Eighteen-Year Follow-Up of 160 Consecutive Individuals Born With Unilateral Cleft Lip or Cleft Lip and Alveolus Treated by the Oslo Cleft Lip and Palate Team.

OBJECTIVE: Describe patients born with unilateral cleft lip with or without cleft alveolus (CL±A) in relation to cleft severity and laterality, gender, associated anomalies and syndromes, number and type of lip- and nose operations, and time of alveolar bone graft (ABG) treatment in relation to dental status in cleft area. MATERIALS AND METHODS: Patients included 220 children born with unilateral CL±A, born between 1988 and 1997 referred to the Oslo Cleft Lip and Palate Team. The data were collected retrospectively. All patients were followed up until 18 years of age. RESULTS: Among all CL±A, 3.6% had recognized syndromes, 6.8% had associated anomalies, and in 89.6% CL±A was the only malformation. CL±A was more common, but not more severe, on the left side. Among the 160 individuals with CL±A without syndromes and associated anomalies, 66.9% had an isolated soft tissue CL, and 33.1% were diagnosed with a CL alveolus (CL+A). Male predominance was observed. Children with CL+A had more severe soft tissue clefts of the lip and underwent more lip and nose surgeries than children born with CL. The time of ABG was found to be at a younger age when the patient had a lateral incisor in the cleft area than when this tooth was missing. CONCLUSION: Findings provide a reference for morphologic variations in CL±A, and insight into the surgical burden of care until the age of 18 years.

Tooth replacements in young adults with severe hypodontia: Orthodontic space closure, dental implants, and tooth-supported fixed dental prostheses. A follow-up study.

INTRODUCTION: Children with severe hypodontia have a substantial impairment of their dental health starting early in life. The purpose of this study was to describe types and locations of substitutes for missing teeth in patients with severe hypodontia and to compare the crown and soft tissue morphologies of orthodontic space closure, dental implants, and tooth-supported fixed dental prostheses for replacing teeth in the anterior region. METHODS: Fifty patients missing 6 or more teeth and aged 18 years or older (mean age, 25.6 years) took part in a follow-up study. The patients were examined clinically with panoramic radiographs and clinical photographs. Crown and soft tissue variables (mucosal discoloration, crown morphology, color, and papilla index) were compared for orthodontic space closure, dental implant fixtures, and fixed dental prostheses. RESULTS: Dental implants, orthodontic space closure, and retaining deciduous teeth were the most commonly prescribed treatments. Persisting deciduous teeth showed a good survival rate at the follow-up examination. Mucosal discoloration was seen only for implant fixtures and was evident for almost all fixtures in the anterior mandible and two thirds of those in the anterior maxilla. The papilla index scored poorer for both implant fixtures and fixed dental prostheses compared with orthodontic space closure. CONCLUSIONS: Dental implants in the anterior region proved to be an inadequate treatment modality in patients with severe hypodontia because of pronounced mucosal discoloration.

The prognosis of retained primary molars without successors: infraocclusion, root resorption and restorations in 111 patients.

This study aimed to assess infraocclusion, root resorption and restorations and their importance for the prognosis of retained primary mandibular molars lacking successors. The sample comprised 188 persisting primary mandibular second molars in 111 subjects, 48 males and 63 females, with a mean age of 12.6 years. The patients had been referred to an interdisciplinary clinic because of extensive hypodontia, missing 8.4 teeth on average. All persisting primary mandibular molars were included in the study, as no decision had been made as to whether they should be kept or extracted. Panoramic radiographs were used to assess infraocclusion, resorption of the mesial and distal roots and whether restorations were present. Clinically significant infraocclusion was observed in 43.6 per cent of the patients and classified as severe in 18.8 per cent. The mesial and distal root exhibited no resorption in 18.9 and 33.3 per cent, respectively (P = 0.01). Most primary molars had no restorations (78.4 per cent). A significant correlation was found between root resorption and infraocclusion. Age was found to be weakly but significantly correlated with root resorption and infraocclusion. No significant relationship was observed between gender and either infraocclusion or root resorption. In conclusion, infraocclusion was estimated to be a more critical factor for the prognosis of retained primary molars than root resorption.

Changes in the supragingival microbiota surrounding brackets of upper central incisors during orthodontic treatment.

