INTRODUCTION: In this study, we investigated prolonged pain reactions in teenage orthodontic patients during a common orthodontic treatment. The aim was to examine factors predicting pain at the end of a follow-up week after placement of elastic separators. METHODS: Fifty-five patients (ages, 12-18 years) were included. Baseline assessments were made of perceived intensity of general and dental pain experiences, motivation for treatment, dental anxiety, and personality factors (self-esteem and temperament). Pain intensity was assessed on a visual analog scale, and pain medications were recorded. The patients were separated into pain and no-pain groups according to pain experiences at day 7. RESULTS: The pain group (mainly girls) had significantly higher ratings of treatment pain than in the non-pain group at all times measured except for the treatment day. Bivariate and multiple logistic regressions showed significant predictive power from motivation, dental anxiety, activity temperament, and vaccination pain. CONCLUSIONS: In this adolescent patient sample, low motivation for orthodontic treatment, high ratings of vaccination pain, elevated dental anxiety level, and low activity temperament characterized patients reporting pain 1 week after the elastic separators were placed.

INTRODUCTION: Several authors have found a correlation between reduced chewing activity and malocclusion. In animal experiments, it has been possible to correlate a diet of low chewing resistance to narrower arches, which predispose the subject to crowding and irregular teeth.

METHODS: In this study, 17 pigs were weaned at 5 weeks of age and divided into 2 groups according to diet and housing. The soft-diet, indoor group was housed in conventional pens, and the animals were fed aliquots of barley and oats with soya and a mineral-vitamin premix added. The food was mixed with water at a dry matter content of about 25%. The hard-diet, outdoor group was kept outdoors; the pigs were fed solid food and also ate organic matter in the soil. All pigs were killed at 22 months of age. The skulls were dissected, and transverse and sagittal craniofacial and dentofacial dimensions were measured.

RESULTS: Chewing hard food caused considerable occlusal and approximal attrition in the experimental animals. The dental arches were shorter due to this attrition and to mesial migration of the molars and premolars. The approximal attrition also reduced the tendency for crowding and rotation of the teeth. Posterior crossbite was more common among the hard-chewing animals.

CONCLUSIONS: The increase in arch width in the hard-diet animals reported in the literature was not duplicated in this study. On the contrary, the soft-diet pigs had significantly wider arches than the hard-diet animals. This was most pronounced in the premolar region and could be the result of an atypical tongue habit, caused by the nonphysiologic feeding of the pigs. The soft-diet pigs also had a greater tendency to postnormal occlusion, especially in the canine region.

Dental arch space and permanent tooth size in the mixed dentition were studied in 4 cohorts: (1) 48 skulls from the 14th to the 19th centuries from The Schreiner Collection in the Department of Anatomy, University of Oslo; (2) 39 boys and 34 girls of Sami origin born in the 1980s living in northern Norway; (3) 31 boys and 30 girls born in the 1960s living in southern Norway; and (4) 32 boys and 26 girls born in the 1980s living in the same part of southern Norway as the previous group. The sexes were unknown in the skeletal sample, and the groups were analyzed with the sexes pooled. The crown sizes of the permanent teeth in the mixed dentition of the Norwegian children who had lived between the 14th and the 19th centuries were smaller than those of contemporary children living in the same country. Probable reasons for this increase in tooth size include improved nutrition and reduced morbidity, because this study ruled out attrition as a major cause of the discrepancy in tooth size. The relative space (arch perimeter minus tooth size) in the group born in the 1960s deviated from that in the other 3 groups, indicating a greater degree of crowding in this group. The relative space in the skulls did not differ significantly from that in the groups born in the 1980s. This means that the improved caries situation during the last decades has changed the dental arch space in these populations. The irregularity index of the 4 mandibular permanent incisors was larger in the skulls than in the modern samples.

This study was carried out in two cohorts of 9-year-olds, born in the 1960s and the 1980s in Sweden and Norway, to test the hypothesis that there has been a change in the lateral arch space conditions of the dentition during the last decades. In Norway, 61 children born in 1963 and 58 children born in 1983 were examined. In Sweden, 66 children born in 1961 and 67 children born in 1984 were examined. Children with a prolonged sucking habit, major dentofacial anomalies, history of orthodontic treatment, and ancestors of foreign origin were excluded to avoid influence of these factors on the development of the dentition. Linear measurements were performed between the mesial surface of the first permanent molars and the distal surface of the permanent lateral incisors in the maxillary and mandibular dental arches with use of a sliding caliper. The results showed that the children born in the 1980s had significantly larger lateral arch spaces in the maxillary dental arch (P <.05) and in the mandibular dental arch (P <.01) than did the children born in the 1960s. The amount of tissue loss in the second deciduous molars (the teeth having caries lesions or having been extracted) was greater in the 1960s groups than in the 1980s groups (P <.001). Thus, the hypothesis, that there has been a change in the lateral arch space conditions during the last decades, was confirmed. The most obvious reason is the decline in caries prevalence that has occurred in the same period; thus, there has been less loss of proximal tooth material of posterior teeth.

The transversal arch dimension has been studied in 2 different cohorts of 9-year-old children, a group of 119 (56 girls and 63 boys) from Norway and a group of 133 (72 girls and 61 boys) from Sweden. Half of the children in each group were born in the 1960s and half in the 1980s. The maxillary and mandibular transversal dimensions did not differ between the 1960s groups and the 1980s groups when the maxilla and the mandible were studied separately. When the intermaxillary relationship was assessed, a significant reduction in the intermaxillary difference was found in the boys born in the 1980s compared with the boys born in the 1960s. This was confirmed with different measurement points. In the girls, the mesial drift of the first permanent molars, because of a greater prevalence of caries in the 1960s groups, masked this effect. When the mesial drift of the first permanent molars in the girls born in the 1960s was considered, the transversal intermaxillary difference showed the same secular pattern as in the boys. When the mesial drift of the first permanent molars was considered, the intermaxillary difference in the 1960s groups resembled that found in an American sample of northwest European ancestry born in the 1940s to a greater extent compared with the children born in the 1980s.

The upper and lower intercanine arch widths and the prevalence of posterior crossbite were registered for 445 3-year-old children with and without a continuing or previous dummy-sucking or finger-sucking habit in different areas in Sweden and Norway. Sami children from northern Norway also took part in the study, as well as 15 medieval skulls with intact deciduous dentitions. Compared with the nonsuckers, an increased prevalence of posterior crossbite was observed for the finger suckers, especially the Swedish girls. Stepwise logistic regression showed that posterior crossbite could be predicted with upper intercanine arch width alone. The finger sucking variable would not improve prediction; neither did other entities such as cohort (residential area), sex, lower intercanine arch width, nor the difference between upper and lower intercanine arch width. High prevalences of posterior crossbite were registered for dummy suckers (pacifiers) especially the Swedish girls (26%). Stepwise logistic regression showed that posterior crossbite in dummy suckers could be predicted with upper and lower intercanine arch width. Stepwise linear regression showed that both arches tended to be narrower in Swedes and girls, and that dummy sucking decreased the upper and increased the lower intercanine arch width. Analyses of covariance revealed that at least 2 years of dummy sucking is necessary to produce a significant effect in the upper jaw and 3 years in the lower jaw.