Associations between the keratinized mucosa width and the underlying alveolar bone dimensions at partial edentulous molar sites: a retrospective cross-sectional study.

BACKGROUND: The assessment of hard and soft tissue at edentulous sites is important for subsequent implant treatment design. The aim of the present study was to explore the associations between the keratinized mucosa width (KMW) and the underlying alveolar bone dimensions at partial edentulous molar sites. METHODS: In this retrospective study, a total of 110 patients with at least one missing molar were selected. The buccal KMW of the edentulous molar sites was evaluated. Cone-beam computed tomography scans were collected, and the height discrepancy between the alveolar crest and the buccal bone plate (HC-B) as well as the alveolar bone height (ABH) were measured. The KMW was compared among the HC-B and ABH groups at both maxillary and mandibular sites. Linear regression and generalized estimation equations (GEEs) were used to explore the associations between the KMW and alveolar bone dimensions at α = 0.05. RESULTS: Among the 110 patients, 158 edentulous molar sites were analyzed. The average HC-B and ABH were significantly lower at the maxillary sites (1.26 ± 1.62 mm, 11.62 ± 3.94 mm) than at the mandibular sites (3.67 ± 2.85 mm, 14.91 ± 3.01 mm, p < 0.001). The KMW was significantly lower at sites with HC-B > 2 mm than at sites with HC-B ≤ 2 mm both in the maxilla and mandible (p < 0.001). No significant differences were found between the KMW at sites with ABH < 10 mm and sites with ABH ≥ 10 mm (p > 0.05). Linear regression and GEEs analyses revealed that the HC-B was significantly associated with the KMW (B = -0.339, p < 0.001), while the association between the KMW and the ABH was not statistically significant (B = -0.046, p = 0.352). CONCLUSIONS: The buccal KMW at edentulous molar sites was significantly associated with the HC-B. Alveolar ridges presenting with a sloped configuration were more prone to possess a narrower band of keratinized mucosa. Both hard and soft tissue augmentation should be considered for implant treatment at these sites. The correlations of dynamic changes between the KMW and alveolar bone dimensions after tooth extraction should be further investigated.

[Study on the consistency between CBCT image features of sphenopalatine foramen and those seen in nasal endoscopy].

Objective:To study the clinical anatomy of the sphenopalatine foramina by dissecting the sphenopalatine foramina during Vidian nerve branch neurotomy. The anatomy and CBCT images of sphenopalatine foramen were analyzed to facilitate the navigational of clinical operation using CBCT images. Methods:From October 2017 to September 2023, 84 cases（168 sides） of Vidian nerve branch neurotomy in our department were collected. The clinical summary was made according to the anatomy of sphenopalatine foramen during the operation. Preoperative CBCT imaging findings of the sphenopalatine foramina were also studied. Results:The clinical anatomy of sphenopalatine foramen could be divided into four types: middle meatus type（1.19%）, trans-meatus type（62.29%）, superior meatus type（33.33%） and double foramen type（1.19%）. The incidence of ethmoidal ridge was 98.81%. The distance from sphenopalatine foramina to posterior nasal canal were（14.63±2.66） mm to left and（14.65±2.63） mm to right, The position Angle ∠a of lower margin of sphenopalatine foramina were（62.36±10.05）° to left and（61.51±11.82）° to right, respectively. Axial CT images can be used to divide the sphenopalatine foramen into five levels: the upper edge of the sphenopalatine foramen level, the Vidian nerve level, the basal plate interaction level, the lower edge of the sphenopalatine foramen level and the pterygopalatine canal level. The agreement between endoscopic anatomy of sphenopalatine foramen and imaging navigation was 100%. Conclusion:The sphenopalatine foramina exhibit various anatomical types. The preoperative navigational CBCT reading can effectively identify the type of sphenopalatine foramina, guide the choice of surgical method, and help avoid serious complications. This has significant clinical application value.

Bringing online adaptive radiotherapy to a standard C-arm linac.

Current online adaptive radiotherapy (oART) workflows require dedicated equipment. Our aim was to develop and implement an oART workflow for a C-arm linac which can be performed using standard clinically available tools. A workflow was successfully developed and implemented. Three patients receiving palliative radiotherapy for bladder cancer were treated, with 33 of 35 total fractions being delivered with the cone-beam computed tomography (CBCT)-guided oART workflow. Average oART fraction duration was 24 min from start of CBCT acquisition to end of beam on. This work shows how oART could be performed without dedicated equipment, broadening oART availability for application at existing treatment machines.

