Effect of anatomical region on the formation of metal artefacts produced by dental implants in cone beam computed tomographic images

Incidental Findings Following Dental Implant Procedures in the Mandible: A New Post-Processing CBCT Software Analysis

Background/Objectives: The aim of this study was to evaluate incidental findings in the mandible after the placement of dental implants using a new cone-beam computed tomography (CBCT) software. Methods: The initial sample consisted of 2872 CBCT scans of patients of both sexes. The parameters evaluated in this study were the location of the implants in the mandible, implant length, anatomical relationship of the implant with the mandibular canal, presence or absence of damage to the adjacent teeth, presence or absence of implant fractures, and presence or absence of bone support. Fisher's exact test was performed to compare the variables. The significance level was set at p = 0.05. Results: Out of 2872 CBCT scans, 214 images of patients with an average age of 44.5 years were included. The most frequent location of the implants was the posterior region (93.5%), with 54% of the implants having a length between 9 and 14 mm. It was found that 92% of the implants were positioned above the mandibular canal. Damage to adjacent teeth was observed, with no correlation with the implant positioning (p = 1.000). In 100% of cases of implants in the anterior region, there was bone support. Fracture was observed in 1.7% of implants with a length between 9 and 14 mm. Conclusions: The installation of implants in the mandible occurs more frequently in the posterior region, with a high presence of bone support and a low incidence of damage to adjacent teeth, anatomical structures, and fractures.

Expression of artefacts from different orthodontic brackets and wires in cone beam computed tomography scans-an in vitro study

OBJECTIVES

To investigate artefacts produced by different orthodontic brackets and wires in cone-beam computed tomography (CBCT) scans.

MATERIALS AND METHODS

Two dental arches were made using extracted human teeth and plaster. Three pairs of acetate plates containing different brackets - metallic, ceramic, and self-ligating ceramic with NiTi clip - along with a control plate (i.e., without brackets) were prepared. Wire changes (NiTi and steel) were made during CBCT acquisitions, performed with a fixed exposure protocol. Axial slices were selected for mean gray values and standard deviation measurement in three regions of interest (buccal, lingual, and tooth). Noise and contrast-to-noise ratio (CNR) were calculated and compared among the different brackets and wires by ANOVA with a significance level of 5%.

RESULTS

Overall, the buccal and tooth region were mostly affected by the metallic and self-ligating brackets, showing higher noise, and lower CNR (p < 0.05). On the other hand, less impact of ceramic brackets in the image quality was observed (p ≥ 0.05). The lingual region did not show expressive differences among the brackets and wire combinations (p ≥ 0.05). The presence of wire associated with the brackets did not worsen image quality (p ≥ 0.05).

CONCLUSIONS

In conclusion, metallic and self-ligating brackets have greater artefact expression than ceramic brackets. The wire did not influence image quality.

CLINICAL RELEVANCE

One should pay attention to the type of brackets when requesting a CBCT scan during treatment, as metallic and self-ligating brackets may express greater artefacts than ceramic brackets.

The Impact of AI on Metal Artifacts in CBCT Oral Cavity Imaging

OBJECTIVE

This study aimed to assess the impact of artificial intelligence (AI)-driven noise reduction algorithms on metal artifacts and image quality parameters in cone-beam computed tomography (CBCT) images of the oral cavity.

MATERIALS AND METHODS

This retrospective study included 70 patients, 61 of whom were analyzed after excluding those with severe motion artifacts. CBCT scans, performed using a Hyperion X9 PRO 13 × 10 CBCT machine, included images with dental implants, amalgam fillings, orthodontic appliances, root canal fillings, and crowns. Images were processed with the ClariCT.AI deep learning model (DLM) for noise reduction. Objective image quality was assessed using metrics such as the differentiation between voxel values (ΔVVs), the artifact index (AIx), and the contrast-to-noise ratio (CNR). Subjective assessments were performed by two experienced readers, who rated overall image quality and artifact intensity on predefined scales.

RESULTS

Compared with native images, DLM reconstructions significantly reduced the AIx and increased the CNR (p < 0.001), indicating improved image clarity and artifact reduction. Subjective assessments also favored DLM images, with higher ratings for overall image quality and lower artifact intensity (p < 0.001). However, the ΔVV values were similar between the native and DLM images, indicating that while the DLM reduced noise, it maintained the overall density distribution. Orthodontic appliances produced the most pronounced artifacts, while implants generated the least.

