Prevalance of malocclusion in young Finnish Skolt-Lapps.

Two hundred Skolt Lapps aged 8 to 16 years were examined for malocclusion with the aid of intraoral radiography and dental casts. The frequency of loss of permanent teeth was high, particularly of the first molars. Also, many teeth were severely defective because of caries. Hypodontia was very common. The frequency of tipped and rotated teeth was high, probably as a consequence of the frequent loss of neighboring teeth. Space and occlusal anomalies were roughly as common as in urbanized Swedish and Danish materials. The need for orthodontic treatment, judged on a 5-grade scale by one examiner, was found to be greater than in Swedish materials.

Prevalence and awareness of malocclusion in Swedish men.

Previous orthodontic treatment, the awareness of malocclusion, the demand for orthodontic treatment and the prevalence of malocclusion were studied in 389 Swedish men, aged 21-54 years (mean age 32 years). Nine percent had been treated with an orthodontic appliance and 15% reported that permanent teeth had been extracted on orthodontic indications. Malposition of teeth was found in 75%, with rotation as the most common type of malposition. Crowding was recorded in 43% and spacing in 18%. Fifty-seven percent had some occlusal anomaly. The need for orthodontic treatment was rated on a four-point scale. It was found that 76% were in need of treatment. The need for treatment was only slight in half of the men but moderate to urgent in 25% of the sample. About a quarter of the men were aware of malposition of front teeth, equally often for maxillary and mandibular teeth, but only about 1% were aware of malposition of posterior teeth. Only a few percent thought they were in need of orthodontic treatment. The presence of malocclusion was correlated to age, place of birth and educational level. This might perhaps be a consequence of tooth loss.

Tooth loss, prosthetics and dental treatment habits in a group of Swedish men.

Dental history, dental status, the need for prosthetic treatment and dental treatment habits were studied in 389 men aged 21--54 years. The men were selected from a group undergoing military refresher training in the south of Sweden. One percent of the men were toothless. About 3% had full dentures in one or both jaws and an equal percentage had partial dentures. About 3% of the men had bridges in the maxilla and 2% in the mandible. Tooth loss was greatest in the mandibular molar segment, followed by the maxillary molar segment. By means of an index for dental status about 8% of the men were judged to be in great need of prosthetic treatment for aesthetic reasons and/or to improve occlusion. Age, place of birth, educational level and smoking habits were among the factors which seemed to be related to dental status. Seventy percent of the men reported that they went to the dentist once a year, while about 10% seemed rarely or never to seek dental treatment. Dental treatment habits were correlated to place of birth, number of brothers and sisters, edentulousness and the need for prosthetic treatment, among other factors.

Facial morphology and activity of temporal and lip muscles during swallowing and chewing.

The correlations between facial and bite morphology and the activity in the temporal muscle and in the musculature of the lip during swallowing and chewing were studied in 50 girls, aged 9-13 years. The activity was recorded electromyographically by determining the maximal mean voltage amplitude and morphologically by analysis of profile roentgenograms and dental casts. The activity in the lower lip during the swallowing was not correlated with any of the variables of the facial morphology with the exception of the width of the upper dental arch. On the other hand, the activity of the upper lip during swallowing, as in the anterior and posterior portions of the temporal muscle, was correlated with a number of variables used for measuring facial form. The activity was low in girls with a facial shape with anterior inclination of the maxilla and mandible, small face height, and pronounced prognathism. The activity in the upper lip during chewing varied, as in the lower lip, independently of facial form, while the activity of the temporal muscle during chewing showed the same relation to facial form as during swallowing. The number of chewing cycles required for trituration of the test media (apples and peanuts) was negatively correlated with the number of teeth and with age. This was interpreted as adaptation in such a way that the number of cycles decreased with development of the dentition.

Correlation between maximum bite force and facial morphology in children.

The correlation between maximum bite force and facial morphology was studied in 54 boys, 8 to 16 years old, and 66 girls, 7 to 17 years old. Bite force was measured at the first molars with a miniature bite force recorder. Facial morphology was evaluated on profile cephalograms. In addition, the number of teeth in contact in the intercuspal position was recorded with occlusal foils. In the girls, maximum bite force was correlated with the inclination of the mandible, the size of the gonial angle, and the ratio between posterior and anterior face heights. The correlations implied a large bite force with a small mandibular inclination and gonial angle, a large posterior face height in relation to the anterior face height, and a small bite force with the opposite facial characteristics. These correlations were nonexistent or weaker in boys. In both sexes, bite force was correlated with the number of occlusal contacts. Elimination of the influence of age and occlusal contact in the group of girls by the use of partial correlations reduced the correlation between bite force and facial morphology. A significant correlation with the size of the gonial angle remained, however, and the correlation with mandibular inclination was close to significance. In addition to the correlations found with facial morphology, the study clearly demonstrated the need to take gender and occlusal contacts into consideration in future studies of masticatory muscle function and strength in relation to facial morphology.

