Third Palatal Rugae as Stable Landmarks for Intraoral Models' Superimposition in Extraction Cases: A Retrospective Cohort Study.

objectivesTo validate the third palatal rugae as stable reference landmarks for the superimposition of maxillary digital models in premolar extraction cases. MATERIALS AND

methodsMaxillary intraoral scanning digital models of 22 extraction patients, obtained before (T0) and after approximately 4 months of incisor retraction (T1), were superimposed using the automated best-fit of the third palatal rugae and palatine raphe. Voxel-based registration of CBCT scans served as the gold standard. Point-to-point displacements between T0 and T1 of the central incisors and cuspids were calculated for both methods.

resultsThe mean differences (mismatch) between methods in the combined vertical and horizontal perspectives of the central incisors were 0.08 mm (right) and 0.12 mm (left), respectively. For the cuspids, the mean 2D differences were 0.02 mm (right) and 0.07 mm (left). The pure horizontal displacement differences of the maxillary central incisors were 0.13 mm (right) and 0.04 mm (left). For the cuspids, the differences were: 0.05 mm (right) and 0.03 mm (left). No statistically significant differences were found between the intraoral-scan and CBCT measurements for either the central incisors or cuspids after maxillary superimpositions. The differences between the two methods were smaller than 0.2 mm in all comparisons.

conclusionsDigital superimposition of the third palatal rugae of models obtained with intraoral scans is a valid method for the 3D evaluation of the short-term (4-month) dental changes in the anterior region of the maxilla in cases of premolar extraction followed by incisor retraction.

trial registrationClinicalTrials.gov: NCT03089996 and NCT05281588.