David Birnie

Effectiveness of early orthodontic treatment with the Twin-block appliance: a multicenter, randomized, controlled trial. Part 1: Dental and skeletal effects.

This study evaluated the effectiveness of early orthodontic treatment with the Twin-block appliance for the developing Class II Division 1 malocclusion. This multicenter trial was carried out in the United Kingdom. A total of 174 children, aged 8 to 10 years old, with Class II Division 1 malocclusion were randomly allocated to receive treatment with a Twin-block appliance or to an untreated, control group. Data were collected at the start of the study and 15 months later. Results showed that early treatment with Twin-block appliances resulted in reduction of overjet, correction of molar relationships, and reduction in severity of malocclusion. Most of this correction was due to dentoalveolar change, but some was due to favorable skeletal change. Early treatment with the Twin-block appliance is effective in reducing overjet and severity of malocclusion. The small change in the skeletal relationship might not be considered clinically significant.

Effectiveness of treatment for Class II malocclusion with the Herbst or twin-block appliances: a randomized, controlled trial.

The aim of this study was to evaluate the effectiveness of Herbst and Twin-block appliances for established Class II Division I malocclusion. The study was a multicenter, randomized clinical trial carried out in orthodontic departments in the United Kingdom. A total of 215 patients (aged 11-14 years) were randomized to receive treatment with either the Herbst or the Twin-block appliance. Treatment with the Herbst appliance resulted in a lower failure-to-complete rate for the functional appliance phase of treatment (12.9%) than did treatment with Twin-block (33.6%). There were no differences in treatment time between appliances, but significantly more appointments (3) were needed for repair of the Herbst appliance than for the Twin-block. There were no differences in skeletal and dental changes between the appliances; however, the final occlusal result and skeletal discrepancy were better for girls than for boys. Because of the high cooperation rates of patients using it, the Herbst appliance could be the appliance of choice for treating adolescents with Class II Division 1 malocclusion. The trade-off for use of the Herbst is more appointments for appliance repair.

Early treatment for Class II Division 1 malocclusion with the Twin-block appliance: a multi-center, randomized, controlled trial.

INTRODUCTION The aim of this study was to evaluate the effectiveness of early orthodontic treatment with the Twin-block appliance for the treatment of Class II Division 1 malocclusion. This was a multi-center, randomized, controlled trial with subjects from 14 orthodontic clinics in the United Kingdom. METHODS The study included 174 children aged 8 to 10 years with Class II Division 1 malocclusion; they were randomly allocated to receive treatment with a Twin-block appliance or to an initially untreated control group. The subjects were then followed until all orthodontic treatment was completed. Final skeletal pattern, number of attendances, duration of orthodontic treatment, extraction rate, cost of treatment, and the childs self-concept were considered. RESULTS At the end of the 10-year study, 141 patients either completed treatment or accepted their occlusion. Data analysis showed that there was no differences between those who received early Twin-block treatment and those who had 1 course of treatment in adolescence with respect to skeletal pattern, extraction rate, and self-esteem. Those who had early treatment had more attendances, received treatment for longer times, and incurred more costs than the adolescent treatment group. They also had significantly poorer final dental occlusion. CONCLUSIONS Twin-block treatment when a child is 8 to 9 years old has no advantages over treatment started at an average age of 12.4 years. However, the cost of early treatment to the patient in terms of attendances and length of appliance wear is increased.

A Comparison of the Forces Required to Produce Tooth Movement ex vivo Through Three Types of Pre-adjusted Brackets When Subjected to Determined Tip or Torque Values

Friction in fixed appliance systems has received considerable attention in recent literature, although that attributable to varying second order (tip) and third order (torque) adjustments in either the bracket or the archwire has not been fully investigated. The ex vivo study of 0·022 × 0·028-inch slot Minitwin®, Activa®, and Standard Straight Wire® brackets investigates friction when known values of tip or torque were applied to 0·018 × 0·025-inch stainless steel wires. The resistance to sliding of the wire through the ligated brackets was measured on a vertically-mounted Instron testing machine. The results showed that the self-ligating Activa® brackets consistently produced less friction than the other conventionally tied brackets. Minitwin® brackets were slightly more resistant to movement than the Standard® brackets during torquing, but the converse was found when tip was applied. Increasing tip and torque (ranges tested 0–6 degrees and 0–25 degrees, respectively) produced almost linear increases in friction for all brackets, although increasing tip had the more profound effect on friction, particularly in Activa brackets.

