The characteristics of the Ricketts maxillary canine retractor

The characteristics of the Ricketts maxillary canine retraction spring (Ricketts, 1974) have been derived using the complementary (strain) energy method. The theoretical predictions of the analysis have been confirmed by experiments on large planar models in a jig fitted with strain gauges capable of measuring the forces and couples developed when the springs were activated in a way simulating clinical use. The verified analysis was used to compare the horizontal stiffness and anti-tilt couple to retraction force ratios of the Ricketts with other simpler retraction components. The behaviour of the Ricketts mandibular sectional, as predicted by the analysis was also examined.