Influence of the Intracanal Material and Metal Artifact Reduction Tool in the Detection of the Second Mesiobuccal Canal in Cone-beam Computed Tomographic Examinations

Assessing the Impact of the Metal Artifact Reduction Tool on Detecting Furcation Lesions in Maxillary Molars with Different Intracanal Posts: An Ex Vivo Cone-beam Computed Tomography Study

INTRODUCTION

Considering the potential image compromise and diagnostic challenges posed by metals, this study aimed to assess the efficacy of the metal artifact reduction (MAR) tool in cone-beam computed tomography examinations for detecting furcation lesions in upper molars treated endodontically and restored with different intracanal posts.

METHODS

This ex vivo study used 45 endodontically treated maxillary first molars, categorized into the following3 groups (n = 15): control (without intracanal post), metal post, and fiberglass post. Simulations were conducted in the laboratory to replicate alveolar bone, periodontal ligament, and grade I, II, and III furcation lesions. Cone-beam computed tomography scans were obtained with and without the MAR tool, and the furcation lesions were evaluated considering a 5-point Likert scale. Data were analyzed at 5%.

RESULTS

In the control group, there was no influence of MAR (P > .05); grade II lesions were not diagnosed, and grade III lesions were the most detected (P < .05). In the metal post group with MAR, grade III lesions were diagnosed more frequently than I and II (P < .05) and grade III without MAR (P < .05). In the fiberglass post group, the diagnosis of grade I lesions decreased with MAR (P < .05), and without MAR, grade III was most diagnosed (P < .05); grade III lesions were the most diagnosed (P < .05).

CONCLUSIONS

The MAR tool was only effective for diagnosing grade III furcation lesions, regardless of the intracanal material. Its application for grade I and II lesions did not contribute to improved diagnosis. Furthermore, in the fiberglass post group with grade I lesions, the MAR tool negatively affected the detection of the lesions.

Can maxillary molar dimensions predict the presence of the second mesiobuccal canal?

OBJECTIVE

To evaluate the potential of maxillary molar dimensions as predictors of the presence of the second mesiobuccal (MB2) canal.

METHODS

Micro-computed tomography scans were obtained from 47 maxillary molars, out of which 26 had the MB2 canal. The distance between root canals, extension of the canals, and thickness of surrounding dentin were obtained from axial images at the furcation level, 3 mm from the apex, and 5 mm from the apex. The association between the measurements and the presence of the MB2 canal was assessed using multiple logistic regression and odds ratio.

RESULTS

At the furcation level, the bucco-palatal extension of the MB1 canal significantly decreased the chance of the presence of the MB2 canal. Regarding the thickness of surrounding dentin measurements, the mesial and distal aspects of the MB1 canal at 3 mm from the apex were statistically significant to decrease and increase the chance of presence of the MB2 canal, respectively. Regarding the extension of the canals, only buccal-palatal extension seems to decrease the chance of the presence of the MB2 canal.

CONCLUSION

The presence of the MB2 canal in the mesiobuccal root of maxillary molars is associated with the bucco-palatal extension and surrounding dentin thickness of the first mesiobuccal canal, and seems to be unrelated to the dimensions of the distobuccal and palatal roots.

Association between intracanal medicament radiopacity and streak artifact production using cone-beam computed tomography: a laboratory study

INTRODUCTION

This study aimed to calculate the correlation between the radiopacity levels of various intracanal medicaments and radiolucent streak formation using cone-beam computed tomography (CBCT).

METHODS

7 commercially-available intracanal medicaments were tested, which contained different amounts of radiopacifier [Consepsis, Ca(OH)₂, UltraCal XS, Calmix, Odontopaste, Odontocide, and Diapex Plus]. Their radiopacity levels were measured according to the ISO 13116 testing standards (mmAl). Subsequently, the medicaments were placed in 3 canals of radiopaque artificial printed maxillary molars (n=15 roots per medicament), leaving the second mesiobuccal canal empty. CBCT imaging was carried out using an Orthophos SL 3D scanner under recommended manufacturer exposure settings. Radiopaque streak formation was assessed by a calibrated examiner using a previously published grading system (0-3). The Kruskal-Wallis and Mann-Whitney U tests with and without Bonferroni correction were used to compare radiopacity levels and radiopaque streak scores for the medicaments. Their relationship was assessed using the Pearson correlation coefficient. The level of significance was set as (α=0.05).

RESULTS

Diapex plus presented with the highest radiopacity levels (4.98±0.01) and radiopaque streak scores [middle third (2.8±0.18); apical third (2.73±0.43)]; which was similar to UltraCal XS's radiopaque streak scores [middle third (2.8±0.92); apical third (2.73±0.77)]. Consepsis had the lowest radiopacity levels (0.12±0.05), followed by Odontocide (0.60±0.05). Consepsis and Ca(OH)₂ were scored 0 for artifacts in all roots at all levels. A high positive correlation (R=0.95) was found between radiopacity and streak formation.

