Prediction of arch perimeter changes due to orthodontic treatment.

A borderline orthodontic case with mild to moderate space deficiency can be treated without extractions. Expansion can be used to relieve space deficiency. The prediction of arch perimeter change for a given amount of expansion is helpful in planning the treatment of a patient who needs expansion, and it can facilitate nonextraction orthodontic treatment. To date, different amounts of arch perimeter change have been proposed for the same amount of expansion. A computer program is explained in this study, and examples of its uses are given. By entering 4 parameters of a dental arch into the computer program before and after an orthodontic procedure, one can simply calculate the total and the anterior arch perimeters and see the differences between them numerically and graphically. The program can save, print, change, and delete the calculated data for each patient. For clinicians who do not choose to use the computer program, 2 regression formulas are also presented to calculate the anterior and the total dental arch perimeters. The perimeters of 23 pairs of well-aligned dental arches were measured to check the accuracy of the computer program and the formulas. Paired t tests did not show statistically significant differences between the actual, the computer-derived, and the formula-derived perimeters of the dental arches at 95% confidence level.