Activity of temporal and masseter muscles in children with a lateral forced bite.

The activity of the temporal and masseter muscles with the mandible in postural position and during chewing, maximal bite in the intercuspal position, and swallowing were recorded electromyographically in nineteen children with laterally forced bite. Of the children, aged 8-12 years, sixteen had unilateral crossbite. In all of the individuals there was lateral deviation between the retruded contact position and the intercuspal position. The magnitude of the lateral deviation was measured with a modified gnathothesiometer. The muscle activity was recorded bilaterally from the temporal muscle and from the masseter muscle. In the postural position asymmetric activity was found in the temporal muscle suggesting that the mandible in postural position was still displaced to the side of forced bite. During chewing the activity was asymmetric both in the anterior and the posterior temporal portions. This asymmetric muscle activity was interpreted as an adaptation to avoid cuspal interferences. Also in maximal bite the muscle activity was asymmetric, while the activity during swallowing was affected less than in the other functions. The swallowing activity was, however, less in children with a forced bite than in children with normal occlusion.

Prediction of breadth of permanent canines and premolars in the mixed dentition.

Multiple stepwise regression was used in the selection of mixed dentition variables capable of predicting the total breadth of the unerupted permanent canine and premolars. The material consisted of 77 children. Stone casts were made before and after eruption of the canine and premolars. At the first examination when the children were, on the average, 10 years old, intraoral roentgenograms were obtained of the canine and the premolars. To predict the total breadth of the upper canine and premolars the buccolingual breadth of the upper first permanent molar and measurements on roentgenograms of the breadths of the upper canine and premolars proved most useful. In the prediction of the total breadth of the lower canine and premolars the best results were obtained with measurement of the breadths of the teeth in the roentgenograms. The breadth of the incisors proved less useful as a predictor of the breadths of unerupted canines and premolars.

Cheek pressure and head posture.

Maxillary cheek pressures are measured in the molar area, at the teeth and high in the buccal sulcus, in both natural and extended head positions, with teeth at rest and in function. Highest pressures are found on the alveolar process, with some increases with the head extended and the jaw at dental rest position.

Influence of surgical tongue reduction on pressure from the tongue on the teeth.

Pressures from the tongue on the teeth were recorded in 21 children and adolescents before and after surgical reduction of the tongue. The recordings were made before surgery, and 6 and 12 months after the operation. Simultaneous measurements were made at the lingual surfaces of the maxillary and mandibular central incisors and at the left first molar, in the rest position and during chewing and swallowing. The method had been used in a previous study of normal cases, which served as a reference. Presurgical pressures recorded in the rest position at the maxillary incisors agreed with measurements recorded in the same location in the reference sample. Measurements recorded during rest in the other locations were somewhat higher than those of the reference group. Pressures recorded before the surgery during chewing and swallowing varied from similar measurements made in the reference group. At the recording 6 months after surgery, resting pressures at the molars were lower than they had been presurgically. No significant differences were found for pressures during chewing. A lower pressure was recorded in one location during swallowing. At the recordings made 12 months after surgery none of the pressures differed significantly from the presurgical values. Resting pressures were, however, lower than they had been before surgery and were closer to those of the reference sample.

Pressure from the tongue on the teeth in young adults.

Pressure from the tongue on the teeth was measured at the upper and lower central incisors and left first molars in 25 young adults with clinically normal occlusion. Repeated recordings with and without a period for accommodation to the intraoral measuring device, which was connected to an extraoral pressure transducer, were made in the rest position and during chewing and swallowing. Only minimal effects of accommodation were found. The system can thus be used without a period of adaptation before the actual test. The intraindividual pressure variations were of the same magnitude as for measurements of the pressure from the oro-facial soft tissues on the teeth recorded in earlier studies. The majority of the subjects had negative pressures at the upper and lower incisors and at the upper molar in the rest position. The pressures on the teeth during swallowing were comparatively great, while pressures during chewing were one-fourth to one-half of the swallowing pressures.

Pressure from the lips on the teeth during speech.