Evaluation of Facial Asymmetry in Patients with Crooked Nose.

BACKGROUND: This study aims to explore the correlation between facial asymmetry and a crooked nose using objective methodologies. METHODS: The cohort of 57 patients who underwent septorhinoplasty surgery for aesthetic reasons between 2019 and 2022. Patients were categorized based on the type of nasal axis deviation. The analysis involved reviewing patients' photographs and cone beam computed tomography images. We identified various anatomical landmarks and compared measurements across the groups. RESULTS: Among the study population, 21 (36.8%) exhibited Type-I (linear) and 15 (26.3%) demonstrated Type-C nasal axis deviation, while no deviation was detected in 21 (36.8%) patients. Upon evaluating the upper face area, significant differences were found in the glabella-lateral orbit (G-LO) and rhinion-lateral orbit (Rh-LO) parameters (p = 0.002 and p < 0.001, respectively). A statistically significant difference was discovered in all three parameters between the three groups in the middle face area [glabella-zygion (G-Zy) p = 0.04, rhinion-zygion (Rh-Zy) P < 0.001, anterior nasal spine-zygion (ANS-Zy) p < 0.001)]. Further, a statistically significant difference was noted in the soft tissue parameters gonion (Go) and LO (p = 0.008 and P = 0.005, respectively). CONCLUSION: Patients with crooked noses, in particular, exhibit asymmetries in the upper and middle faces. The glabella in the upper face and the anterior nasal spine in the middle face are stable points, and the fact that the parameters derived from these two reference points are significant, when considered in conjunction with other significant parameters, strongly supports the aforementioned statement. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Pre- and Post-Operative Cone Beam Computed Tomography Assessment of the Temporomandibular Joint in Patients with Orthognathic Surgery.

This study aimed to compare the pre- and post-operative temporomandibular joint (TMJ) condylar position in dentofacial deformity (DFD) patients who had orthognathic surgeries using cone beam computed tomography (CBCT). A retrospective study evaluating the pre- and post-operative CBCT for 79 DFD patients (equivalent to 158 TMJs) (mean age = 26.62 ± 9.5 years) with a bilateral sagittal split osteotomy with or without Le Fort I surgeries (n = 29 Class II DFD, n = 50 Class III DFD) was performed. This included the compartmental measurement of TMJ spaces, in addition to the measurement of intercondylar distances and angles. Condylar position centricity was assessed using the Pullinger and Hollender formula. Clinical data were analysed for DFD class, the type of surgery and post-operative CBCT timing. Pre- and post-operative measurements were compared statistically using a paired t-test, Wilcoxon signed-rank test, and Stuart-Maxwell test. TMJ condyles tended to relocate post-operatively in a posterosuperior position with internal rotation in Class II DFD and a superior position with internal rotation in Class III DFD. However, the overall changes were within <0.5 mm translation and <4° rotation and the number of concentrically positioned condyles (according to the Pullinger and Hollender formula) did not change significantly. Orthognathic surgery is associated with minor post-operative translational and rotational condylar positional changes in Class II and III DFDs.

Three-dimensional assessment of root changes after Le Fort I osteotomy.

The study aim was to assess the volumetric, linear, and morphological changes of the maxillary incisor, canine, and premolar roots following Le Fort I osteotomy. Sixty patients (585 teeth) were included retrospectively from among individuals who underwent combined orthodontics and orthognathic surgery. The study group comprised 30 patients who underwent orthodontics and one-piece Le Fort I osteotomy, while the control group consisted of 30 patients who underwent orthodontics and bilateral sagittal split osteotomy but no maxillary surgery. CBCT scans were obtained at four time points: preoperative, 6 months, 1 year, and 2 years postoperative. A fully automated three-dimensional evaluation protocol was utilized to assess root changes of the maxillary teeth. Significant differences in the apical and middle parts of the teeth were observed between the study and control groups at 1 and 2 years postoperative, with greater percentage changes in the study group (all P < 0.05). Greater root remodelling in the canines, first and second premolars was observed in the study group (all P < 0.005). Spearman correlation analysis indicated a positive relationship between root remodelling and maxillary advancement, with larger advancements contributing to increased root remodelling in the apical and middle root parts (both P < 0.05). These findings can be valuable for surgeons and orthodontists in evaluating root changes.

