Impact of voxel size variation on CBCT-based diagnostic outcome in dentistry: a systematic review

Influence of exposure protocol, voxel size, and artifact removal algorithm on the trueness of segmentation utilizing an artificial-intelligence-based system

PURPOSE

To evaluate the effects of exposure protocol, voxel sizes, and artifact removal algorithms on the trueness of segmentation in various mandible regions using an artificial intelligence (AI)-based system.

MATERIALS AND METHODS

Eleven dry human mandibles were scanned using a cone beam computed tomography (CBCT) scanner under differing exposure protocols (standard and ultra-low), voxel sizes (0.15 mm, 0.3 mm, and 0.45 mm), and with or without artifact removal algorithm. The resulting datasets were segmented using an AI-based system, exported as 3D models, and compared to reference files derived from a white-light laboratory scanner. Deviation measurement was performed using a computer-aided design (CAD) program and recorded as root mean square (RMS). The RMS values were used as a representation of the trueness of the AI-segmented 3D models. A 4-way ANOVA was used to assess the impact of voxel size, exposure protocol, artifact removal algorithm, and location on RMS values (α = 0.05).

RESULTS

Significant effects were found with voxel size (p < 0.001) and location (p < 0.001), but not with exposure protocol (p = 0.259) or artifact removal algorithm (p = 0.752). Standard exposure groups had significantly lower RMS values than the ultra-low exposure groups in the mandible body with 0.3 mm (p = 0.014) or 0.45 mm (p < 0.001) voxel sizes, the symphysis with a 0.45 mm voxel size (p = 0.011), and the whole mandible with a 0.45 mm voxel size (p = 0.001). Exposure protocol did not affect RMS values at teeth and alveolar bone (p = 0.544), mandible angles (p = 0.380), condyles (p = 0.114), and coronoids (p = 0.806) locations.

CONCLUSION

This study informs optimal exposure protocol and voxel size choices in CBCT imaging for true AI-based automatic segmentation with minimal radiation. The artifact removal algorithm did not influence the trueness of AI segmentation. When using an ultra-low exposure protocol to minimize patient radiation exposure in AI segmentations, a voxel size of 0.15 mm is recommended, while a voxel size of 0.45 mm should be avoided.

Intraoral ultrasonography image registration for evaluation of partial edentulous ridge: A methodology and validation study

OBJECTIVES

Ultrasound (US) reveals details for diagnosing soft- and hard-tissue dimensions around teeth, implants, and the edentulous ridge, not seen in 2D radiographs. Co-registering free-hand US scans with other 3D modalities presents reliability challenges. This study first aims to develop and validate a registration method to longitudinally reproduce US images of the jawbone on a simulator. In addition, it also evaluates the degree of the anatomical match in humans between US images acquired by the proposed registration method and the commonly used freehand acquisitions in comparison to cone beam computed tomography (CBCT) and intra-oral optical scan (IOS), used as references.

METHODS

A previously introduced ultrasound phantom was employed as a CBCT-US hybrid, suitable for training and technique development of US guides in edentulous ridges. After establishing feasibility in the phantom, the methodology was validated in a cohort of 24 human subjects (26 cases). Soft tissues were delineated on US and IOS, and hard tissues on US and CBCT. US accuracy and repeatability from both guided and freehand scans (non-guided) was assessed as the average distance between US and the references.

RESULTS

Guided US images resembled the references more closely than freehand (non-guided) scans. Notably, delineation of soft and hard tissues was significantly more accurate when employing guides. In the phantom, guided scans exhibited an absolute mean deviation of 81.8 µm for gingiva and 90.4 µm for bone, whereas non-guided scans showed deviations of 150.4 µm and 177.2 µm, respectively. Similarly, in vivo, guided US outperformed non-guided US, with gingiva deviations of 125 µm and 196 µm, and bone deviations of 354 µm and 554 µm, respectively.

CONCLUSIONS

By using a registration method, guided US scans improved repeatability and accuracy of mapping hard and soft tissue of the edentulous ridge when compared to non-guided scans.

CLINICAL RELEVANCE

This guided US imaging method could lay the foundation for longitudinal evaluation of tissue behavior and dimensional changes with improved accuracy.

Optimization of orofacial cleft imaging protocols using device-specific low-dose cone-beam computed tomography

OBJECTIVE

The aim of this study was to present optimized device-specific low-dose cone-beam computed tomography (CBCT) protocols with sufficient image quality for pre-surgical diagnostics and three-dimensional (3D) modelling of cleft defects.

METHODS

Six paediatric skulls were acquired, and an artificial bony cleft was created. A high-resolution CBCT scan acted as a reference standard (Accuitomo 170, Morita, Kyoto, Japan) for comparing eight low-dose protocols of Newtom VGi-evo (QR Verona, Cefla, Verona, Italy), which included Eco and Regular protocols with different field of views (FOVs). Delineation of lamina dura, cementoenamel junction (CEJ), trabecular bone and bony bridge were assessed. A 3D model of the defect was also evaluated.

RESULT

The dose area product of low-dose protocols ranged from 31 to 254 mGy*cm2. Despite the dose difference of up to eight times between applied protocols, trabecular bone and CEJ exhibited appropriate image quality in all scans. However, Regular small FOV protocols (5 × 5 and 8 × 5 cm2), for both lamina dura and bony bridge, demonstrated a significant improvement in image quality compared to Eco FOV counterparts. Based on 3D defect analysis, no significant difference existed between low-dose protocols and the reference standard.

CONCLUSION

The findings highlight the possibility of achieving a considerable reduction (up to eight times) in the radiation dose using low-dose CBCT protocols while maintaining sufficient image quality for assessing anatomical structures and 3D modelling in cleft cases.

Is the assessment of the mandibular molar danger zone affected by field of view and voxel size in cone beam computed tomography examinations?

OBJECTIVE

To verify if assessment of the danger zone (DZ) in the mesial root of mandibular molars is affected by field of view (FOV) and voxel sizes in cone beam computed tomography (CBCT) scans.

STUDY DESIGN

Forty mandibular molars were scanned by micro-computed tomography, creating the reference standard. The teeth were then submitted for CBCT scans with FOVs of 10 × 5.5 cm and 5 × 5.5 cm and voxel sizes of 0.4, 0.2, 0.15, and 0.075 mm3. The smallest dentin thickness in the DZ from the mesiobuccal and mesiolingual canals was measured at 2, 4, and 6 mm apical to the root furcation. Descriptive statistics, paired t-tests, and intraclass correlation coefficients were used for statistical analysis with significance established at P < .05.

RESULTS

All CBCT measurements overestimated the DZ dentin thickness (P < .001) compared to the reference standard. The greatest overestimation occurred in the 5 × 5.5 cm FOV with 0.4 mm3 voxels (P = .007). Dentin thickness measured with the 5 × 5.5 cm FOV and 0.075 mm3 voxels was significantly smaller and produced the best ICC value with the reference standard (0.936).

CONCLUSIONS

CBCT overestimates the dentin thickness of the DZ regardless of FOV and voxel sizes. The 5 × 5.5 cm FOV showed the best performance with the 0.075 mm3 voxel size, but it performed poorly with 0.4 mm3 voxels.

Machine learning assisted 5-part tooth segmentation method for CBCT-based dental age estimation in adults

BACKGROUND

The utilization of segmentation method using volumetric data in adults dental age estimation (DAE) from cone-beam computed tomography (CBCT) was further expanded by using current 5-Part Tooth Segmentation (SG) method. Additionally, supervised machine learning modelling -namely support vector regression (SVR) with linear and polynomial kernel, and regression tree - was tested and compared with the multiple linear regression model.

MATERIAL AND METHODS

CBCT scans from 99 patients aged between 20 to 59.99 was collected. Eighty eligible teeth including maxillary canine, lateral incisor, and central incisor were used in this study. Enamel to dentine volume ratio, pulp to dentine volume ratio, lower tooth volume ratio, and sex was utilized as independent variable to predict chronological age.

