Bernard J. Schneider

Long-term stability after orthodontic treatment: nonextraction with prolonged retention.

A sample of 22 previously treated orthodontic cases was studied to evaluate long-term stability. All cases were treated nonextraction with fixed edgewise appliances and were without retainers a minimum of 5 years. Data were obtained from study models, although 14 of the 22 cases had longitudinal cephalometric radiographs. The average retention time with a mandibular fixed lingual retainer was 8.4 years. The irregularity index pretreatment was 8.0 mm in the maxillary arch and 5.2 mm in the mandibular arch; at the end of treatment it was 0.9 mm and 1.0 mm, respectively, and at the postretention stage it was 2.0 mm and 2.4 mm, respectively. Resolution of the lower irregularity index was accomplished without incisor advancement or distal movement of the mandibular molar, however, both arches were expanded transversely. During the posttreatment stage all variables showed relapse except for the expanded maxillary canines and premolars. However, the mandibular anterior segment demonstrated relatively good alignment at the long-term stage, which may be a reflection of prolonged mandibular retention.

Facial and dental arch asymmetries in Class II subdivision malocclusion.

The purpose of this investigation was to determine if any significant differences existed with regard to dental arch and facial asymmetries between persons having malocclusions with well-defined asymmetric characteristics, specifically Angles Class II subdivision malocclusions, and persons having normal occlusions. Secondarily, it was sought to determine the nature of the differences that contributed to the asymmetric occlusal relationship of buccal segments observed in Class II subdivision malocclusions. The sample consisted of 28 subjects in each of the two groups. All possessed a full complement of permanent teeth including first molars. The average age of subjects in both groups was 17 years. Measurements primarily of a linear nature were obtained from posteroanterior and lateral cephalometric radiographs in addition to dental models. Specific measurements were summed to produce various indices of asymmetry. Variables were analyzed with multivariate discriminant analysis. A significant discrimination between the two groups resulted; variables describing asymmetry of the dentoalveolar region of the mandible appeared to be the primary contributors to the difference obtained. Asymmetry of the maxillary dentoalveolar region appeared to make a secondary contribution.

Effectiveness and duration of orthodontic treatment in adults and adolescents

The purpose of this investigation was to compare the effectiveness and duration of orthodontic treatment in adults and adolescents with a valid and reliable occlusal index. Another aim was to evaluate variables that may influence the effectiveness and duration of orthodontic treatment in general. Pretreatment and posttreatment study models were scored using the Peer Assessment Rating Index. The difference in scores between pretreatment and posttreatment stages reflects the degree of improvement and therefore the effectiveness of treatment. Variables that reflect patient compliance were recorded from written treatment records from three private orthodontic practices. The sample consisted of 32 adults (mean age, 31.3 years) and 40 adolescents (mean age, 12.9 years), all of whom had four premolars extracted as part of the treatment strategy. The results indicated that there were no statistically significant differences (P > .05) between adults and adolescents regarding treatment effectiveness (occlusal improvement) and treatment duration. Multiple regression techniques revealed that the number of broken appointments and appliance repairs explained 46% of the variability in orthodontic treatment duration and 24% of the variability in treatment effectiveness. Furthermore, orthodontic treatment of the buccal occlusion and overjet explained 46% of the variability in treatment duration.

A comparative study of anchorage in bioprogressive versus standard edgewise treatment in Class II correction with intermaxillary elastic force

The primary purpose of this study was to evaluate the effectiveness of cortical anchorage, by comparing two groups of patients with Class II malocclusions that were treated successfully with Class II elastics. One group of 30 previously treated patients had a utility arch used to set up cortical anchorage in the lower arch before Class II elastic wear; the second group was treated with standard edgewise mechanics where anchorage preparation consisted of full appliances, a well-aligned mandibular arch, and a rectangular arch wire. The groups were selected according to age, sex, and the amount of Class II elastic usage. Pretreatment and posttreatment cephalometric radiographs were used to generate 32 variables. A Students t test was used to evaluate treatment change between the groups and revealed that there were no statistically significant differences. Lower molar teeth extruded and moved mesially equally in both groups. Although cortical anchorage did not retard lower molar movement, it was no less effective in controlling molar movement with a partial appliance than the fully banded standard edgewise appliance.

