Dental and alveolar arch forms in a Caucasian population compared with commercially available archwires

The aim of this study was to identify an arch form, comprising dentition and alveolus, representative of the Caucasian population, and to compare it with the shape of the main archwires on the market.

The study sample comprised 35 pairs of dental casts, taken from the arches of 35 Southern Europeans with ideal natural occlusion. After the dental casts were scanned, the reference points of the dental arches (FA points) and alveolar bone (WALA ridges) were identified with 3D software. Cartesian coordinates and intercanine and intermolar diameters were calculated for each patient, and curves representing the upper and lower dentition, as well as those showing the shape of the lower supporting bone, were traced and compared with those pertaining to different types of commonly used orthodontic archwires.

Ideal shapes of the mandibular alveolus and of the upper and lower archwires were calculated and compared with those actually on the market. Statistical analysis showed significant differences between the two, particularly at the upper and lower molars and canines. Likewise, there were significant differences between the shapes of the available archwires and the WALA ridge, except for the intercanine width.

None of the commercial archwires examined faithfully represented the shape of the 'ideal' dentition we calculated, particularly at the molars and canines. The bone structure of the mandibular support cannot be used as a guide to the shape of the arch form during orthodontic treatment.