Mapping the expression of beam hardening artefacts produced by metal posts positioned in different regions of the dental arch

Influence of the metal post material, tooth location in the dental arch, and metal artifact reduction tool on vertical root fracture diagnosis in cone beam CT

This study aimed to evaluate the influence of the metal post composition, tooth location in the dental arch, and metal artifact reduction (MAR) on vertical root fracture (VRF) diagnosis in cone beam computed tomography (CBCT). Twenty-two unirradicular premolars (12 sound and 10 fractured) and two alveolar sockets of a mandible (anterior and posterior regions) composed the sample. CBCT scans of each tooth with a metal post placed into the root canal-silver-palladium (Ag-Pd), cobalt-chromium (Co-Cr), or nickel-chromium (Ni-Cr)-were individually acquired for each mandibular region, and two conditions of MAR, using a OP300 device (Instrumentarium, Finland). Images were assessed by five evaluators independently for VRF detection. Diagnostic values were calculated and compared among all groups using multi-way ANOVA with Tukey post hoc test to investigate the effect of post material, anatomical region, and MAR on VRF diagnosis (α = 0.05). Values of area under the receiver operating curve and specificity were not influenced by the studied factors (p > 0.05). Sensitivity was influenced by the MAR in both mandibular regions (p < 0.05). In the anterior region, sensitivity values increased when the MAR was enabled, regardless of the metal post material (p < 0.05). Similar behavior was noticed in the posterior region for Ni-Cr (p < 0.05) but not for Ag-Pd and Co-Cr posts (p > 0.05). The MAR improved the sensitivity in VRF diagnosis for all tested metal posts in the mandibular anterior region and for the Ni-Cr post in the mandibular posterior region. Therefore, for images obtained in the OP300 CBCT device, activation of the MAR is suggested in these cases.

Mapping artifacts generated in a tooth adjacent to titanium and zirconia implants located in the endomass and exomass in cone beam computed tomography: an ex vivo study

OBJECTIVE

We evaluated artifact expression in a root adjacent to a dental implant located in the endomass or exomass in cone beam computed tomography (CBCT).

STUDY DESIGN

We placed a single titanium or zirconia implant adjacent to a premolar root in a dried human mandible and acquired CBCT scans using an OP300 Maxio and a Picasso Trio 3D unit exposing a 5x5cm field of view with the implant in the endomass or exomass (implant groups) or without an implant (control group). We measured the mean gray values (MGVs) for 8 lines of interest (LOIs) around the root canal of the premolar and compared the MGVs by analysis of variance, with significance established at P < 0.05.

RESULTS

For the OP300 Maxio scans, the MGVs of both implant groups in the endomass were lower than the MGVs of the control group. In the exomass, the titanium group had MGVs similar to the control group, but the zirconia group produced significantly lower MGVs than control and titanium groups (P <.0001), indicating the presence of hypodense artifacts. For the Picasso Trio 3D scans, the MGVs of both implant groups in the endomass were similar to the MGVs of the control group. In the exomass, the zirconia group generated lower MGVs than control and titanium groups (P <.0001), indicating hypodense artifacts.

CONCLUSIONS

When performing CBCT examination, titanium implants produce less artifact expression in the exomass, and zirconia implants have less artifact expression in the endomass.

Quantitative evaluation of artifact expression in conebeam computed tomography of mesoporous calcium silicate nanoparticles as a promising root canal sealer

OBJECTIVES

We aimed to quantitatively compare the area and volume of artifacts in cone beam computed tomography produced by mesoporous calcium silicate nanoparticles (MCSNs), AH Plus sealer, and iRoot SP sealer when used as root canal sealers.

METHODS

We prepared 40 single-rooted mandibular premolars and divided them into an MCSN sealer group, an AH Plus sealer group, an iRoot SP sealer group, and a no-sealer (control) group. We filled the canals with gutta-percha using the single-cone method and subjected them to conebeam computed tomography before and after the placement of root fillings using the same exposure parameters. We evaluated the images to quantify the areas of hyperdense and hypodense artifacts and non-affected teeth and reconstructed 3-dimensional image models of the materials to study volume distortion artifacts.

RESULTS

The MCSN sealer group produced a significantly smaller hyperdense and volume distortion artifacts than the AH Plus and iRoot SP groups (P < .01), but the area and volume of hypodense artifacts did not differ significantly among the groups (P > .05).