OBJECTIVE: The aim of this study was to determine how fixed orthodontic appliances affect microbiota of supragingival plaque over 5 months. MATERIALS AND METHODS: Twenty individuals of Scandinavian origin, aged 10-16 years, were included. All subjects were fitted with fixed orthodontic appliances in both the maxillary and mandibular tooth arches. Pooled supragingival plaque samples from the labial surface of the two maxillary central incisors were collected before bonding (T1) and afterwards at 4 weeks (T2), 3 months (T3) and 5 months (T4). The plaque index (PI) was recorded for each sampling. The gingival status was documented at T1 and T4 by using clinical photographs. Plaque microbiota was identified using the Human Oral Microbe Identification Microarray (HOMIM). RESULTS: Increased plaque levels were recorded after bonding, however the increase was not significant. The prevalence of gingivitis at the maxillary central incisors increased from 25% at T1 to 74% at T4. No significant changes of the plaque microbiota from the sample area were detected during the 5-month period. Trends toward a microbiota containing more periodontitis- and caries-associated bacteria were detected. CONCLUSIONS: Although trends toward a microbiota containing more periodontitis- and caries-associated bacteria were detected, the changes were not severe enough to be significant. Treatment with fixed orthodontics does not necessarily shift the microbiota to a more pathogenic composition.

Clinical color intensity of white spot lesions might be a better predictor of enamel demineralization depth than traditional clinical grading.

INTRODUCTION: The aims of this study were to calculate the volume of white spot lesions by using microcomputed tomography and to determine which clinical attribute of the white spot lesion could better predict its volume: the clinically visible white spot lesion surface area or its color intensity. METHODS: White spot lesions were induced in 8 patients in vivo on 23 healthy premolars destined for extraction during orthodontic treatment by using specially designed plaque-retaining orthodontic bands. After 7 weeks, the premolars were extracted. After extraction, the resulting white spot lesions were photographed and clinically graded. The teeth were analyzed with microcomputed tomography. RESULTS: After 7 weeks, 70% of the teeth developed clinical white spot lesions. Clinically, the size of the lesions varied from minor to severe. Their volumes varied from 0 to 1.2931 mm(3). The traditional grades for white spot lesions correlated significantly with color intensity. A significant correlation was found between white spot lesion color intensity and lesion volume. This correlation was found to be better than that between the white spot lesion clinical score and lesion volume. CONCLUSIONS: Our results indicate that white spot lesion color intensity might predict the depth of enamel demineralization as well as or better than traditional white spot lesion scoring. Therefore, the dentist could use this information when planning treatment for white spot lesions.

The incidence of caries and white spot lesions in orthodontically treated adolescents with a comprehensive caries prophylactic regimen--a prospective study.

The aim of the study was to assess the effect of a comprehensive prophylactic regimen in reducing the incidence of white spot lesions (WSL) and caries during orthodontic treatment. Eighty consecutive patients, scheduled for fixed appliance treatment in both jaws were compared with a non-orthodontic matched-control group. The oral hygiene regimen consisted of brushing two to three times daily, flossing, fluoride rinse, and plaque disclosing tablets. Patients were requested to avoid carbonated soft drinks/acidic juices and candies. The WSL index of Gorelick et al. (Gorelick L, Geiger A M, Gwinnett A J 1982 Incidence of white spot formation after bonding and banding. American Journal of Orthodontics 81: 93-98) was used. Caries were scored according to Amarante et al. (Amarante E, Raadal M, Espelid I 1998 Impact of diagnostic criteria on the prevalence of dental caries in Norwegian children aged 5, 12 and 18 years. Community Dental Oral Epidemiology 26: 87-94). We collected data from all finished cases. It comprised 40 subjects in the orthodontic group (mean age: 13.6 years, range: 12-16 years) and 40 matched controls. The average treatment time was 18 months (range: 9-25 months). The mean increase in WSL index in the orthodontic group was 1.9 and 0.4 in the control group (P = 0.001). The mean increase in dentine caries was 0.5 lesions and 0.7 lesions in the in the orthodontic group and control group, respectively (P = 0.62). Twenty-three per cent of treated patients showed good compliance, 68 per cent moderate compliance, and 9 per cent poor compliance. The mean increase in WSL was 1.0, 1.4, and 3.3 in the good, moderate, and poor compliance group, respectively (P = 0.155). Orthodontically treated patients have significantly higher risk for developing WSL than untreated patients, while there is no difference with respect to development of new dentinal caries lesions. This study showed that a possible relationship between compliance and WSL development existed.

