile radiographs. Lip training was performed for one year and was found to maintain lip function in the test group, in contrast to impairment of lip function in the control group. Lip training favorably influenced lip morphology, increasing the height of both lips and decreasing the interlabial gap. In the control group, the interlabial gap increased. The beneficial effect of the training on the function and morphology of the lips could not be shown to affect tooth position during the one-year study period.
The associations between different types of occlusal interference and of occlusal anomalies were studied in children 7, 11 and 15 years of age. Incisor and buccal crossbite and post-normal occlusions were positively related to large antero-posterior distance or lateral deviation between the retruded and intercuspal mandibular positions, and to nonworking side interference. There was a positive correlation between frontal open bite and nonworking side interference, while large overbite was negatively correlated. The correlations found were numerically small, indicating that other factors apart from those studies must be significantly involved in such occlusal interferences.
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The activity of the masseter and anterior and posterior temporal muscles was studied by electromyography (EMG) in the thirteen subjects with unilateral balancing side interferences and in twelve control subjects without such interferences. In both groups the EMG recordings were made during postural activity and various functions of the masticatory system and in the interference group they were repeated on two occasions following occlusal adjustment. The postural muscle activity was significantly lower in the interference than in the control group while there was no difference during maximal bite. The number of chewing cycles was somewhat longer in the interference than in the control group. During swallowing of water the maximal mean voltage amplitude was smaller in the interference than in the control group. The findings are discussed in relation to previous results and the conflicting ideas concerning occlusal factors in the aetiology of mandibular dysfunction.
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The strength of the lips was measured with a dynamometer in fifty children, aged 7 to 13 years, with varying types of malocclusion. The lip strength was related to the electromyographically recorded activity of the lips during the lip strength measurements and to bite and facial morphology. The morphology was recorded on dental casts and profile radiographs. The lip strength measurements were found, in duplicate determinations, to have limited reproducibility. There was no correlation between lip strength and the EMG activity of the lips during the recordings. Lip strength was not correlated to dentoalveolar cephalometric variables, including relationship and inclination of the incisors. Nor was there any correlation between lip strength and lip morphology. The value of lip strength measurements seems to be limited, due either to difficulties in recording lip strength or to a small influence of lip muscle forces on the dentition.
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The activity of the anterior and posterior portions of the temporal muscle, of the masseter muscle, and of the upper and lower lips was studied with electromyography in 10 individuals with complete dentures. Recordings were made when the patients had old, ill-fitting dentures and 6 months after these were replaced with new dentures. The muscle activity was studied in the postural position of the mandible, during chewing and swallowing of three test foods, and during maximal biting. The maximal tooth tapping rate was also recorded. The postural muscle activity was the same with old and new dentures and comparable with that in patients with natural teeth. The muscle activity during maximal biting was markedly lower than in patients with natural teeth and lower with new than with old dentures. There was no difference in muscle activity between chewing with old and new dentures, but the activity was lower than in patients with natural teeth. This was not compensated for by a longer duration of chewing. The lips were not especially active during chewing in the complete denture wearers.
The activity of the temporal and masseter muscles and of the upper lip was examined by electromyography in five adults and in five children who had sustained uni- and bilateral fractures of the mandibular condyle. Electromyographic recordings were done in the postural position of the mandible, during maximal bite in the intercuspal and retruded mandibular positions, during chewing and swallowing of peanuts and during swallowing of water. In the children, who were examined on three occasions after the trauma, a reduced muscle activity was found shortly after the trauma, but it had normalized at follow-up examination 1 year after the injury. The adults, who were examined 4-6 years after the trauma, had, in general, normal muscle function. In subjects with a unilateral fracture, no difference in muscle activity was found between the two sides. An enlarged distance between the retruded and intercuspal positions of the mandible did not, in these subjects, seem to influence the muscle activity during the functions studied.