Two-dimensional versus three-dimensional Frankel Manoeuvre: a reproducibility study

Background/Objectives: To assess intra- and inter-observer reproducibility of the evaluation of the Frankel Manoeuvre (FM) on three-dimensional (3D) scans and to compare it to the assessment on two-dimensional (2D) pictures. Materials/Methods: This study included 44 individuals with a skeletal Class II malocclusion [9-16-years old mean age +/- standard deviation: 13.5 +/- 2.01 years]. All patients had a full Class II molar relationship, overjet >= 6 mm and point A, Nasion, point B angle (ANB) >= 5 degrees. During the FM, each patient was invited to bite in centric occlusion and then to posture the mandible forward to reach a Class I molar relationship.The FM was recorded both by a normal camera and a 3D scanner (3dMD system). Six examiners divided into two groups according to their orthodontic clinical experience (<5 and >10 years), and one gold standard in the evaluation of FM, commented twice (every 15 days) on both 2D photographs (T0 and T2) and 3D scans (T1 and T3). The intraobserver agreement and the inter-observer agreement compared to the gold standard were evaluated by computing the Cohen's K. Results: The agreement between observations for each examiner ranged from 0.36 to 1 on 2D pictures (T0 versus T2), and from 0.22 to 0.69 on 3D scans (T1 versus T3). The overall agreement was 0.63 (95 per cent CI = 0.35-0.91) in 2D analysis and 0.5 (95 per cent CI = 0.35-0.64) in 3D analysis. Conclusions/Implications: The FM was less reproducible when performed on 3D records than on 2D pictures.