Dental health assessed after interproximal enamel reduction: caries risk in posterior teeth.

INTRODUCTION: We investigated whether careful interdental enamel reduction (using extrafine diamond disks with air cooling, followed by contouring with triangular diamond burs and polishing) leads to increased caries risk in premolars and first molars. METHODS: Our subjects were 43 consecutive patients from 19 to 71 years of age who had received mesiodistal enamel reduction of anterior and posterior teeth 4 to 6 years previously. Dental caries were assessed on standardized bite-wing radiographs according to a 5-grade scale and with a fine-tip explorer catch. The incidence of interproximal caries was compared between reproximated and unground contralateral surfaces in the same patient. Patients were asked about their toothbrushing habits, use of dental floss and toothpicks, and regular fluoride supplementation after the orthodontic appliances were removed. RESULTS: The overall clinical impression generally showed healthy dentitions with excellent occlusion. Only 7 (2.5%) new caries lesions (all grade 1) were found among 278 reproximated mesial or distal surfaces, in 3 patients. Among 84 contralateral unground reference tooth surfaces, 2 lesions (2.4%) were seen. On nonpaired premolars and molars that had not been ground, 23 surfaces had to be referred for caries treatment (grade 3 or occlusal caries). Eleven of these occurred in 1 patient. None of the 43 patients reported increased sensitivity to temperature variations. CONCLUSIONS: Interdental enamel reduction with this protocol did not result in increased caries risk in posterior teeth. We found no evidence that proper mesiodistal enamel reduction within recognized limits and in appropriate situations will cause harm to the teeth and supporting structures.

Average craniofacial development from 6 to 35 years of age in a mixed group of patients with juvenile idiopathic arthritis.

OBJECTIVE: To investigate long term the average changes in craniofacial morphology in a group of Norwegian juvenile idiopathic arthritis (JIA) patients with mixed diagnosis from 6 to 35 years of age. A matched group of healthy individuals was included as controls. MATERIAL AND METHODS: Craniofacial development in 38 females and 16 males with JIA was followed on lateral cephalograms from childhood for 23-31 years. The patients were compared with the healthy individuals at the ages of 6, 9, 12, and 35 years. RESULTS: At 6 and 9 years of age, the average craniofacial morphology in the JIA patients was similar to that of the control subjects. At 12 years of age, significant craniofacial morphological differences between the JIA and the control subjects appeared. These included a steeper mandibular plane angle and a more retrognathic position of the mandible. The length of the mandible (ar-gn), the height of the ramus (ar-tgo), and the length of the corpus (tgo-gn) were significantly smaller in the JIA patients. The average growth direction of the chin was more downward in the JIA patients. A smaller posterior facial height and a higher ratio between the anterior and posterior facial heights were also observed. The differences in craniofacial morphology between the patients and the control group were more pronounced at 35 years of age than at earlier ages. CONCLUSION: The typical craniofacial morphological pattern in JIA patients was established between 9 and 12 years of age. From the age of 12 until the age of 35, this morphological pattern remained relatively stable, in contrast to the pattern in the healthy control subjects.

Are malocclusions more prevalent and severe now? A comparative study of medieval skulls from Norway.

