Mathias Pante Fontana

CBCT-based volume of simulated root resorption - influence of FOV and voxel size.

AIM To examine the influence of the field of view (FOV) and voxel size on the measurement of the volume of simulated internal root resorption (IRR) lesions through cone-beam computed tomography (CBCT). METHODOLOGY Eleven single-rooted teeth with IRR simulated by acid demineralization were studied. CBCT images were acquired using large FOV (voxel sizes of 0.200, 0.250 and 0.300 mm) and limited FOV (voxel sizes of 0.076, 0.100 and 0.200 mm). The IRR volumes were calculated using the Dolphin(®) software. Volumetric measurements were validated using IRR silicone putty casts. The analysis of variance (anova) for randomized block design complemented with the Tukeys test was employed. RESULTS IRR volumes obtained using voxel sizes of 0.200 and 0.250 mm were similar (P > 0.05). However, both these values were significantly different from that obtained using the 0.300-mm voxel (P < 0.05). There was no significant difference between IRR volumes measured through voxel sizes of 0.076 and 0.100 mm (P > 0.05), but both differed significantly from that obtained through the 0.200-mm voxel (P < 0.05). There was no significant difference between the volumetric measurements of the 0.200-mm voxel images of the restricted and large FOV protocols. The mean volumes of the silicone casts were smaller than those calculated using a 0.200-mm voxel, but were similar to those obtained using voxel sizes of 0.076 and 0.300 mm. CONCLUSIONS Despite the FOV protocol, voxel size can influence measurement of simulated IRR volumes. The importance of standardization of CBCT image acquisition protocols is emphasized, especially during follow-up of an IRR lesion, to prevent misinterpretation of its extent, which can create a bias in clinical decisions.

Is cone beam computed tomography accurate for postoperative evaluation of implants? An in vitro study

OBJECTIVE The aim of this study was to evaluate the accuracy of cone beam computed tomography (CBCT) for evaluation of the bone-implant interface in comparison with periapical radiography. STUDY DESIGN Titanium implants were inserted in 74 bovine rib blocks in intimate contact with bone walls and with a gap of 0.125 mm (simulating failure in the osseointegration process). Periapical radiographs were taken with conventional film, and CBCT scans were acquired with i-CAT (0.2 mm and 0.125 mm voxel) and Kodak (0.2 mm and 0.076 mm voxel) units. Three examiners evaluated the images using a 5-point scale. Diagnostic accuracy was analyzed through sensitivity, specificity, and the area under the receiver operating characteristic (ROC) curve (AUC) with 95% confidence intervals (CIs). Intra- and interexaminer agreements were analyzed through Kendalls concordance test. RESULTS Intra- and interexaminer agreements showed satisfactory results. The greatest accuracy was observed with conventional radiography (AUC = 0.963; CI 95% = 0.891-0.993). I-CAT 0.125-mm images showed good accuracy (AUC = 0.885; CI 95% = 0.790-0.947), with no significant difference compared with conventional radiography. Kodak images had high specificity and low sensitivity, presenting more false-negative results. CONCLUSIONS Conventional radiography showed the highest accuracy for assessment of the bone-implant interface. However, CBCT (i-CAT; 0.125-mm voxel), if available or if performed for preoperative assessment of another implant site, may provide similar accuracy.

Development and evaluation of an extraoral radiographic simulator model

Objectives: To describe the development of an extraoral radiographic simulator model that allows the demonstrations of head position and practical training of extraoral radiographic techniques and its usability evaluation by the users. Methods: It was used a macerated human skull, autopolymerising acrylic resin, orthodontic elastics, screws, polyvinyl chloride pipe and a photograph tripod to build it. After theoretical and demonstration classes, and practical training using the simulator model, twenty-nine professionals from the last five classes of an Oral Radiology Specialization Course filled out a form to evaluate its usability. Results: the modified SUS (System Usability Scale) final score obtained for usability was eighty-three, indicating high acceptance of the simulator model. Conclusion: this extraoral radiographic simulator model can be built at a very low cost, is useful for practice extraoral radiographic techniques and it should be encouraging its use as a teaching aid in other institutions. Correspondence to: Heraldo Luis Dias da Silveira, Dental School – Federal University of Rio Grande do Sul, Oral Radiology Division, Rua Ramiro Barcelos, 2492/5 floor, Porto Alegre, RS – Brazil, Tel: 55–51–33085199, E-mail: heraldo@ufrgs.br