RESULTS

No multicollinearity was detected in the models. The best performing model comes from maxillary lateral incisor using SVR with polynomial kernel ( = 0.73). The lowest error rate achieved by the model was given also by maxillary lateral incisor, with 4.86 years of mean average error and 6.05 years of root means squared error. However, demands a complex approach to segment the enamel volume in the crown section and a lengthier labour time of 45 minutes per tooth.

Accuracy of linear measurements for implant planning based on low-dose cone beam CT protocols: a systematic review and meta-analysis

OBJECTIVES

The aim of this systematic review was to verify the accuracy of linear measurements performed on low-dose CBCT protocols for implant planning, in comparison with those performed on standard and high-resolution CBCT protocols.

METHODS

The literature search included four databases (Pubmed, Web of Science, Embase, and Scopus). Two reviewers independently screened titles/abstracts and full texts according to eligibility criteria, extracted the data, and examined the methodological quality. Risk of bias assessment was performed using the Quality Assessment Tool For In Vitro Studies. Random-effects meta-analysis was used for pooling measurement error data.

RESULTS

The initial search yielded 4684 titles. In total, 13 studies were included in the systematic review, representing a total of 81 samples, while 9 studies were included in the meta-analysis. The risk of bias ranged from medium to low. The main results across the studies indicate a strong consistency in linear measurements performed on low-dose images in relation to the reference methods. The overall pooled planning measurement error from low-dose CBCT protocols was -0.24 mm (95% CI, -0.52 to 0.04) with a high level of heterogeneity, showing a tendency for underestimation of real values. Various studies found no significant differences in measurements across different protocols (eg, voxel sizes, mA settings, or dose levels), regions (incisor, premolar, molar) and types (height vs. width). Some studies, however, noted exceptions in measurements performed on the posterior mandible.

CONCLUSION

Low-dose CBCT protocols offer adequate precision and accuracy of linear measurements for implant planning. Nevertheless, diagnostic image quality needs must be taken into consideration when choosing a low-dose CBCT protocol.

Do voxel size and filter application on CBCT images improve the diagnosis of condylar morphological alterations? An ex vivo study

BACKGROUND

There is no established protocol for the low doses of cone-beam computed tomography (CBCT) acquisition and filter application on the diagnosis of condylar morphological alterations.

OBJECTIVES

The objective of the study was to evaluate the influence of voxel size and filter application on the diagnosis of condylar morphological alterations in CBCT using an ex vivo model.

METHODS

CBCT scans of 36 temporomandibular joints were acquired using OP300 Maxio with voxel sizes of 0.085, 0.125 and 0.280 mm. Three radiologists evaluated the condyles in the CBCT volumes under three filter modes: no filter, '1x' sharpen filter and '2x' sharpen filter. The area under the ROC curve, sensitivity and specificity were calculated by comparing the evaluators' responses with the reference standard and compared among experimental groups using analysis of variance (ANOVA) (α = 5%).

RESULTS

The area under the ROC curve, sensitivity and specificity were not affected by voxel size and filter application (p > .05). For osteophyte and flattening, there were more true-positive responses in smaller voxel size. For erosion, the increase of true- and false-positive responses occurred with a larger voxel size. Overall, there was a tendency to decrease true positives for osteophyte and erosion and increase false positives for flattening with the '2x' sharpen filter.

CONCLUSIONS

The diagnosis of condylar morphological alterations assessed in this ex vivo analysis is not influenced by the voxel size and the application of the filters. However, attention is needed with the occurrence of false-positive diagnosis with a larger voxel size for erosion and '2x' sharpen filter for flattening.

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.

The effect of optimum, indication-specific imaging fields on the radiation exposure from CBCT examinations of impacted maxillary canines and mandibular third molars

OBJECTIVE

Indication-specific optimum field-of-views (FOVs) have been assessed for CBCT scans of impacted maxillary canines and mandibular third molars, as 40∅ × 35 mm and 35∅ × 35 mm, respectively. The objective was to investigate possible changes in absorbed organs and effective doses, for these two imaging indications, performing CBCT examinations with optimum FOV sizes instead of commonly used FOVs. Additionally, radiation exposure-induced cancer risk was calculated for both imaging indications with optimum FOVs.

METHODS

An adult female head phantom (ATOM 702-D, CIRS, Norfolk, VA, USA) was scanned using Planmeca Viso G7 CBCT-device (Planmeca, Helsinki, Finland). Scanning factors, different FOV sizes, dose-area product (DAP) values and anatomical FOV locations were used for Monte Carlo PCXMC-simulation and ImpactMC software. In the PCXMC- simulation, 10-year-old child and 30-year-old adult phantoms were used to estimating effective and absorbed organ doses.

RESULTS

The effective dose varied from 58 µSv to 284 µSv for impacted maxillary canines, and from 38 µSv to 122 µSv for mandibular third molars, the lowest dose value for each corresponding to optimum FOV. Effective dose reduction between the optimum FOV and the smallest common FOV of 50∅ × 50 mm, maintaining other scanning factors constant, was 33% for impacted maxillary canines, and 45% for mandibular third molars. At all examinations, the highest absorbed organ doses were in salivary glands or in oral mucosa.

CONCLUSIONS

Optimum FOVs, 40∅ × 35 mm for impacted maxillary canine and 35∅ × 35 mm for mandibular third molar, could decrease effective doses received by young patients, and improve radiation safety in these common CBCT imaging procedures.

Adjacent tooth migration after maxillary first molar loss in patients with sinus augmentation: A retrospective research

PURPOSE

The objectives of this study are to: (1) investigate the extent of antagonistic and distal neighboring tooth migration in the maxillary posterior single tooth-missing site during the healing period of bone augmentation and implant surgery; (2) identify factors associated with tooth migration.

MATERIALS AND METHODS

One hundred and forty-three cases that lost the maxillary first molar were included, and their CBCT data during the edentulous period were obtained. Dentition models were reconstructed from CBCT, and superimpositions were performed, followed by measuring migration distances and calculating migration rates of antagonistic and distal neighboring teeth. Factors were analyzed using multivariate generalized estimating equations (GEE).

RESULTS

The mean migration distances were 208 ± 137 μm and 403 ± 605 μm for antagonistic teeth and distal teeth, and the mean migration rates were 26.8 ± 21.2 μm/month and 48.5 ± 76.7 μm/month, respectively. One hundred and nineteen out of 143 distal neighboring teeth migrated toward the edentulous site, and all antagonistic teeth migrated occlusally. Occlusal contact loss and chronic apical periodontitis both significantly accelerated antagonistic tooth migration (p < 0.05), the latter also accelerated distal tooth migration (p < 0.05). Besides, the displacement of the distal teeth was somewhat accelerated by the impacted adjacent third molar and root protrusion into the sinus.

CONCLUSIONS

The neighboring teeth tend to migrate toward the edentulous gap in the maxillary posterior region. Occlusal contact loss and chronic apical periodontitis are two significant risk factors for accelerating antagonistic tooth migration, and for distal teeth, chronic apical periodontitis is the risk factor. The impacted adjacent third molar and root protrusion into the sinus are also potential risk factors for accelerating the migration of the maxillary distal tooth. Thus, to prevent maxillary edentulous gap reduction, the factors mentioned above should be taken into consideration when planning treatment flow.

Effects of the cone-beam computed tomography protocol on the accuracy and image quality of root surface area measurements: An in vitro study

Purpose

The objective of this study was to evaluate and compare the accuracy and image quality of root surface area (RSA) measurements obtained with various cone-beam computed tomography (CBCT) protocols, relative to the gold standard of micro-computed tomography (CT), in an in vitro setting.

Materials and Methods

Four dry human skulls were scanned using 8 different protocols, with voxel sizes of 0.15 mm, 0.3 mm, and 0.4 mm. Three-dimensional models of the selected teeth were constructed using CBCT and micro-CT protocols, and the RSA was automatically measured by the image-processing software. The absolute difference in the percentage of the RSA (%ΔRSA) was calculated and compared across the 8 CBCT protocols using repeated-measures analysis of variance. Finally, image quality scores of the RSA measurements were computed and reported in terms of percent distribution.