The Assessment of C-shaped Canal Prevalence in Mandibular Second Molars Using Endodontic Microscopy and Cone Beam Computed Tomography: An In Vivo Investigation.

Background Understanding root canal anatomy variations, particularly C-shaped canals, is crucial for successful endodontic treatment. This study used clinical and radiographic methods to assess the prevalence and characteristics of C-shaped canals in mandibular second molars in Western Maharashtra. Materials and methods This prospective study was conducted in the western region of Maharashtra, India. The samples included patients requiring endodontic treatment for mandibular second molars. Clinical evaluation was conducted using a surgical endodontic microscope and cone beam computed tomography (CBCT) imaging. Inclusion and exclusion criteria ensured the selection of a focused and homogeneous sample. Data analysis included assessment of unilateral/bilateral occurrence, canal distribution, and cross-sectional characteristics. Results Out of 200 mandibular second molars, 7.5% exhibited C-shaped root canals, with no significant gender differences. Canal distribution varied across coronal, middle, and apical levels, with prevalent configurations being C1, C2, C3, and C4. No significant differences were observed in canal distribution based on root levels. No significant gender differences were found in the presence of grooves on the root surfaces. Conclusion This study provides valuable insights into the prevalence and characteristics of C-shaped canals in mandibular second molars in Western Maharashtra. Further research into histological and genetic aspects can enhance our understanding, leading to improved treatment strategies for complex root canal anatomy variations.

Management of a bulbous blunderbuss maxillary central incisor with one root and three canals in a patient with cleft lip and palate.

Unique anatomical deviations in canal structure are rare in anterior teeth, especially central incisors, and thus risk being overlooked. For successful intervention, a meticulous diagnostic procedure and treatment plan, significantly aided by cone-beam computed tomography (CBCT), are crucial. The case at hand explores the management of a maxillary left central incisor in a cleft palate patient, characterized by multiple developmental lobes, a bulbous crown, and an atypical root anatomy. The primary symptom was pain, accompanied by a history of trauma at age 8 years and ensuing tooth discoloration. Initial evaluations, augmented by CBCT, revealed pulpal necrosis in a single-rooted tooth with three distinct canals. Initial clinical examination was supplemented by electrical pulp testing, RadioVisioGraphy (RVG), and CBCT, after which the root canal therapy was initiated. Informed consent was obtained from the patient. The access cavity preparation resulted in a three-orifice cavity. Subsequently, the canals were enlarged and sufficiently debrided. Calcium-hydroxide was applied for 2 weeks before the commencement of apexification and obturation, followed by esthetic rehabilitation. This case highlights the importance of recognizing rare anatomical variations in anterior teeth and demonstrates the invaluable role of CBCT in both diagnosing and managing such complexities.

Influence of periapical lesion volume on the radiodensity of surrounding bone: A CBCT study.

Aim: This study assesses if the size of periapical lesions has an effect on the bone immediately peripheral to an apical lesion. Methods: Cone-beam computed tomography (CBCT) images of 271 periapical lesions were analyzed using Mimics Research™ to determine the CBCT periapical lesion volume index (CBCTPAVI) score, along with the radiodensity of the lesion, lesion border, and surrounding bone in 0.5 mm increments up to 2.0 mm peripheral to the apical lesion. The one-way analysis of variance was used to assess for significant differences in the radiodensity of the lesion, border, and peripheral bone, as well as differences among CBCTPAVI scores. Results: The radiodensity of bone peripheral to the apical lesion increased significantly up to 1.0 mm around the lesion's perimeter. In addition, lesions with higher CBCTPAVI scores showed a significantly greater difference in the radiodensity from the lesion to the lesion border and the peripheral bone, compared to lesions with smaller CBCTPAVI scores. Conclusions: This study for the first time shows the influence of periapical lesion size on the radiodensity of bone peripheral to an apical lesion. Variations in radiodensity at the perimeter of a periapical lesion can be influenced by the size of the lesion, possibly indicating differences in defense response. Knowledge of these phenomena may provide information on bone healing and enhance our understanding of bone peripheral to a periapical lesion.