CONCLUSIONS

AI-based noise reduction using ClariCT.AI significantly enhances CBCT image quality by reducing noise and metal artifacts, thereby improving diagnostic accuracy and treatment planning. Further research with larger, multicenter cohorts is recommended to validate these findings.

Influence of the presence of dental implants on the accuracy and difficulty level of diagnosis of furcation involvement in molars: An in vitro CBCT study

OBJECTIVE

The aim of this study was to investigate the possible interference of image artifacts (IA) generated by dental implants in the evaluation of furcation involvement (FI) in molars.

METHODS

Tomographic scans of first molars (1M) were performed in dry skulls in the absence and presence of titanium (TI) and zirconia (ZI) dental implants. FI grades were simulated in the alveoli of the 1Ms. Diagnostic accuracy of FI and level of difficulty were verified. Chi-squared test and logistic regression analysis were used.

RESULTS

There was no difference in the diagnostic accuracy of FI between the arches (p = .117). The highest diagnostic accuracy value for the implant variable was found in the absence of implants (88.3%) and the lowest in the presence of two ZI implants (66.7%). The highest diagnostic accuracy value for FI was observed in grade 0 (G0). There was no significant difference between the arches regarding the evaluators' perception of difficulty (p > .05). Assessments were considered difficult in 12.7% of the TI implants and in 29% of the ZI implants. Regarding the number of dental implants, assessments were considered difficult in 24.4% cases including one implant and 17.4% cases including two implants. The logistic regression model showed a significant p-value only for one and two ZI implants (p = .0061 and p = .0096, respectively).

CONCLUSION

The presence of dental implants in the region adjacent to the area of investigation of FI decreased the diagnostic accuracy while increasing the perception of difficulty by the examiners, especially in cases with ZI implants.

Does the shape of the field-of-view influence the magnitude of artefacts from high-density materials in cone-beam computed tomography?

OBJECTIVE

To compare cylindrical and convex triangular field-of-views (FOVs) concerning the magnitude of artefacts from high-density materials in cone-beam CT (CBCT).

METHODS AND MATERIALS

Cylinders of amalgam, chromium-cobalt, titanium, and zirconia were individually placed in the anterior and posterior regions of a polymethylmethacrylate phantom and scanned using cylindrical and convex triangular FOVs of the Veraview X800 CBCT device. Using the Image J software, 15 square regions of interest (ROIs) were placed in the axial reconstruction around the middle level of the cylinder and at distances of 0.5, 1.0, and 1.5 cm from the centre of the cylinder. Mean grey value and standard deviation of each ROI were averaged for each distance and subtracted from the values of a control ROI to calculate the magnitude of the artefacts by the grey value mean difference (GVMD) and grey value standard deviation (GVSD). Multiway analysis of variance with Tukey post-hoc test with a significance level of 5% evaluated the effect of the shape of the FOV, position inside the FOV, high-density material, and the distance of the artefact from the material.

RESULTS

The convex triangular FOV increased the GVSD for all materials in the anterior and posterior regions at 0.5 cm compared to the cylindrical FOV (p < 0.0001). The convex triangular FOV showed greater GVMD for chromium-cobalt and zirconium in the anterior region and all materials in the posterior region at all distances (p < 0.0001).

CONCLUSION

The FOV shape influences the magnitude of artefacts from high-density materials. The convex triangular FOV showed greater artefact magnitude with variability among the high-density materials, region in the FOV, and distance from the material.

The Effect of Changes in the Angular Position of Implants on Metal Artifact Reduction in Cone-Beam Computed Tomography Images: A Scoping Review

OBJECTIVE

Dental implant artifacts can compromise the quality of cone-beam computed tomography (CBCT) scans and challenge radiographic detection in surrounding regions. This literature review was conducted to examine the impact of implant angle modification on reducing metal artifacts in CBCT scans.

MATERIALS AND METHODS

A scoping review of literature was carried out in PubMed, Embase, Scopus, and Cochrane databases.

RESULTS

Different spatial planes, including alpha, beta, gamma, and phi, along with 0°, 5.2°, 9.8°, 14.5°, 15°, 30°, 45°, 60°, 75°, and 90° angles were studied. Changes in the angular position of implants may reduce metal artifacts and improve the quality of CBCT scans.

