Transverse adjustment of preformed stainless steel archwires to the dental arch form

Purpose

Stable orthodontic treatment results require the preservation of the pretreatment mandibular dental arch form. Therefore, this study aimed to evaluate the amount of transverse adjustment of preformed stainless steel archwires require to fit the dental arch form.

Materials and methods

A fourth-order polynomial curve was applied to the 30 normal mandibular dental arches, and interpolated widths at the mean depths at the canine, first and second premolars, and first molar were measured. Widths of 42 types of 0.016-in. stainless steel preformed archwires were measured at the same mean depths. The widths of the dental arch and archwires were compared by the Mann–Whitney U test. Transverse adjustment values as the difference between dental and archwire widths for each tooth from the canine to first molar were calculated for each archwire and compared between tooth types. Correlation coefficients between tooth types were also analyzed.

Results

Preformed archwire width was significantly narrower than the dental arch. Significant difference between transverse adjustment values between each tooth type were found except between canine and first premolar. Significant correlations between each tooth types were also observed.

Conclusion

To reduce these adjustments, preformed stainless steel archwires that are designed to be approximately 1–2 mm at the canine, 1–3 mm at first premolar, 2–4 mm at second premolar, and 3–6 mm at first molar wider in the transverse dimension could be clinically recommended.