Comparison of direct and indirect three-dimensional placement methods of facial soft tissue

Abstract

Objective To compare the reproducibility and reliability of facial soft tissue landmarks using a direct and an indirect placement methods in facial three-dimensional (3D) soft tissue assessment.Methods 3D coordinates of 37 soft tissue landmarks were obtained respectively in 35 normal healthy volunteers from 3D optical capture system and Materialise's interactive medical image control system (Mimics).Landmarks were affixed on the cutaneous surface (direct method) and marked on the 3D reconstructed craniofacial model (indirect method).Intra-class correlation coefficients (ICCs) and paired t-tests were used to compare the reliability and reproducibility of facial landmarks between two placement methods.Results For the direct placement method,86.5 ％ landmarks had an ICC higher than 0.75.For the indirect placement method,75.7％ landmarks had an ICC higher than 0.75.The inter-observer variability using the direct placement method was (1.259±0.566) mm,which was significantly smaller (P＜0.05) than (1.420±0.638) mm obtained by the indirect placement method.Conclusions Compared with indirect method,direct method has higher reliability and reproducibility in evaluating facial soft tissue. Key words: Computed tomography; Cephalometrics; Optical capture technology