CONCLUSIONS

Rotating implants within the alpha plane and angling them at 90° in the alpha plane enables reducing dental implant artifacts.

Image quality for visualization of cracks and fine endodontic structures using 10 CBCT devices with various scanning protocols and artefact conditions

The aim of this study was to evaluate CBCT exposure protocols and CBCT devices in terms of image quality for the detection of cracks and fine endodontic structures using 3 conditions of metallic artifacts. An anthropomorphic phantom containing teeth with cracks, isthmus, narrow canal, and apical delta was scanned using ten CBCT devices. A reference industrial CT image was used to detect and measure all structures. Three conditions were created: (1) metal-free, (2) 'endo' and (3) 'implant' with metallic objects placed next to the teeth of interest. For each condition, three protocols were selected: medium field of view (FOV) standard resolution, small FOV standard and high resolution. The results showed that only small FOV high-resolution metal-free images from two devices (A and H) were appropriate to visualize cracks. For fine structure identification, the best result was observed for small FOV high resolution. However, the visualization significantly worsened in the presence of metallic artefacts. The ability of CBCT images for visualizing cracks is restricted to certain CBCT devices. Once metallic artefacts are present, crack detection becomes unlikely. Overall, small FOV high-resolution protocols may allow detection of fine endodontic structures as long as there are no high-dense objects in the region of interest.

Comparison of the amount of artifacts induced by zirconium and titanium implants in cone-beam computed tomography images

Background

This study aimed to compare the amount of artifacts induced by the titanium and zirconium implants on cone-beam computed tomography (CBCT) and assess the effect of different exposure settings on the image quality for both materials.

Methods

In this experimental study, 30 zirconium and 30 titanium implants were placed in bovine rib bone blocks. CBCT images were taken in two different fields of view (FOV: 4 × 6 cm² and 6 × 8 cm²) and at two resolutions (133 µ and 200 µ voxel size). Subsequently, two observers assessed the images and detected the amount of artifacts around the implants through gray values. Data were analyzed by paired t test and independent t test using SPSS 21 and the 0.05 significance level.

Results

The results showed that titanium implants caused lower amounts of artifacts than zirconium implants, which was statistically significant (P < 0.001). The larger FOV (6 × 8 cm²) resulted in a lower amount of artifacts in both groups, although the results were only statistically significant in the zirconium group (P < 0.001). The amount of artifacts was increased when using the 133 µ voxel size in both groups, which was only significant in the zirconium group (P < 0.001).

Conclusion

Our results suggest that zirconium implants induce higher amounts of artifacts than titanium ones. We also concluded that the artifacts could be minimized using the larger FOV and voxel size.

Influence of artefacts generated by titanium and zirconium implants in the study of trabecular bone architecture in cone-beam CT images

OBJECTIVES

To evaluate the influence of artefacts generated by titanium and zirconium implants on trabecular bone architecture assessment through cone-beam CT (CBCT). The influence of kilovoltage (kVp) and metal artefact reduction (MAR) in such analysis was also assessed.

METHODS

CBCT scans were obtained with Picasso Trio with or without a titanium or zirconium implants in a posterior region of a mandible using 70, 80 or 90 kVp, with or without MAR. The other acquisition settings were constant: field of view 8 × 5 cm, voxel size 0.2 mm, 5 mA, 24 s and 720 frames. Two volumes of interest (VOIs) were determined comprising trabecular bone mesial and distal to the implant area. The following morphometric parameters were measured: connectivity density (Conn. Dn.), fractal dimension (FD), bone volume fraction (BV/TV), bone surface density (BS/TV), trabecular thickness (Tb. Th.), and trabecular spacing (Tb. Sp.), and compared by multiway ANOVA (α = 0.05).

RESULTS

For Conn. Dn. and FD, with MAR, the zirconium group showed values significantly lower than the other groups (p < 0.05). For BV/TV, BS/TV, Tb. Th. and Tb. Sp., the zirconium group showed the highest values, regardless of MAR condition (p < 0.05). MAR increased BS/TV and Tb. Th. values, and decreased FD values for zirconium group. In general, the kVp level did not influence trabecular morphometric parameters.

