Search

This study employed e-Vol DXS cone beam computed tomography (CBCT) software to assess dentin remnants in the furcation area of mesial canals in mandibular molars during root canal retreatment (RCR). Four groups (Reciproc®, ProTaper Next®, Race Evo®, Protaper Gold®) were subjected to RCR, and CBCT images were captured before (T1) and after (T2) treatment. Measurements of remaining dentin thickness at 1 mm and 3 mm below the furcation were scrutinized. Results revealed no significant differences in mean thicknesses of mesiobuccal (MB) and mesiolingual (ML) canals at 1 mm and 3 mm from the furcation pre-treatment (T1). Post-treatment (T2) showed analogous findings, with no significant differences in mean thicknesses. However, disparities were found between MB and ML canals at both distances, both before and after retreatment. In essence, the evaluated instruments exhibited safety in RCR, implying that they are appropriate for use in critical areas of mandibular molars without inducing excessive wear. This study underscores the reliability of these instruments in navigating danger zones during RCR, and contributes valuable insights for dental practitioners who handle complex root canal scenarios in mandibular molars.

Objective: The imbalanced nature of real-world datasets is an ongoing challenge in the field of machine and deep learning. In medicine and in dentistry, most data samples represent patients not affected by pathologies, and on imagery, pathologic image areas are often smaller than healthy ones. Selecting suitable loss functions during deep learning is essential and may help to overcome the resulting imbalance. We assessed six different loss functions for one exemplary task, tooth structure segmentation on bitewing radiographs, for their performance., Methods: Six different loss functions (Focal Loss, Dice Loss, Tversky Loss and hybrid losses of Cross-Entropy and Dice Loss, Focal and Dice Loss, Focal and Generalized Dice Loss) were compared on a tooth structure segmentation task of 1,625 bitewing radiographs. Training was performed using three different model architectures (U-Net, Linknet, DeepLavbV3+) over a 5-fold cross-validation. Tooth structures consisted of the classes (occurrence in% of samples/captures areas measured on pixel level) enamel (100 %/25 %), dentin (100 %/50 %), root canal (100 %/10 %), filling (81 %/8 %) and crown (28 %/5 %)., Results: Hybrid loss functions significantly outperformed standalone ones and provided robust results over the different architectures for the classes enamel, dentin, root canal and filling. Specifically, the Dice Focal loss reached high performance to conquer both image level and pixel level class imbalance, respectively., Clinical Significance: In dental use cases it is often important to predict minority classes such as pathologies accurately. Using specific loss function may be an effective strategy to overcome data imbalance when training deep learning models., Competing Interests: Declaration of competing interest FS and JK are co-founders of the startup dentalXrai GmbH. dentalXrai GmbH did not have any role in conceiving, conducting or reporting this study. The authors are solely responsible for the contents of this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Background: It is common to see patients who need orthodontic treatment but with insufficient alveolar bone volume. However, safe and effective tooth movement requires sufficient alveolar bone width and height. The aim of this study is to compare the bone augmentation efficacy of Autologous Partially Demineralized Dentin Matrix (APDDM) and Deproteinized Bovine Bone Mineral (DBBM) in orthodontic patients with insufficient bone by using a randomized controlled clinical trial approach., Materials and Methods: Twenty-seven orthodontic patients involving 40 posterior teeth alveolar sites (n = 40) with insufficient alveolar bone volume were randomly divided into a control group (n = 20) and an experimental group (n = 20). The patients in the experimental group were treated with APDDM, and those in the control group were treated with DBBM. After surgery, the adjacent teeth are moved toward the bone grafting sites according to the orthodontic treatment plan. Patients completed a postoperative response questionnaire by the Visual Analogue Scale (VAS) score to indicate pain and swelling in the bone grafted area at the time of suture removal; and CBCT scans were conducted before surgery, 6 months and 2 years after surgery to assess changes in buccal and central alveolar heights, as well as widths at the alveolar ridge apex and 3 mm, 5 mm below the apex, respectively. The CBCT image sequences were imported into Mimics 21.0 software in DICOM format. The data of the patients in both groups were collected and analyzed by SPSS 25.0., Results: The VAS scores were significantly lower in the APDDM group than in the DBBM group (p < 0.05). Significant increases were observed in alveolar bone height and width at 6 months and 2 years postoperative (p < 0.05); At 2 years, the APDDM group exhibited a reduction in buccal crest height and in 3 mm, 5 mm width below alveolar ridge apex, relative to 6 months (p < 0.05), while the DBBM group showed a decrease only in the central height of the alveolar bone (p < 0.05). There was a significant bone augmentation increase found only 3 mm below the alveolar ridge apex in the APDDM group compared with the DBBM group among all 6 months group comparison (p < 0.05). At 2 years, the augmentation effects were similar across both groups (p > 0.05)., Conclusion: Radiomics analysis indicates that APDDM serves as a viable bone augmentation material for orthodontic patients with insufficient alveolar bone volume, achieving comparable clinical efficacy to DBBM. Additionally, APDDM is associated with a milder postoperative response than DBBM., The Registration Number (trn): ChiCTR2400084607., (© 2024. The Author(s).)