In vitro Accuracy of Ultra-Low Dose Cone-Beam Computed Tomography for Detection of Proximal Caries.

OBJECTIVES: This study aimed to assess the accuracy of ultra-low dose (ULD) cone-beam computed tomography (CBCT) for detection of proximal caries. METHODS: This in vitro study evaluated 104 molar and premolar teeth. The teeth were mounted in dry skulls and underwent CBCT with four protocols of high-resolution (HR), normal (NORM), ULD-HR, and ULD-NORM; 78 CBCT images were scored by three observers for presence and penetration depth of caries twice with a 2-week interval using a 5-point Likert scale. The teeth were then sectioned and observed under a stereomicroscope (gold standard). The four protocols were compared with each other and with the gold standard. The receiver operating characteristic (ROC) curve was drawn, and the area under the curve (AUC) was calculated and compared by the Chi-square test (alpha = 0.05). RESULTS: The interobserver agreement ranged from 0.5233 to 0.6034 for ULD-NORM, 0.5380 to 0.6279 for NORM, 0.5856 to 0.6300 for ULD-HR, and 0.6614 to 0.7707 for HR images. The intra-observer agreement ranged from 0.6027 to 0.8812 for ULD-HR, 0.7083 to 0.7556 for HR, 0.6076 to 0.9452 for ULD-NORM, and 0.7012 to 0.9221 for NORM images. Comparison of AUC revealed no significant difference between NORM and ULD-NORM (P > 0.05), or HR and ULD-HR (P > 0.05). The highest AUC belonged to HR (0.8529) and the lowest to NORM (0.7774). CONCLUSIONS: Considering the significant reduction in radiation dose in ULD CBCT and its acceptable diagnostic accuracy for detection of proximal caries, this protocol may be used for detection of proximal carious lesions and assessment of their depth.

A comparative analysis of sphenoid and frontal sinuses using cone beam computed tomography for sex determination.

Objectives: This study aimed to evaluate linear measurements of the frontal sinus (FS) and sphenoid sinus (SS) for sex identification on cone beam computed tomography (CBCT) images. Methods: A comparative CBCT analysis was conducted on 200 full field of view (FOV) scans taken as part of routine dental investigations. Dimensions of the bilateral frontal and sphenoid sinuses were measured. Intra- and interobserver reliability were calculated. Independent t tests were used to compare the various parameters between sexes. Stepwise discriminant function analysis was used to determine sex. Additionally, the receiver operating characteristic (ROC) curve, area under the curve (AUC), sensitivity, and specificity were also determined. A p value < 0.05 was considered significant. Results: A total of 200 CBCT scans were included in the study. The mean age (±SD) among males was 25.66 (±7.11) and that among females was 24.64 (±5.12). The ROC curve revealed that the right length of the frontal sinus showed the greatest accuracy in sex identification in comparison to other linear measurements of the FS and SS. The results of our study indicated that the equation obtained from stepwise discriminant function analysis can aid in sex determination with an accuracy of 76.5 %. Conclusion: Our findings support the sexual dimorphism of linear measurements of FS and SS. There was an improvement in the accuracy of sex prediction when the linear measurements of FS and SS were considered in combination rather than in isolation. The derived equation can be an adjunctive tool for sex identification for the representative population.

[A dual-domain cone beam computed tomography reconstruction framework with improved differentiable domain transform for cone-angle artifact correction].

OBJECTIVE: We propose a dual-domain cone beam computed tomography (CBCT) reconstruction framework DualCBR-Net based on improved differentiable domain transform for cone-angle artifact correction. METHODS: The proposed CBCT dual-domain reconstruction framework DualCBR-Net consists of 3 individual modules: projection preprocessing, differentiable domain transform, and image post-processing. The projection preprocessing module first extends the original projection data in the row direction to ensure full coverage of the scanned object by X-ray. The differentiable domain transform introduces the FDK reconstruction and forward projection operators to complete the forward and gradient backpropagation processes, where the geometric parameters correspond to the extended data dimension to provide crucial prior information in the forward pass of the network and ensure the accuracy in the gradient backpropagation, thus enabling precise learning of cone-beam region data. The image post-processing module further fine-tunes the domain-transformed image to remove residual artifacts and noises. RESULTS: The results of validation experiments conducted on Mayo's public chest dataset showed that the proposed DualCBR-Net framework was superior to other comparison methods in terms of artifact removal and structural detail preservation. Compared with the latest methods, the DualCBR-Net framework improved the PSNR and SSIM by 0.6479 and 0.0074, respectively. CONCLUSION: The proposed DualCBR-Net framework for cone-angle artifact correction allows effective joint training of the CBCT dual-domain network and is especially effective for large cone-angle region.