CONCLUSION

The assessment of the trabecular bone architecture was mainly influenced by the expression of the artefacts generated by zirconium implants. MAR decreased the FD and increased the BS/TV and Tb.Th. values regardless of the kVp level.

Does the size of an object containing dental implant affect the expression of artifacts in cone beam computed tomography imaging?

Background

Artifacts fault image quality but handling several factors can affect it. This study was conducted to investigate the effect of object size on artifacts in cone-beam computed tomography systems.

Methods

Five phantoms, each containing a titanium implant in a sheep bone block, were fabricated of various sizes ranging from XS to XL: The M phantom was the same size as the device’s field of view (FOV). The L and XL phantoms were 20 and 40% larger than the FOV while the S and XS phantoms were 20 and 40% smaller than FOV, respectively. Ballistic gelatin was used to fill the phantoms. Phantoms were scanned by NewTom VGI and HDXWill Q-FACE. The mean and standard deviation (SD) of gray values in each 120 ROI was obtained by OnDemand software. The contrast to noise ratio (CNR) was also calculated.

Results

The gray value in S and M phantoms were more homogenous. The lowest SD value (10.20) was found in S phantom. The highest value for SD (125.16) was observed in XL phantom. The lowest (4.47) and highest (9.92) CNR were obtained in XL and S phantoms, respectively. HDXWill Q-FACE recorded a higher SD and a lower CNR than NewTom VGI (P < 0.05).

Conclusion

Object dimensions of the FOV size or up to 20% smaller provided better image quality. Since the dimensions of soft tissue in most patients are larger than the selective FOV, it is recommended that in CBCT artifacts studies, an object with dimensions closer to the patient’s dimensions be used to better relate the results with the clinical condition, because the sample dimensions affect the amount of artifacts.

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.

Distortion or magnification? An in vitro cone-beam CT study of dimensional changes of objects with different compositions

OBJECTIVES

To assess whether dimensional changes occur as shape distortion (unevenly), contraction or magnification (evenly) in cone beam computed tomography (CBCT) considering materials, anatomical regions and metal artefact reduction algorithms.

METHODS

Four cylinders of amalgam (Am), cobalt-chromium (Co-Cr), gutta-percha (Gu), titanium (Ti) and zirconium (Zi) were inserted inside a polymethylmethacrylate phantom in anterior and posterior regions for acquisitions in Picasso Trio and OP300 with MAR enabled and disabled. Two observers measured the dimensions of each cylinder in three axes: Y (height), Z (antero posterior diameter) and X (latero-lateral diameter). Repeated measures ANOVA with Tukey post-hoc test compared the data (α = 5%).

RESULTS

Shape distortion occurred for all materials in anterior region of Picasso Trio without MAR (p < 0.05). With MAR enabled, Gu and Ti contracted (p ≥ 0.05), while the others showed distortion (p < 0.05). In posterior region, all materials distorted in both MAR conditions (p < 0.05), except Gu, which magnified without MAR (p ≥ 0.05) and contracted unevenly with MAR (p < 0.05). In anterior region of OP300, all materials magnified without MAR, (p ≥ 0.05) and had shape distortion with MAR (p < 0.05). In posterior region, only Am showed magnification without MAR (p ≥ 0.05), while all materials presented shape distortion with MAR (p < 0.05).

CONCLUSION

Dimensional changes of high-density materials in CBCT can be either a magnification, a contraction or a distortion; the last condition is the most prevalent. Furthermore, changes differ considering material, anatomical region and MAR condition.

Cone-beam computed tomography artifacts in the presence of dental implants and associated factors: an integrative review

Purpose

This study was conducted to review the literature regarding the types of cone-beam computed tomography (CBCT) artifacts around dental implants and the factors that influence their formation.

Materials and Methods

A search strategy was carried out in the PubMed, Embase, and Scopus databases to identify published between 2010 and 2020, and 9 studies were selected. The implants included 306 titanium, titanium-zirconium, and zirconia implants, as well as 5 titanium cylinders.

Results

The artifacts around the implants were the beam-hardening artifact, the streaking artifact, and band-like radiolucent areas. Some factors that influenced the formation of artifacts were the implant material, bone type, evaluated regions, distance, type of CBCT, field of view (FOV) size, milliamperage, peak kilovoltage (kVp), and voxel size. The beam-hardening artifact was the most widely reported, and it was minimized in protocols with a smaller FOV, larger voxels, and higher kVp.