CONCLUSIONS

The radiopacity of intracanal medicaments varies and strongly correlates with the formation of radiolucent streak artifacts during CBCT.

The Effect of Cone-Beam Computed Tomography (CBCT) Evaluation on Treatment Planning after Endodontic Instrument Fracture

Intracanal instrument fracture is a procedural iatrogenic event during endodontic treatment that may affect treatment planning and eventually treatment outcome. Cone Beam Computed Tomography (CBCT) has offered several advantages, especially in endodontic cases in which information from conventional periapical radiograph may not be adequate to allow a precise treatment planning decision and a subsequent appropriate management of the cases. The present study was firstly conducted to assess the effect of CBCT evaluation on the decision-making process after instrument fracture; secondly, to introduce a new clinical approach in cases with fractured instruments located in the mesial roots of mandibular and maxillary molars. The study design was observational. The sample comprised all cases of mandibular and maxillary molars where an instrument fracture had occurred in the mesial roots. Two qualified (National and Kapodistrian University of Athens, Greece) and experienced (more than fifteen years of daily practicing) endodontists evaluated all the cases. The initial treatment plan made by evaluating periapical radiographs of each case was compared to the final plan set after CBCT evaluation. A marginal homogeneity test for paired data was conducted to test the concordance of treatment planning with periapical radiographs versus CBCT. Multivariable logistic regression was structured to identify predictors of modification in treatment planning following CBCT assessment, and to record estimators for decision to remove, bypass or retain the fragment. The level of statistical significance was pre-specified at p < 0.05. Of a total 52 cases evaluated, change in treatment planning with conventional periapical radiograph as a reference, following evaluation of CBCT, was observed in more than half of the teeth. The difference was statistically significant (p < 0.001). Apical location of the fragment was more likely to induce a perceived change in treatment planning after CBCT evaluation (p < 0.01). Canal merging induced 95% lower odds (p = 0.01) for taking a decision to remove or bypass, revealing that retaining the fragment was by far a more likely decision. A significant impact of CBCT preoperative evaluation on treatment planning for the management of such cases was demonstrated. Apical location of the fragment and canal merging seem to influence the decision-making process.

Accurate internal deformation measurement of an indentation test using micro-CT and self-adaptive digital volume correlation

Mechanical indentation testing is a widely used technique for determining local mechanical properties of materials. Accurate measurement of internal deformation in the indentation test is necessary for further study of material properties. Therefore, an in situ experimental measurement strategy combining micro-CT imaging and self-adaptive digital volume correlation (SA-DVC) is proposed. Unlike conventional DVC, SA-DVC can automatically identify the optimal subvolume size for each calculation point, which can effectively minimize measurement errors. The efficacy of the proposed method is first verified by the simulated indentation experiment. Then, it is used to analyze the deformation of epoxy resin composite in a real indentation experiment. Measurement results indicate that the proposed method can estimate three-dimensional displacement and strain fields with enhanced accuracy, and further application of the obtained measurement results on material parameter identification and stress field reconstruction is expected.

Assessment of the Metal Artifact Reduction Tool for the Detection of Root Isthmus in Mandibular Molars with Intraradicular Posts in Cone-beam Computed Tomographic Scans

INTRODUCTION

This study evaluated the performance of the metal artifact reduction (MAR) tool in cone-beam computed tomographic scans using different fields of view (FOVs) in the detection of a root isthmus in mandibular molars with intraradicular posts.

METHODS

Twenty-eight teeth were scanned by micro-computed tomographic imaging (gold standard images). Thereafter, specimens were allocated into the following groups: gutta-percha (teeth without posts, n = 10), a prefabricated metal post (n = 9), and a fiberglass post (n = 9). Cone-beam computed tomographic scans were taken using 8 acquisition protocols, varying the size of the FOV (10 × 5.5 cm and 5 × 5.5 cm) and the MAR tool (disabled, low, normal, and high modes). A root isthmus was evaluated considering a 5-point scale. Data were analyzed considering a 5% significance level.

RESULTS

Intra- and interexaminer agreement varied from moderate to substantial. The frequency of correct diagnosis varied significantly in all groups regardless of the image acquisition protocol selected (P < .05). In the gutta-percha group, there was no difference in the accuracy, sensitivity, and specificity values between the tested protocols. In the metal and fiberglass post groups, the accuracy values were higher with the "disabled" and "low" modes of the MAR tool regardless of the FOV size. This was also observed for the sensitivity values in the metal post group (P < .05).

CONCLUSIONS

The size of the FOV did not affect the performance of the MAR tool in the diagnosis of a root isthmus in molars with intraradicular posts. Our findings suggest that the use of the tool in the "normal" and "high" modes is contraindicated for this purpose.

