RESUMO
INTRODUCTION: The dental arch forms were compared of untreated Class I and Class II div 1 malocclusions to those of non-customized preformed archwires manufactured by American Orthodontics, G&H, Highland, Ormco, RMO, and 3MUnitek. Arch forms of post-treatment Class II div 1 malocclusions treated by four 1st premolar extractions are also compared. MATERIALS AND METHODS: Four metrics of archform shape and size (canine and 1(st) molar depth and inter-canine and inter 1(st) molar width) were measured on dental casts of 40 Class I and 22 Class II div 1 patients. These same metrics were also used to describe preformed archwire forms. RESULTS: Non-customized preformed wires all showed significantly narrowed mandibular arch forms. This was true for maxillary archwires, with four exceptions. The Highland Natural Arch form, G&H True form I, and RMO natural preformed archwires showed both inter-canine and 1(st) molar widths statistically the same as mean dental arch widths in both the untreated and post-treatment Class II groups. In Class I patients, these three archwires showed only inter-canine widths equivalent to dental measurements. The Highland Progressive archwire matched only the 1(st) molar width in the untreated Class II group. CONCLUSION: None of these archwires - if used unadjusted, will produce a significant expansive force in either the maxillary or mandibular arch. Three maxillary non-customized preformed archwires showed both inter-canine and 1(st) molar arch widths statistically the same as Thai Class II div 1 dental arch dimensions. Using them to treat this malocclusion should minimally affect both pre and post-treatment maxillary arch form.