Experimental force analysis of the contraction utility arch wire.

An experimental apparatus consisting of a metal framework, a strain gauge, and a Wheatstone bridge was used to measure the retraction force delivered to the mandibular incisors by a contraction utility arch wire (0.016 by 0.016 inch blue Elgiloy). The contraction utility arch wire was activated 1 mm. and retraction forces were recorded as the deflection of a point image on an oscilloscope. The results indicated that the retraction forces at the incisor positions were reasonably within an optimal force range to move teeth quickly with minimal tissue damage and discomfort. However, the lateral incisor positions in both ovoid and narrow arch forms received significantly more force than the central incisor positions, and the narrow tapered arch form delivered more retraction force than the ovoid arch form.