The initial effects of the treatment of Class II, division 1 malocclusions with the van Beek activator compared with the effects of the Herren activator and an activator-headgear combination

The effects of the van Beek activator in the correction of Class II, division 1 malocclusions were studied in 39 children, aged 9-13 years (median 11 years), and compared with the effects of treatment with an activator according to Herren and with those of an activator-headgear combination. Profile cephalograms were made before treatment and at the attainment of a Class I molar relationship (median observation time 9 months). The median improvement of the overjet was 4.7 mm and of the molar relationship 3.6 mm. This was largely achieved skeletally by an increase in mandibular prognathism while the skeletal effect on the maxilla was clinically insignificant. The maxillary incisors retroclined and the mandibular incisors proclined moderately. In general, no intrusion of the maxillary incisors was found and the eruption of the molars could not be stopped. The effects differed partly between the sexes, with a larger mandibular skeletal and molar reaction in boys, and a larger maxillary molar movement in girls. The larger mandibular reaction in the boys might have been due to the on average 4.5 months longer treatment time. The skeletal effects of the treatment were similar with all three activator types. The control of the incisors was, however, superior with the van Beek activator, especially when compared with the Herren activato

A pilot study of the effect of masticatory muscle training on facial growth in long-face children

Daily chewing of a tough chewing material consisting of resin from a pine tree (Mastix from the island of Chios, Greece) was instituted in 13 children (aged 7-12 years) with long-face morphology. The chewing exercise therapy was maintained for one year and aimed at revealing the possibility of strengthening the masticatory muscles and influencing facial growth. Masticatory muscle strength was monitored by measurement of bite force and electromyo-graphic recording of the activity of the anterior temporal and masseter muscles during biting and chewing. The facial morphology was recorded with profile cephalograms and dental casts. During the one-year experimental period, there was a significant increase in bite force and muscle activity during maximal bite. The change was already evident at the first control recording 3 months after the start of the chewing exercise therapy. The muscle activity during chewing of apple and peanuts did not change significantly. The facial growth was characterized by anterior mandibular rotation in 9 of 12 cases while a posterior rotation occurred in 2 cases. The anterior rotation was, on average, 2.5 degrees and thus considerably greater than would be expected during normal growth. There were no signs of reduced vertical growth of the maxilla, a reduced rate of molar eruption or increased growth of the mandibl

Effect of muscle exercise with an oral screen on lip function

The study aimed at evaluating how training of the lips with an oral screen affects the strength of the lips and the pressure of the lips on the teeth. In addition, the effect of the treatment with an oral screen on the dentition was studied. The treatment and lip training programme was instituted for 9 months in 16 children, 7-11 years old, with protruding maxillary incisors. The effect on the dentition was studied on dental casts made before and at the end of the treatment, and 5 months thereafter, as well as on lateral cephalograms. The lip strength was recorded with a dynamometer. The pressure from the lips on the upper and lower central incisors at rest, and during chewing and swallowing was measured with an extraoral pressure transducer incorporated in a water-filled system with an intra-oral measuring point. Measurements of lip strength and pressure were made regularly before and during the treatment; and continued for up to 10 months thereafter. The treatment resulted in a decrease of the overjet and upper dental arch length, but with some relapse after the treatment. The strength of the lips increased during the treatment, but decreased afterwards. The pressure from the lips on the teeth at rest and during swallowing was unaffected by the lip training. The pressure from the lower lip during chewing increased temporarily during the treatment perio

Function of masticatory muscles during the initial phase of activator treatment

The function of masticatory muscles and the development of the bite force were studied in 15 children before and during the first six months of the treatment of distal occlusion with an activator. Electromyographic recordings of the activity of the anterior and posterior portions of the temporal muscle, the masseter muscle and the anterior belly of the digastric muscle were made bilaterally in the rest position of the mandible and with the activator inserted. Recordings were also made during chewing and swallowing of apple and peanuts and during chewing of chewing gum as well as during maximal bite in the intercuspal position and on the activator. The mean voltage amplitude, the duration and the coordination of the activity were analysed. The maximum bite force was measured at the first molars and at the incisors. In most of the children, the clinical improvement was rapid as evident from a decrease in overjet and in the ANB angle as well as a change in the molar relation. The bite force measured at the incisors increased during the period of treatment. The muscle activity in the rest position was low and was the same with or without the activator. Thus, insertion of the activator did not increase the muscle activity. The activity of the posterior portion of the temporal muscle in the rest position was comparatively high at the start of treatment but decreased during the period of observation. The activity of the masseter and temporal muscles during maximal bite and chewing was influenced by the occlusal instability created during the course of treatment. The decrease of the postural activity of the posterior temporal muscle may reflect an adaptation to a new mandibular positio

The effect of treatment of skeletal open bite with two types of bite-blocks

The treatment of anterior skeletal open bite was studied in two groups of children. The children of one group wore a removable spring-loaded bite-block in the lower jaw for one year. The bite-block exerted an intrusive force on the upper and lower posterior teeth. The children of the other group were treated for 3 months with bite-blocks with repelling magnets. These bite-blocks were cemented on the posterior teeth of both jaws. The effects of treatment were monitored by measurement of the bite-force (group with spring bite-blocks only), by electromyographic recording of the activity of the temporal and masseter muscles, and by X-ray cephalometry. Recordings were made before, during, and at the end of the treatment, and at a follow-up observation. The bite-force increased during the first months of treatment, but was then unchanged. The activity of the masseter muscle during maximal bite also increased in the first part of the period of treatment with a spring bite-block. In the group treated with magnetic bite-blocks, there was an increase in the resting activity of the masseter muscle and in the chewing activity of the anterior temporal muscle. The effects of the treatment on bite and facial morphology were less marked in the group with spring bite-blocks than in the group with magnetic bite-blocks, with an average improvement of the overbite of 1.3 mm with the spring bite-block therapy. In the group with magnetic bite-blocks, the average improvement in overbite was 3 mm. This was thought to be due to anterior rotation of the mandible and increased eruption of the incisors. The mandibular rotation was a result of intrusion of the upper and lower posterior teeth and possibly also increased mandibular growth. A follow-up of the cases treated with magnetic bite-blocks revealed a tendency for the beneficial effects of the treatment to relapse which possibly could be counteracted by a long phase of active retentio

