The Conventional Double Slot Orthodontic Bracket

The Double Slot System presents a bracket with two slots, one active and the other passive. This allows for a new array of biomechanical possibilities.

The first bracket with a rectangular slot height of 0.022” was developed by E. H. Angle in 1925 to be used during orthodontic treatment. He filled the bracket slot with a 0.022” X 0.028” gold archwire, thus allowing three-dimensional control in the positioning of teeth. In the early 1930s, however, stainless steel alloy was introduced, with chromium and nickel in its composition, making it much more rigid than gold. This led orthodontists to start finishing cases with smaller size wires.

Then, in 1952, C. Steiner calculated the slot size needed to have the same strength in the steel wire as in the gold wire with the bracket slot fully filled. He concluded that the height of this slot should be 0.018”. Later in the 1950s, R. M. Ricketts adapted this idea into his Bioprogressive technique. From this point, two large groups of orthodontists were created: those who used a 0.018” slot and those who used a 0.022” slot. The latter, developed a greater acceptance during the 1970s, when L. Andrews first developed and R. Roth improved the Straight Wire technique.