[A deep blur learning-based motion artifact reduction algorithm for dental cone-beam computed tomography images].

OBJECTIVE: We propose a motion artifact correction algorithm (DMBL) for reducing motion artifacts in reconstructed dental cone-beam computed tomography (CBCT) images based on deep blur learning. METHODS: A blur encoder was used to extract motion-related degradation features to model the degradation process caused by motion, and the obtained motion degradation features were imported in the artifact correction module for artifact removal. The artifact correction module adopts a joint learning framework for image blur removal and image blur simulation for treatment of spatially varying and random motion patterns. Comparative experiments were conducted to verify the effectiveness of the proposed method using both simulated motion data sets and clinical data sets. RESULTS: The experimental results with the simulated dataset showed that compared with the existing methods, the PSNR of the proposed method increased by 2.88%, the SSIM increased by 0.89%, and the RMSE decreased by 10.58%. The results with the clinical dataset showed that the proposed method achieved the highest expert level with a subjective image quality score of 4.417 (in a 5-point scale), significantly higher than those of the comparison methods. CONCLUSION: The proposed DMBL algorithm with a deep blur joint learning network structure can effectively reduce motion artifacts in dental CBCT images and achieve high-quality image restoration.

Partial tooth formation diagnosed eight years after an extraction of the maxillary third molar germ in a complete crown formation stadium: A case report.

INTRODUCTION: Orthodontic purposes, such as the prevention of anterior crowding, are common and controversial indications for surgical removal of the third molar (M3) germ in young patients. A higher tooth bud position and the risk of tooth displacement in the infratemporal fossa when surgery of the maxillary M3 germ is planned makes the success of germectomy unlikely with little benefit. A rare complication of maxillary M3 germ surgery is partial tooth building after germectomy. PRESENTATION OF CASE: We report the case of a 14-year-old patient who was referred for germectomy of the maxillary M3 in the early development germ stadium to address space constraints and obstruction to the eruption of the second molar (M2) teeth. Computed tomography (CT) examination was used to verify the position and development of the maxillary M3 germ. The surgical procedure was performed without any complications. Eight years after the surgery, the patient presented with indefinable pain in the right upper jaw in the germectomy area. Cone-beam CT revealed a partial tooth formation in the form of a radix relict in the region of the maxillary M3. DISCUSSION: The ongoing debate surrounding germectomy revolves around its indications and timing, considering factors such as patient age, anatomical appearance, and root formation stage. Complications, like partial tooth formation postgermectomy, highlight the importance of precise timing in treatment. CONCLUSION: This is the first report of partial tooth formation as a complication after germectomy of the M3 germ in a complete crown-formation stadium.

Investigating the postoperative soft tissue changes in different vertical facial divergent patients with mandibular prognathism.

Background/purpose: The extent of three-dimensional soft tissue changes in patients with varied facial skeletal patterns following mandibular setback surgery remains unclear. In this study, we aimed to investigate the postoperative changes in soft tissue chin thickness among mandibular prognathism patients, focusing on those presenting different divergence patterns, such as hyperdivergent and normodivergent patients. Materials and methods: Cone-beam computed tomography images were obtained from 56 skeletal Class III patients who underwent only mandibular setback. Based on vertical craniofacial skeletal relationship, patients were divided into normodivergent group (27°37°) group. The three-dimensional displacements of Infradentale (Id), B point (B), and Pogonion (Pog), the soft tissue thickness of Id-Li (Labrale inferius), B-B' (soft tissue B point), and Pog-Pog' (soft tissue Pog point) were measured. Factors influencing the change in soft tissue thickness were investigated. Results: Preoperative B-B' and Pog-Pog' thickness were significantly thinner in the hyperdivergent group than normodivergent group. Postoperative changes in B-B' and Pog-Pog' thickness were significantly larger in the hyperdivergent group than normodivergent group. A significant correlation was found between soft tissue thickness change (B-B' and Pog-Pog') and the preoperative soft tissue thickness and superior movement (B and Pog). Conclusion: Hyperdivergent patients with skeletal class III have thinner preoperative soft tissue thickness (B-B' and Pog-Pog') than normodivergent patients in the preoperation. Postoperative changes in B-B' and Pog-Pog' thickness were significantly larger in the hyperdivergent group than normodivergent group. Postoperative superior movement of B and Pog correlated with postoperative change of soft tissue thickness.