Results

No significant differences were observed in the %ΔRSA across the 8 protocols (P>0.05). The deviation in %ΔRSA ranged from 1.51% to 4.30%, with an increase corresponding to voxel size. As the voxel size increased, the image quality deteriorated. This decline in quality was particularly noticeable at the apical level of the root, where the distribution of poorer scores was most concentrated.

Conclusion

Relative to CBCT protocols with voxel sizes of 0.15 mm and 0.3 mm, the protocols with a voxel size of 0.4 mm demonstrated inferior image quality at the apical levels. In spite of this, no significant discrepancies were observed in RSA measurements across the different CBCT protocols.

Microsurgery Robots: Applications, Design, and Development

Microsurgical techniques have been widely utilized in various surgical specialties, such as ophthalmology, neurosurgery, and otolaryngology, which require intricate and precise surgical tool manipulation on a small scale. In microsurgery, operations on delicate vessels or tissues require high standards in surgeons' skills. This exceptionally high requirement in skills leads to a steep learning curve and lengthy training before the surgeons can perform microsurgical procedures with quality outcomes. The microsurgery robot (MSR), which can improve surgeons' operation skills through various functions, has received extensive research attention in the past three decades. There have been many review papers summarizing the research on MSR for specific surgical specialties. However, an in-depth review of the relevant technologies used in MSR systems is limited in the literature. This review details the technical challenges in microsurgery, and systematically summarizes the key technologies in MSR with a developmental perspective from the basic structural mechanism design, to the perception and human-machine interaction methods, and further to the ability in achieving a certain level of autonomy. By presenting and comparing the methods and technologies in this cutting-edge research, this paper aims to provide readers with a comprehensive understanding of the current state of MSR research and identify potential directions for future development in MSR.

Evaluation of the accuracy of cone-beam computed tomography image segmentation of isolated tooth roots based on the dynamic threshold method

OBJECTIVE

Accurate quantification of the root surface area (RSA) plays a decisive role in the advancement of periodontal, orthodontic, and restorative treatment modalities. In this study, we aimed to develop a dynamic threshold-based computer-aided system for segmentation and calculation of the RSA of isolated teeth on cone-beam computed tomography (CBCT) and to assess the accuracy of the measured data.

METHOD

We selected 24 teeth to be extracted, including single-rooted and multi-rooted teeth, from 22 patients who required tooth extraction. In the experimental group, we scanned 24 isolated teeth using CBCT with a voxel size of 0.3 mm. We designed a computer-aided system based on a personalized dynamic threshold algorithm to automatically segment the roots of 24 isolated teeth in CBCT images and calculate the RSA. In the control group, we employed digital intraoral scanner devices to perform optical scanning on 24 isolated teeth and subsequently manually segmented the roots using 3-matic software to calculate the RSA. We used the paired t-test (P < 0.05) and Bland-Altman plots to analyze the consistency of the two measurement methods.

RESULTS

The results of the paired t-test showed that there was no significant difference in the RSAs obtained using the dynamic threshold method and the optical scanning image reconstruction (t = 1.005, P = 0.325 > 0.05). As per the Bland-Altman plot, the results were evenly distributed within the region of ± 1.96 standard deviations of the mean, with no increasing or decreasing trends and good consistency.

CONCLUSION

In this study, we designed a computer-aided root segmentation system based on a personalized dynamic threshold algorithm to automatically segment the roots of isolated teeth in CBCT images with a voxel size of 0.3 mm. We found that the RSA calculated using this approach was highly accurate, and a voxel of 0.3 mm in size could accurately display the surface area data in CBCT images. Overall, our findings in this study provide a foundation for future work on accurate automatic segmentation of tooth roots in full-mouth CBCT images and the computation of RSA.

Ex vivo detection of mandibular incisors' root canal morphology using cone-beam computed tomography with 4 different voxel sizes and micro-computed tomography

BACKGROUND

In recent years, cone-beam computed tomography (CBCT) has been widely used to evaluate patients' root canal anatomy due to its high resolution and noninvasive nature. As voxel size is one of the most important parameters affecting CBCT image quality, the current study evaluated the diagnostic potential of CBCT with 4 different voxel sizes in the detection of double root canal systems and accessory canals (ACs) in permanent mandibular incisors.

METHODS

A total of 106 extracted mandibular permanent incisors were collected from the dental clinics, and then were scanned by using micro-CT with a voxel size of 9 μm. The teeth were then fixed in the tooth sockets of human dry mandibles and scanned by using a CBCT device with 4 different voxel sizes (300, 200, 250, and 125 μm). Four observers detected in blind the root canal morphology of the teeth according to the CBCT images, and the presence or absence of a double root canal system, and the presence or absence of ACs, were scored according to a 5-point scale, respectively. Receiver operating characteristic (ROC) analysis was performed, and DeLong test was used to compare the area under the curve (AUC) values and the micro-CT data was taken as a gold standard.

RESULTS

Among 106 sample teeth, 25 specimens with a double root canal system were identified by the micro-CT. ROC curve analysis of the data obtained by the four observers showed that in the detection of double root canal systems, the AUC values ranged from 0.765 to 0.889 for 300 μm voxel size, from 0.877 to 0.926 for 250 μm voxel size, from 0.893 to 0.967 for 200 μm voxel size, and from 0.914 to 0.967 for 125 μm voxel size (all p < 0.01). In general, we observed a trend that the AUC values, sensitivity, and specialty increased with the decrease in the voxel size, and significantly higher AUC values were detected in 125 μm voxel size images. In the detection of ACs, ROC curve analysis showed that among the four observers, the AUC values ranged from 0.554 to 0.639 for 300 μm voxel size, from 0.532 to 0.654 for 250 μm voxel size, from 0.567 to 0.626 for 200 μm voxel size, and from 0.638 to 0.678 for 125 μm voxel size. CBCT images at a voxel size of 125 μm had a weak diagnostic potential (AUC: 0.5-0.7, all p < 0.05) in the detection of AC, with a lower sensitivity ranging from 36.8 to 57.9% and a higher specialty ranging from 73.6 to 98.8%.

CONCLUSIONS

CBCT with 300 μm voxel size could only provide moderate diagnostic accuracy in the detection of a double canal system in mandibular incisors. CBCT with a voxel size of 125 μm exhibited high diagnostic value in the detection of double canal systems, while showing low but statistically significant value in the detection of ACs.

Quantitative assessment of image artifacts from zygoma implants on CBCT scans using different exposure parameters

This study was aimed at quantifying artifacts from zygoma implants in cone-beam computed tomography (CBCT) images using different exposure parameters. Two cadaver heads, one with two zygoma implants on each side and the other for control, were scanned using 18 different exposure parameters. Quantitative analysis was performed to evaluate the hypodense and hyperdense artifact percentages calculated as the percentage of the area. Hyperdense artifacts and hypodense artifacts were detected, followed by the calculation of the hyperdense and hypodense artifact percentages in the image. In the qualitative analysis of the artifacts, the scores used were as follows: absence (0), moderate presence (1), or high presence (2) for hypodense halos, thin hypodense lines, and hyperdense lines. Artifact analysis was performed qualitatively and quantitatively using the post-hoc Tukey and Two-way ANOVA tests. As a result, in the qualitative analyses, zygoma implants showed a significant difference compared to the control group with regard to hyperdense and hypodense artifacts (p < 0.05). There was a significant difference between the means according to the FOV size arithmetic averages (p < 0.05). In terms of voxel size, the difference was found to be significant, where 400 microns showed the highest hypodense artifact while 200 microns showed the lowest hypodense artifact. In conclusion, hypodense and hyperdense artifacts were significantly higher in cadavers with zygoma implants than in controls. As FOV and voxel size increase, more hypodense artifacts are produced by zygoma implants so smaller FOV and voxel sizes should be used to prevent poor image quality of adjacent teeth.

Effect of field of view and voxel size on CBCT-based accuracy of dynamic navigation in endodontic microsurgery: an in vitro study

INTRODUCTION

This study aimed to evaluate the influence of field of view (FOV) and voxel size on the accuracy of dynamic navigation (DN)-assisted endodontic microsurgery (EMS).