Background: The purpose of this in vitro study was to compare and evaluate the stress distribution of maxillary first premolar residual crowns restored with post-core crowns, endocrowns and inlay crowns after deep margin elevation, to explore the fitting restoration for residual crowns using finite element analysis., Methods: A healthy complete right maxillary first premolar from a male adult was scanned by cone beam computed tomography (CBCT). The finite element model of the tooth was established by reverse engineering software such as Mimics, Geomagic and Hypermesh. On this basis, the residual crown model after deep margin elevation was made, and the experimental group models were divided into three groups, those restored with post core crowns, endocrowns and inlay crowns. Vertical and oblique static loads were applied to the experimental models to simulate the force on the tooth during mastication (the loading position was located in the central fossa of the occipital surface, and the load was 100 N) using Abaqus software., Results: The peak value and distribution of von Mises stress in each part of the experimental model were observed. After deep margin elevation, the peak dentin von Mises stresses were lower than the tensile strength of normal dentin in the post-core crown, endocrown, and inlay crown groups; the lowest stress results were found in the post-core crown group for the dentin, restoration, enamel, and deep margin elevation (DME) layers under vertical and oblique loading. In terms of stress distribution clouds, the peak stresses in the dentin tissue were located in the apical 1/3 of the root after postcore crown restorations for both loads, while stress concentrations were evident in the cervical and root areas after endocrown and inlay crown restorations; regardless of the load and restoration method, the corresponding stress concentration areas appeared at the junction of the DME and dentin tissue at the loading site of the restorations; CONCLUSIONS: Post-core crowns, endocrowns and inlay crowns can be used to restore residual crowns after deep margin elevation, and post-core crowns can better protect the residual tooth tissue., (© 2024. The Author(s).)