Conclusion

The risk and benefit of these protocols in individuals with dental implants must be considered, and clinical examinations and complementary radiographs play an essential role in implantology.

Implant-to-root dimensions projected by panoramic radiographs inthe maxillary canine-premolar region: implications for dental implant treatment

BACKGOUND

This study aimed to compare panoramic radiography (PAN) and cone beam computed tomography (CBCT) determinations of implant-to-root dimensions (IRD) in anterior and posterior maxillary regions, and to help determine in which instances increased radiation exposure from CBCT scans may be justified.

METHODS

IRD measured by PAN (PAN-D) from implant-to-root sites (central incisor, lateral incisor, canine, first premolar, and second premolar) was collected from 418 implant sites in 110 adults. The CBCT technique was used as the reference method for the estimation of IRD. The PAN analysis equations were developed using stepwise multiple regression analysis and the Bland-Altman approach was applied to assess the agreement between PAN and CBCT methods.

RESULTS

The odds ratio that an implant at the canine-to-first premolar (9.7:1) (P = 0.000) or at the first premolar-to-second premolar region (4.5:1) (P = 0.000) belongs to the underestimation group was strong and highly significant. The root mean square error (RMSE) and pure error (PE) were highest for the canine-to-first premolar (RMSE = 0.886 mm, PE = 0.45 mm) and the first premolar-to-second premolar region (4.5:1) (RMSE = 0.944 mm, PE = 0.38 mm).

CONCLUSIONS

This study provides evidence of site-specific underestimations of available horizontal bone dimensions for implants when assessed by PAN. These data suggest that the canines and first and second premolars may have to be excluded when assessing root angulations via PAN.

Quantitative assessment of artefacts and identification of gaps in prosthetic crowns: a comparative in vitro study between periapical radiography and CBCT images

OBJECTIVES

To evaluate, in an in vitro study, the quantity of artefacts generated by two different restorative materials, and to determine the diagnostic accuracy of cone beam CT (CBCT) scans and periapical radiographs in identifying gaps in prosthetic crowns.

METHODS

A total of 30 teeth restored with metal-ceramic (n = 15) and all-ceramic (n = 15) crowns, properly adapted and with 0.30- and 0.50 mm gaps, underwent CBCT exams (with voxel sizes of 0.25 and 0.30 mm) and periapical radiographs. The artefacts generated by two different crowns were quantified and compared by the Mann-Whitney test. In addition, five examiners evaluated the presence or absence of gaps in periapical radiographs and CBCT images. The accuracy of tests was determined by the area under the receiver operatring characteristic curve and these values were compared by using the Kruskal-Wallis test.

RESULTS

There was no significant difference in artefact values between the different restorative materials and the different resolutions of CBCT images. Regarding the accuracy of the tests evaluated, periapical radiography and CBCT with voxel size 0.25 mm showed the best performance for smaller gaps (0.30 mm). For larger gaps (0.50 mm), all exams tested showed the same performance.

CONCLUSIONS

Periapical radiography was still the most cost-beneficial method for the diagnosis of maladaptation in dental restorations. CBCT exams did not improve accuracy in detecting gaps in prosthetic crowns.

Artefacts at different distances from titanium and zirconia implants in cone-beam computed tomography: effect of tube current and metal artefact reduction

OBJECTIVES

To evaluate the effect of cone-beam computed tomography (CBCT) tube current (mA) on the magnitude of artefacts at different distances from titanium or zirconia implants, with and without activation of a proprietary metal artefact reduction (MAR).

MATERIAL AND METHODS

Human mandibles were scanned on an OP300 Maxio CBCT unit (Instrumentarium, Tuusula, Finland) before and after the installation of dental implants, with four different tube currents (4 mA, 6.3 mA, 8 mA and 10 mA), with and without activation of proprietary MAR. The effect of mA on the standard deviation (SD) of gray values and contrast to noise ratio (CNR) were assessed in regions of interest located 1.5 cm, 2.5 cm, and 3.5 cm from implants.

RESULTS

In the presence of titanium implants, a significant decrease in SD was found by increasing tube current from 4 mA to 6.3 mA or 8 mA. For zirconia implants, 8 mA yielded better results for all distances. MAR improved CNR in the presence of zirconia implants at all distances, whereas no differences were observed with the use of MAR for titanium implants.

