Evaluation of cone-beam computed tomography data

CBCT images, obtained from the database of the Radiology Clinic of the Faculty of Dentistry of UFJF, were acquired with the i-CAT next-generation tomography (Imaging Sciences International, Hatfield, PA, USA) with the following acquisition protocol: 0.25 mm voxel, 26.9 s rotation, and a field of view varying between 7 cm × 13 cm and 10 cm × 13 cm. The examinations were performed with an acrylic lip retractor (Arcflex, FGM, Joinville, SC, Brazil), following the protocol used at the Radiology Clinic at UFJF [Figure 1]. The acrylic retractor removes soft tissues such as lips and cheeks, allowing gingival thickness measurement on CBCT images. The images of parasagittal sections were analyzed in the i-CAT Vision software (Imaging Sciences International, Hatfield, PA, USA), by a single experienced observer in CBCT images.

Patient using the acrylic lip retractor during cone-beam computed tomography exam

From the 60 students evaluated, 13 students were selected by convenience sample since they had recent CBCT examinations of the evaluated area. The tooth was used as a unit of measurement, including a total sample of 78 teeth, 26 central incisors, 26 lateral incisors, and 26 canines.

Thickness of the buccal bone and gingival tissues was obtained in the most central parasagittal section of each examined tooth. To determine the thickness of the vestibular bone, two measurements were taken perpendicularly along the long axis of the tooth, represented by the letters BT (tomographic bone thickness): BT1, 1 mm above the alveolar bone crest and BT3, 3 mm above the alveolar bone crest [Figure 2]. To measure the thickness of the buccal gingival tissue, tomographic measurements were also obtained perpendicularly along the long axis of the tooth and corresponding to the bone measurements described above. These measures, used to correlate bone thickness with gingival thickness obtained by CBCT, are represented by gingival thickness (GT) (tomographic gingival thickness): GT1, 1 mm above the alveolar bone crest and GT3, 3 mm above the alveolar bone crest [Figure 2].

Parasagittal sections of cone-beam computed tomography for measurements of bone and gingival thickness and the distance from the cement enamel junction to the bone crest; (a) Measures for bone thickness, BT1, 1 mm above the bone crest and BT3, 3 mm above the bone crest; (b) Measurements for gingival thickness, GT1, 1 mm above the bone crest and GT3, 3 mm above the bone crest; (c) Measurement of the cementoenamel junction to the crest to the cementoenamel junction–bone crest

The distance from the enamel cementum junction to the starting point of the alveolar cementum enamel junction and bone crest (CEJ-BC) was also measured [Figure 2], which represents the periodontal biological width.[14]