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Six hundred microorganisms were isolated from sugar beets collected from different parts of Finland to study their slime production. A total of 170 of them produced exopolysaccharides, of which 35% were heteropolysaccharides. The yield of heteropolysaccharides from sucrose was lower than that of dextrans. Five isolates, which were chosen for closer study, were identified as Leuconostoc mesenteroides (two species), Rahnella aquatilis (two species), and Enterobacter amnigenus.

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The aim of the study was to examine the effect of an oral shield treatment on orofacial muscle activity and facial morphology in children with lip and/or tongue dysfunction. The sample consisted of 7 girls and 2 boys, 7 to 12 years old. EMG recordings with and without the shield in situ were obtained when the shield was placed, and 3, 6, and 12 months later. Lateral cephalograms were obtained at the initial and 1-year stages. The lip muscles showed dominant activity when the subjects were sucking on an empty straw and during swallowing; this was strongest during the first 3 months. The mentalis, buccinator, and digastric muscles generally showed weaker activity. The anterior temporal muscle showed dominant activity during maximal clench, but after the 3-month stage a significant decrease was noted. After 1 year of treatment, no significant changes in overjet or overbite were observed. Most of the craniofacial growth changes were normal for the age group. The results indicate that treatment with an oral shield caused a decrease in orofacial muscle activity during oral functions. Although there was a slight average retraction of the maxillary incisors, the change in position was not statistically significant.

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A longitudinal electromyographic study of the swallowing activity of the anterior temporal and masseter muscles was performed on 21 subjects with complete dentures. In six patients, the lip activity was recorded. At the pretreatment stage, when the patients had a residual anterior dentition, the peak mean voltages of the elevators showed low values (range 18 to 30 microV), and after denture placement, the anterior temporal muscles showed a further decrease. After denture relining, slight increases in temporal activity were noted at the 1-year stage. During the second year, when no corrections of the dentures were made, the temporal activity decreased below the pretreatment level. The masseter activity showed no significant changes during the 2-year observation period. The mandibular lip showed significantly stronger swallowing activity than the maxillary lip. The mean durations of the swallows were markedly longer than values reported for subjects with a complete natural dentition.

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In a sample of 30 partially edentulous subjects, provided with an immediate complete upper denture and a partial lower denture and followed for 2 years, a correlation analysis was performed between facial morphology, as measured by lateral head films, and EMG peak mean voltages of the anterior temporal and masseter muscles when clenched and during swallowing and chewing, and of the lip muscles during swallowing. At the pre-treatment stage, when the patients occluded on a residual anterior dentition, correlations between facial morphologic characteristics and peak mean voltages of the jaw closing muscles indicated stronger muscle activity in individuals with a square facial type. No significant associations were observed between muscle activity and the age of the subjects, which ranged from 36 to 71 years. After placement and use of the dentures a significant forward-upward rotation of the mandible with a decrease in overbite occurred, as a result of resorption of the edentulous maxillary ridge. At the 1 year stage of denture use, the elevator activity showed no significant correlations with facial morphology. On the other hand, negative correlations were observed especially between the anterior temporal activity and anterior overbite. Similar negative correlations were observed for the lip activity during swallowing, especially of the upper lip. These findings suggest occlusal contact between the incisors during the various functions in subjects with a small overbite. The findings further suggest that the anterior temporal and the upper lip muscles are sensitive to changes in anterior occlusal relations of the dentures.