Objectives: To compare effectiveness of Autologous Particulate Dentin (APD) with Demineralized Freeze-Dried Bone Allograft (DFDBA) in ridge preservation, using radiographic and clinical parameters., Materials and Methods: Thirty subjects with indication of mandibular posterior teeth extraction were randomly assigned to either test or control group. After atraumatic extraction, ridge preservation was performed using APD or DFDBA mixed with i-PRF in test and control groups respectively. Both groups had sockets sealed with A-PRF membrane. Clinical parameters (plaque, gingival and healing indices) and radiographic parameters (vertical ridge height, horizontal ridge width) were assessed at baseline and 6 months using CBCT. Statistical analysis was performed using an independent t-test to compare clinical and radiographic parameters between the groups., Results: Both groups had significant decreases in ridge dimensions over 6 months (p < 0.001). The test group showed less reduction in ridge dimensions than control group at 6 months (p < 0.001). Mean change in vertical height was not significant (1.37 ± 1.32, 1.7311 ± 0.563), but in horizontal ridge width (1.3120 ± 1.13, 1.8093 ± 1.16) was significantly different between test and control groups respectively. There was no statistical difference in clinical parameters between the groups at 6 months (p > 0.001)., Conclusions: APD grafts resulted in significant improvements in radiographic parameters, specifically in vertical ridge height and horizontal ridge width, compared to DFDBA group., Clinical Relevance: Autologous particulate dentin is a promising, versatile substitute for regenerative procedures. While more research on its long-term efficacy and application is needed, current evidence suggests it could significantly improve patient care and outcomes., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: The purpose of this study was to compare the effectiveness of three different instruments on cement loss, porosity and micro-crack formation, which was not evaluated before, following scaling and root planning (SRP) using micro-computed tomography (micro-CT)., Methods: In this experimental study, 30 single-rooted extracted human teeth were used and divided into three groups. All the teeth were scanned with micro-CT before and after SRP. Group 1: SRP was performed with Gracey curettes, Group 2: SRP was performed by using an ultrasonic device, and Group 3: SRP was performed by using diamond burs. Cement loss from the root surface, porosity, and micro-crack formation in the root dentine were analysed. Micro-CT is used for qualitative and quantitative analysis of samples. The obtained data were analysed statistically (p < 0.05)., Results: Minimum cement loss following SRP was detected with ultrasonic scaler (26.98 mm 3 ), whereas the highest was created by diamond burs (96.20 mm 3 ) (p < 0.05). The total porosity values after SRP were 0.278%, 0.334% and 0.252% for Groups 1, 2 and 3, respectively. Although Group 3 had the least porosity values, there was no statistically significant difference between the groups. The highest micro-crack formation was seen in Group 2 and the lowest was in Group 1 with a significant difference (p < 0.05)., Conclusions: More cement loss was observed with diamond burs. Ultrasonic devices appear to be a viable alternative to instrumentation with curettes. However, ultrasonic devices should be used carefully because of micro-crack formation since the micro-crack resulting from instrumentation with hand instruments is the least of all., (© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Computed tomography (CT) and microcomputed tomography (μCT) require calibration against density phantoms scanned with specimens or during routine internal calibration for assessment of mineral concentration (MC) and density. In clinical studies involving bone, alternative calibration methods using bodily tissues and fluids ("phantomless" calibration) have been suggested. However, such tissues are seldom available in archeological and osteological research. This study investigates the potential of dental tissue as internal reference for calibration of μCT scans, facilitating the analysis of bone MC. We analyzed 70 molars from 24 extant primate species, including eight human teeth, each scanned with density phantoms for calibration. Our findings indicate that sampling specific regions of molars (lateral aspects of the mesial cusps) yields low variation in enamel and dentine MC values, averaging 1.27 g/cm 3 (±0.03) for dentine and 2.25 g/cm 3 (±0.03) for enamel. No significant differences were observed across molar types or among scanning procedures, including scanner model, resolution, and filters. An ad hoc test on 12 mandibles revealed low variance in MC between the conventional phantom and dental tissue calibration methods; all 36 measurements (low, medium, and high MC for each mandible) were within 0.05 g/cm 3 of each other -81% were within 0.03 g/cm 3 and 94% within 0.04 g/cm 3 . Based on these results, we propose a new "phantomless" calibration technique using these mean enamel and dentine MC values. The presented phantomless calibration method could aid in the assessment of bone pathology and enhance the scope of studies investigating bone structure and physical property variations in archeological, osteological, and laboratory-based research., (© 2024 The Authors. American Journal of Biological Anthropology published by Wiley Periodicals LLC.)