METHODS

Nine sets of maxillary and mandibular three-dimensional-printed jaw models composed of 180 teeth were divided into nine groups with different FOVs (80 × 80 mm, 60 × 60 mm, and 40 × 40 mm) and voxel sizes (0.3, 0.16, and 0.08 mm). The endodontic DN system was used to plan and execute the EMS. The accuracy of the DN-EMS was represented by the platform deviation, end deviation, angular deviation, resection angle, and resection length deviation. Statistical analyses were performed using SPSS 24.0, and the significance level was set at p < 0.05.

RESULTS

The average platform, end, angular, resection angle, and resection length deviation were 0.69 ± 0.31 mm, 0.93 ± 0.44 mm, 3.47 ± 1.80°, 2.35 ± 1.76°, and 0.41 ± 0.29 mm, respectively. No statistically significant differences in accuracy were observed between the nine FOV and voxel size groups.

CONCLUSION

FOV and voxel size did not appear to play an important role in the accuracy of DN-EMS. Considering the image quality and radiation dose, it is reasonable to select a limited FOV (such as 40 × 40 mm and 60 × 60 mm) to cover only the registration device, involved teeth, and periapical lesion. The voxel size should be selected according to the required resolution and CBCT units.

Quantitative and qualitative comparisons of pulp cavity volumes produced by cone beam computed tomography and micro-computed tomography through semiautomatic segmentation: An ex vivo investigation

OBJECTIVE

The aim of this study was to measure the volume and visually assess 3-dimensional (3D) virtual models of pulp cavities obtained through semiautomatic segmentation on images from 6 cone beam computed tomography (CBCT) units compared with the reference standard of micro-CT.

STUDY DESIGN

Fifteen mandibular premolar teeth were scanned with 6 CBCT units: Prexion 3D Elite, i-CAT Next Generation, NewTom 5G, Cranex 3D, 3Shape X1, and Orthophos SL 3D, using the smallest available field of view and highest resolution settings. Pulp cavity volumes were quantitatively assessed by 2 calibrated examiners. The volumes from each CBCT unit were compared with micro-CT. Qualitative assessment of the 3D reconstructions was also performed. Repeated-measures analysis of variance and the Friedman test compared the CBCT reconstructions to micro-CT. Intra- and interexaminer agreements were calculated with the intraclass correlation coefficient and kappa statistic.

RESULTS

The CBCT-based volumes were all significantly larger than micro-CT (P ≤ .0061). Prexion, X1, and Orthophos provided the segmentations that most closely resembled the reference standard. Intra- and interexaminer agreements ranged from good to excellent for quantitative measurements. Interexaminer agreement for qualitative evaluation was substantial.

CONCLUSIONS

Semiautomatic segmentation of CBCT images is a feasible method to produce virtual 3D models of the pulp cavity. Prexion, X1, and Orthophos were the CBCT units that resulted in 3D reconstructions most similar to the reference standard.

Assessment of the Prevalence of Middle Mesial Canal in Mandibular First Molar: A Multinational Cross-sectional Study with Meta-analysis

BACKGROUND

An additional canal found in the mandibular first molar (M1M) is the middle mesial canal (MMC), which is often missed during root canal treatment. In this study, the prevalence of MMC in M1M on cone-beam computed tomography (CBCT) images was evaluated in 15 countries, along with the effect of some demographic factors on its prevalence.

METHODS

Deidentified CBCT images were scanned retrospectively, and the ones including bilateral M1Ms were included in the study. A written and video instruction program explaining the protocol to be followed step-by-step was provided to all observers to calibrate them. The CBCT imaging screening procedure consisted of evaluating three planes (coronal, sagittal, and axial) after a 3-dimensional alignment of the long axis of the root(s). The presence of an MMC in M1Ms (yes/no) was identified and recorded.

RESULTS

In total, 6304 CBCTs, representing 12,608 M1Ms, were evaluated. A significant difference was found between countries (P < .05). MMC prevalence ranged from 1% to 23%, and the overall prevalence was 7% (95% confidence interval [CI]: 5%-9%). No significant differences were found between the left and right M1M (odds ratio = 1.09, 95% CI: 0.93, 1.27; P > .05) or between genders (odds ratio= 1.07, 95% CI: 0.91, 1.27; P > .05). As for the age groups, no significant differences were found (P > .05).

CONCLUSIONS

The prevalence of MMC varies by ethnicity, but it is generally estimated at 7% worldwide. Physicians must pay close attention to the presence of MMC in M1M, especially for opposite M1Ms, due to the prevalence of MMC being significantly bilateral.

The Accuracy of Lateral Cephalogram for Measuring Alveolar Bone Thickness and Root Diameter on Mandibular Incisors

Background: The objective of the study was to ascertain whether the alveolar bone and root of the mandibular central incisor measured from cephalograms can represent the same measurements of both mandibular central and lateral incisors from CBCT. Methods: A total of 38 sets of CBCT images and cephalograms before treatment were selected for this study. Thicknesses included alveolar bone, cortical bone, and cancellous bone at the labial and lingual sides. Root diameter and total root-bone thickness were also evaluated. The measurements were performed at 3, 6, and 9 mm from the cemento-enamel junction. Heights included labial bone height and lingual bone height. All measurements were performed on cephalograms and CBCT images of the mandibular central incisor (L1CT) and mandibular lateral incisor (L2CT). The data were statistically analyzed using one-way ANOVA and Bonferroni tests (p < 0.01) to compare the cephalograms, L1CT, and L2CT. Results: The cephalograms presented thicker alveolar bone and cortical bone (labial: 0.16−0.31 mm, lingual: 0.14−0.29 mm; p < 0.001) as well as higher alveolar crest (labial: 0.46−0.48 mm, lingual: 0.38−0.39 mm; p < 0.001) than the CBCT images on both the labial and lingual sides, whereas lingual cancellous thicknesses were not significantly different (p = 0.257). The cephalograms presented greater total root-bone thicknesses than L1CT (0.19−0.30 mm; p < 0.001), whereas the cephalograms traced thinner roots than L1CT (0.18−0.23 mm; p < 0.001) and L2CT (0.39−0.59 mm; p < 0.001). Conclusion: Lateral cephalograms cannot represent both mandibular central and lateral incisor dentoalveolar thicknesses, heights, and root diameters the same as CBCT. However, the differences were less than 0.5 mm.

A Three-Dimensional Scale for the Qualitative and Quantitative Assessments of Secondary Alveolar Bone Grafting (SABG) in Unilateral Cleft Lip and Palate Patients Using Cone-Beam Computed Tomography (CBCT)

Background The objective of our study was to derive an objective assessment scale for three-dimensional (3D) qualitative and quantitative evaluation of secondary alveolar bone grafting (SABG) using cone-bone computed tomography (CBCT) in patients with unilateral cleft lip and palate (UCLP).

Methods CBCT scans for pre- and 3-month post-SABG were reviewed for bone volume, height, width, and density of the bony bridge formed in the cleft defect in 20 patients with UCLP. Basic descriptive and principal component analysis was used to extract the various sub-components of the scale. Spearman's correlation was used to check the validity of the scale, and intra-class coefficient (ICC) and Cronbach's α were calculated to establish the reliability and retest applicability of the scale.

Results Each CBCT scan was assessed in five areas: cementoenamel junction (CEJ), root apex, root midpoint, 3 and 6 mm below CEJ, and tabulated in percentiles of 20, 25, 40, 50, 60, and 75 for all the parameters (bone volume, density, and width). These scores were validated when correlated to the scale given by Kamperos et al. Cronbach's α for the domains demonstrated acceptable to excellent internal consistency. The ICC showed good test–retest reliability having a range of scores from 0.89 to 0.94.

Conclusion The proposed scale for the 3D assessment of SABG in patients with UCLP provides gradation for the objective assessment of the bony bridge. This gradation enables the qualitative and quantitative assessments of the bony bridge, thus allowing each clinician to judge SABG more conclusively.