INTRODUCTION: The prevalence of malocclusion in modern populations is higher than in excavated samples from ancient times. Presently, more than 30% of children and adolescents in the Scandinavian countries receive orthodontic treatment. The aims of this study were to describe the prevalence and severity of malocclusions in a sample of medieval Norwegians, to evaluate the need for treatment by using the Norwegian need for orthodontic treatment index (NOTI), and to compare these findings with a modern sample already analyzed with the same index. METHODS: The material consisted of 85 male and 61 female medieval skulls from abandoned and later excavated graveyards of 16th century Oslo that were evaluated with the NOTI. RESULTS: Only 36% of the medieval group showed objective assessed needs for orthodontic treatment, compared with 65% of the present-day sample. Among the skulls, the objective needs for treatment were 27% for the males and 49% for the females. No sex differences related to severity or prevalence of malocclusion were found in the modern sample. The medieval sample arranged according to severity was great need (B), 7%; obvious need (C), 29%; and little/no need (D/E), 64%. The findings in the modern sample were B, 20%; C, 44%; and D/E, 35%. The female skulls showed greater severity and prevalence than the male skulls. No skull had very great need (A). CONCLUSIONS: This study indicates a significant increase in both the prevalence and the severity of malocclusions during the last 400 to 700 years in Oslo, Norway. Furthermore, although no sex differences were found in the modern sample, females had both a higher prevalence of malocclusions and more severe malocclusions than did males in the past.

Scanning electron microscopic evaluation of enamel surfaces exposed to 3 orthodontic bonding systems.

INTRODUCTION: This in-vitro study investigated the effects of conventional etching with a 35% phosphoric etching gel and priming/bonding with Transbond XT primer/adhesive (3M Unitek, Monrovia, Calif), conditioning with 10% polyacrylic acid and bonding with a resin-modified glass ionomer cement (Fuji ORTHO LC, GC Corporation, Tokyo Japan) or using a self-etching bonding system (Transbond Plus) and bonding with Transbond XT adhesive on the surface morphology of the enamel. The study was conducted at the Faculty of Dentistry, University of Oslo, in Norway, 2004. METHODS: The enamel surfaces of extracted premolars where conditioned with 1 of the 3 systems and evaluated with environmental scanning electron microscope. Brackets were then bonded with 1 of 3 bonding agents and examined with a conventional scanning electron microscope. RESULTS: The bonding systems induced different effects on the enamel structure. Phosphoric acid etching produced a rough, etched surface with the typical honeycomb pattern. Bonding brackets to such a surface resulted in thick resin tags relatively deep into the enamel. Less pronounced etching of the surface enamel was obtained by the self-etching primer system, and bonding resulted in smaller and fewer resin tags. The resin-modified glass ionomer bonded after conditioning the enamel with polyacrylic acid showed no resin tags. CONCLUSIONS: Bonding systems with self-etching primers or conditioners with polyacrylic acid might offer potential benefits compared with conventional acid etching and priming because of fewer irreversible changes to the enamel surface.

Feeding, artificial sucking habits, and malocclusions in 3-year-old girls in different regions of the world.

PURPOSE: The way babies and young children are reared is important to their health and development. Extensive breast-feeding has also been shown to reduce the development of artificial sucking habits like digit or pacifier-sucking. The aim of this study was to determine feeding methods, artificial sucking habits, and the presence of malocclusions in 3-year-old girls living in different regions of the world. METHODS: Children from the following countries were involved in the present study: (1) Brazil (Porto Alegre); (2) Japan (Niigata); (3) Mexico (Mexico City); (4) Norway (Oslo); (5) Sweden (Falköping); (6) Turkey (Istanbul); (7) and the United States (Iowa City, Iowa). During the interview and examination, the following variables were evaluated and registered: (1) breastfeeding and bottle-feeding; (2) duration and frequency; (3) sucking habits; (4) posterior and anterior crossbites; and (5) other malocclusions/normal occlusion. RESULTS: The prevalence of breast-feeding was very high in all groups, ranging between 78% and 98%. The prevalence of bottle-feeding in the different areas was also high. Except for Iowa City, the prevalence of digit-sucking was relatively low. Pacifier-sucking is fairly popular in most areas, with the exception of Niigata. The prevalence of normal occlusion in different cities ranged from 38% to 98%. CONCLUSIONS: There are considerable differences in feeding, as well as artificial sucking habits, in different areas of the world and at different periods.

Transverse dental and dental arch depth dimensions in the mixed dentition in a skeletal sample from the 14th to the 19th century and Norwegian children and Norwegian Sami children of today.