CONCLUSIONS

When used as a root canal sealer, MCSNs generate a significantly smaller area and volume of hyperdense artifacts than AH Plus and iRoot SP sealers. By significantly reducing the generation of high-density artifacts, MCSNs may facilitate the evaluation of root canal filling quality and the diagnosis of root canal abnormalities.

Comparative Evaluation of Artifacts Originated by Four Different Post Materials Using Different CBCT Settings

The aim of this study was to evaluate whether cone beam computed tomography (CBCT) images in the presence of four different post materials, obtained from different kVps with varying resolutions and varying metal artifact reduction (MAR) algorithms, differed in artifact estimation, and to compare tooth regions in terms of artifact value.

MATERIALS AND METHODS

Forty premolar teeth were used in this study. Root canals were treated, and teeth were randomly distributed into four subgroups (n = 10) for the preparation of post materials: titanium, gold (Nordin), quartz fiber (Bisco DT Light), and glass fiber (Rely X). The CBCT images were taken with two different kVps, three different metal artifact reduction (MAR) algorithm options, and two different resolutions. For each protocol, the effective dose was calculated according to the dose area production (DAP) value. The standard analysis of variance technique and the Tukey multiple comparison adjustment method were used to assess interactions among material types, kVp, MAR, and voxel settings.

RESULTS

More artifacts were found in the middle third than in the cervical third (p < 0.05). The mean value of artifacts was highest for gold (Nordin), 90 kVp, no MAR, and 100 voxel size. Glass or quartz fiber posts at low resolution, with high MAR and 96 kVp, originated fewer artifacts. Moreover, the use of 90 and 96 kVp with 200 voxel size and high MAR provided the least amount of radiation.

CONCLUSION

The best setting for radiographic follow-up of post materials on the Planmeca ProMax is 96 kVp with low resolution and high MAR; this setting produced one of the lowest effective doses.

CLINICAL SIGNIFICANCE

This study estimated the best scanning protocol by lowering the effective dose to a minimum level according to the "as low as reasonably achievable" principle, as well as assessing the tooth region and the post material generating the fewest artifacts, in order to prevent image interpretation challenges such as false-positive and false-negative results stemming from the deterioration of the visibility of the root canal due to perforation, fractures, and voids in the root canal region.

In Vitro Quantitative Evaluation of Postprocessing Filter for Metal Artifact Reduction in Cone Beam Computed Tomography Images of Titanium and Zirconium Dioxide Implants

Objective

To evaluate a postprocessing filter of a new imaging-processing software for analysis of metal artifact reduction.

Methods

Eight artificial edentulous mandibles (phantoms), where titanium and zirconium dioxide implants had been installed in four different regions (i.e., incisors, canine, premolars, and molars). CBCT volume was acquired, and then, four types of filters were applied to the images: BAR filter and Multi-CDT NR filter (e-Vol DX) and Sharpening Filters 1x and 2x (OnDemand). Artifact was assessed by measuring the standard deviation (SD) of the gray values of filtered and unfiltered images. The comparison between implant material, teeth, and filters was performed by using ANOVA, whereas multiple comparisons were performed by using Bonferroni's test. The level of significance adopted was 5%.

Results

The results showing higher SD values, which suggests a worse image, were obtained with titanium implants compared to zirconium dioxide ones. With regard to the four filters used, it can be seen that the lowest SD values were obtained with BAR and Multi-CDT NR filters and the highest with Sharpening Filters 1x and 2x, with no statistical difference between them, except regarding the molar region in titanium implants.

Conclusion

The highest SD values were seen in zirconium dioxide implants, mainly in the region of anterior teeth. The BAR filter was found to be the most effective as its SD value decreased significantly, indicating that the image quality was improved.