Objectives: This study aimed to measure the distribution of silver ion (Ag + ), mineral recovery, and nanohardness in carious lesions and comprehensively evaluate the degree of dentin restoration., Methods: Sixty human teeth with root caries were randomly assigned to the control, silver diammine fluoride (SDF) [Safo], and SDF+Glass ionomer cement (GIC) treatment [Safo+Fuji] groups. Micro-computed tomography (micro-CT) was performed at five time points for each sample before/after treatment to evaluate mineral density within and around carious lesions. Three months following treatment, 12 samples were selected for synchrotron radiation X-ray fluorescence analysis to evaluate Ag + distribution, while 15 samples were selected for nanoindentation. Data were analyzed using Dunnett's T3 test for micro-CT and Wilcoxon rank sum test with Bonferroni correction (p = 0.017) for nanoindentation. The correlation between hardness and mineral change was analyzed using the Spearman rank correlation coefficient., Results: The Safo and Safo+Fuji groups showed significantly higher mineral recovery rates than did the control group (p < 0.001). In the Safo group, Ag + accumulated in the deeper layers rather than the superficial layer of caries. In the Safo+Fuji group, Ag + was found evenly distributed throughout caries, with only a few Ag + detected in the GIC layer. Hardness in the Safo+Fuji group was significantly higher compared with the Safo group at depths in the range of 10-50 µm., Conclusion: In the presence of GICs, SDF exhibited high remineralization capacity when diffusing throughout carious lesions over time. Combined treatment with SDF and GIC could strengthen root dentin even in the presence of caries., Clinical Significance: We found that combination treatment with SDF and GIC could increase mineral density in caries and improve the hardness of the tooth structure compared with fluoride-based agents alone. These findings might pave the way for future clinical trials to determine the therapeutic potential of nanotechnology-based restorative materials., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objective: This systematic review aims to comparatively analyse the amount of dentin removal by free hand and static guided endodontics with dynamic navigation system (DNS) in endodontic access cavity preparation., Methods: The systematic review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. Based on the structured PICO framework of "Comparative evaluation of dynamic navigation system (I) to freehand (C) and static guided endodontics (C) in endodontic access cavity preparation on the preservation of tooth structure (O) when assessed on permanent human teeth (P)", the keywords were formulated and the articles were retrieved from three databases namely PubMed, Scopus and Embase, based on the keywords from the time of inception of DNS till June 2023. The risk of bias assessment was done using a modified Joanne Briggs Institute checklist, which evaluated domains such as randomisation, sample size, image acquisition using CBCT, angulation, accuracy and time taken. As the data was heterogenous, a quantitative meta-analysis was not performed., Results: Initially, 174 articles were retrieved from the three databases, 30 duplicates were removed, after title check 108 articles were excluded and following abstract check only 10 articles qualified for full text analysis. On reviewing the 10 full text articles, 5 articles were excluded and the remaining 5 articles were subjected to the risk of bias analysis which showed that 2 articles displayed low risk of bias and three articles showed high risk of bias. The RoB analysis revealed that only 2 studies evaluated the preservation of dentin in terms of accuracy, angulation and time taken proving the increased precision with minimal loss of tooth structure using DNS. In both the studies, DNS proved to be superior to free hand technique in terms of precision, accuracy and efficiency in locating the canals during access cavity preparation with maximal preservation of tooth structure., Conclusion: With the minimal literature evidences, the present systematic review highlights maximal preservation of dentin using DNS. However, further invitro and invivo studies comparing the free hand, static guided endodontics to DNS must be carried out for its translation into clinical practice., Clinical Significance: Dynamic navigation system provides maximal preservation of dentin during access cavity preparation., (© 2024. The Author(s).)

Purpose: To evaluate the proximal caries progression in primary molars using the radiographic International Caries Detection and Assessment System (ICDAS)., Methods: A study was conducted on 196 children aged 3-9 years old who underwent the clinical examination and bitewing radiography during baseline and 6-month (and over) follow-up visits. The primary molars bitewing radiographs with initial enamel caries (RA1 and RA2) or outer dentine caries (RA3) of proximal surfaces were included. Caries advancement was scored using ICDAS criteria and statistical analyses with the chi-square test. Median survival time was evaluated using Kaplan-Meier survival curves and log-rank tests., Results: A total of 439 surfaces of primary molars were included in this study and an averaged follow-up period of enamel and dentine caries group were 18.3 ± 9.6 months and 16.5 ± 9.5 months respectively. The progression of proximal enamel lesions significantly differed between primary maxillary and mandibular molars (p = 0.002) and among each patient's primary mandibular second molar and the others (p = 0.002). On the contrary, the outer dentine caries of each group of primary molars was not different. The median survival time of the initial enamel proximal caries (23.30 months) was non-significantly longer than that of the dentine (20.80 months)., Conclusions: Progressions of the initial enamel proximal caries were significantly different among primary molars at the average 18.3-month follow-up. The median survival period of the enamel proximal caries was more extended than that of dentine but without statistical difference. These results provide essential information for dentists regarding an appropriate appointment for bitewing examinations., (© 2024. The Author(s), under exclusive licence to European Academy of Paediatric Dentistry.)