Pressure on the teeth from the labial soft tissues during the articulation of a given sentence was measured in 24 children, 8 to 14 years old, with normal incisor relationships. The points of measurement were labial in the midlines between the maxillary and mandibular central incisors and between the right maxillary canine and first premolar (the modiolus point). A mouthpiece was attached to the teeth at these three positions and connected via a water-filled system to an extraoral pressure transducer. A microphone recorded the volume and speed of articulation while the activity of the lip muscles was surveyed by electromyography. The maximal pressure during pronunciation of the consonant /p/, the pressure at rest (RP), the speech posture pressure (SPP), the time pressure integral (TPI), and the mean speech pressure (MSP) during articulation were analyzed. Maximal pressure during pronunciation of /p/ and TPI were highest at the modiolus, second highest at the lower midline, and lowest at the upper midline. RP and SPP were highest at the lower midline. SPP was 2 to 3 times higher than RP, and MSP was 4 to 7 times higher than RP. The pressures during articulation recorded at the lower midline were closely correlated with those at the modiolus, with weaker correlations between the upper and lower midlines and between the upper midline and modiolus. There was a close correlation between RP and SPP. SPP, MSP, and TPI may, along with RP, contribute to the positions of the teeth.

Effect of lip training in children with short upper lip.

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.

Anomalies of occlusion predisposing to occlusal interference in children.

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.

Treatment results in dental school orthodontic patients in 1983 and 1993.

The effect of incremental changes in materials and techniques on orthodontic treatment outcomes is difficult to evaluate objectively. Treatment results for two groups of patients whose treatments were completed approximately 10 years apart were evaluated using the peer assessment rating (PAR) index and the index of orthodontic treatment need (IOTN) using the Wilcoxon matched-pairs signed-rank test. Patients in the later group who had been treated by postgraduate students primarily (using fixed appliances) had significantly lower IOTN and PAR scores at the end of treatment and showed a significantly greater reduction in the PAR score than a similar group of patients in the earlier group. There were no significant differences in treatment results between patients in the early and late groups who were treated with removable appliances. Differences in treatment results were most likely the result of changes in materials and techniques that had occurred in the 10 intervening years.

Little influence on tooth position from playing a wind instrument.

The morphology of the face and dentition of 62 adult professional wind instrument musicians was recorded with roentgencephalometry and dental casts. The musician group was comprised of 31 brass instrument players, and 31 reed instrument or flute players. The results were compared between the two subgroups and between these and a control group. The few differences found between groups were small. Overbite and upper dental arch width at the canines were smaller in the musicians than in the control group. Width at the maxillary and mandibular molars was somewhat smaller in the reed instrument and flute players than in the control group. No difference in overjet was found. Cephalometric analysis showed similar, normal facial morphology in all groups. The range of variables recorded was large in all groups.

Treatment of Class II, div. 1 malocclusion with the activator and with the Begg technique.

The effect of treatment of Angle Class II, division 1 malocclusion with an Andresen activator or with the Begg technique with or without premolar extraction was studied retrospectively with X-ray cephalometry. The treatment with the Begg technique was followed by a phase of retention with an activator. Three groups of 25 children who had been treated with one of the methods were compared regarding facial morphology and soft tissue profile before and after the treatment and changes during the period of treatment. The treatment effect (correction of the distal occlusion and normalisation of the overjet and overbite) was similar with the three methods. The overjet was mainly corrected through skeletal changes, which accounted for 70%, 77% and 62% of the overjet correction produced by the activator, Begg extraction and Begg non-extraction treatment, respectively. Thus, all three methods of treatment had a skeletal (orthopedic) effect. The dental component of the overjet correction was with all three methods of treatment a retroclination of the upper incisors. This was to some extent offset by a retrusion of the lower incisors, which also occurred in all groups. The facial morphology and the soft tissue profile after the treatment were similar in the three groups. There were no differences in the soft tissue profile and only marginal differences in facial morphology as a result of the three methods of treatment.

Long-term stability of treatment results in cleft lip and palate patients.

The stability of the orthodontic and prosthetic results of the treatment of 18 individuals with isolated cleft of the palate, 18 subjects with a complete unilateral and 8 with a complete bilateral cleft was evaluated in an eight-year follow-up period. The subjects were examined at the age of 19 years, after completed orthodontic and surgical treatment, and again at the age of 27 years. After the first examination the majority of the individuals with a complete cleft had at the age of 20 to 21 years been treated with a fixed bridge which was only minimally extended. The width of the upper dental arch at the second bicuspid decreased slightly in the subjects with an isolated cleft of the palate and in those with a bilateral cleft. In the subjects with a unilateral cleft there was a slight decrease of the upper dental arch widths at both bicuspids and at the first molar. In the subjects with complete clefts the slight decrease in upper dental arch widths was accompanied by a slight increase of the number of posterior teeth in cross-bite. The total number of teeth in cross-bite was small, however. On the whole, the upper dental arch was relatively stable during the follow-up period. This was found in the group with bilateral clefts, reconstructed with 5-8 unit bridges, as well as in the subjects with a unilateral cleft who had received no or only minimally extended reconstructions and in the group with an isolated cleft of the palate (no bridge).