Friction testing apparatus. The buccal segment model consists of a 0.022-inch second molar buccal tube, a 0.022-inch convertible first molar buccal tube in the converted state, three stainless steel 0.022-inch preadjusted brackets for the right second premolar, first premolar, and canine. The brackets and the tubes are aligned and blocked inside a vicelike device. The test wire is ligated into the testing unit and its bottom end clamped by a vice mounted on the Instron crosshead