The Changes in Size of Periapical Lesions after Root Canal Treatments Assessed by Digital Periapical Radiography and Cone-Beam Computed Tomography: A 2-Years Prospective Clinical Study

Background and Objectives: There is limited information regarding comparison of long-term dynamics of periapical bone destruction estimated by digital periapical radiography (DPR) and by cone-beam computed tomography (CBCT). This study aimed to compare the radiographically assessed periapical changes of endodontically treated teeth over 2 years of follow-up and to analyse disagreements in periapical lesion size estimates around the same roots using DPR and CBCT. Materials and Methods: A total of 176 endodontically treated teeth, of 128 patients with apical periodontitis, were assessed by DPR and CBCT, at baseline and after 2 years. All periapical radiolucencies were categorised by severity (S0, S1, S2, S3) concerning their size. Descriptive statistics were used to report distribution of the radiolucencies at baseline and at follow-up, and their size transitions over 2 years. Site-specific comparison of the radiolucencies identified by two methods was performed using Z test and Pearson’s chi-square test. Results: majority of the detected radiolucencies were scored as S0: 65% and 68% at baseline; 89% and 83% at follow-up, by DPR and CBCT, respectively. Site-specific score comparison showed that disagreements comprised 18% and 20% of the total number of radiolucencies detected by DPR and CBCT, respectively. There were more disagreements between DPR and CBCT within categories S1 and S2 + S3 compared to S0: at baseline, they comprised 17–33% and after two years 62–95% of all detected radiolucencies within the category. 65% of non-matching score transitions over two years occurred between S0 and S1. The CBCT-based evaluation resulted in negative treatment outcomes for 10 more root canals than the DPR-based result. Conclusions: Most remarkable disagreement between DPR and CBCT recordings was observed within the radiolucency categories S2 and S3. However, the diagnostic accuracy of both radiographic methods was questionable as it resulted in a high proportion of non-matching S0-S1 lesion transitions over 2 years.

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.

Accuracy evaluation of cone beam computed tomography applied to measure peri-implant bone thickness in living patients: an ex vivo and in vivo experiment

OBJECTIVES

This study aims to study the accuracy of cone beam computed tomography (CBCT) for measuring peri-implant bone thickness in living patients via a novel visualization method (NVM).

MATERIAL AND METHODS

The validity of the NVM was verified ex vivo by measuring the same peri-implant bone thicknesses in bovine ribs by using raw postoperative CBCT (clinical measurement, CM), the visualized fused images obtained using the NVM (visualized fused measurement, VF), and hard tissue sections (gold standard measurement, GS). The NVM was applied by deconstructing the postoperative CBCT model into the Model_post-bone and Model_implant and replacing it with bone from preoperative CBCT and standard implant models, respectively. In vivo, 52 implants were included, and the VF of each implant was obtained using data processing methods similar to those used ex vivo. Then, we compared the results of CM and VF.

RESULTS

Ex vivo, the VF was similar to GS, while CM usually underestimated the peri-implant bone thickness, especially at the implant shoulder (P < 0.01). In vivo, on CBCT, areas with a peri-implant bone thickness of 0-0.50 mm were not visible, while those with a thickness of 0.50-1.00 mm were occasionally visible. There was less underestimation of bone along the implant long axis.

CONCLUSIONS

Thin peri-implant bones could be completely underestimated on CBCT. CBCT scans alone are insufficient to warrant surgical intervention. Our NVM facilitates the accurate visual assessment of implant dimensions.

CLINICAL RELEVANCE

The thickness of peri-implant bone could be completely underestimated when thinner than 1.0 mm in living patients. Familiarity with these confusing CBCT results may help clinicians and patients avoid further unnecessary evaluation, misdiagnosis, and invasive treatment.

Evaluation of different registration methods and dental restorations on the registration duration and accuracy of cone beam computed tomography data and intraoral scans: a retrospective clinical study

OBJECTIVES

To evaluate whether the accuracy and duration of registration for cone beam computed tomography (CBCT) and intraoral scans differ according to the method of registration and ratio of dental restorations to natural teeth.

MATERIALS AND METHODS

CBCT data and intraoral scans of eligible patients were grouped as follows according to the ratio of the number of dental restorations to the number of natural teeth (N): group 1, N = 0%; group 2, 0% < N < 50%; group 3, 50% ≤ N < 100%; and group 4, 100% ≤ N. Marker-free registration was performed with a deep learning-based platform and four implant planning software with different registration methods (two point-based, one surface-based, and one manual registration software) by a single operator, and the time consumption was recorded. Registration accuracy was evaluated by measuring the distances between the three-dimensional models of CBCT data and intraoral scans.

RESULTS

A total of 36 patients, one jaw per patient, were enrolled. Although registration accuracy was similar, the time consumed for registration significantly differed for the different methods. The deep learning-based registration method consumed the least time. Greater proportions of dental restorations significantly reduced the registration accuracy for semi-automatic and deep learning-based methods and reduced the time consumed for semi-automatic registration.

CONCLUSIONS

No superiority in registration accuracy was found. The proportion of dental restorations significantly affects the accuracy and duration of registration for CBCT data and intraoral scans.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: KCT0006710 CLINICAL RELEVANCE: Registration accuracy for virtual implant planning decreases when the proportion of dental restorations increases regardless of registration methods.

The Impact of Cone-Beam Computed Tomography Exposure Parameters on Peri-Implant Artifacts: A Literature Review

Cone-beam computed tomography (CBCT) amounts to an excellent diagnostic tool to evaluate the peri-implant bone thickness in all dimensions. Despite the unquestionable advantages of CBCT, potential artifacts around dental implants might disturb the proper assessment of the surrounding structures. The artifacts may mask osseointegration, shallow bone defects, and other types of radiolucency, which make it difficult to establish an early diagnosis of bone loss. Proper diagnosis of bone defect is necessary to decide about surgical intervention. The aim of this literature review is to assess the CBCT exposure causing artifacts on the peri-implant structures. An electronic search of MEDLINE (PubMed) database includes studies published before July 2021 and supplemented by manual research. Clinical, ex vivo, in vitro, and animal studies evaluating the relationship between exposition parameters and occurrence of artifacts around the dental implant in CBCT studies were included. A literature review revealed that kilovoltage, tube current, and field of view may affect the occurrence of artifacts around dental implants, all of which would compromise radiological evaluation. Therefore, it is feasible to reduce the incidence of artifacts and improve the image quality by appropriate modification of the exposure parameters. However, the reduction of artifacts is often associated with a significant increase in radiation exposure; hence, an effort should be made to minimize the radiation dose in line with the ALARA (as low as reasonably achievable) principle.

Can gray values be converted to Hounsfield units? A systematic review

OBJECTIVES

The purpose of this systematic review was to answer the focus question: "Could the gray values (GVs) from CBCT (cone beam computed tomography) be converted to Hounsfield units (HUs) in multidetector computed tomography (MDCT)?"

METHODS

The included studies try to answer the research question according to the PICO strategy. Studies were gathered by searching several electronic databases and partial grey literature up to January 2021 without language or time restrictions. The methodological assessment of the studies was performed using The Oral Health Assessment Tool (OHAT) for in vitro studies and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) for in vivo studies. The Grading of Recommendations Assessment, Development and Evaluation (GRADE system) instrument was applied to assess the level of evidence across the studies.

RESULTS

2710 articles were obtained in Phase 1, and 623 citations remained after removing duplicates. Only three studies were included in this review using a two-phase selection process and after applying the eligibility criteria. All studies were methodologically acceptable, although in general terms with low risks of bias. There are some included studies with quite low and limited evidence estimations and recommendation forces; evidencing the need for clinical studies with diagnostic capacity to support its use.

CONCLUSIONS

This systematic review demonstrated that the GVs from CBCT cannot be converted to HUs due to the lack of clinical studies with diagnostic capacity to support its use. However, it is evidenced that three conversion steps (equipment calibration, prediction equation models, and a standard formula (converting GVs to HUs)) are needed to obtain pseudo Hounsfield values instead of only obtaining them from a regression or directly from the software.