The metal post material influences the performance of artefact reduction algorithms in CBCT images

Abstract This study aimed to assess the effect of the MAR tool on the expression of artefacts in different regions of a tooth restored with different types of metal posts. Alveolar sockets (anterior, and posterior region) of a mandible and an unirradicular tooth were used. Cone beam computed tomography scans of the tooth without a metal post, and with cobalt-chromium (Co-Cr), nickel-chromium (Ni-Cr), or silver-palladium (Ag-Pd) were individually obtained, with 2 MAR conditions: disabled, and enabled. In an axial reconstruction, lines of interest (LOIs) were set around the canal: 4 in oblique (mesiobuccal, distobuccal, mesiolingual, distolingual) directions, and 4 in orthogonal (mesial, distal, buccal, lingual) directions. Beam-hardening artefacts expression was determined by calculating the difference in the mean of gray values (DMGV) between the experimental and control groups for each LOI. There was no significant difference in the DMGV values between “without MAR” and “with MAR” for any LOI, in neither anterior nor posterior mandible (p>0.05), for the Ni-Cr and Co-Cr groups. For the Ag-Pd, significant differences in the DMGV values were observed between “without MAR” and “with MAR” for most LOIs (p<0.05), mainly in oblique directions in the anterior region, and mesio-distal direction in the posterior region. MAR acted mostly in hypodense artefacts (negative DMGV). The effectiveness of the MAR tool of the OP300 CBCT unit varied according to the post material tested. It was effective in reducing the expression of artefacts raised by the Ag-Pd post, mainly in the tooth regions affected by hypodense artefacts, regardless of the mandibular region.

Influence of endodontic sealers artifacts in the detection of vertical root fractures

Abstract The aim of this study was to compare the influence of endodontic sealers artifacts on the detection of vertical root fracture in cone beam computed tomography (CBCT). Premolars and central incisors were assigned into five different groups: Control, Pulp Canal Sealer, AH Plus, Sealer 26, and BC Sealer (n= 10, per group). VRFs were mechanically induced and the teeth were inserted into an image phantom. Subsequently, CBCT (Cranex 3Dx, Soredex, Tuusula, Finland) images were obtained and two observers were asked separately to identify root fracture, by visual analysis. For both premolar and central incisors, kappa coefficients of intraobserver agreement varied from good to excellent (K: 80% - 87%), and the values for interobserver agreement varied from fair to moderate (K: 30% - 35%). As follows, the area under the curve (AUC) of receiver operating characteristic (ROC) values for VRFs highlighted that the use of BC sealer reduced the observers’ ability to discriminate VRFs relative to other sealers. Moreover, sensitivity values for premolars teeth ranged from 20% to 60%, and specificity ranged from 60% to 100%; while sensitivity values for central incisors ranged from 30% to 70%, and specificity ranged from 70% to 100%. In conclusion, the low sensitivity values, mainly for premolars, demonstrated the difficulty in VRF diagnosis. Furthermore, BC Sealer induced significantly more imaging artifacts than other sealers. These results highlighting that endodontic sealers may interfere with the diagnosis of VRFs.

Artifact expression of polyetheretherketone in cone beam computed tomography: An in vitro study

STATEMENT OF PROBLEM

Dental prosthetic materials can cause artifacts in cone beam computed tomography (CBCT) images, adversely affecting diagnostic quality, although the problem may be less with polyetheretherketone (PEEK). Studies evaluating the artifacts caused by frequently used prosthetic materials are lacking.

PURPOSE

The purpose of this in vitro study was to compare the artifacts in CBCT images caused by PEEK, zirconia, cobalt-chromium (Co-Cr) alloy, and titanium (Ti).

MATERIAL AND METHODS

A polymethylmethacrylate phantom (Ø4.0×4.0 cm) with a central cylindrical aperture (Ø0.5×0.5 cm) was produced. Co-Cr, Ti, zirconia, and PEEK cylinders (0.5×0.5 cm) were manufactured, and CBCT images of the empty phantom (control group) with the test cylinders inside were made 3 times. In all images, the axial sections passing through the middle of the materials were evaluated. Eight regions of interest (ROI) area were determined around the materials (0.5×0.5 cm). The presence of artifacts was evaluated by making gray value standard deviation (SD) calculations in these ROI areas. The average SD values of 8 ROI fields from the 3 CBCT scans were made, and the materials were compared with each other in terms of the presence of artifacts by using 1-way analysis of variance (α=.05).

RESULTS

The difference between the SD values of the control and the PEEK cylinder was not statistically significant (P>.05). The SD values of both the control and PEEK groups were significantly lower than those of the zirconia, Co-Cr, and Ti groups (P<.05).

CONCLUSIONS

Zirconia, Ti, and Co-Cr caused artifacts in CBCT images, but the artifacts with PEEK were similar to those in the control group, suggesting it was the optimal choice in terms of achieving diagnostic quality.