The accuracy (trueness and precision) of Bellus3DARC-7 and an in-vivo analysis of intra and inter-examiner reliability of digital and manual anthropometry

Abstract

Background Three dimensional (3D) facial imaging is becoming a popular method of facial analysis and a means of anthropometry. There is potential for 3D imaging to provide enough diagnostic information to parallel lateral cephalograms, which could, in time, reduce the need for radiation exposure to patients. The present study aimed to assess the accuracy of the Bellus3D ARC-7 (Bellus) camera by comparing the measurements of soft tissue facial landmarks obtained from Bellus scans to the measurements taken using Vernier callipers. Method Nineteen anatomical points were located on four subjects using a standard black ballpoint pen on a white, circular sticker. Distances were measured between these points using digital callipers, with the subject in a resting pose. This was repeated twice by two examiners for each subject. Two examiners subsequently performed measurements of each subject in a smiling pose. Following landmark identification, images were captured under standard conditions, using the Bellus camera. The same measurements were obtained digitally, repeated twice by two examiners for each subject in both resting and smiling poses. Results There was high precision in repeated measurements on the digital models, with less than 1.5 mm deviation between measurements. Both intra-examiner and inter-examiner reproducibility were greater following the digital measurements compared to manual measurements, with 100% of the digital measurements of landmarks falling within a set threshold deviation of ≤1.5 mm. When comparing the manual and digital measurements, the greatest deviations (>1.0 mm) occurred in regions around the cheeks and lower third of the face, while the measurements for the ears and midline structures (forehead and nose bridge) deviated the least (≤1.0 mm). This was demonstrated in models at rest and smiling. Conclusions The Bellus system produced an accurate and true image of the face from which reproducible measurements can be made within and between examiners. 3D facial images from the Bellus3D ARC-7 system were comparable to direct anthropometry, therefore the use of 3D facial scanning in orthodontics for diagnosis and treatment planning appears promising.