Reproducibilidad y validez de criterio de dos técnicas radiográficas para variaciones de premolares mandibulares comparadas con CBCT

Introducción: La existencia de variaciones anatómicas ocasiona fracasos en tratamientos endodónticos, por lo que es importante diagnosticarlas. El objetivo fue determinar la reproducibilidad y la validez de criterio de las radiografías con placa de fósforo y la radiovisografía con sensor para identificar las variaciones anatómicas detectadas por tomografía computarizada de haz cónico (CBCT) en premolares inferiores. Métodos: En 140 premolares se obtuvieron imágenes por CBCT, radiografía y radiovisografía. Se realizó lectura independiente por dos endodocistas, evaluándose la clasificación de Vertucci y las ramificaciones. Se determinó la reproducibilidad intraobservador e interobservador. Se calcularon sensibilidad, especificidad y áreas bajo la curva operador-receptor (AUC) utilizando como estándar de oro la CBCT. Resultados: La reproducibilidad intraobservador e interobservador fue mayor para radiografía. Para la Clase I de Vertucci, la radiografía presentó mayor sensibilidad (94,7%), especificidad (64,9%) y AUC (0,795) que la radiovisiografía (89,3%, 62,2% y 0,757, respectivamente), al igual que para la Clase V (Radiografía 69,2%, 93% y 0,811; Radiovisiografía 50%, 84,2% y 0,671, respectivamente). Ninguna de las técnicas aportó al diagnóstico de la Clase III (AUC <0,5). Las ramificaciones fueron infrecuentes (2,9%) y su detección fue baja (Sensibilidad 25% para radiografía y 0% para radiovisiografía). Discusión: Este es el primer estudio que evalúa la reproducibilidad y validez de estas dos técnicas radiográficas comparadas con la CBCT para la detección de variaciones anatómicas en dientes. Conclusiones: La radiografía con placa de fósforo presentó mayor reproducibilidad y validez para el diagnóstico de las Clase I y V de Vertucci, que fueron las variaciones más frecuentes.

Validity and reliability of masseter muscles segmentation from the transverse sections of Cone-Beam CT scans compared with MRI scans

BACKGROUND

To evaluate the validity and reliability of cone-beam computed tomography (CBCT) masseter muscle segmentation by comparing with the magnetic resonance imaging (MRI) masseter muscle segmentation of the same patients.

METHODS

Seventeen volunteers were included in this study. CBCT and MRI scans of the volunteers were taken, respectively, within one month. The masseter muscles in the CBCT scans were segmented by a generative adversarial network (GAN)-based framework combined with manual check. The masseter muscles in the MRI scans were segmented manually. The segmentations were repeated by the first examiner and a second examiner. For cross-sectional area (CSA), paired t-test, intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were calculated to evaluate the validity and reliability of the segmentations. The validity and reliability were also calculated by Dice similarity coefficient (DSC) and average Hausdorff distance (aHD) between different segmentations. Seventeen volunteers were included in this study. CBCT and MRI scans of the volunteers were taken, respectively, within one month. The masseter muscles in the CBCT scans were segmented by a generative adversarial network (GAN)-based framework combined with manual check. The masseter muscles in the MRI scans were segmented manually. The segmentations were repeated by the first examiner and a second examiner. For cross-sectional area (CSA), paired t-test, intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were calculated to evaluate the validity and reliability of the segmentations. The validity and reliability were also calculated by Dice similarity coefficient (DSC) and average Hausdorff distance (aHD) between different segmentations.

RESULTS

Paired t-test showed that there was no significant difference in CSA between CBCT and MRI masseter segmentations. The ICCs were all larger than 0.95 and the SEM was less than 4.85 mm² for CSA. The DSC was all larger than 0.95 showing over 95% of similarity between CBCT and MRI masseter segmentations. The aHD was all smaller than 0.09 mm showing great consistency of the contour of CBCT and MRI segmentations.

CONCLUSION

Masseter muscle segmentation from CBCT scans was not significantly different from the segmentation from MRI scans. CBCT muscle segmentation showed great validity compared with MRI scans, and great reliability in retests.

Dimensional measurement accuracy of 3-dimensional models from cone beam computed tomography using different voxel sizes

OBJECTIVES

To compare the geometric accuracy and measurement reliability of 3-dimensional (3D) reconstructed models of the mandible created from cone beam computed tomography (CBCT) images obtained with 0.2-mm and 0.4-mm voxel sizes with the reference standard model and compare the accuracy of the CBCT-based models to each other.

STUDY DESIGN

The reference standard 3D model of a dry human mandible was obtained using a white light scanner. The mandible was scanned with CBCT 10 times at each voxel size. The models created from the CBCT data were compared with the reference standard by using a point-based rigid registration algorithm where the distance differences between the superimposed CBCT models and the reference standard model were recorded. The measurements derived from the 2 CBCT-based scans were also compared.

RESULTS

Mean deviations from the reference standard for 0.2-mm and 0.4-mm voxel scans were 0.4342 mm and 0.4580 mm, respectively (P ≥ .16). The CBCT scans with both 0.2-mm and 0.4-mm voxels produced good measurement reliability and did not significantly differ from each other (P ≥ .20).

CONCLUSIONS

CBCT scans with 0.2-mm and 0.4-mm voxel sizes delivered similarly accurate models. Larger voxels can be used to minimize radiation exposure.

Effect of cone beam computed tomography voxel size and dental specialty status on the agreement of observers in the detection and measurement of periapical lesions

OBJECTIVE

To compare observer agreement between endodontists and oral and maxillofacial radiologists (OMRs) in the detection and measurement of periapical lesions as depicted in cone beam computed tomography (CBCT) with 2 voxel sizes.

STUDY DESIGN

In total, 256 CBCT images of maxillary molars were evaluated by 2 endodontists and 2 OMRs. Images were obtained at voxel sizes of 0.2 and 0.4 mm. Observers evaluated 64 endodontically and 64 nonendodontically treated teeth for the presence of periapical lesions using a 5-point confidence scale. Weighted κ values were calculated to determine intra- and interobserver agreement. Intraclass correlation coefficients (ICCs) were calculated to assess intra- and interobserver agreement in width and height measurements of the lesions.

RESULTS

Intraobserver agreement ranged from fair to almost perfect, with κ values higher for the OMRs than for the endodontists. Interobserver agreement between endodontists ranged from fair to moderate at the 0.2mm voxel size and was slight at 0.4 mm. Agreement between OMRs was almost perfect at 0.2 mm and ranged from substantial to almost perfect at 0.4 mm. ICC was excellent for all observers in all conditions.

CONCLUSIONS

Intra- and interobserver reliability was affected by voxel size and specialty. Correlation for measurements exhibited no variation.

Effects of Exposure Parameters and Voxel Size for Cone-Beam Computed Tomography on the Image Matching Accuracy with an Optical Dental Scan Image: An In Vitro Study

This study is aimed at assessing the effects of exposure parameters and voxel size for cone-beam computed tomography (CBCT) on the image matching accuracy with an optical dental scan image. CBCT and optical scan images of a dry human mandible were obtained. Different CBCT settings were used: tube voltage, 60, 80, and 100 kVp; tube current, 6 and 8 mA; and voxel size, 100, 200, and 300 μm. Image matching between the CBCT and optical scan images was performed using implant planning software by dental professionals (n = 18). The image matching accuracy in each combination of CBCT settings was evaluated by assessing the linear discrepancy between the three-dimensionally reconstructed radiological image and the registered optical scan image using an image analysis software program. The Kruskal-Wallis test and a post hoc Mann–Whitney U test with Bonferroni correction were used to compare the accuracy of image registration between the groups (α = 0.05). Overall, the image matching accuracy was not significantly different between tube voltage and current settings; however, significantly higher image registration errors were found at the combination of 100 kVp tube voltage/8 mA tube current (F = 8.44, P < 0.001). Changes in voxel sizes did not significantly interfere with the image registration results. No interaction was found among voltage, current, and voxel size in terms of image registration accuracy (F = 2.022, P = 0.091). Different exposure parameter settings in tube voltage and tube current did not significantly influence the image matching accuracy between CBCT and optical dental scan images; however, a high radiation dose could be inappropriate. The image matching accuracy was not significantly affected by changing the voxel sizes of CBCT.