Function of masticatory muscles during the initial phase of activator treatment

The function of masticatory muscles and the development of the bite force were studied in 15 children before and during the first six months of the treatment of distal occlusion with an activator. Electromyographic recordings of the activity of the anterior and posterior portions of the temporal muscle, the masseter muscle and the anterior belly of the digastric muscle were made bilaterally in the rest position of the mandible and with the activator inserted. Recordings were also made during chewing and swallowing of apple and peanuts and during chewing of chewing gum as well as during maximal bite in the intercuspal position and on the activator. The mean voltage amplitude, the duration and the coordination of the activity were analysed. The maximum bite force was measured at the first molars and at the incisors. In most of the children, the clinical improvement was rapid as evident from a decrease in overjet and in the ANB angle as well as a change in the molar relation. The bite force measured at the incisors increased during the period of treatment. The muscle activity in the rest position was low and was the same with or without the activator. Thus, insertion of the activator did not increase the muscle activity. The activity of the posterior portion of the temporal muscle in the rest position was comparatively high at the start of treatment but decreased during the period of observation. The activity of the masseter and temporal muscles during maximal bite and chewing was influenced by the occlusal instability created during the course of treatment. The decrease of the postural activity of the posterior temporal muscle may reflect an adaptation to a new mandibular position

The effect of a lip bumper on lower dental arch dimensions and tooth positions

The effect of a lip bumper on the dimensions of the lower dental arch and on the inclination of the incisors and first molars was studied in 40 children, aged 9-12 years. The children wore their lip bumper full time for 7-10 months. The effects of the lip bumper therapy were recorded on dental casts and profile cephalograms made before and after the treatment. The positions and stages of development of the lower second molars were determined on pretreatment intra-oral radiographs. The lip bumper treatment resulted in an increase of the dental arch widths between the molars, premolars, and canines. The arch length increased through proclination of the incisors and uprighting of the first molars. The stages of development and the positions of the second molars had no influence on the effect of the treatment. Simultaneous treatment in the maxilla with a headgear, a transpalatal arch or a removable plate had no influence on the outcome of the lip bumper therap

Laboratory and intra-oral tests of the degradation of elastic chains

Two brands of elastic chain, Alastic (Unitek Co.) and Power Chain II (Ormco Co.), were tested for force development in laboratory and intra-oral experiments. During the laboratory test, the chains were extended to 180 and 215 per cent of their original passive length and the force exerted at this length was measured at the start and after 15 minutes, 2, 8 and 24 hours, 3 days and 1, 2, 3 and 4 weeks of continuous extension. The two brands behaved similarly. After 4 weeks, they had lost 25-30 per cent of their initial force. The decrease of the force value was greatest in the beginning of the test period, with a decline of 6-11 per cent during the first 15 minutes and 10-16 per cent during the first 2 hours. The intra-oral tests were performed in 10-25 subjects, who wore the elastic chains continuously for up to 4 weeks. The chains were extended up to 200 per cent of their original passive length. In one test, the force development was measured at the start and after 8 and 24 hours, 5 days and 1, 2, 3 and 4 weeks. In two other tests the force was measured after 1 day and 4 weeks, respectively. The two brands behaved similarly. The decline of the force value during intra-oral use was greater than in the laboratory tests. After 4 weeks, the force was only 43-52 per cent of the original value. The decline was greatest in the initial phase after insertion; after 8 hours the force had declined by 28-34 per cent. Thus, an initial force of 300g was reduced to 200g after 8 hours and to less than 150g after 4 weeks: in no specimen was the force after 4 weeks less than 100

Lack of correlation between mouth-breathing and bite force

The correlation between mouth-breathing and bite force was studied in 81 children, 7 to 16 years old. Mouth-breathing was diagnosed on the basis of the subject history, the rhinomanometrically determined nasal airflow and the size of the airway measured on the profile cephalogram. The maximum bite force was measured at the first molars. In addition, the facial morphology was analysed on profile cephalograms. Both mouth-breathing and bite force were associated with the facial morphology but there was no association between mouth-breathing and bite force. It was concluded that the longface morphology characteristic of mouth-breathing children is not due to weak masticatory muscle

Further studies of the pressure from the tongue on the teeth in young adults

The pressures from the tongue on the teeth were recorded simultaneously in four locations lingual to the upper and lower central incisors, and left first molars in 20 young adults with largely normal occlusion. Measurements in the rest position, and during chewing and swallowing were made with an extra-oral pressure transducer incorporated in a fluid-filled system with intra-oral mouthpieces. The size of the dental arches was determined from dental casts. The median pressures in the rest position were low and negative at the upper incisors. Negative pressures at rest were recorded in a few subjects at all four points of measurement, most frequently at the upper incisors and least frequently at the lower molar. The pressures during swallowing were 2-4 times greater than those during chewing. There were no significant correlations between the pressures found and those recorded in the same individuals at an examination 2 years earlier. Positive correlations were found between the pressures recorded in the four locations during the various functions. This was interpreted as being an effect of the size of the tongue. The relatively few correlations between the pressures and the parameters describing the dental arch size indicated an adaptive role of the tongue within the confines of the dental arche