Secular changes in transverse dental arch dimensions and dental arch depth were studied. Four cohorts with mixed dentitions were selected. The skull group comprised 48 skulls dating from the 14th to the 19th century and belonging to The Schreiner Collection at the Department of Anatomy, University of Oslo. The 1980s Sami group was comprised of 39 boys and 34 girls born in 1987 and living in the northern part of Norway. The 1960s Oslo group was comprised of 31 boys and 30 girls born in 1963 and living in the southern part of Norway. The 1980s Oslo group was comprised of 32 boys and 26 girls born in 1983 and living in the same area in southern Norway as the previous Oslo group. Sex was unknown in the skeletal sample, and the groups were analyzed with the sexes pooled; separate descriptive values are presented for the modern groups. The mandibular intercanine distance was smaller in the skulls compared with the modern groups. The transverse intermaxillary difference between the molars was larger in the skull group than in the 1980s Oslo group. The difference between the maxillary and mandibular intercanine distances was larger in the skulls compared with the modern groups, although the small number of measurements in the skull group impeded further analysis. The arch depth was smaller in the skull group compared with the modern groups; the 1960s Oslo group deviated because of a higher prevalence of caries in the second deciduous molars. The overjet was smaller among the skulls. The arch form measured as the angle between the left and right molar tooth rows was more acute in the skulls than in the modern groups. It was concluded that smaller arch depths are found in skeletal samples at early ages and that attrition does not explain the more upright incisors found in skeletal samples. A secular trend was found in the intermaxillary relation, which indicated that children in the 1980s Oslo group were at greater risk of developing a posterior cross-bite than children born in the 14th to 19th centuries.

Microbial community succession on developing lesions on human enamel.

BACKGROUND: Dental caries is one of the most common diseases in the world. However, our understanding of how the microbial community composition changes in vivo as caries develops is lacking. OBJECTIVE: An in vivo model was used in a longitudinal cohort study to investigate shifts in the microbial community composition associated with the development of enamel caries. DESIGN: White spot lesions were generated in vivo on human teeth predetermined to be extracted for orthodontic reasons. The bacterial microbiota on sound enamel and on developing carious lesions were identified using the Human Oral Microbe Identification Microarray (HOMIM), which permits the detection of about 300 of the approximate 600 predominant bacterial species in the oral cavity. RESULTS: After only seven weeks, 75% of targeted teeth developed white spot lesions (8 individuals, 16 teeth). The microbial community composition of the plaque over white spot lesions differed significantly as compared to sound enamel. Twenty-five bacterial taxa, including Streptococcusmutans, Atopobiumparvulum, Dialisterinvisus, and species of Prevotella and Scardovia, were significantly associated with initial enamel lesions. In contrast, 14 bacterial taxa, including species of Fusobacterium, Campylobacter, Kingella, and Capnocytophaga, were significantly associated with sound enamel. CONCLUSIONS: The bacterial community composition associated with the progression of enamel lesions is specific and much more complex than previously believed. This investigation represents one of the first longitudinally-derived studies for caries progression and supports microbial data from previous cross-sectional studies on the development of the disease. Thus, the in vivo experiments of generating lesions on teeth destined for extraction in conjunction with HOMIM analyses represent a valid model to study succession of supragingival microbial communities associated with caries development and to study efficacy of prophylactic and restorative treatments.

Stannous fluoride in dentifrice: an effective anti-plaque agent in the elderly?

OBJECTIVE: The aim of this study was to examine differences in plaque accumulation in elderly patients using two toothpastes, with either 0.2% sodium fluoride (NaF) or 0.4% stannous fluoride (SnF(2)), but otherwise identical. BACKGROUND DATA: The prevalence of denate elderly is increasing. Plaque both causes caries and is associated with an increased mortality rate in frail elderly patients with pneumonia. Therefore, the effective removal of plaque is important. Ingredients with an anti-plaque effect, such as SnF(2), that can be used in toothpaste, are effective in plaque inhibition MATERIALS AND METHODS: Thirty-two frail elderly women, 82-98 years of age (mean, 88 years) and living in a residential home, participated in a double-blind crossover study. They brushed their teeth for 4 weeks with each toothpaste. Treatment outcome was a change in the plaque index (PI) on four anterior teeth and four molars. RESULTS: anova showed statistically significant differences between the treatments (F = 4.21, p = 0.02). A post hoc test showed that SnF(2) produced a statistically significantly lower PI than did NaF. CONCLUSION: SnF(2) in toothpaste may be effective in inhibiting plaque accumulation in the elderly.