Prevalence and Anatomical Characteristics of Bifid and Trifid Mandibular Canals: A Computer Tomography Analysis.

PURPOSE: To assess the prevalence and configuration of bifid (BMC) and trifid (TMC) mandibular canals using computed tomography (CT), describing the anatomical characteristics of the accessory canals, especially of the retromolar type. MATERIALS AND METHODS: CT scans of 123 patients were analysed. BMCs were identified and the patterns of bifurcation were classified, including trifid canals. The width of accessory canals was measured. Retromolar canals were further classified according to their course and morphology, while their position and width were evaluated using linear measurements on CT images. RESULTS: The majority of patients (53.6%) presented at least one BMC or TMC. 36.2% of mandibular canals were bifid, while 4.5% were trifid. The forward canals (12.6%) and retromolar canals (10.2%) were the most common among BMCs. In relation to the retromolar canals, 60% were vertical and 40% curved, with a mean width of 1.03 ± 0.28mm. CONCLUSION: BMCs and TMCs are common 3D radiographic findings, so that they should be considered as anatomical variations, not anomalies. Preoperative CT or CBCT evaluation should aid in identifying these variations and analysing their position and course in surgical planning.

A cross-sectional CBCT assessment of the relative position of one-piece titanium-zirconium mini-implants placed for mandibular overdentures using non-guided surgery.

OBJECTIVE: To assess the relative position of mini-implants to retain a mandibular overdenture, according to the surgical protocol, technical and anatomical factors. METHODS: Mandibular cone-beam computed tomography (CBCT) scans were analyzed for 73 patients who received four one-piece titanium-zirconium mini-implants. Drilling was performed using a 1.6 mm needle drill and a 2.2 mm Pilot Drill, according to the bone density with a surgical stent. Post-insertion CBCT images in DICOM format were analyzed using the E-Vol-DX software with BAR filters. Divergence angle between implants and between implants and the overdenture path of insertion was measured using CliniView 10.2.6 software. RESULTS: Divergence between implants ranged from 0° to 22.3° (mean = 4.2; SD = 3.7) in the lateral and from 0° to 26.2° (mean = 5.3; SD = 4.1) in the frontal projections (p < .001). Only 1 (0.2%) and 3 (0.7%) of the measurements were higher than 20° in the lateral and frontal views, respectively. The mean angulations between the implant and the path of insertion for the overdenture were 9.3° (SD = 7.5) and 4.0° (SD = 2.9) for the lateral and frontal views, respectively (p < .001). Regression analyses showed a significant association between the divergence of implants and the frontal view projection (p < .001), greater distance between the paired implants (p = .017), the flapped surgical protocol (p = .002), higher final insertion torque (p = .011), and deeper preparation with the needle drill (p < .001). CONCLUSIONS: The mini-implants were placed with low divergence angles and satisfactory parallelism. Factors including shorter distances between the implants, higher density bone, and a flapless surgical approach all contributed positively to improved parallelism of the mini-implants.

[Tooth segmentation and identification on cone-beam computed tomography with convolutional neural network based on spatial embedding information].

