A novel method for superimposition and measurements on maxillary digital 3D models—studies on validity and reliability

Digital 3-dimensional models are widely used for orthodontic diagnosis. The aim of this study was to assess the validity, reliability, and reproducibility of digital models obtained from the Lava Chairside Oral scanner (3M ESPE, Seefeld, Germany) and cone-beam computed tomography scans of alginate impressions for tooth-width measurements and the Bolton analysis.

Currently, cephalometric superimpositions are the accepted means for the assessment of orthodontic tooth movement. The present investigation evaluated the use of palatal rugae as reference points for the measurement of tooth movement, in a manner comparable with cephalometric superimpositions. The sample consisted of pretreatment and posttreatment maxillary study models and lateral cephalometric radiographs from 33 patients who had received orthodontic treatment that involved the extraction of the maxillary first permanent premolars. The mean age at the start of treatment was 13 years 11 months, and the average time between records was 35 months. The anteroposterior movement of the maxillary first molars and central incisors was evaluated with the use of 2 cephalometric variables and 12 study model variables that were reduced to 6 by the combining of the left and right sides. No statistical differences were found between the mean molar movement that was measured cephalometrically and the mean molar movement that was relative to the medial and lateral ends of the first and second palatal rugae or relative to the medial end of the third palatal ruga. Also, no statistical differences were found between the mean incisor movement that was measured cephalometrically and the mean incisor movement that was relative to the medial and lateral end of the third palatal ruga. These findings suggest that ruga landmarks can be used as reliably as cephalometric superimpositions to assess anteroposterior molar movements.