Labial sensory function following sagittal split osteotomy

A retrospective assessment of labial sensory function following sagittal split osteotomy was undertaken by a combination of record analysis, postal questionnaire and objective sensory testing. Case records for 90 sides operated upon by a single consultant surgeon between 1979 and 1992 identified a prevalence of persisting sensory changed at 2 years of 6.7%. A higher incidence of sensory change was seen in patients treated with intermaxillary fixation/upper border wires than those managed with buccal monocortical miniplates. Postal questionnaire returns for 67 consultant operated sides identified a higher incidence of sensory change than recorded in the notes. 5.9% had long term persisting anaesthesia. Another 28% had more variable subtle sensory impairment. A similar relation to method of fixation was seen. An association between duration of temporary sensory change and magnitude of forward mandibular advance was noted. Objective sensory testing validated the subjectively reported sensory status but also identified many patients self-assessed as normal had some undetected sensory impairment. Possible mechanisms for the above findings and implications for clinical practice are presented.

Digital Image Processing of Cephalometric Radiographs: A Preliminary Report

The principles of image capture, image storage and image processing in digital radiology are described. The enhancement of radiographic images using digital image processing techniques and its application to cephalometry is discussed. The results of a pilot study which compared some common cephalometric measurements made from manual point identification with those made by direct digitization of digital radiographic images from video monitors are presented. Although in an early stage of development, the results from the image processing system were comparable with those obtained by traditional methods.

Computerized predictionof the results of orthognathic surgery

Methods of visually and numerically predicting the results of orthognathic treatment are reviewed. The use of a computer program written by the authors and employing computer graphics for orthognathic prediction is described and illustrated. Suggested advantages and disadvantages of such a method are discussed.

Sensory nerve morbidity following Le Fort I osteotomy

The Le Fort I osteotomy has been used increasingly frequently in the management of dentofacial deformity since the wide acceptance of the down-fracture technique. The improved access provided by this technique allows movement of the Le Fort I segment in three planes. This paper reviews briefly the neuroanatomy of the area and considers how the surgical technique of Le Fort I osteotomy interferes with the sensory nerve supply. The sensory nerve function in ten patients who underwent Le Fort I osteotomy is reviewed.

Early treatment for Class II malocclusion and perceived improvements in facial profile

INTRODUCTION The aims of this study were to assess whether early Twin-block appliance treatment improves the attractiveness of Class II profiles and to determine the orofacial features of a profile that most influence the perception of attractiveness. METHODS Silhouetted profiles of 20 treated patients and 20 untreated controls randomly selected from 174 subjects (ages, 8-10 years) of a randomized, controlled trial into the effectiveness of early Class II treatment were assessed by 30 children (ages, 10-11 years) and 24 teaching staff using a 5-point Likert scale. Independent samples t tests were used to compare attractiveness ratings between the treated and untreated groups. Linear regression was used to determine the features defining attractiveness. RESULTS Early orthodontic treatment resulted in improved perceptions of facial profile attractiveness. Profiles were likely to be rated as attractive if the overjet was smaller (P = 0.001) and no teeth showed (P <0.05). CONCLUSIONS Profile silhouettes of children who had received early orthodontic treatment for Class II malocclusion were perceived to be more attractive by peers than those of children who did not receive treatment.

The Consultant Orthodontists Group Survey of Hospital Waiting Lists and Treated Cases

A questionnaire sent to all U.K. hospital orthodontic consultants resulted in an 88 per cent response rate. The average waiting time for initial consultation was 31·6 weeks for routine cases and 3·6 weeks for urgent cases. The average waiting time for out patient treatment was 68·7 weeks for routine cases and 7·5 weeks for urgent cases. Nearly 33 per cent of hospitals used the Dental Health Component of the Index of Orthodontic Treatment need (IOTN) as a guide to placing patients on waiting lists. ‘Urgency’ and ‘Complexity’ were used more frequently than indices. Sixty-nine per cent of hospitals exclude some categories of malocclusion from treatment in their departments. A prospective survey reported on 2480 completed treatments over a six week period and there was an average discontinuation rate of 9·2 per cent of all cases finished during the period. Comparison of the completed and discontinued groups revealed few significant treatment-related factors. There was some evidence that the more senior and experienced the operator, the less the rate of discontinuation. A greater rate of discontinuation was seen in removable appliance cases when compared with fixed appliance cases.