Performance of Bioceramic-based Root Filling Material with Artifact Reduction Properties in the Detection of Vertical Root Fractures Using Cone-beam Computed Tomography

Introduction:

In Cone-beam Computed Tomography (CBCT) images, metallic artifacts by root filling materials reduce the quality of images. It seems that bioceramic sealers produce fewer artifacts than gutta-percha. In this situation, the possibility of VRF detection could increase, and therefore, flap and exploratory surgery would not be needed. The purpose of this study was to evaluate the performance of a bioceramic-based root filling material in the detection of Vertical Root Fractures (VRF) in CBCT imaging.

Materials and Methods:

This study was conducted at the dental school from March to August 2019, and 100 healthy human mandibular premolar teeth were obtained and randomly divided into two equal groups. The teeth were filled with either AH26 and gutta-percha or bioceramic root filling materials. VRF was induced on half of the decoronated teeth in each group using a Global Testing Machine, and the others were considered control. CBCT imaging was performed by the Cranex 3D machine. Comparisons of the 2 groups were made using the Mann-Whitney test.

Results:

There was a significant difference between the two groups of bioceramic and gutta-percha in the measured indices, including sensitivity (P=0.017), specificity (P=0.018), positive predictive value (P=0.018), negative predictive value (P=0.018), and accuracy (P=0.011). The Area Under Curve (AUC) also showed a significant difference between the two groups (P=0.011). According to Kappa test results, no significant difference was obtained between the findings of the two observers.

Conclusion:

Different root filling materials showed a different extent of artifact in CBCT images. Bioceramic root filling material induces fewer artifacts in CBCT images, and the diagnostic value of VRF in CBCT images in the root canals filled with it is greater than those filled with AH26 and gutta-percha.

Two decades of research on CBCT imaging in DMFR - an appraisal of scientific evidence

OBJECTIVE

This article aims to appraise how scientific evidence related to CBCT has changed over the years, based on levels of evidence and diagnostic efficacy.

METHODS

A general search strategy was used in different databases (Pubmed, Embase, and Web of Science) to identify systematic reviews (SRs) on CBCT until November of 2020. The SRs included were divided according to different specialties of dentistry. A critical review of the articles was made, describing the level of evidence and efficacy.

RESULTS

In total, 75 articles were selected. There was an increase in the number of SRs on CBCT from 2014 onwards, as 83% of the SRs on this topic were published after 2013, and 72% between 2016 and to date. Twenty SRs (27%) performed meta-analysis. Only 28% of the SRs provided a detailed description of CBCT protocols. According to SR evidence, almost all specialties of dentistry have advanced concomitantly with the introduction of CBCT. The majority of SRs were related to clinical applications (level 2 of efficacy), followed by technical parameters (level 1 of efficacy). Only some CBCT models were mentioned in the SRs selected.

CONCLUSION

Over the course of 20 years, SRs related to CBCT applications for a broad range of dental specialties have been published, with the vast majority of studies at levels 1 and 2 of diagnostic efficacy. Not all CBCT models available on the market have been scientifically validated. At all times, one should remain cautious as such not to simply extrapolate in vitro results to the clinical setting. Also, considering the wide variety of CBCT devices and protocols, reported results should not be overstated or generalized, as outcomes often refer to specific CBCT devices and protocols.

Evaluation of various low-dose cone-beam computed tomography protocols in the diagnosis of specific condylar defects

INTRODUCTION

This study aimed to determine the identifiability and measurement accuracy of defined bony defects of the temporomandibular joint (TMJ) in cone-beam computed tomographies, depending on different milliampere-second (mAs)-reduced protocols.

METHODS

Defined artificial defects were prepared on 30 condyles from 15 intact pig heads, with a maximum of surrounding soft tissue preserved. Three-dimensional imaging was performed using ProMax 3D Mid (Planmeca, Helsinki, Finland). The scan protocol with maximum resolution and without mAs-reduction was defined as control. Twenty-six mAs-reduced imaging protocols were analyzed by 1 examiner regarding the protocol-specific measurement accuracy. Defect depth (DD) was divided into 3 categories: I, <2 mm; II, 2-3 mm; and III, >3 mm. The protocol-specific sensitivity and specificity were evaluated in relation to localization and defect size as determined from the results of 3 examiners.

RESULTS

There was a significant difference from the control protocol in DD measurement in 8 mAs-reduced protocols, P <0.001-0.027. In most protocols, there was no significant difference in measurement accuracy concerning defect size and localization. The mean sensitivity reached values between 93.3% and 98.6% and differed significantly among protocols (P = 0.002). The mean specificity amounted to 97.0%-98.1% and did not differ among protocols (P = 0.462). The specificity of DD III (99.1%) was higher than DD I (97.7%) and DD II (97.1%). There was a significant difference in specificity and sensitivity concerning defect localization (P <0.001).

CONCLUSIONS

This study showed that mAs-reduced cone-beam computed tomographies protocols are suitable for the analysis of defined osseous TMJ defects. When 3-dimensional TMJ imaging is indicated because of potential erosive defects, validated mAs-reduced scan protocols should be applied instead of high-definition protocols.

Effect of voxel size on detection of fenestration, dehiscence and furcation defects using cone-beam computed tomography

OBJECTIVES

This study aimed to assess the effect of voxel size on detection of fenestration, dehiscence, and furcation defects using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

This in vitro, experimental study evaluated 4 sheep skulls with both the maxilla and mandible accompanied by the surrounding soft tissue. Fenestration (n = 30), dehiscence (n = 65), and furcation defects (n = 46; 18 grade I, 25 grade II, and 3 grade III) were randomly created by round and needle burs in both jaws, and 40 areas served as control sites. CBCT scans were obtained with 0.300 and 0.150 mm³ voxel sizes and 8 × 11cm² field of view (FOV), and were randomly observed by four observers (two oral and maxillofacial radiologists and two periodontists). The kappa values, sensitivity and specificity were calculated for each voxel size and compared using paired t test.

RESULTS

By an increase in image resolution, diagnostic sensitivity increased while specificity decreased. The kappa values for fenestration (0.602-0.623), and grade III furcation defects (0.903-1.00) were optimal (> 0.6), and almost similar for both voxel sizes. The kappa values for dehiscence, and grades I and II furcation defects were unfavorable (< 0.6) and almost similar for both voxel sizes, except for grade I furcation defects, which had a significant difference in kappa values between the two voxel sizes (0.014 and 0.34).

CONCLUSION

Smaller voxel size had higher sensitivity and lower specificity for detection of all defects except for grade I furcation defects, for which the smaller voxel size had higher sensitivity and higher specificity.

Comparison of the different voxel sizes in the estimation of peri-implant fenestration defects using cone beam computed tomography: an ex vivo study

Background

To examine the influence of voxel sizes to detect of peri-implant fenestration defects on cone beam computed tomography (CBCT) images.

Materials and methods

This study performed with three sheep heads both maxilla and mandible and two types of dental implant type 1 zirconium implant (Zr⁴⁰) (n = 6) and type 2 titanium implant (Ti²²) (n = 10). A total of 14 peri-implant fenestrations (8 buccal surfaces, 6 palatal/lingual surface) were created while 18 surfaces (8 buccal, 10 palatal/lingual) were free of fenestrations. Three observers have evaluated the images of fenestration at each site. Images obtained with 0.75 mm³, 0.100 mm³, 0.150 mm³, 0.200 mm³, and 0.400 mm³ voxel sizes. For intra- and inter-observer agreements for each voxel size, Kappa coefficients were calculated.

Results

Intra- and inter-observer kappa values were the highest for 0.150 mm³, and the lowest in 0.75 mm³ and 0.400 mm³ voxel sizes for all types of implants. The highest area under the curve (AUC) values were found higher for the scan mode of 0.150 mm³, whereas lower AUC values were found for the voxel size for 0.400 mm³. Titanium implants had higher AUC values than zirconium with the statistical significance for all voxel sizes (p ≤ 0.05).

