THE CURVE OF SPEE REVISITED

Through the use of a sophisticated measuring device and support comput er technology,accurate arch circumferences were determined for 27 cast s that exhibited moderate to severe curves of Spee. Arch circumference differences were subsequently obtained by comparing the measured arch length to a planar projection formed by the center of the incisal tip s anteriorly and the distobuccal cusp tips of the second molars distal ly, A general relationship has been derived for the arch circumference differential, resulting from the elimination of the curve of Spee, ve rsus the severity of the curve. The arch circumference reduction is co nsiderably less than that found by earlier investigators, implying tha t the incisor protrusion often associated with leveling the curve of S pee is not primarily due to the aforementioned differential, but rathe r more directly due to the mechanics used in leveling the curve of Spe e.