Introduction: Pericervical root dentin is decisive for the long-term mechanical integrity of root-filled teeth. Current treatment protocol does not include a customized step to determine the pretreatment residual pericervical root dentin., Objective: To determine and compare the residual root dentin and canal width using digital periapical radiography (DPR) and cone-beam computed tomography (CBCT) at the apical limit of the pericervical area (PCA) in mandibular first molars., Methods: DPR and CBCT images of 60 patients with age between 22 and 76 years were used to determine (a) the mesiodistal widths of the root canal (pericervical dimensions [PCL]-C) and the root (PCL-R) of mandibular first molars at the apical limit of the PCA and (b) the intracanal distance from the apical limit of the PCA to the radiographic apex (intracanal distance [ICD]). The correlation between the PCL and ICD measurements obtained from DPR and CBCT were evaluated., Results: Values between 0.10-0.80 mm and 0.00-1.10 mm were obtained for PCL-C using DPR and CBCT respectively (95% CI). The PCL values between 0.90-2.30 mm and 0.00-2.30 mm were obtained from DPR and CBCT respectively (95% CI). The ICD ranged between 4.6-12.3 mm in DPR and 4.40-12.0 mm in CBCT (95% CI). The comparative analysis showed differences from -0.9 to 0.5 mms for PCL and -2.00 to 1.5 mms for ICD between DPR and CBCT techniques respectively., Conclusion: The PCL and ICD determined from DPR and CBCT provided the pericervical dentin metrics that could be utilized clinically as a guideline for decision-making in endodontic treatment., (Copyright © 2024 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Thin root dentin after post space preparation will increase the risk of root fracture. However, the minimum residual root dentin thickness to be preserved after post space preparation is unclear., Purpose: The purpose of this finite element analysis (FEA) study was to measure the residual root dentin thicknesses and analyze the stress distributions of post-restored mandibular premolars., Material and Methods: The cone beam computed tomography (CBCT) data of 90 first and second mandibular premolars from Chinese participants (44 men, 46 women; aged between 20 and 79 years) were analyzed. Cross-sections 5 to 9 mm from the radiologic apex were used to measure the buccolingual and mesiodistal root diameters. The probability that the residual thickness of the buccolingual and mesiodistal root walls would be no less than 0.5, 0.6, 0.7, 0.8, 0.9, and 1 mm after post space preparation with a #2 Peeso reamer was calculated. Six 3-dimensional finite element models of cast post-restored mandibular premolars with 0.5, 0.6, 0.7, 0.8, 0.9, and 1 mm mesial and distal root dentin thicknesses were established. A static force of 100 N was applied to the buccal cusp tip at 45, 60, 75, and 90 degrees to the long axis of the tooth, and the maximum tensile stress and von Mises stress were analyzed. The Bonferroni post hoc test (α corrected =.003) was used for multiple comparisons., Results: The buccolingual root diameter of mandibular premolars was wider than the mesiodistal root diameter. The probabilities that the mesiodistal residual root dentin thickness of mandibular first and second premolars at 5 mm from the apex would be no less than 1 mm after post space preparation with a #2 Peeso reamer were only 10% and 28%, respectively. The maximum tensile stress was at a minimum when the mesial and distal residual root dentin thickness was 0.6 mm in the external cervical dentin adjacent to the crestal bone and 1 mm in the apical dentin corresponding to the apex of the post. The maximum tensile stress of the mandibular premolar model with 0.6-mm mesial and distal residual root dentin thicknesses was lower than that with 0.9 mm and 1.0 mm thicknesses (P corrected <.001)., Conclusions: Short posts or smaller instruments for post space preparation are recommended to obtain a 1-mm residual root dentin thickness in the mesiodistal direction of mandibular premolars. If a 1-mm thickness cannot be preserved, a minimum residual root dentin thickness of 0.6 to 0.9 mm in the mesiodistal direction should be retained., (Copyright © 2022 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

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., Competing Interests: The authors report no conflicts of interest in this work., (Copyright© 2024 IOFOS This work is published and licensed by International Organization for Forensic Odonto-Stomatology.)

