A study on the reproducibility of cephalometric landmarks when undertaking a three-dimensional (3D) cephalometric analysis

Abstract

Objectives: Cone Beam Computerized Tomography (CBCT) allows the possibility of modifying some of the diagnostic tools used in orthodontics, such as cephalometry. The first step must be to study the characteristics of these devices in terms of accuracy and reliability of the most commonly used landmarks. The aims were 1- To assess intra and inter-observer reliability in the location of anatomical landmarks belonging to hard tissues of the skull in images taken with a CBCT device, 2- To determine which of those landmarks are more vs. less reliable and 3- To introduce planes of reference so as to create cephalometric analyses appropriated to the 3D reality. Study design: Fifteen patients who had a CBCT (i-CAT®) as a diagnostic register were selected. To assess the reproducibility on landmark location and the differences in the measurements of two observers at different times, 41 landmarks were defined on the three spatial axes (X,Y,Z) and located. 3.690 measurements were taken and, as each determination has 3 coordinates, 11.070 data were processed with SPSS® statistical package. To discover the reproducibility of the method on landmark location, an ANOVA was undertaken using two variation factors: time (t1, t2 and t3) and observer (Ob1 and Ob2) for each axis (X, Y and Z) and landmark. The order of the CBCT scans submitted to the observers (Ob1, Ob2) at t1, t2, and t3, were different and randomly allocated. Multiple comparisons were undertaken using the Bonferroni test. The intra- and inter-examiner ICC´s were calculated. Results: Intra- and inter-examiner reliability was high, both being ICC ≥ 0.99, with the best frequency on axis Z. Conclusions: The most reliable landmarks were: Nasion, Sella, Basion, left Porion, point A, anterior nasal spine, Pogonion, Gnathion, Menton, frontozygomatic sutures, first lower molars and upper and lower incisors. Those with less reliability were the supraorbitals, right zygion and posterior nasal spine. Key words:Cone Beam Computed Tomography, cephalometry, landmark, orthodontics, reliability.

Evaluation of cephalometric landmark identification on CBCT multiplanar and 3D reconstructions

“…These results are in agreement with those of Zamora et al, 12 who found high reliability in the identification of central incisors and molars, while the region of tuberosity showed the highest error. The difficulty in locating these anatomic landmarks can be caused by lack of practice since they are not often used in conventional cephalometry.…”

“…Subsequently, the MPR views were used without the operators having access to 3D visualization, unlike other studies that used MPR images associated with a 3D image. 3,7,[10][11][12] In the present study, ICC values were #0.45 for 11 landmarks in 3D image visualization, compared with seven points in the MPR image. That is, in general, the identification of landmarks using MPR views proved to be more reliable than the direct marking on the 3D surfaces of the skull.…”

“…However, the identification of the landmark S showed high reliability when used for MPR associated with 3D image reconstruction in previous studies. 8,12 The identification of the landmarks B, Pg, Me, and SNA showed to be reliable in both image reconstructions. This result is in agreement with Schlicher et al 8 who affirm that the structures in the midsagittal plane are more easily identified because of factors such as ease of identification in the sagittal slice due to similarities with the lateral cephalogram and because they were identified in sequence, with little change in the image position.…”

“…2,3,10,12 For the MPR views, intraobserver (86.92%) and interobserver values (84.52%) were less variable when compared with the visualization in 3D image reconstruction (74.42% and 63.66%, respectively). According to Hassan et al, 3 the association between 3D and MPR views increases precision in the identification of cephalometric landmarks.…”

Konvansiyonel ve Bilgisayarlı Sefalometrik Metotların Karşılaştırması

“…In agreement with our findings, Polat-Ozsoy et al (3) found high levels of reproducibility for both conventional and computerized methods except for some measurements such as nasolabial angle, Witts appraisal, SN-PP for both methods. Zamora et al (14) found high degree of intra-observer agreement following the operator's prior learning process. The reason of the low intra-observer agreement for some measurements in the present study might be due to the lack of the operator's prior learning process.…”