CONCLUSION

Increased tube current can improve overall image quality in the presence of implants, at all the distances tested. When a zirconia implant is present, such increase in mA should be higher in comparison to that for examinations with titanium implants. Activation of OP300 Maxio proprietary MAR improved image quality only among examinations with zirconia implants.

CLINICAL RELEVANCE

Artefact-generating implants are common in the field of view of CBCT examinations. Optimal exposure parameters, such as tube current, ensure high image quality with lowest possible radiation exposure.

Evaluation of the Metal Artifact Caused by Dental Implants in Cone Beam Computed Tomography Images

Statement of the problem: The presence of a metal object such as dental implants in the scan field may cause artifacts on the cone-beam computed tomography (CBCT) images, which can reduce the diagnostic quality and accuracy of images. Purpose: The aim of this in vitro study was to compare the severity of implant-induced metal artifacts on CBCT images. Materials and method: To this end, a dry human mandible and a maxilla were selected, then two Roxolid and two Zirconium fixtures with different diameters were placed in the central incisor and first molar sockets and fixed with dental wax. The mandible and maxilla were placed in the simulated phantom for soft tissue, and the occlusal plane was adjusted parallel to the horizon. Images were taken at standard and high resolutions using two CBCT units. The CBCT gray values were measured in three longitudinal sections of the fixture (cervical, middle and apical) and the contrast noise ratio (CNR) was calculated. The CNR values of images were analyzed based on the fixture material, resolution, jaw, unit parameters and fixture size by using the paired t-test and different fixture sections by one-way ANOVA. Results: Depending on the CBCT unit, the CNR values in Roxolid and Zirconium fixtures are completely different. Under higher exposure parameters, the CNR values of the Roxolid and Zirconium fixtures were significantly higher in the maxilla than mandible. However, the fixture size and longitudinal section type did not have a significant effect on the CNR values. Conclusion: In contrast to the fixture material, scanning parameters and jaw type, differences in the size and longitudinal section of the fixtures had no impact on artifact severity.

Does the metal artifact reduction algorithm activation mode influence the magnitude of artifacts in CBCT images?

Purpose

This study was conducted to assess the effectiveness of a metal artifact reduction (MAR) algorithm activated at different times during cone-beam computed tomography (CBCT) acquisition on the magnitude of artifacts generated by a zirconium implant.

Materials and Methods

Volumes were obtained with and without a zirconium implant in a human mandible, using the OP300 Maxio unit. Three modes were tested: without MAR, with MAR activated after acquisition, and with MAR activated before acquisition. Artifacts were assessed in terms of the standard deviation (SD) of gray values and the contrast-to-noise ratio (CNR) in 6 regions of interest with different distances (10 to 35 mm, from the nearest to the farthest) and angulations (70° to 135°) from the implant region.

Results

In the acquisitions without MAR, the regions closer to the implant (10 and 15 mm) had a higher SD and lower CNR than the farther regions. When MAR was activated (before or after), SD values did not differ among the regions (P>0.05). The region closest to the implant presented a significantly lower CNR in the acquisitions without MAR than when MAR was activated after the acquisition; however, activating MAR before the acquisition did not yield significant differences from either of the other conditions.

Conclusion

Both modes of MAR activation were effective in decreasing the magnitude of CBCT artifacts, especially when the effects of the artifacts were more noticeable.

Evaluation of metal artefacts for two CBCT devices with a new dental arch phantom

OBJECTIVES

To create a new phantom design to evaluate the real impact of artefacts caused by titanium on bone structures in cone beam CT images considering different positions and quantity of metals in the dental arch, with and without metal artefact reduction (MAR).

METHODS

A three cylindrical polymethyl methacrylate (PMMA) plate phantom was designed containing eight perforations arranged to simulate the lower dental arch in the intermediate plate. Three titanium cylinders were positioned in different locations and quantities to test different clinical conditions and to quantify the impact of the metal artefact around five bone cylinders. Scans were carried out in seven different protocols (Control, A-F) in two cone beam CT devices (OP300 Maxio and Picasso Trio). Eight regions of interest around each cortical and trabecular bone were used to measure the grey value standard deviation corresponding the artefact expression in the Image J software. Both the artefact expression and the MAR effect were assessed using the Wilcoxon, Friedman (Dunn) and Kruskal-Wallis tests (significance level of 5%).

