Diagnosis of external root resorption in teeth close and distant to zirconium implants: influence of acquisition parameters and artefacts produced during cone beam computed tomography

AIM

To assess the influence of artefacts, the metal artefact reduction (MAR) tool and kilovoltage (kVp) on the diagnosis of simulated external root resorption (ERR) in teeth close and distant to zirconium implants in cone beam computed tomography (CBCT) images.

METHODOLOGY

Cavities (0.62 mm in diameter and 0.19 mm deep) were created in the apical thirds of 12 roots on the buccal, lingual, distal or mesial surface; ten roots served as controls. The roots were randomly positioned in the first and second right and left premolar sockets of a dry human mandible, and a zirconium implant was placed in the socket of the first right molar. A ProMax 3D unit varying kVp (70, 80, or 90 kVp) and with the MAR tool activated or not was used to obtain CBCT scans. Five examiners evaluated all images to determine the area under the receiver operating characteristic (ROC) curve, sensitivity and specificity.

RESULTS

The ROC values and sensitivity were not affected by MAR or artefacts regardless of the distance to the implant (P > 0.05), whilst increasing kVp from 70 to 90 led to a significant increase in these values (P = 0.0202 and 0.0199, respectively). Specificity was not affected by the factors studied (P > 0.05).

CONCLUSIONS

Amongst the factors studied, only kVp influenced the diagnosis of simulated external root resorption in CBCT images. Increasing kVp from 70 to 90 improved the accuracy in diagnosing the simulated lesions.

Correlation between the visibility of submandibular fossa and mandibular canal cortication on panoramic radiographs and submandibular fossa depth on CBCT

BACKGROUND

To identify a correlation between the submandibular fossa (SF) visibility and mandibular canal (MC) cortication on panoramic image and the depth of SF measured on CBCT and also correlation between the depth of SF and vertical and horizontal location of MC on CBCT.

MATERIAL AND METHODS

500 CBCT scans and panoramic radiographs were evaluated. SF depth types were classified as type I (< 2mm); type II (2-3mm) and type III (> 3mm) on CBCT. Visibility of SF and the cortication of MC on panoramic radiographs were compared with the depth of SF on CBCT. Distances between MC and mandibular inferior, buccal and lingual cortices were measured.

RESULTS

No statistically significant correlation was found between radiolucent appearances of SF, cortication of MC, and depth of SF. The deepest part of the fossa was in the second molar area followed by third and first molars. Negative weak correlations were found between B-MC, L-MC distances and depth of SF.

CONCLUSION

Visibility of SF and cortication of MC on panoramic radiographs did not correlate with the depth of SF. A marked radiolucent submandibular fossa on panoramic image does not undoubtedly indicate a deep fossa, which emphasizes the importance of 3-D imaging in implant planning.

Comparison of cone beam CT scans with enhanced photostimulated phosphor plate images in the detection of root fracture of endodontically treated teeth

OBJECTIVES

Two-dimensional intraoral radiography is the most common tool for diagnosing root fractures (RFs). Cone beam CT (CBCT) is widely used to depict RFs in endodontically treated teeth. Beam hardening and other artefacts caused by gutta percha may result in an incorrect diagnosis when using CBCT only. A comparison of two CBCT machines with photostimulated phosphor (PSP) plate images enhanced with the equalization tool was carried out to detect RFs in endodontically treated teeth.

METHODS

66 roots were collected, decoronated and treated endodontically using the same technique with gutta percha. 33 of these roots were randomly selected and fractured; the 2 root fragments were glued together with 1 layer of methyl methacrylate and placed randomly in 8 prepared beef rib fragments. Large fields of view (FOVs) were acquired with one CBCT unit and small FOVs with the second CBCT unit. Periapical radiographs (using intraoral PSP plates) were also acquired. A contrast enhancement tool was used when evaluating the PSP plate images.

RESULTS

Small FOV images had significantly higher accuracy (area under the receiver operating characteristic curve) and sensitivity in detecting RFs than PSP plates and large FOV images. The specificity of the enhanced PSP images was higher than, although not significantly higher than, the small FOV images and was significantly higher than the large FOV images.

CONCLUSIONS

CBCT small FOVs should be acquired for depicting RFs of endodontically treated teeth. Images obtained using PSP plates had the lowest rate of false-positive results and their use can save the patient a radiation dose.

