Gutta-percha was heated and glued to mark 13 points on a dry human skull in order to measure the following specific mandibular, maxillary, and skull-base distances: (1) distance between left and right foramen mentales, (2) distance between left and right distal tubercules of mandibular second molars, (3) distance between left and right angulus mandibulae, (4) distance between left and right coronoid process, (5) distance between left and right incisura mandibulae, (6) distance between left and right fovea pterygoidea, (7) distance between spina nasalis anterior and spina nasalis posterior, (8) distance between left and right foramen infraorbitalis, (9) distance between left and right infraorbital suture, (10) distance between left and right foramen palatinum majus, (11) distance between left and right foramen ovale, (12) distance between left and right canalis caroticus, and (13) distance between left and right occipital condyle. Figures and show schematic drawing of mandible and human skull along with specific distances measured, respectively.
Schematic drawing of the mandible and specific distances measured
Schematic drawing of the human skull and specific distances measured
The Frankfurt line (a line from the center of the ear through the lowest point of the eye socket) was held parallel to the horizontal plane. The skull was imaged using two different CBCT units: the Iluma CBCT (3M Imtec, OK, USA) and the 3D Accuitomo 170 CBCT (3D Accuitomo; J Morita Mfg. Corp., Kyoto, Japan). The Iluma CBCT has a 24.4
19.5 cm amorphous silicon flat-panel image detector and offers a cylindrical volume of reconstruction up to 21.1
14.2 cm. The 3D Accuitomo 170 CBCT has a flat-panel detector offering five different FOVs—40
100, and 170
120 mm. With the Iluma system, images were obtained at 120 kVp and 3.8 mA with an exposure time of 40 s and were reconstructed using voxel sizes of 0.2 mm3
(high resolution) and 0.3 mm3
(low resolution). With the Morita system, images were obtained at 65 kVp, 2 mA with an exposure time of 30.8 s using a 170
120 mm FOV (0.250 mm3
voxel size). With both CBCT systems, axial scans and multi-planar reconstructions were obtained, and dedicated software was used to produce volumetric data and create 3-D reconstructions. A total of six image sets were obtained, as follows: (1) Accuitomo, 170
120 mm FOV 2-D (0.250 mm3
); (2) Accuitomo, 170
120 mm FOV 3-D (0.250 mm3
); (3) Iluma, high-resolution 2-D (0.2 mm3
); (4) Iluma, high-resolution 3-D (0.2 mm3
); (5) Iluma, low-resolution 2-D (0.3 mm3
); (6) Iluma, low-resolution 3-D (0.3 mm3
). Figure shows 3-D reconstruction digital tomographic image obtained by Iluma CBCT.
3-D reconstructed image obtained by Iluma CBCT
An Absolute Digimatic (Mitutoyo Corp., Kawasaki, Japan) digital caliper accurate to 0.01 mm was used to directly measure the mandibular, maxillary, and skull-base distances described above, and the same distances were measured on the CBCT images using the built-in measurement tools provided. One Data Viewer is a unique Morita software feature which is a stand-alone, executable application. It allows 3-D images to be viewed on any computer without installing special software. One Data Viewer is made by exporting the data files with the execution file of One Data Viewer, from i-Dixel. Data files can be taken from anywhere and viewed on all computers within the clinic network, including 3-D images and patient data. Functions to measure distances and angles, zoom, invert the gray scale, adjust brightness, contrast, and gamma are also available options. ILUMA Vision is a software application used for the display and 3-D visualization of medical image files from scanning devices, such as the ILUMA scanner. Additionally, ILUMA Vision is a preoperative software application used for the simulation and evaluation of dental implants, orthodontic planning, and surgical treatments. The ILUMA software suite provides all the capabilities needed for thorough image analysis and treatment planning. An image from one scan can be reconstructed at different levels of resolution, as many times as needed, without rescanning the patient. With a wide array of preset formats, a variety of full, multi-sectional and cross-sectional views can be accessed. The digital caliper measurements were considered the “gold standard” to which all CBCT measurements were compared. Figure shows the caliper utilized for direct measurements.
Photography of the digital caliper used for direct measurements. An Absolute Digimatic (Mitutoyo Corp., Kawasaki, Japan)
All caliper and CBCT measurements (millimeter) were separately recorded in a random order by three independent trained observers. Reproducibility of measurements was assessed by having each observer separately repeat both caliper and CBCT measurements after a 1-week interval to eliminate memory bias. No time restriction was placed on the observers. Images were viewed in a dimly lit room on a 22-in. LG Flatron monitor (LG, Seoul, Korea) with a screen resolution of 1,440
900 pixels and 32-bit color depth.
Agreement between observers and image type was assessed by calculating Pearson correlation coefficients with a level of significance set at p