Validity and reproducibility of a tripoding method in point registration-based 3D superimposition software compared to a conventional cephalometric method

Abstract Objective: The present study aimed to assess the validity and reproducibility of a tripoding reference method for digital study cast superimposition to measure maxillary tooth movement. Methods: This retrospective study used 30 treated orthodontic cases which required premolar extractions. Pre- and post-treatment cephalograms were conventionally superimposed, while digitised study casts were superimposed using point registration-based software (Materialise 3-matic Research 12.0) and a tripoding method. This method involved superimposing the digital study casts using the medial two-thirds of the third palatal rugae, and the bilateral depression of the greater palatine foramen as references. Incisor and molar orthodontic tooth movements in the vertical and horizontal planes were measured using the Pancherz analysis for cephalograms and Materialise 3-matic software for the digitised study casts. Validity and agreement were assessed by a paired t test and a Bland-Altman analysis while reproducibility was assessed by an intraclass correlation coefficient (ICC) and a paired t test. Clinical significance was set at 2 mm. Results: The paired t tests found no statistically significant differences (p > 0.05) in tooth movements between the cephalometric and digitised cast measurements, and between the same measurement methods. However, the Bland-Altman analysis showed the 95% limits of agreement were greater than 2 mm but less than 4.3 mm for all measurements. The ICC showed all measurements had good to excellent reproducibility. Conclusion: The tripoding method is a valid and reliable method to superimpose the maxillary study casts for measuring incisor and molar orthodontic movements but it is not interchangeable with the Pancherz analysis.