Cone beam CT scans with and without artefact reduction in root fracture detection of endodontically treated teeth

OBJECTIVES

Cone beam CT (CBCT) is used widely to depict root fracture (RF) in endodontically treated teeth. Beam hardening and other artefacts due to gutta-percha may increase the time of the diagnosis and result in an incorrect diagnosis. Two CBCT machines, ProMax(®) (Planmeca, Helsinki, Finland) and Master 3D(®) (Vatech, Hwaseong, Republic of Korea), have the option of applying an artefact reduction (AR) algorithm. The aim of this study was to determine whether using an AR algorithm in two CBCT machines enhances the accuracy of detecting RFs in endodontically treated teeth.

METHODS

66 roots were collected and decoronated. All roots were treated endodontically using the same technique with gutta-percha and zinc oxide cement. One-half of the roots were randomly selected and fractured using a nail that was tapped gently with a hammer until complete fracture resulted in two root fragments; the two root fragments were glued together with one layer of methyl methacrylate. The roots were placed randomly in eight prepared beef rib fragments.

RESULTS

The highest accuracy was obtained when the ProMax was used without AR. The lowest accuracy was obtained with the Master 3D when used with AR. For both machines, accuracy was significantly higher without AR than with AR. Both with and without AR, the ProMax machine was significantly more accurate than the Master 3D machine. The same rank ordering was obtained for both sensitivity and specificity.

CONCLUSIONS

For both machines, AR decreased the accuracy of RF detection in endodontically treated teeth. The highest accuracy was obtained when using the ProMax without AR.

A mathematical model relating changes of grey values to changes of thicknesses of a stepwedge

The purpose of this report is to present a mathematical model relating changes in grey values to changes of thicknesses of a stepwedge. Radiographs of a stepwedge were obtained through a limited exposure range on a single Kodak 6100 charge-coupled device detector at 63 kVp and 70 kVp. Grey values from each step were evaluated relative to the corresponding step thickness. All possible regression fits were evaluated based on their coefficient of determination (R(2)) value and their mean squared errors (MSEs) relative to the original thickness. For all exposure settings, the fifth-degree polynomial was the best possible fit, with the highest R(2) value and the lowest MSE.

Evaluation of a cone beam CT artefact reduction algorithm

OBJECTIVES

An algorithm and software to reduce metal artefact has been developed recently and is available in the Picasso Master 3D® (VATECH, Hwaseong, Republic of Korea), which under visual assessment produces better quality images than were obtainable previously. The objective of this in vitro study was to investigate whether the metal artefact reduction (MAR) algorithm of the Picasso Master 3D machine reduced the incidence of metal artefacts and increased the contrast-to-noise ratio (CNR) while maintaining the same gray value when there was no metallic body present within the scanned volume.

METHODS

20 scans with a range of 50-90 kVp were acquired, of which 10 had a metallic bead inserted within a phantom. The images obtained were analysed using public domain software (ImageJ; NIH Image, Bethesda, MD). Area histograms were used to evaluate the mean gray level variation of the epoxy resin-based substitute (ERBS) block and a control area. The CNR was calculated.

RESULTS

The MAR algorithm increased the CNR when the metallic bead was present; it enhanced the ERBS gray level independently of the presence of the metallic bead. The image quality also improved as peak tube potential was increased.

CONCLUSION

Improved quality of images and regaining of the control gray values of a phantom were achieved when the MAR algorithm was used in the presence of a metallic bead.

Metal artefact reduction with cone beam CT: an in vitro study

BACKGROUND

Metal in a patient's mouth has been shown to cause artefacts that can interfere with the diagnostic quality of cone beam CT. Recently, a manufacturer has made an algorithm and software available which reduces metal streak artefact (Picasso Master 3D® machine; Vatech, Hwaseong, Republic of Korea).

OBJECTIVES

The purpose of this investigation was to determine whether or not the metal artefact reduction algorithm was effective and enhanced the contrast-to-noise ratio.

METHODS

A phantom was constructed incorporating three metallic beads and three epoxy resin-based bone substitutes to simulate bone next to metal. The phantom was placed in the centre of the field of view and at the periphery. 10 data sets were acquired at 50-90 kVp. The images obtained were analysed using a public domain software ImageJ (NIH Image, Bethesda, MD). Profile lines were used to evaluate grey level changes and area histograms were used to evaluate contrast. The contrast-to-noise ratio was calculated.