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In growing subjects, obstruction of the upper airway may lead to excessive vertical facial development. According to the soft-tissue stretching hypothesis (Solow and Kreiborg, 1977) this could be due to an increased cranio-cervical angulation triggered by the airway obstruction. The present study aimed to examine the effect of airway obstruction on cranio-cervical posture in a sample of adult patients with severe obstructive sleep apnoea (OSA). Lateral cephalometric radiographs taken in the natural head position (mirror position) were obtained from 50 male patients aged 28-70 with polysomnographic diagnosis of obstructive sleep apnoea. The Apnoea Index ranged from 21 to 98 episodes per hour with a mean of 54.6. Control samples were available from previous cephalometric studies of head posture in five samples of healthy subjects and one sample of congenitally blind subjects. The average cranio-cervical angle, NSL/OPT, was found to be extremely large (mean 104.1, SD 9.1) exceeding the average values in the control samples by 1-2 standard deviations (P < 0.001). It is suggested that the large cranio-cervical angle in OSA patients is a physiological adaptation aiming to maintain airway adequacy while the head, and thus the visual axis, is kept in its natural relationship to the true vertical. The findings thus provide evidence for the hypothesis that upper airway obstruction may trigger an increase in the cranio-cervical angulation.

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A longitudinal electromyographic study of the anterior temporal and masseter activity during habitual chewing of apple was performed on 21 subjects provided with immediate complete dentures. At the pretreatment stage, when the patients having an anterior residual dentition were chewing, the peak mean voltages showed low values (range, 48 to 58 microV). After denture placement, there was a further decrease of the temporal activity that persisted to the 6-month stage. After the dentures were relined, a significant increase in chewing force of the temporal muscles was noted at the 1-year stage. During the second year, when no corrections of the dentures were made, the temporal activity decreased below the pretreatment level. The masseter muscle chewing activity generally showed no significant changes during the 2-year observation period. The mean durations of the chewing strokes and chewing cycles were longer than values reported in dentate samples and generally displayed no significant changes during the 2-year period.

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In 30 partially edentulous subjects provided with an immediate complete upper and a partial lower free-end denture the lip activity in swallowing was studied before and after denture treatment and during a 2-year period of denture wearing. Electromyographic recordings of the right side upper and lower orbicularis oris, mentalis and anterior temporal muscles were obtained during swallowing saliva and during swallowing of water with and without the dentures in the mouth. In the different types of swallows recorded, the lower lip and mentalis muscles showed much stronger activity than the upper lip and anterior temporal muscles and also initiated the swallowing activity. No significant changes in mean voltages of the swallowing activity were observed during the 2-year observation period. On the other hand, the durations of the swallows showed marked increases after 1 year of denture use, when no further rebasings of the complete upper denture had been made.

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The chewing and swallowing activity of jaw-closing muscles was studied longitudinally in 30 partially edentulous subjects who were provided with an immediate complete upper and a partial lower denture. Electromyographic recordings of the anterior temporal and masseter muscles were obtained during habitual chewing of apple and during swallowing of saliva and water, before final extractions and 7 weeks, 6 months, 1 year and 2 years after denture insertion. At the pre-treatment stage, when the patients were chewing with a residual anterior dentition, the mean voltages showed low values compared to findings reported in subjects with a complete natural dentition. After 6 months of denture use, the chewing forces showed significant increases in amplitude, and the increased force of contraction persisted to the 2-year stage. The recordings of swallowing revealed no significant changes in maximal mean voltage during the observation period. However, there was a significant increase in the duration of the swallows after 1 year of denture wearing, which might be related to stabilization of the complete upper denture due to continuing resorption of the maxillary ridge.

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A previous study of age differences in facial morphology in a dentate sample representing young, middle, and old age (Tallgren and Solow, 1987) indicated an increase in lower anterior face height during adulthood. The aim of the present study was to examine in detail the accompanying age differences in dentoalveolar heights. The material consisted of lateral head films of 191 dentate Finnish women divided into the age groups 20-29, 30-49, and 50-81 years. The present study comprised 26 variables calculated from digitized reference points. The maxillary and mandibular anterior dentoalveolar heights were significantly larger in the middle and old age groups than in the young group, and the mean differences were of the same magnitude for the maxilla and the mandible. Analysis of the dentoalveolar components showed that in the mandible the extra-alveolar height of the incisors was significantly larger in the two older age groups than in the young group, while no significant differences were found in the maxilla. The mean differences in anterior mandibular ridge height between the older age groups and the young group were smaller than in the maxilla. No significant differences in dentoalveolar morphology were observed between the middle and the old age groups.