RESULTS

For both devices, MAR was statistically efficient only for the protocols E, and F. Protocol F (three metals on the adjacent area of the analysis region) showed higher artefact expression when compared to the others.

CONCLUSION

In conclusion, the new phantom design allowed the quantification of the metal artefact expression caused by titanium. The metal artefact expression is higher when more metal objects are positioned in the adjacent bone structures. MAR may not be effective to reduce artefact expression on the adjacencies of those objects for the devices studied.

Electronic processing of digital panoramic radiography for the detection of apical periodontitis

INTRODUCTION

This study aimed to evaluate the accuracy of both digital complete and small portion of panoramic radiography (PAN) in the detection of clinically/surgically confirmed asymptomatic apical periodontitis (AP) lesions with and without endodontic treatment.

METHODS

A total of 480 patients/teeth including 120 AP with and without endodontic treatment, and 120 healthy periapex with and without endodontic treatment were detected via CBCT using the periapical index system. Each diseased and healthy patient underwent PAN first and a CBCT scan within 40 days. All 480 cases were assessed by four different methods, as follows: complete PAN with clinical examination of each tooth available and not available, respectively, and small portion of PAN in which a root with crown and root without crown were displayed, respectively. Periapical index system was also used to assess AP by PAN. Accuracy for both complete and small portion of PAN with respect to CBCT was analyzed.

RESULTS

The overall accuracy of the four methods for teeth with endodontic treatment (73.4) was higher than teeth without endodontic treatment (66.6). Accuracy of complete PAN and portion of PAN was 71.3 and 68.7, respectively. As regards teeth without endodontic treatment, accuracy was higher for complete PAN in the upper/lower incisive area and for small portion of PAN in the upper molar area. No difference was found in teeth with endodontic treatment.

CONCLUSION

Complete and small portion of PAN showed greater accuracy in the upper/lower incisive area and upper molar area of untreated teeth, respectively, whereas no difference was found in treated teeth.

Quantitative assessment of variation in CBCT image technical parameters related to CBCT detector lateral-offset position

OBJECTIVES

To assess the effect of CBCT detector position (aligned/lateral-offset) on image technical parameters (mean voxel value - MVV, standard deviation of voxel value (SDVV) distribution), comparing peripheral regions of interest (ROIs) to the central ROI in CBCT volumes.

METHODS

40 CBCT volumes of a wax phantom were acquired in six units with aligned and/or lateral-offset detectors: Cranex 3Dx (CRA), Ortophos SL (ORT), Picasso Trio (PIC), Promax 3D Mid (PRO), Scanora 3D (SCA), and X1. Four image-acquisition protocols used an aligned detector, and four a lateral-offset detector. In each volume, 13 ROIs (12 peripheral and 1 central) were evaluated. MVV and SDVV of the peripheral ROI were compared to those of the central ROI in the volume. MVVD (the difference in percentage, between the MVV of a peripheral and the central ROI) was calculated.

RESULTS

For aligned-detectors, MVV increased (ORT and PRO) or decreased (CRA and X1) in the ROIs farther from the centre. For lateral-offset detectors, ROIs farther from the centre showed increased MVV. SDVV for most aligned detectors was lower, the nearer the ROI was to the centre. For lateral-offset detectors, it was lower for the peripheral ROIs, except with PIC. Range for MVVD was -32.8% to 22.8% for units with aligned detectors, and -20.7% to 69.5% for lateral-offset detectors.

CONCLUSION

Lateral-offset detectors to acquire CBCT images significantly change SDVV distribution within the field-of-view, and lead to MVVD with increased range, compared to aligned detectors. This must be taken in consideration in the clinic, if voxel-value dependent measurements are to be performed.

Difference in the artefacts production and the performance of the metal artefact reduction (MAR) tool between the buccal and lingual cortical plates adjacent to zirconium dental implant

OBJECTIVES

To quantify the artefacts production and the performance of the metal artefact reduction (MAR) tool, enabled before or after the acquisition, in cortical plates (buccal and lingual) and other regions adjacent to zirconium implants.

