Comparative Study of Three Methods to Compute 3D Craniofacial Angular Measurements

Objectives: The purpose of this study is to validate 3 methods of calculating angles in 3D (three-dimensional) virtual surface models acquired from cone-beam computed tomography scans: (1) using 3D pre-existing planes, (2) creating a 3D plane based on landmarks and (3) calculating angles between lines created from landmarks.
Methods: Twenty 3D virtual surface models de-identified previously created from CBCT scans were randomly selected. Three observers placed the planes and landmarks to determine angular measurements using two modules (AnglePlanes and Q3DC) from an open-source software. One observer repeated the measurements with an interval of 15 days. Five anatomic angles between planes and lines were calculated. ICC tests were applied to assess the repeatability and reproducibility of the measurements.
Results: A very strong intra-rater correlation was found for all 3 methods (AnglePlanes_Plane; AnglePlanes_Landmarks; Q3DC). A strong inter-rater correlation was found, varying from 0.84 to 1.00 using the "AnglePlanes_Plane" method; from 0.91 to 1.00 using the "AnglePlanes_Landmarks" method; and from 0.88 to 1.00 using the Q3DC module.
Conclusions: The three methods are a valid option to three-dimensionally calculate angles in surface models.