Background: Accurate assessment of remaining dentin thickness (RDT) is paramount for restorative decisions and treatment planning of vital teeth to avoid any pulpal injury. This diagnostic accuracy study compared the validity and patient satisfaction of an electrical impedance based device Prepometer™ (Hager & Werken, Duisburg, Germany) versus intraoral digital radiography for the estimation of remaining dentin thickness in carious posterior permanent teeth., Methods: Seventy patients aged 12-25 years with carious occlusal or proximal permanent vital posterior teeth were recruited. Tooth preparation was performed to receive an adhesive restoration. Pre- and post-excavation RDT were measured radiographically by two calibrated raters using the paralleling periapical technique. Prepometer™ measurements were performed by the operator. Patients rated their satisfaction level with each tool on a 4-point Likert scale and 100 mm visual analog scale (VAS). Inter and intragroup comparisons were analyzed using signed rank test, while agreement between devices and observations was tested using weight kappa (WK) coefficient., Results: the intergroup comparisons showed that, before and after excavation, there was a significant difference between measurements made by both techniques (p < 0.001). After excavation, there was a weak agreement between measurements (WK = 0.2, p < 0.001), whereas before excavation, the agreement was not statistically significant (p = 0.407). Patients were significantly more satisfied with Prepometer™ based on scales and VAS (p < 0.001)., Conclusion: Prepometer™ could be a viable clinical tool for determining RDT with high patient satisfaction, while radiographs tended to overestimate RDT in relation to the Prepometer™., (© 2024. The Author(s).)

This study evaluated the impact of long-term storage conditions (medium and time) on the development of experimental dentinal microcracks through micro-computed tomography. Sixty freshly extracted premolars were stored in formalin, water, or dry conditions (n = 20) and scanned after 72 h, 30 days, 6 months and 3 years of extraction. The effect of the storage medium and time on the occurrence of dentinal defects was statistically evaluated. A total of 211 000 images were screened revealing the existence of 11 519 slices with dentinal defects. Dry conditions significantly contributed to the development of new defects in all time points. During the 3-year follow-up period, no new defects were detected in the teeth that were stored in water and, in a single tooth, in the formalin group, after 6 months of storage., (© 2023 Australian Society of Endodontology Inc.)

Introduction: This study aimed to assess the influence of different coronal flaring files on dentin removal in mandibular teeth using cone-beam computed tomographic (CBCT) images., Methods: CBCT images of 48 mandibular molar teeth were acquired and randomly divided into 2 main groups, with each main group further divided into 3 subgroups. In the first main group, root canal preparation was performed using TruNatomy (Dentsply Sirona, Ballaigues, Switzerland), ProTaper Gold (Dentsply Sirona), and One Curve (Micro-Mega, Besancon, France) files without the use of coronal flaring files. In the second main group, root canal preparation was performed using the same files with the use of coronal flaring files. After the completion of root canal preparation, a second set of CBCT images was obtained. Subsequently, the dentin removal and remaining critical dentin were assessed by measuring at 4 distinct points below the furcation level. Data were compared between groups using the Mann-Whitney U and Kruskal-Wallis tests with alpha set at 5%., Results: The ProTaper Gold files demonstrated higher dentin removal compared with the TruNatomy files. In the no-flaring groups, the One Curve files exhibited greater dentin removal than the TruNatomy files at specific levels. The use of coronal flaring files generally did not significantly impact dentin removal, except for certain cases in the TruNatomy and ProTaper Gold groups., Conclusions: The TruNatomy instrument group was more effective in preserving pericervical dentin compared with the other instrument groups. Coronal flaring files can be confidently used to preserve critical dentin during root canal treatment., (Copyright © 2024 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