Conclusion

A voxel size of 0.150 mm³ can be used to detect peri-implant fenestration bone defects. CBCT is the most reliable diagnostic tool for peri-implant fenestration bone defects.

Evaluation of secondary dentin formation for forensic age assessment by means of semi-automatic segmented ultrahigh field 9.4 T UTE MRI datasets

Dental methods are an important element of forensic age assessment of living persons. After the development of all the teeth, including third molars, is completed, degenerative characteristics can be used to assess age. The radiologically detectable reduction of the dental pulp cavity has been described as such a feature. We investigated the suitability of ultrahigh field 9.4 T ultrashort time echo (UTE) magnetic resonance imaging (MRI) for the evaluation of pulp cavity volume in relation to the total tooth volume in 4 extracted human teeth. The volume calculations were performed after semi-automatic segmentation by software AMIRA using the different intensities of the structures in the MRI dataset. The automatically selected intensity range was adjusted manually to the structures. The visual distinction of pulp and tooth structure was possible in all cases with in-plane resolution < 70 μm. Ratios of tooth/pulp volume were calculated, which could be suitable for age estimation procedures. Intensity shifts within the pulp were not always correctly assigned by the software in the course of segmentation. 9.4 T UTE-MRI technology is a forward-looking, radiation-free procedure that allows the volume of the dental pulp to be determined at high spatial resolution and is thus potentially a valuable instrument for the age assessment of living persons.

Misfit detection in implant-supported prostheses of different compositions by periapical radiography and cone beam computed tomography: An in vitro study

STATEMENT OF PROBLEM

Misfits at the implant-abutment joint (IAJ) can cause the biological and mechanical failure of implant therapy. Standard parallel periapical radiography (PERI) is the method of choice for assessing the fitting of implant-supported prostheses. Although current guidelines do not support the use of cone beam computed tomography (CBCT) solely for misfit detection, CBCT scans can also register misfits as imaging findings. Whether the material used for prostheses manufacturing influences misfit appearance in PERI and CBCT images is unknown.

PURPOSE

The purpose of this in vitro study was to assess the influence of the type of prosthesis material on misfit detection at the IAJ by using PERI and CBCT.

MATERIAL AND METHODS

Thirty-two implants with an external hexagon connection were placed in dried human mandibles. Implant-supported crowns were manufactured with different materials and allocated to 3 experimental groups: metal-ceramic (MC), titanium abutment veneered with acrylic resin (TIT), and zirconia abutment veneered with glass-ceramic (ZIR). All crowns were installed both with and without a simulated 200-μm-thick gap at the IAJ (n=64) and were assessed by PERI and CBCT scans. Four dentists evaluated the images for the presence or absence of misfit. Statistical analysis included the Kappa test and areas under the receiver operating characteristics curve (Az values) comparisons (α=.05).

RESULTS

Kappa values indicated almost perfect intraevaluator and interevaluator reproducibility for PERI and ranged from fair to almost perfect for CBCT. For PERI, Az values were not significantly different among the MC (0.995), TIT (0.997), and ZIR groups (1.000) (P>.05). Regarding CBCT, the Az values found for TIT (0.941) and MC (0.890) were significantly higher than for ZIR (0.762) (P<.05). Az values for PERI were significantly higher than for CBCT (P<.05).

CONCLUSIONS

The type of prosthesis material did not influence misfit detection at the IAJ with PERI; however, ZIR had lower diagnostic accuracy than TIT and MC implant-supported crowns with CBCT.

Cone-beam Computed Tomographic-based Assessment of Filled C-shaped Canals: Artifact Expression of Cone-beam Computed Tomography as Opposed to Micro-computed Tomography and Nano-computed Tomography

INTRODUCTION

The present study investigated the assessment of root canal fillings in a series of cone-beam computed tomographic (CBCT) images obtained from endodontically treated mandibular molars with C-shaped canals.

METHODS

Clinically comparable high (HR) and normal (NR) resolution protocols were selected in 3D Accuitomo 170 (J Morita Corporation, Kyoto, Japan), NewTom VGi evo (Cefla QR Verona, Verona, Italy), ProMax 3D Max (Pro; Planmeca, Helsinki, Finland), and Pax-i3D Green Premium (Pax; Vatech, Gyeonggi, South Korea). Micro-computed tomographic and nano-computed tomographic images were considered as the reference standard. The set of images was evaluated according to beam hardening artifact patterns (dark streaks, hypodense areas, and volume distortion).

RESULTS

Regarding dark streaks, the Fleiss kappa test showed that Pax HR and NR and Pro HR images showed the highest artifact expression. Hypodense areas were detected in 100% and 99.1% of the images obtained using Pax HR and NR, respectively. Kappa tests showed highest distortion for images derived from the Pax and Pro CBCT devices. Root canal filling assessment was considered appropriate in 100% of the 3D Accuitomo 170 HR, NewTom VGi evo NR, micro-computed tomographic, and nano-computed tomographic images.

CONCLUSIONS

The present study confirms the large variability in CBCT-derived artifact expression. Highlighting the increased artifact expression for particular CBCT systems, it may be concluded that for diagnosis of endodontically filled molars with C-shaped canals, the choice of CBCT unit and protocol is essential.

Assessment of fractures in endodontically treated teeth restored with and without root canal posts using high-resolution cone beam computed tomography

Background

Root fractures are a diagnostic challenge for dentists in endodontic treatment. This study aimed to determine the relationship between the characteristics of tooth fractures and the presence of root canal posts in endodontically treated teeth using high-resolution cone beam computed tomography (CBCT).

Material and Methods

Fifty high-resolution CBCT scans of endodontically treated teeth with a diagnosis of fracture were obtained, of which 30 were from women and 20 were from men. These scans were acquired with three Veraviewepocs 3D units and one 3D Accuitomo 170 unit, with a 40 × 40-mm field of view and 125 μm voxel size. The variables assessed included the type of fracture, extent of fracture, type of retention, post length, cause of endodontic failure, location of the lesion, and time required to detect the fracture (difficulty score). For data analysis, the chi-squared test, Student’s t-test, and multiple linear regression (α <0.05) were used.

Results

No association was found between the type of fracture and type of retention or between the type of fracture and its extent (P>0.05). On the other hand, the type of fracture significantly influenced the time required for its detection. Additionally, the most difficult plane for detecting the fracture and the difficulty score were associated, with statistically significant results.

Conclusions

The type of fracture in endodontically treated teeth was not associated with the type of post used for restoration. All of the CBCT systems used to detect tooth fracture showed the same efficiency.

Key words:Cone-Beam CT, Tooth Fracture, Root Canal Post.

Cone-beam computed tomography and its applications in dental and maxillofacial radiology

Cone-beam computed tomography (CBCT) was first used in dental and maxillofacial radiology (DMFR) at the end of the 1990s. Since then, it has been successfully established as the standard three-dimensional radiographic imaging technique in DMFR, with a wide variety of applications in this field. This manuscript briefly reviews the background information on the technology and summarises available data on effective dose and dose optimisation. In addition, typical clinical applications and indications of the technique in DMFR are presented.

The crucial role of imaging in digital dentistry

One of the recent trends in dentistry - and this in every field from the restorative to the orthodontic one- is the introduction of simplified completely digital workflows. Digital dentistry is supposed to allow dentists to work more efficiently, and this at higher precision, and with the possibility of all-in-one sessions using in-house computerized techniques. In this workflow, one of the major tools for simulating and transferring dental treatments is imaging. Both 3D low dose radiographic as well as optical imaging are playing crucial roles and have been overwhelming the market. Novel design platforms, compact and extremely fast milling and printing units are now also plentiful and rapidly being adopted in practice. Nevertheless, many of the steps in this digital dentistry process, no matter how simplified, present risks that can contribute to reduced precision and clinical difficulties. It is therefore the purpose of the article to briefly describe the role of imaging in this digital workflow, and where the pitfalls can be found that may lead to errors and imprecision.