Juha Varrela

Early developmental traits in Class II malocclusion

The occlusal traits of Class II occlusion in the deciduous dentition include distal terminal plane of the second deciduous molars, distal canine relation, large overjet, and large overbite. Other findings are narrow upper dental arch and maxillary base and poor anterior spacing. Skeletally, Class II children differ less from normal children. The cranial base, including the base flexure, and the maxilla are normal. The mandibular corpus and lower facial height are short, the gonial angle is large, and the dentoalveolar position of the mandible is retruded. The height of the ramus is normal, as is the skeletal position of the mandible, with the exception of the chin, which becomes slightly retruded after 5 years of age. As most skeletal traits of Class II occlusion develop later than the occlusal characteristics, it is suggested that no evidence can be found for a skeletal Class II growth pattern in the deciduous dentition. The deficient transversal growth of the maxilla and the sagittal growth of the mandible seem to cause the typical Class II occlusion. Further skeletal changes are likely to develop as secondary adaptations.

Acceptability of dental appearance in a group of Finnish 16- to 25-year-olds.

OBJECTIVE To define a grade in the Aesthetic Component (AC) of the Index of Orthodontic Treatment Need (IOTN) that would differentiate between esthetically acceptable and unacceptable occlusions and that would also be both subjectively and objectively meaningful. MATERIALS AND METHODS Dental appearance and self-perceived orthodontic treatment need were analyzed in a group of Finnish young adults (171 males, 263 females, age range 16-25 years). Subjective data were gathered using a questionnaire, and the respondents were requested to score their dental appearance on a visual analog type 10-grade scale. Professional assessment of dental appearance was performed by two orthodontists using the AC of the IOTN. The cutoff value between esthetically acceptable and unacceptable occlusions was defined using receiver operating characteristic curves. RESULTS Sixty-six percent of orthodontically treated and 74% of the untreated respondents were satisfied with their own dental appearance. Every third respondent reported one or more disturbing traits in their dentition. The most frequently expressed reason for dissatisfaction was crowding; girls expressed dissatisfaction more often than boys did (P = .005). A self-perceived treatment need was reported infrequently by 8% of orthodontically treated and 6% of untreated respondents. In the logistic regression analysis, self-perceived need for orthodontic treatment was the only significant factor explaining dissatisfaction with own dental esthetics. On the applied scales, grades 1 and 2 fulfilled the criteria for satisfactory dental esthetics. CONCLUSION The results suggest that the AC grade 3 could serve as a cutoff value between esthetically acceptable and unacceptable occlusions.

Dentofacial changes after orthodontic intervention with eruption guidance appliance in the early mixed dentition.

OBJECTIVE To evaluate skeletal and dentoalveolar changes induced by the eruption guidance appliance in the early mixed dentition. MATERIALS AND METHODS Pre- and posttreatment cephalometric radiographs of 115 consecutively treated children, 62 boys and 53 girls, were compared with those obtained from a control group of 104 children, 52 boys and 52 girls. Pretreatment radiographs were taken at the deciduous-mixed dentition interphase (T1) and after full eruption of all permanent incisors and first molars (T2). The mean age of the children in both groups was 5.1 years at T1 and 8.4 years at T2. RESULTS A significant difference between the groups at T2 was found in the mandibular length, midfacial length, and maxillomandibular differential. The increase in mandibular length was 11.1 mm in the treatment group and 7.2 mm in the control group. No differences were found in measurements of maxillary position or size. There was a significant shift toward a Class I relationship in the treatment group. Labial tipping and linear protrusion of the mandibular incisors was evident in the treatment group at T2. There was no effect on the inclination or position of the maxillary incisors. CONCLUSIONS Occlusal correction was achieved mainly through changes in the dentoalveolar region of the mandible. In addition, the appliance enhanced condylar growth resulting in a clinically significant increase in mandibular length. No effect was observed on maxillary position, maxillary size, inclination or protrusion of the maxillary incisors, or facial height.