METHODS

Cone beam CT scans were acquired using the OP300 Maxio unit before (control group) and after (implant group) the insertion of a zirconium implant into the posterior region of a dry mandible. Three conditions of MAR tool were tested: "without MAR", with "MAR activated after acquisition", and with "MAR activated before acquisition". The standard deviation (SD), contrast-to-noise ratio (CNR) and voxel values were calculated in the buccal and lingual cortical plates, medullary bone and water region, close to the implant. The structural bone analysis was performed in the medullary bone close to the implant.

RESULTS

Overall, in control and implant groups, the lingual cortical had higher SD, lower CNR and lower voxel values than the buccal cortical, regardless of the MAR condition (p < 0.05). Implant caused higher SD values and lower voxel values in adjacent regions "without MAR" (p < 0.05). MAR activation decreased SD and changed voxel values when the implant was present, regardless of MAR activation mode (p < 0.05). The activation of MAR increased the trabecular thickness values for the implant group (p < 0.05).

CONCLUSION

The expression of artefacts adjacent to zirconium implants is greater in the lingual than in the buccal cortical. The greater the expression of artefacts in this region, the greater the effectiveness of the MAR tool in homogenizing the grey values, regardless of the time of its activation.

Is Panoramic Radiography an Accurate Imaging Technique for the Detection of Endodontically Treated Asymptomatic Apical Periodontitis?

INTRODUCTION

This study aimed to evaluate the diagnostic accuracy of panoramic radiography (PAN) for the detection of clinically/surgically confirmed apical periodontitis (AP) in root canal-treated teeth using cone-beam computed tomographic (CBCT) imaging as the reference standard.

METHODS

Two hundred forty patients with endodontically treated AP (diseased group) were detected via CBCT imaging using the periapical index system. They were divided into groups of 20 each according to lesion size (2-4.5 mm and 4.6-7 mm) and anatomic area (incisor, canine/premolar, and molar) in both the upper and lower arches. Another 240 patients with root filling and a healthy periapex (healthy group) were selected. All diseased and healthy patients underwent PAN first and a CBCT scan within 40 days. The periapical index system was also used to assess AP using PAN. Sensitivity, specificity, diagnostic accuracy, positive predictive value, and negative predictive value for PAN images with respect to CBCT imaging were analyzed. The k value was calculated to assess both the interobserver reliability for PAN and the agreement between PAN and CBCT.

RESULTS

PAN showed low sensitivity (48.8), mediocre negative predictive value (64.7), good diagnostic accuracy (71.3), and high positive predictive value (88.6) and specificity (93.8). Both interobserver reliability for PAN and agreement between PAN and CBCT were moderate (k = 0.58 and 0.42, respectively). The best identified AP was located in the lower canine/premolar and molar areas, whereas the worst identified AP was located in the upper/lower incisor area and upper molar area.

CONCLUSIONS

PAN showed good diagnostic accuracy, high specificity, and low sensitivity for the detection of endodontically treated AP.

Magnitude of cone beam CT image artifacts related to zirconium and titanium implants: impact on image quality

OBJECTIVES

To evaluate the magnitude of artifacts related to titanium and zirconium implants at different distances and angulations and their impact on cone beam CT(CBCT) image quality.

METHODS

CBCT images were obtained before and after the insertion of titanium and zirconium implants in a mandible on different CBCT units: Picasso Trio, ProMax 3D and 3D Accuitomo 80. Artifact was assessed by measuring the standard deviation (SD) of gray values and contrast-to-noise ratio (CNR) of 11 regions of interest (ROIs) at different distances (1.5 cm, 2.5 cm and 3.5 cm) and angulations (65°, 90°, 115° and 140°) from implant region.

RESULTS

For titanium images, SD values did not differ from those of images without implant in all ROIs; however, some effect occurred in Picasso images as higher values were observed in ROIs closer to the implant (p < 0.05). Zirconium images showed higher SD values than the others in some ROIs for Picasso and ProMax (p < 0.05). In ProMax, the difference was observed even in the farthest ROIs from the implant. CNR values were not influenced by the ROI in Picasso, but presented lower values in ROIs closer to the zirconium implant for ProMax and Accuitomo.

CONCLUSIONS

The quantity and magnitude of artifacts in CBCT are influenced by the type of implant and CBCT unit. Although they are more pronounced in regions closer to the implant and located at 90° in relation to the mandibular long axis, they can reach as far as 3.5 cm from the artifact-generator object.