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The gradual changes in the skeletal and soft-tissue profile of complete denture wearers resulting from residual ridge reduction were studied using profile cephalometric films obtained from 21 subjects during a 2-year period of denture use. The variables for each observation stage were calculated from 58 digitized reference points. During the first 6 months of denture use, a marked anterosuperior rotation of the mandible as a result of ridge resorption caused a similar profile change of the soft-tissue chin and mandibular lip. Continuing ridge reduction resulted in a marked change of mandibular position at the 2-year stage, leading to a pronounced protrusion of the chin and mandibular lip and a more outward position of the maxillary lip.

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Changes in functional jaw movements during a 2-year period of denture wear were investigated. The sample consisted of 27 partially edentulous subjects who were provided with an immediate complete maxillary denture and a removable partial mandibular denture. Recordings of habitual chewing of apple and empty open-close cycles were made with a mandibular kinesiograph. At the pretreatment stage, when the patients occluded on a residual anterior dentition, irregular patterns of movement were observed. After placement of the dentures, which restored posterior occlusion, the chewing and open-close patterns showed marked improvement and were characterized by significant mean decreases in sagittal and transversal range of movement. Relining of the maxillary dentures further stabilized the functional patterns. During the second year, significant reductions in vertical range of movement and lateral chewing excursions were observed, and were probably related to impaired retention of the complete upper denture.

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A longitudinal electromyographic (EMG) investigation was performed on thirty subjects provided with an immediate complete upper and a partial lower denture. Electromyographic recordings in maximal clench, light tapping and postural position were obtained from the anterior temporal and masseter muscles before final extractions and 7 weeks, 6 months, 1 year and 2 years after denture insertion. The maximal clench activity of the jaw closing muscles showed an average tendency to decrease upon insertion of the dentures, but thereafter significant increases in mean voltages were observed during the first year of denture wear. During the second year no significant changes in EMG clenching force were noted. At the 2-year stage most of the muscles showed significantly greater clench activity than at the post-insertion stage, but did not exceed the pre-extraction level. The jaw muscle activity in light tapping showed no significant mean changes during the observation period. The postural activity tended to decrease during the period of denture wear, the decrease being significant for some of the muscles at the 2-year stage.

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Electromyographic silent periods in response to chin taps during clench were recorded from the anterior temporalis and masseter muscles. Ten complete denture wearers were observed up to the 1-year stage of denture wear and eight patients up to the 2-year stage. Silent periods were also recorded from patients clenching on paper rolls in place of the dentures. Regarding the patterns of the silent periods, similar observations of double silent periods were made as in our previous study up to the half-year stage of denture wear (McCall, Tallgren & Ash, 1979). The frequency of the double silent periods was 13.8% at the 1-year stage and 7.3% at the 2-year stage. The mean duration of the silent periods did not differ significantly at the 1-year and 2-year stages. The mean silent period duration when clenching on paper rolls without dentures in the mouth was significantly shorter than when clenching with the dentures.

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A longitudinal radiographic cephalometric and electromyographic investigation was performed on eighteen subjects provided with an immediate complete upper and a partial lower denture. The observation stages were: before final extractions and 7 weeks, 6 months and 1 year after denture insertion. The cephalometric analysis was based on measurements from lateral head films taken in centric occlusion. The EMG activity of the anterior temporal and masseter muscles was studied in postural position, light tapping and in maximal clench. The changes in jaw and occlusal relationships due to resorption of the edentulous maxillary ridge were slight, the mean decrease in occlusal vertical dimension during one year being 0.7 mm. The EMG clench activity at the pre-extraction stage, when the patients occluded on a residual anterior dentition, showed low mean values round 100 microV, and a further decrease was observed at the post-insertion stage. At the 1-year stage all muscles displayed significant increases to above the post-insertion level. The jaw muscle activity in light tapping and in postural position generally showed no significant mean changes during the observation period. The results indicate that preservation of a residual dentition in the lower jaw prevents marked changes in jaw and occlusal relationships and resulting changes in muscle activity.