Enhanced Degree of Monomer Conversion of Orthodontic Adhesives Using a Glass-Fiber Layer under the Bracket

OBJECTIVE To test the hypothesis that there is no difference in the degree of conversion (DC%) of orthodontic composites during the light-curing process with or without the use of a glass-fiber reinforcement. MATERIALS AND METHODS Two light-curing orthodontic adhesives, Transbond XT (TB) and Beauty Ortho Bond (BO), were used with woven preimpregnated glass fibers. The degree of monomer conversion was determined for both adhesives in three settings (n = 5 per group): in the first group, the adhesive was cured without a bracket (control); in the second group, the bracket was bonded using adhesive without fiber reinforcement; and in the third group, a layer of glass-fiber net was added between the bracket and resin. The adhesive resin was light cured, and the DC% was determined by Fourier transform infrared spectroscopy. RESULTS A two-way analysis of variance revealed significant differences in the DC% (P < .001) between adhesives and between the fiber-reinforced and nonreinforced groups. When the nonreinforced adhesives were light cured under the brackets, the DC% was significantly lower (TB: 37.0%, SD 3.4; BO: 36.9%, SD 1.9) compared with the control (TB: 54.7%, SD 0.6; BO: 65.9%, SD 0.5). A higher DC% was found when the resin was light cured in the presence of a glass-fiber net (TB: 44.1%, SD 0.3; BO: 55.3%, SD 1.7). CONCLUSION The hypothesis is rejected. The degree of monomer conversion of the light-curing adhesive resin under stainless steel bracket can be improved by adding a thin layer of glass-fiber-reinforced composite between the bracket and adhesive resin.

Occlusal status in orthodontically treated and untreated adolescents

In order to evaluate the outcome of orthodontic care, all available 16-year-old adolescents (n = 138) living within the catchment area of one Finnish health center were invited for a clinical examination. A total of 126 adolescents participated, corresponding to 79% of the whole age cohort. Of these, 47% had been treated orthodontically, 2% were still wearing appliances, and 51% were untreated. In 80% of cases, a non-extraction treatment was carried out. All occlusions were evaluated using a recently developed occlusal morphology and functional index (OMFI) based on assessment of 6 morphological and 4 functional traits which are classified applying an acceptable-non-acceptable dichotomy. The occlusal status in untreated individuals was used as a second reference in comparisons between the treated and untreated occlusions. The morphological criteria for an acceptable occlusion were met by 42% of the participants and the functional criteria by 64%. Although the treated occlusions failed to meet the criteria of morphological acceptability more often than the untreated ones (73% vs 40%), the proportions of non-acceptable occlusions were fairly high among untreated occlusions. The main reasons for non-acceptability were the failure of the canine relationship, overbite, and protrusion movement to fulfill the criteria of acceptability. Only 19% of the adolescents had occlusions classified as acceptable, both morphologically and functionally. In the evaluated health center, the allocation of resources resulted in a high coverage of orthodontic care. However, our results indicate that the general occlusal status in the examined age cohort did not reach an optimal level.

Selection of criteria for assessment of occlusal acceptability

There is no general agreement on criteria that could be applied to distinguish between orthodontically acceptable and non-acceptable occlusions after the completion of dental development. The aim of the present study was to analyse morphological and functional features that could be used as an index to define an acceptable occlusion in young adults. Three expert panels representing specialists in orthodontics and stomatognathic physiology participated in a modified Delphi method. Each panel responded to a questionnaire concerning the usefulness of various occlusal features, and a set of characteristics was selected on the basis of the responses; thereafter, applicability of the chosen characteristics and their cutoffs for an acceptable-non-acceptable dichotomy was tested clinically. To obtain a consensus level of 100%, the last panel session was completed with a group discussion. Assessments made using the morphological criteria were compared with those made with the dental health component of the Index of Orthodontic Treatment Need. The selected morphological characteristics consisted of overjet, overbite, canine relationship, crossbite, scissors bite and midline deviation. The functional evaluation comprised assessments of discrepancy between the centric relation and the intercuspal position, working- and non-working-side contacts and protrusion contacts. The dental health component and our morphological criteria showed different sensitivity to contact point displacements, interdigitation in buccal segments and increased overbite. This study provides a set of morphological and functional indicators reflecting the current consensus opinion of Finnish professionals. Further studies are needed to analyse the reproducibility of assessment of the characteristics included.