A static occlusal analysis based on ideal interarch and intraarch relationships.

Study models were visually assessed to quantify the number of ideal tooth relationships actually present relative to the potential total. Both intraarch and interarch relationships were used to generate an ideal tooth relationship index (ITRI). Index scores were generated for the entire dentition, which could be divided into anterior, posterior, interarch, and intraarch relationships. Index scores were determined at various time intervals so the longitudinal changes could be studied. Treated orthodontic cases (n = 92) showed an initial total ITRI score of 26% that increased to 52% at the end of orthodontic treatment and continued to improve to 59% during the retention and postretention periods. Anterior segment scores were higher (64%) than posterior segment scores (44%). The intraarch relationships of the anterior segment registered the highest (75%), whereas the lingual cusp relationships of the posterior segment had the lowest scores (35%). Various types of malocclusions exhibited different ITRI scores before treatment but responded equally to treatment showing similar improvement in scores at the end of treatment and the posttreatment period.

Histological evaluation of the effect of transseptal fibre resection on the rate of physiological migration of rat molar teeth

Twenty-seven female Sprague-Dawley rats were given lead acetate as a vital stain, and rates of alveolar bone formation, representative of drift, were measured histologically. Teeth around which the transseptal fibre system had been destroyed drifted less quickly on both functioning (p less than 0.01) and non-functioning (p less than 0.001) sides than those with intact transseptal fibres. Both horizontal and vertical components of physiological drift were equally affected by destruction of the transseptal fibre system. It was felt that the transseptal fibres probably exerted their primary effect on the tooth, with bone remodelling around the drifting tooth being affected secondarily.

Effects of orthodontic treatment on mandibular rotation and displacement in angle class II division 1 malocclusions

The aim of this retrospective cephalometric study was to investigate the effects of orthodontic treatment on rotation and displacement of the mandible in Angle Class II, division 1 malocclusions. Thirty patients in the treated group (15 boys and 15 girls; mean age at pretreatment, 12.27 +/- 1.36 years) were compared with 28 subjects who had untreated Class II, division 1 malocclusions (15 boys and 13 girls; mean age at T1, 12.01 +/- 0.07 years). The patients in the first group were treated nonsurgically, without extraction, and without the use of functional appliances. Cephalometric data were obtained from three lateral cephalograms per case representing pretreatment (T1), posttreatment (T2), and at least 2-years postretention (T3). Thirty-seven variables were measured representing craniofacial morphology, tooth measurements, and mandibular displacement. Some variables were obtained from cranial base, maxillary, or mandibular superimposition. Statistical significance was established at P < .05, P < .01, and P < .001. The findings indicated that orthodontic treatment of Class II, division 1 malocclusions induced a more vertical mandibular growth direction associated with an increased vertical displacement of pogonion. Occlusal or vertical movement of maxillary and mandibular molars was not correlated to mandibular rotation or horizontal displacement of pogonion. When compared with controls, the treated group did not exhibit a significant difference in mandibular rotation or occlusal movement of maxillary molars; however, it did show a greater occlusal movement of mandibular molars during treatment.

Identical twins treated differently

This case study is intended to demonstrate the effects of two different orthodontic treatment methods on one set of identical twins.

Experimental Studies on the Interrelations of Condylar Growth and Alveolar Bone Formation. II. Effects of Growth Hormone

Abstract No Abstract Available. Departments of Oral Pathology and Orthodontics, University of Illinois Medical Center; and Dental College, University of Calcutta, Calcutta, India.

The Effects of Reduced Attrition on Craniofacial and Dentoalveolar Development in the Rat

Abstract No Abstract Available. Given before the Univ. of Illinois Orthodontic Alumni Society, March 1976.