Influence of Voxel Size and Filter Application in Detecting Second Mesiobuccal Canals in Cone-beam Computed Tomographic Images

INTRODUCTION

This study assessed the influence of voxel size and filter application in detecting second mesiobuccal (MB2) canals in cone-beam computed tomographic (CBCT) images.

METHODS

Using the OP300 CBCT system (Instrumentarium, Tuusula, Finland) and 3 voxel size protocols (80 μm, 125 μm, and 200 μm), we scanned 40 first molars: 20 with an MB2 canal and 20 without. All molars received silver palladium pins on the palatal root, whereas the non-MB2 molars were also filled with gutta-percha. Five oral radiologists assessed the presence of an MB2 canal under 3 filter application conditions: without filter, with sharpen 1 × filter, and with sharpen 2 × filter. Intra- and interobserver reproducibility was evaluated using the weighted kappa index. We compared the area under the receiver operating characteristic curves with SPSS Statistics v.20.0 (IBM Corp, Armonk, NY) using 2-way analysis of variance and the Tukey post hoc test with 5% significance level.

RESULTS

Our analysis found median intra- and interobserver agreement values of 0.70 and 0.56, respectively. The 80-μm voxel with sharpen 1 × filter image group had the highest sensitivity, accuracy, and negative predictive values. As for specificity and positive predictive, the 80-μm voxel group without filter application presented the highest values. The areas under the receiver operating characteristic curve were higher in the 80-μm groups than in the 125-μm and 200-μm voxel size groups (P < .05). We found no differences among the filters used (P = .22) or for the filter-voxel size interactions (P = .88).

CONCLUSIONS

A smaller voxel size increased the accuracy in detecting MB2 canals, whereas the enhancement filters did not.

Do the number of basis images and metal artifact reduction affect the production of artifacts near and far from zirconium dental implants in CBCT?

OBJECTIVES

This study aimed to evaluate the influence of the number of basis images and the metal artifact reduction (MAR) tool on the production of artifacts near and far from a zirconium implant in cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

CBCT scans of a mandible were acquired before and after insertion of an implant, using 450 and 720 basis images, with and without MAR activation. The mean and standard deviation (SD) of the gray values of the regions of interest (ROIs) located on the cortices adjacent to the implant and at different distances from it (in the soft tissue) were calculated. The mean of the gray values was used to calculate the absolute contrast difference (ACD) between the control and implant scans.

RESULTS

In general, the number of basis images did not affect the SD and the ACD values of the buccal and lingual ROIs (p > 0.05). The implant increased the SD in the lingual cortical plate (p < 0.05). In this case, MAR activation decreased SD (p < 0.05). All ROIs located at different distances from the implant showed higher SD on scans acquired with 450 basis images (p < 0.05), regardless of MAR condition.

CONCLUSIONS

A higher number of basis images reduces the magnitude of artifacts but does not influence the image quality in bone cortical plates. MAR improves the image in the areas most affected by artifacts.

CLINICAL RELEVANCE

The number of basis images is known as a factor capable of influencing the image quality and radiation dose for the patient. Therefore, it is important to investigate its effect on the expression of artifacts in the CBCT images.

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

OBJECTIVES

To objectively assess the expression and direction of artefacts in the vicinity of metal posts positioned in different mandibular regions.

MATERIALS AND METHODS

A human mandible had two sockets prepared-anterior and posterior regions-to accommodate a single-rooted tooth. Two CBCT units, Picasso Trio and OP300, were used. CBCT images of the tooth without metal post, and with silver-palladium, nickel-chromium, or cobalt-chromium posts (experimental groups) were individually acquired. Then, 8 lines of interest (LOIs) were determined around the root canal, in an axial reconstruction: 4 in orthogonal (buccal, lingual, mesial, and distal) directions, and 4 in oblique (mesiobuccal, distobuccal, mesiolingual, and distolingual) directions. The mean of gray values was measured for each LOI.

RESULTS

For the OP300, in general, all experimental groups showed greater expression of hyperdense streaks in orthogonal LOIs and greater expression of hypodense streaks in oblique LOIs. For the Picasso Trio, for both mandibular regions, the buccal LOI showed greater expression of hypodense streaks; conversely, greater expression of hyperdense streaks was observed in the distal and distobuccal LOIs in the anterior region and in the mesiolingual LOI in the posterior region. The silver-palladium group showed significantly greater expression of beam hardening artefacts in the posterior region of the mandible, regardless of the CBCT unit (p < 0.05). The mandibular posterior region showed significantly lower gray values than the anterior region (p < 0.05).

CONCLUSION

The expression and direction of artefacts produced in the vicinity of metal posts vary according to the mandibular region, composition of the post, and CBCT unit.

CLINICAL RELEVANCE

The mapping of artefacts produced by metal posts reveals the root regions with greater expression of hypodense and hyperdense artefacts, which may contribute to recognizing regions more likely to mimic or hide root fracture lines.