Advantage of Square Slot Bracket for Lingual Straight Wire System
E line Tokyo, Tokyo, Japan
From many years of experience of using the mushroom archwire, a number of problems were encountered, such as detailing requiring many complicated bends or the difficulties in arch co-ordination between the upper and lower. Because of these problems, in 1996 the author began researching a lingual multi-bracket system using a plain archwire that did not require bending. 3 main points which are indispensable for the straight wire method are 1) a gingival off set. 2) Th e ideal arch wire must pass as close as possible to the lingual surface of the central incisors, the fi rst premolars and the fi rst molars. 3) Th e bracket slot width must be designed to be as small as possible. For the above reasons, new passive self-ligation bracket with a square slot was designed. Considering both the possible degree of play between the wire and the bracket slot in the leveling stage and the stiff ness of wire needed to carry out retraction without the bowing eff ect during space closing, it was decided to use a .018×.018 slot size. Th e thickness of the bracket on the front teeth which has been designed with a maximum of 1.7 mm is very thin. Th e slot width on the upper anterior teeth is 1.5 mm and on the lower anterior teeth is 1.2 mm. Th e result is that the inter-bracket distance is increased and so treatment with lighter force becomes possible. Th e quality of the treatment depends on whether or not suffi ciently close attention has been paid to the preparation of treatment such as an accurate diagnosis, a precise impression taken, an accurate set-up model and accurate bonding positioning of the brackets. Th en favorable treatment without wire bend can be achieved.
Key words: Lingual straight wire, Plain archwire, Square slot, Self-ligation bracket
Korean J Lingual Ortho 2012;1(1):24-40