The aim of this study was to assess the centralization and dentin thickness of mesial root canals of the first mandibular molars by microcomputed tomography (micro-CT). Material and methods: Ninety-nine mandibular molars of Vertucci's type IV canals were scanned by micro-CT. The mesiodistal deviation and centroid were assessed, in both mesiobuccal (MB) and mesiolingual (ML) canals, for the apical 4mm and the full canal length. Results: The dentin thickness was similar for both MB and ML canals. The narrowest thickness was in the distal wall of an MB canal (0.07mm), while the widest was found in the mesial wall of an MB canal (2.46mm). In centroid analysis, both the MB and ML canals exhibited deviations when compared to the root centroid, along the full canal length and the apical 4mm. For the MB canal, the mean deviation was 0.83mm (0.02 mm-2.30 mm) for the full canal and 0.18mm (0.01 mm-1.01 mm) for apical 4mm. Similarly, for the ML canal, the mean deviation measured 0.83 mm (0.05mm-3.99mm) for the full canal and 0.21 mm (0.01mm-1.01mm) for the apical 4 mm. Overall, deviations were observed towards the mesial of the roots, with 69% for MB and 57% for ML canals for the full canal, and 51% for MB canals within the 4 mm. The exception was the ML canal, which exhibited a higher deviation towards distal in the apical 4mm, accounting for 52% of cases. The dentin thickness was consistent between the mesial canals of mandibular molars. However, there is no centrality of mesial canals in their roots, with frequent deviation to mesial.

Objective: The aim of this study was to evaluate six files on the pericervical dentin (PCD) and the smallest dentin thickness zones (SDTZ) in mesial root canals of mandibular molars., Materials and Methods: Sixty mandibular molars with two mesial canals and Vertucci configuration were aleatory allocated in 6 experimental groups of 10 molars and 20 root canals. Specimens were scanned before instrumentation using the SkyScan 1275 (Bruker microCT, Kontich, Belgium). Group 1 was treated with WaveOne Gold (WG), group 2 with Reciproc Blue (RB), group 3 with TRUShape (TS), group 4 with XP-endo Shaper (XP), group 5 with iRace (IR), and group 6 with TruNatomy (TN). After instrumentation, the molars were scanned again and the images recorded were reconstructed with the NRecon v.1.7 (Bruker micro-CT) and analyzed with CTAn v.1.20.8 software (Bruker micro-CT) quantifying the changes produced in the surface, volume, structure thickness, SMI, and centroids at the Pericervical Dentin area of the root canals (PCD) located from the root canal orifices at the floor of the pulp chamber to 4 mm in the apical direction, and the changes in the Smallest Dentin Thickness Zones (SDTZ) located (from the furcation to 4 mm and 7 mm in the apical direction. The data obtained were compared using Wilcoxon and ANOVA with a 5% significance level., Results: XP and TN were similar in all the parameters (P >.05) at the PCD, but TN showed significant differences from WG, RB, TS, and IR (P <.05), while XP showed significant differences from WG (P <.05) in volume, surface, and structure thickness. Regarding the changes in the SDTZ, the amount of dentin removed was similar between the groups in both canals at the middle 1/3, at the cervical 1/3 for MB canals, and in ML canals for RB, TS, XP, IR, and TN (P>.05). The action of WG was significantly different from that of XP and TN in the cervical 1/3 of the ML canal (P <.05)., Conclusions: XP and TN rotatory files with small taper and volume maintained better with minor changes at the PCD and SDTZ, while WG reciprocation file produced the largest change. All the files were maintained centered at the PCD, and their performances were safe with a minimal thickness higher 0.5 mm at the SDTZ, and without risk of perforation., Trial Registration: No clinical trials were indicated in this study., Clinical Relevance: The choice of endodontic files is a relevant factor in the conservative performance of root canal treatments., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Significance: Managing caries is imperative in a rapidly aging society. Current diagnoses use qualitative indices. However, a quantitative evaluation of hardness in a clinical setting may lead to more accurate diagnoses. Previously, hardness meter using indenter with light for tooth monitoring (HAMILTOM) was developed to quantitatively measure tooth hardness. Herein, the physical interpretation of dentin hardness measured using HAMILTOM and the dentin hardness measurement mechanism are discussed., Aim: This study evaluates the mechanism of dentin hardness measurements using HAMILTOM physically and compare the invasiveness to dentin by HAMILTOM with those using a dental probe for palpation., Approach: Eleven bovine dentin samples were used to create caries models. HAMILTOM measured the dark areas, and its indentations were observed using scanning electron microscopy. Also, its invasiveness was evaluated by comparing the results with those from dental probe palpation., Results: The indentation areas were smaller than the dark areas in HAMILTOM, which may be due to exuded water from the dentin sample and the elastic recovery of dentin sample. Additionally, the dental probe indentation was deeper than the HAMILTOM indentations., Conclusions: The results demonstrate that the indentation areas were smaller than the dark areas measured by HAMILTOM, which might contain the influence of exuded water and the deformation of dentin sample. Also, HAMILTOM is less invasive than dental probe palpation. In the future, HAMILTOM may become a standard hardness measuring method to diagnose root caries., (© 2024 The Authors.)