Orthodontic treatment practices in Finnish municipal health centres with differing timing of treatment

The aim of this study was to compare orthodontic practices in eight Finnish municipal health centres selected on the basis of an earlier survey to represent early and late timing of treatment. The health centres were grouped according to the mean age of starting treatment; earlier versus later than 9 years of age. A random sample of 16 and 18 year olds (n = 2325) living in these municipalities were invited for a clinical examination, and 1109 adolescents participated. The participants reported on their previous or ongoing orthodontic treatment by means of a questionnaire. Data on orthodontic treatment received were collected from the dental files of the adolescents who reported a treatment history and for those who did not recall exactly whether or not they had received orthodontic treatment. Analysis of the non-respondents was made on the basis of their dental files. Differences between the features of orthodontic treatment in the early and late starting health centres were analysed using a two-tailed t-test. In the early group, 70 per cent, and in the late group 42 per cent, of adolescents had a history of orthodontic treatment. General dentists carried out 90 per cent of the treatment in the early group and specialists every third treatment in the late group. An early start resulted in more frequent visits (P = 0.004) and a longer treatment duration (P < 0.001), while later timing resulted in an increase in the number of appliances (P < 0.001).

Reproducibility of Characteristics Assessing the Occlusion of Young Adults

The aim of the present investigation was to analyze the reproducibility in the assessment of six morphological and three functional characteristics included in a new method evaluating the occlusion in young adults. These characteristics comprised coincidence of midlines, overjet, overbite, canine relationship, crossbite, scissors bite, recurrent deviation on opening, guided lateral excursions, and discrepancy between the centric relation and the intercuspal position. The study was conducted in three stages: (1) five observers assessed the occlusions of five volunteers, (2) seven observers assessed nine volunteers, and (3) five observers assessed nine volunteers. Two calibrated orthodontists were used as references. For numerical variables, the nonparametric method for repeated measurements (Friedmans test) was used to test the significance of differences, while the proportion of agreement was calculated for categorical assessments. The results were analyzed using two precision levels: within a measurement unit/the same category and an acceptable/nonacceptable dichotomy. The magnitude of systematic differences was small and of minor clinical importance except in measurements of recurrent deviation on opening. The proportional agreement for acceptance was good in the assessment of overjet, coincidence of midlines, crossbite, scissors bite, open bite, and discrepancy between the centric relation and the intercuspal position. Moderate agreement was achieved in the assessment of overbite, canine relationship, recurrent deviation on opening, and guided lateral excursions. Among the nonacceptable cases, the agreement ranged from poor to good. The results indicated that noncalibrated observers assess categorical characteristics inconsistently.

Trends in Finnish Public Orthodontic Care from the Professionals' Perspective

The study maps out orthodontic care in Finnish municipal health centres in 2001, describes changes during the previous ten years reported by chief dental officers, and assesses the views of orthodontists on current public orthodontic services. The data were collected by questionnaires sent to all health centres and all orthodontists in Finland. Of all 0–18-year-olds, 11% were receiving orthodontic treatment with an appliance (range 2–43% among the health centres). The most frequently used appliances were headgear, quadhelix, and fixed appliances. Limited economic resources and the lack of orthodontic expertise were mentioned by the chief dental officers as factors decreasing the volume of services. The orthodontists mentioned the large regional variation and the lack of national guidelines as the most important aspects that should be improved on a national basis. To bring about improvement, they suggested increasing the number of specialist orthodontists and the delegation of orthodontic tasks to auxiliaries.

The medial axis branch point in the human mandible

The medial axis method was applied to radio-cephalometric images of the mandible in 20 adults and 18 children and to panoramic X-ray images of these children, and also directly to 50 halves of dry mandibles. It was found that the location of the posterior branch point coincided almost invariably with the mandibular foramen/lingula. The foramen may be regarded as the posterior limit of the mandibular body, from which the condylar and coronoid processes branch off. The medial axis appears to reflect the developmental and functional anatomy of the human mandible.