Efficacy of swm appliance in the expression of first-, second- and third-order information in Class I and Class II

BACKGROUND: To assess the efficacy of a multibracket appliance—Straight-wire Mirabella (SWM) prescription—in terms of achieving the ideal first-, second- and third-order values proposed by Andrews. MATERIAL AND METHODS: A total sample of 46 Caucasian subjects was divided into two groups: 23 with class I malocclusion (Group 1), and 23 with class II malocclusion (Group 2). The treatment protocol involved fixed multibracket appliances—SWM prescription—for both groups, with the addition of class II elastics for Group 2. Values for ΔU1-PP, ΔIMPA, in-out, tip and torque were measured on digital scans, and the results obtained were compared with the ideal values proposed by Andrews. RESULTS: Statistically significant differences were revealed between the entire sample and Andrews’ values for: in-out on upper lateral incisors and upper canines; tip on the upper first premolars, upper second premolars, upper first molars and upper canines; and torque on the lower central incisors, lower lateral incisors, lower canines and lower first premolars. However, comparison of Groups 1 and 2 revealed statistically significant differences only at the lower lateral incisors. The use of class II elastics influenced ΔIMPA values, but not ΔU1-PP. CONCLUSIONS: The efficacy of the multibracket appliance—SWM prescription—in expressing first- second- and, to a lesser extent, third-order information was demonstrated in both class I and class II malocclusions. Class II elastics only influenced the third-order expression on the lower lateral incisors and the ΔIMPA. Key words:Straight wire fixed appliances, prescription efficacy, Class I malocclusions, Class II malocclusions.