OBJECTIVE: To propose a novel neural network to achieve tooth instance segmentation and recognition based on cone-beam computed tomography (CBCT) voxel data. METHODS: The proposed methods included three different convolutional neural network models. The architecture was based on the Resnet module and built according to the structure of "Encoder-Decoder" and U-Net. The CBCT image was de-sampled and a fixed-size region of interest (ROI) containing all the teeth was determined. ROI would first through a two-branch "encoder and decoder" structure of the network, the network could predict each voxel in the input data of the spatial embedding. The post-processing algorithm would cluster the prediction results of the relevant spatial location information according to the two-branch network to realize the tooth instance segmentation. The tooth position identification was realized by another U-Net model based on the multi-classification segmentation task. According to the predicted results of the network, the post-processing algorithm would classify the tooth position according to the voting results of each tooth instance segmentation. At the original spatial resolution, a U-Net network model for the fine-tooth segmentation was trained using the region corresponding to each tooth as the input. According to the results of instance segmentation and tooth position identification, the model would process the correspon-ding positions on the high-resolution CBCT images to obtain the high-resolution tooth segmentation results. In this study, CBCT data of 59 cases with simple crown prostheses and implants were collected for manual labeling as the database, and statistical indicators were evaluated for the prediction results of the algorithm. To assess the performance of tooth segmentation and classification, instance Dice similarity coefficient (IDSC) and the average Dice similarity coefficient (ADSC) were calculated. RESULTS: The experimental results showed that the IDSC was 89.35%, and the ADSC was 84. 74%. After eliminating the data with prostheses artifacts, the database of 43 samples was generated, and the performance of the training network was better, with 90.34% for IDSC and 87.88% for ADSC. The framework achieved excellent performance on tooth segmentation and identification. Voxels near intercuspation surfaces and fuzzy boundaries could be separated into correct instances by this framework. CONCLUSIONS: The results show that this method can not only successfully achieve 3D tooth instance segmentation but also identify all teeth notation numbers accurately, which has clinical practicability.

Performance of different cone-beam computed tomography scan modes with and without metal artifact reduction in detection of recurrent dental caries under various restorative materials.

Purpose: We aimed to compare the diagnostic performance of different cone-beam computed tomography (CBCT) scan modes with and without the application of a metal artifact reduction (MAR) option under 5 different restorative materials. Material and methods: Our research was an in vitro study with 150 caries-free premolars and molars. The teeth were randomly divided into experimental (with artificially induced caries, n = 75) and control (without caries, n = 75) groups and were prepared based on 5 types of restorative materials, including conventional composites (Filtek Z250, Gradia), flow composite, glass ionomer, and amalgam. The teeth were examined under 2 CBCT scan modes (high-resolution [HIRes] and standard) with and without MAR application. Finally, the diagnostic accuracy index values (area under the receiver operating characteristic curve [AUC], sensitivity, and specificity) were calculated. Results: The AUC of standard scan mode with the MAR option was significantly lower than that of HIRes with MAR (p = 0.018) and without MAR option (p = 0.011) in detecting recurrent caries. Also, without MAR option, the diagnostic accuracy (AUC) of the standard mode was significantly lower than that of the HIRes (p = 0.020). Similar findings were observed for sensitivity and specificity. Moreover, diagnostic performance of standard and HIRes scan modes with and without MAR in the amalgam group was lower than that in other restorative material groups. Conclusions: Diagnostic performance of HIRes CBCT mode was higher than that of standard mode for recurrent caries and remained unaffected by MAR application. However, the accuracy in detecting recurrent caries was lower in the amalgam group compared with other restorative material groups.

Morphological evaluation of maxillary arch in unilateral buccally and palatally impacted canines: a cone-beam computed tomography (CBCT)-based study in Northern Iran.

Purpose: This study investigated the association between the maxillary impacted canines' position and the maxilla's morphological features in an Iranian population based on cone-beam computed tomography (CBCT) images. Material and methods: In this cross-sectional descriptive-analytical study, 47 CBCT images of unilateral buccally impacted maxillary canines and 47 CBCT images of unilateral palatally impacted maxillary canines were examined. Several morphological variables were compared between the impacted and non-impacted sides, and between the buccal and palatal impaction types. Results: Gender and age were not significantly associated with the canine impaction type. The alveolar bone height at the impacted side was significantly greater in the buccally impacted group than in the palatally impacted group (p = 0.016). In a comparison of the impacted and non-impacted sides, all variables of alveolar bone thickness at depth of 2 mm, maxillary arch width, and palatal volume had significantly smaller values in the impacted side in both buccally and palatally impacted groups (p < 0.05). The alveolar bone was significantly thicker at the depth of 10 mm in the impacted side of the buccal group (p = 0.024). The maxillary arch perimeter was significantly smaller in the impacted side of the buccal group (p = 0.008). The palatal depth did not significantly differ between the groups. Conclusion: Among the studied variables, the alveolar bone thickness showed contrary results at different depths. The palatal volume and maxillary arch width were significantly smaller on the impacted side in both buccal and palatal groups, and the arch perimeter showed the same results only in the buccal group.