An in vitro comparison of the shear bond strength of a resin-reinforced glass ionomer cement and a composite adhesive for bonding orthodontic brackets.

The shear bond strength (SBS) of a light-cured, resin-reinforced glass ionomer and a composite adhesive in combination with a self-etching primer was compared after different setting times to evaluate when orthodontic wires could be placed. Additionally, the fracture site after debonding was assessed using the Adhesive Remnant Index (ARI). Eighty freshly extracted human premolars were used. Twenty teeth were randomly assigned to each of four groups: (1) brackets bonded with Transbond XT with a Transbond Plus etching primer and debonded within 5 minutes; (2) brackets bonded with Fuji Ortho LC and debonded within 5 minutes; (3) brackets bonded as for group 1 and debonded within 15 minutes; (4) brackets bonded as for group 2 and debonded within 15 minutes. The SBS of each sample was determined with an Instron machine. The mean SBS were, respectively: (1) 8.8 +/- 2 MPa; (2) 6.6 +/- 2.5 MPa; (3) 11 +/- 1.6 MPa and (4) 9.6 +/- 1.6 MPa. Interpolating the cumulative fracture probability by means of a Weibull analysis, the 10 per cent probabilities of fracture for the groups were found to be attained for shear stresses of 6.1, 3.1, 8.3 and 7.1 MPa, respectively. Chi-square testing of the ARI scores revealed that the nature of the remnant did not vary significantly with time, but the type of bonding material could generally be distinguished in leaving more or less than 10 per cent of bonding material on the tooth. After debonding, the Transbond system was likely to leave adhesive on at least 10 per cent of the bonded area of the tooth. The present findings indicate that brackets bonded with either Transbond XT in combination with Transbond Plus etching primer and Fuji Ortho LC had adequate bond strength at 5 minutes and were even stronger 15 minutes after initial bonding.

Craniofacial and dentofacial development in pigs fed soft and hard diets.

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.

Bond failure of a no-mix adhesive during orthodontic treatment.

Bond failure of a no-mix adhesive was evaluated in 320 patients followed longitudinally during orthodontic treatment. Factors evaluated were the patient's gender, the complexity of the appliance, the bond site location, initial crowding, and caries development. The overall bond failure rate was 7.2%. Bond failures were significantly higher in the mandible, with the second premolars showing the highest prevalence (23%) (P <.001). There were significantly higher bond failure rates in boys than in girls (P <.05). There was a significant negative correlation between initial crowding and bond failure. Increased white spot lesions during treatment and complex appliance design were significantly correlated with high bond failure rates.

Dental arch space and permanent tooth size in the mixed dentition of a skeletal sample from the 14th to the 19th centuries and 3 contemporary samples.

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.

Longitudinal changes in gingival condition in crowded and noncrowded dentitions subjected to fixed orthodontic treatment.

A previous study showed that initial crowding in the dentition was negatively correlated with gingival bleeding at the end of orthodontic treatment, whereas visible plaque on the labial surfaces had apparently no significant association with gingival health. The present study further examined the relationship between initial crowding and gingival health during fixed orthodontic treatment. A total of 220 patients were followed longitudinally during treatment. In this population, 2 groups, 1 consisting of 45 patients with severe crowding and 1 consisting of 52 patients with no crowding, were examined more closely. The gingival bleeding index (GBI) was recorded at bonding, at 12, 24, and 48 weeks after bonding, and at debonding. At bonding, the GBI was the same in the 2 groups. However, the GBI improved significantly from 12 weeks after bonding to debonding in the patients with crowded dentitions, whereas the patients with noncrowded dentitions showed no changes. Possible reasons for this difference were identified: to have the same GBI at bonding, despite the severe crowding, the patients in this group probably had better oral hygiene. Those with crowded dentitions had received more oral hygiene instruction within 2 years before bonding than those with noncrowded dentitions, according to the general practitioners' records. When the crowding was eliminated after approximately 3 months, the conditions for cleaning the teeth were improved, and, accordingly, the patients' improved oral hygiene resulted in lowered GBI scores. One could also speculate that correcting the crowding during the first few months of treatment had a positive psychological effect, motivating the patients to use the skills in oral hygiene that they had adopted before treatment.