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Changes in hyoid position in relation to changes in mandibular inclination and craniocervical posture were studied by roentgen cephalometrics in a sample of 24 long-term complete denture wearers over a 15-year period. The measurements were made on lateral occlusion films obtained with the subjects in the sitting position and with the head oriented according to its natural balance. The changes in mandibular inclination ranged from -5.5 degrees to 8.6 degrees, with a mean of zero. The cervical column became significantly more forward inclined (mean, 5 degrees), and the craniocervical angulation became on an average 5 degrees larger. Correlation analyses indicated that the hyoid position was influenced by two postural systems: the changes in mandibular inclination and the changes in cervical and craniocervical posture. The vertical changes in hyoid position in relation to the upper face largely followed the patterns of increase or decrease in mandibular inclination, whereas the horizontal changes mainly followed the changes in cervical inclination and craniocervical angulation.

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In a group of 18 partially edentulous patients provided with immediate complete dentures, changes in hyoid bone position and craniocervical posture were examined on cephalometric radiographs made during 1 year of denture use. The findings indicated that the changes in hyoid bone position largely followed the pattern of forward-upward rotation of the mandible due to ridge resorption. During this course the hyoid position in relation to the cervical spine showed a mean increase. The hyocervical changes, however, showed less variability than the hyomaxillary and hyomandibular changes. The posture of the head and cervical column showed no definite mean changes during the 1-year period. On the other hand, analysis of individual changes revealed that a pronounced decrease in mandibular inclination due to ridge resorption was associated with retroclination of the cervical column and decreased craniocervical angulation. These postural changes may be regarded as adaptive changes to a marked initial change in mandibular position.

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In a sample of fifteen partially edentulous subjects assigned for immediate complete denture treatment, a correlation analysis was performed between pre-extraction facial morphology determined from lateral cephalograms, and EMG activity of the anterior temporal and masseter muscles in maximal clench and tapping of teeth. Marked correlations observed between vertical and sagittal jaw relations and mean voltages of the jaw-closing muscles indicated strong biting activity in subjects with a square facial type. No significant associations were observed between biting strength and the age of the subjects. Correlations between facial morphological changes and changes in EMG biting activity after denture insertion and during 1 year of denture wear indicated that the anterior temporal muscles were extremely sensitive to sagittal changes in anterior occlusion. The masseter muscles were less sensitive, but responded in some instances to changes in vertical jaw relationship.

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EMG study of subjects wearing immediate complete upper and lower dentures revealed marked alterations in activity of the jaw closing muscles during the biting actions recorded. This finding suggests that changes in jaw and occlusal relationships due to resorption of residual ridges and settling of the dentures also affects jaw muscle activity. The relations between EMG and morphologic findings will be analyzed further in a separate article.

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In eighteen subjects assigned for immediate complete upper and lower dentures, roentgen cephalometric recordings were made before extraction of the residual anterior dentition and 3 weeks, 3 months, 6 months and 1 year after denture insertion. The cephalometric analysis was based on electronic measurements of linear and angular morphological variables and computer head plots generated from 177 reference points (Walker, 1967), derived for each subject for each of the five observation stages. The reduction of the alveolar ridges was most rapid during the first 3 months of denture wear and particularly during the post-extraction period of 3 weeks. The reduction in anterior height of the lower ridge was on average twice as great as that of the upper ridge. The ridge resorption and the accompanying settling of the dentures on the basal seats, measured from lead shots inserted in the dentures, brought about an upward rotation of the mandible with a resulting decrease in occlusal vertical dimension and reduction in overjet of the dentures. In accordance with the amount of ridge reduction, these changes showed great individual variation.

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