ABSTRACT
OBJECTIVES: The aim of this study was to determine the impact of fixture location and crown restoration on the accuracy of linear measurements by two cone-beam computed tomography (CBCT) systems. MATERIALS AND METHODS: Six dental implants were inserted in a dry human mandible in two stages. CBCT images were obtained in each stage by Alphard VEGA 3030 and Promax 3D Max systems. Imaging procedures were repeated after metallic crown placement. Two observers measured the alveolar height and width using five radiopaque markers. Values were compared to the same measurements made on initial images (prior to implant insertion) using t-test. The linear regression test was used to evaluate the effect of implant location on the accuracy of linear measurements. RESULTS: The impact of fixture and fixture-crown combination on the accuracy of linear measurements of height (t = -5.2, P=0.0001 and t=-5.98, P<0.0001, respectively) and width (t=-3.42, P=0.004 and t= -2.7, P=0.015, respectively) was significantly underestimated. Metal crowns had no significant effect on measurements of bone height and width (t=-1.38, P=0.19 and t=0, P=1.00, respectively). Although both systems showed some underestimations, Promax 3D Max underestimated bone width significantly more than the other system (Alphard VEGA 3030=- 0.51mm and Promax 3D Max=-0.80). Regarding implant location, the measurements in the canine sites were found to be more accurate than the region between adjacent implants. CONCLUSIONS: CBCT is an accurate and reproducible system for dental implant follow-up examinations. Metal artifacts can lead to underestimation of measurements. However, this was not statistically significant in our study.
ABSTRACT
OBJECTIVES: The purpose of this study was to develop and test a new tool for radiographic densitometry by combining periapical films and aluminum step wedge. MATERIALS AND METHODS: We reviewed 50 Kodak E-speed intraoral films. An aluminum step wedge consisting of 16 steps was constructed. Each step was 1mm×3m×10mm. The step wedge was exposed to varying exposure times, ranging from 0.05 second to 0.5 second, increasing in 0.05 second increments. Films were digitalized after processing and the MATLAB software algorithm was ran subsequently. Density of the films was measured again using a digital densitometer. In order to compare the two imaging techniques, three steps were selected. Output data from the MATLAB algorithm were compared with data obtained from the digital densitometer. RESULTS: The new method could detect significant differences between subsequent exposure times in step 7, while the densitometer did that in steps 7 and 12. The new method's sensitivity in determining density changes was 5.26%, 84.1% and 93.02% in steps 2, 7, and 12 respectively. CONCLUSIONS: Our new method has an acceptable sensitivity for determining density changes of at least 7 mmEq/Al.
ABSTRACT
OBJECTIVES: This study aimed to assess the effect of voxel size and object location in the field of view (FOV) on diagnostic accuracy of cone beam computed tomography (CBCT) for detection of simulated bone defects. MATERIALS AND METHODS: In this in vitro study, bone defects were drilled in four sections of a dry human mandible. Bone blocks were fixed on a platform parallel to the horizontal plane and CBCT images were acquired using 0.2mm and 0.3mm resolutions and five locations of FOV (anterior, posterior, left, right and center). Three reviewers viewed the images twice and the presence or absence of simulated bone defects was determined in positive and negative cases. RESULTS: Sensitivity in different locations of FOV ranged between 0.25-1.0 and 0.75-1.0 in low and high resolutions, respectively. These values were 0.625-1.0 and 0.69-1.0, respectively for specificity. Intra-observer agreements were in the range of 0.84-1.0 and 0.75-1.0 and inter-observer agreements were in the range of 0.3-0.61 and 0.46-0.69 in high and low resolutions, respectively. The highest sensitivity was seen at the center of the FOV and with an increase in resolution from 0.3mm to 0.2mm, the sensitivity increased specially in the posterior region of the FOV while image resolutions and FOV locations did not affect specificity. CONCLUSIONS: The highest sensitivity values were obtained at the center of the FOV and lowest values were seen in images acquired in the posterior region in low resolution. Diagnostic accuracy improved with increased resolution.
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OBJECTIVES: The aim of this study was to assess the effect of tube current, kilovoltage peak (kVp), metal type, and the position of metal objects on metal artifacts in cone-beam computed tomography (CBCT) images. MATERIALS AND METHODS: Titanium and cobalt-chromium rods were fabricated and placed in a dry human mandible. Samples were scanned using a Promax 3D CBCT unit with different milli-amperages and kVp. The artifacts induced by metal objects were evaluated using the Image J software in four regions of interest (ROIs) on each image. RESULTS: A higher kVp decreased artifacts of the buccal surface of the rods in 97% of the cases (P=0.046) but did not affect the severity of artifacts between the two metal objects (P>0.05). Increasing the tube current had no effect on metal artifacts in 93% of the cases (P>0.05). Artifacts induced by a cobalt-chromium alloy were more severe than those with titanium (P<0.001). Artifacts were more intense in the buccal surface of anterior rods compared to the posterior rods (P<0.003). CONCLUSIONS: Tube voltage, metal type and the position of metal objects affected the severity of metal artifacts on CBCT images. The metal type had the greatest effect on metal artifact intensity in this study.
ABSTRACT
BACKGROUND: Vertical root fractures (VRFs) can only be detected by radiography. In recent years, direct digital dental radiography (DDR) has become a substitute to film-based radiography. Purpose of this study was to compare accuracy and reliability of charge couple device (CCD)-based direct digital radiography with conventional radiography (CR) in VRF diagnosis. METHODS AND MATERIALS: In this in vitro study, 230 extracted single-rooted human teeth were endodontically instrumented. VRFs were performed experimentally in half of the samples. Each tooth was imaged using the paralleling technique with E-speed film and a CCD-based digital image receptor. Two oral radiologists interpreted the images and repeated the procedure a month later with half of the samples. The accuracy, sensitivity, and specificity of each technique were determined. The reliability and degree of agreement were also determined by the means of Cohen's Kappa analysis. χ² test was used to compare two observers' diagnosis, considering the location of fracture line. RESULTS: The accuracy of CR and DDR was 65% and 70% retrospectively. The sensitivity was 60% for CR, 61% for DDR and the specificity was 70% for CR, 78% for DDR, but the differences were not significant. The interobserver reliability was moderate for CR (K = 0.366, 95% CI) and fair for DDR (K = 0.538, 95% CI). CONCLUSION: No significant difference was seen between the two techniques. The specificity of DDR was slightly better than CR, and their accuracy and sensitivity showed small differences.