RESULTS

The metal artefact reduction option reduced grey value variation and increased the contrast-to-noise ratio. The grey value varied least when the phantom was in the middle of the volume and the metal artefact reduction was activated. The image quality improved as the peak kilovoltage increased.

CONCLUSION

Better images of a phantom were obtained when the metal artefact reduction algorithm was used.

Pre-clinical evaluation of a new dental panoramic radiographic system based on tomosynthesis method

OBJECTIVES

The purpose of the study was to compare the image generated by a classic panoramic machine equipped with a cadmium telluride sensor capable of digital tomosynthesis and special software with images produced by other popular panoramic X-ray machines using a charge-coupled device and native software for image capture.

METHODS

Panoramic images were made using a phantom of a human skull on Planmeca ProMax, Planmeca EC Proline, Kodak 8000 and PC-1000. With the last machine we used the PanoACT® software to adjust the entire arch and to adjust the image in selected regions of interest (ROIs). Ten viewers evaluated the images and provided the viewer data. ANOVA for repeated measures was used to compare the means by pairwise comparisons of means.

RESULTS

The image of the entire arch adjusted by the PanoACT® software was statistically superior to the images produced by other machines. The images generated and individually adjusted by PanoACT® were statistically superior to all other images.

CONCLUSIONS

The image generated by the cadmium telluride sensor has great potential and can be processed to create superior images to those taken with other machines. Furthermore, the ROI individual images enhanced by the PanoACT® were superior to the entire arch adjusted by the same software.

Development of a new dental panoramic radiographic system based on a tomosynthesis method

The objective of this study was to develop a new practical method to reconstruct a high-quality panoramic image in which radiographers would be free from the onerous task of correctly locating the patient's jaws within the image layer of the panoramic unit. In addition, dentists would be able to freely select any panoramic plane to be reconstructed after the acquisition of the raw scan data. A high-speed data acquisition device was used with a CdTe (cadmium telluride) semiconductor detector and a sophisticated digital signal-processing technique based on tomosynthesis was developed. The system processes many vertical strip images acquired with the detector and generates a high-resolution and high-contrast image. To apply the tomosynthesis technique to the acquired strip images correctly, the actual movement of the panoramic unit was measured, including the X-ray tube and detector, in a scan using a calibration phantom and the authors generated a shift amount table needed for the shift-and-add tomosynthesis operation. The results of the experiments with a PanoACT-1000 panoramic unit, which was a PC-1000 panoramic unit fitted with a high frame rate semiconductor detector SCAN-300FPC, demonstrated the capability of a tomosynthesis technique which, when applied to the strip images of a dry skull phantom, could change the location and inclination of an imaging plane. This system allowed the extraction of an optimum-quality panoramic image regardless of irregularities in patient positioning. Moreover, the authors could freely reconstruct a fine image of an arbitrary plane with different parameters from those used in the original data acquisition to study fine anatomical details in specific locations.

Evaluation of high-resolution cone beam computed tomography in the detection of simulated interradicular bone lesions

OBJECTIVES

The purpose of this study is to assess the accuracy of limited-volume high-resolution cone beam CT (CBCT) in the detection of periodontal bone loss.

METHODS

163 simulated periodontal lesions of different depths were created in dried human hemimandibles. Specimens were imaged using the intraoral paralleling technique and limited-volume CBCT (3DX Accuitomo; Morita Co. Ltd, Kyoto, Japan). Ten viewers examined the images. Data were analysed with receiver operating characteristics (ROC) analysis. ROC curves were generated and the areas under the maximum-likelihood curves (A(z)) were compared. Other statistical analyses were used to detect the normality of the distribution of the results.

RESULTS

The results are reported as the individual viewer ROC curve areas for each of the two imaging modalities. In all experiments the A(z) area for CBCT (0.770-0.864) was larger than the A(z) area for periapical film (0.678-0.783); statistical tests showed a statistically significant difference between the two modalities.

CONCLUSIONS

Results indicate that the CBCT technique has better accuracy and diagnostic value than periapical films in the detection of interradicular periodontal bone defects.