A calibration method used for volumetric measurement of orthodontically induced root resorption craters

The aim of this study was to measure the accuracy and reproducibility of volumetric estimations obtained by a commercial software used to measure resorption craters induced by orthodontic forces. Twenty human first maxillary premolars were selected and divided into light and heavy force groups with 25 and 225 g of force applied to the upper-right first premolars, respectively. The contralateral teeth served as controls. Samples were extracted and prepared for SEM stereoimaging after 28 days of force application. Volumetric measurements of these resorption craters were generated by the software. Standardized pyramidal indentations by the Vickers microhardness tester on four solid metallic cylindrical rods (brass, copper, stainless steel, and aluminum) similar to the dimensions of human premolars were used for calibration. Mathematically calculated volumes of these indentations were compared to volumes estimated by the software. The software estimated the errors of volumes of pyramidal indentations of the harder and softer materials to within 11 and 19%, respectively. Non-uniform plastic deformation that occurred in softer materials during indentation distorts the calculated results. The estimates obtained by the software even for distorted indentations caused by non-uniform plastic deformation have high degrees of reproducibility and accuracy.