The influence of bracket design on frictional losses in the bracket/arch wire system

In arch guidad tooth movement, the essential role played by bracket configuration with respect to sliding friction has been recognized by the manufacturers, a fact which has had an increasing impact on the design and marketing of new bracket models in recent years. The aim of the present in-vitro study was to investigate the influence of different bracket designs on sliding mechanics.Five differently shaped stainless steel brackets (Discovery: Dentaurum, Damon SL: A-Company, Synergy: Rocky Mountain Orthodontics, Viazis bracket and Omni Arch appliance: GAC) were compared in the 0.022II-slot system. The Orthodontic Measurement and Simulation System (OMSS) was used to quantify the difference between applied force (NiTi coil spring, 1.0 N) and orthodontically effective force and to determine leveling losses occurring during the sliding process in arch guided tooth movement. Simulated canine retraction was performed using continuous arch wires with the dimensions 0.019II×0.025II (Standard Steel, Unitek) and 0.020II×0.020II (Ideal Gold, GAC).Comparison of the brackets revealed friction-induced losses ranging from 20 to 70%, with clear-cut advantages resulting from the newly developed bracket types. However, an increased tendency towards leveling losses in terms of distal rotation (maximum 15°) or buccal root torque (maximum 20°) was recorded, especially with those brackets giving the arch wire increased mobility due to their shaping or lack of ligature wire.ZusammenfassungBei der bogengeführten Zahnbewegung ist die Bracketkonfiguration im Rahmen der Gleitreibung ein nicht zu vernachlässigender Faktor, der inzwischen auch von den Herstellerfirmen erkannt wurde. Gestaltung und Vermarktung neuer Brackettypen werden hiervon zunehmend beeinflußt. In der vorliegenden In-vitro-Studie wurde die Bedeutung, die einer unterschiedlichen Bracketgestaltung auf das Gleiverhalten zukommt, untersucht.Fünf Brackettypen aus Stahl mit unterschiedlicher Formgebung (Discovery: Firma Dentaurum, Damon SL: A-Company, Synergy: Firma Rocky Mountain Orthodontics, Viazis-Bracket und Omni Arch Appliance: Firma GAC) wurden im 0.022II-Slot-system gegenübergestellt. Zur quantitativen Bestimmung der Differenz von eingesetzter Kraft (NiTi-Zugfeder, 1,0 N) und orthodontisch wirksamer Kraft sowie der beim Gleitvorgang auftretenden Nivellierungsverluste wurde die bogengeführte Zahnbewegung mit Hilfe des orthodontischen Meß- und Simulations-Systems (OMSS) dargestellt. Die Eckzahnretraktion erfolgte am durchgehenden 0.019II×0.025II-Bogen (Standardstahl, Unitek) sowie am 0.020II×0.020II-Draht (Ideal Gold, GAC).Die Ergebnisse der In-vitro-Studie zeigten für die untersuchten Brackets einen stark unterschiedlichen Kraftverlust von 20 bis 70% der eingesetzten Kraft mit deutlichem Gleitvorteil für die neukonzipierten Brackettypen. Gleichzeitig war jedoch auch festzustellen, daß insbesondere bei den Brackets, bei denen aufgrund ihrer Geometrie sowie der teilweise fehlenden Drahtligatur eine erhöhte Manövrierfähigkeit am Bogen zu ermitteln war, mit verstärkten Nivellierungsverlusten im Sinne einer Distalrotation (maximal 15°) und eines bukkalen Wurzeltorques (maximal 20°) zu rechnen ist.

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