Introduction: This in vitro study aimed to evaluate the effect of three different chemical agents on stain removal and mineral uptake of artificial dentin caries (ADC) lesions treated with silver diamine fluoride (SDF)., Methods: Baseline L*a*b* values were determined in polished human permanent dentin blocks, and ADC lesions were induced with an acid gel for 1 week. Samples were assigned to four groups; in three groups, half of each sample received SDF (30% SDF for 3 min), while the other half received SDF followed by a bleaching treatment protocol (garlic extract, bentonite, or 35% hydrogen peroxide). The fourth group had one SDF-treated half and one half without SDF. Color changes (ΔE) were measured by spectrometry, and transversal microradiography was used to quantify integrated mineral loss (ΔZ) 24 h after treatment (SDF or SDF + bleaching). A two-way mixed ANOVA was applied to thirty percent., Results: SDF application increased mineral uptake by ADC (p = 0.001). The type of chemical agent evaluated (p &lt; 0.0001), time (p = 0.01), and their interaction (p &lt; 0.0001) bleached the ADC treated with SDF. However, 35% hydrogen peroxide was the only compound with a bleaching effect (p &lt; 0.001), without returning to baseline color. None of the compounds altered the mineral uptake effect of SDF (p = 0.30)., Conclusion: This in vitro study showed mineral uptake effect in ACD within 24 h after SDF application and the ability of hydrogen peroxide to partially remove (reduction of 24%) the staining caused by SDF without affecting its mineral uptake effect., (© 2023 S. Karger AG, Basel.)

Background: Most studies assessing the sensitivity and specificity of caries detection methods have been performed in vitro using the histological method as the gold standard showing inconsistent values. The aim of this study was to compare the sensitivity and specificity in detecting occlusal caries using the International Caries Detection and Assessment System (ICDAS II) with the radiographic method (RM), while using the Spectra™ Caries Detection System (SCDS) as the reference test., Methods: One hundred sixty children, ages 7-12 years, participated in the study. Five zones in the occlusal surfaces of 859 primary and 632 first permanent molars were examined visually using ICDAS-II, the RM using bitewing radiographs and SCDS. The descriptive statistics of sensitivity and specificity were calculated and compared., Results: For all molars combined and for primary molars only, the sensitivity of ICDAS II was higher for detecting total caries (p < 0.001), caries in enamel (p < 0.001), and caries in dentin (p = 0.016), but it was not different for detecting caries in the dentin of permanent first molars (p = 0.214), and primary second molars (p = 0.761). The specificity of RM was higher for detecting total caries, caries in enamel for all molars combined and for permanent first molars (p < 0.001). For caries in dentin, the specificity of ICDAS II was higher for all molars combined and for primary molars only (p < 0.001). For total caries in primary molars only, and caries in dentin of permanent first molars only, the specificity was not different (p = 0.156 and p = 0.181 respectively)., Conclusions: The sensitivity and specificity of ICDAS II and RM changes depending on whether the carious lesion compromises the enamel or dentin, and if the caries detection is performed in the primary molars or permanent first molars., (© 2023. The Author(s).)

A significant advancement in micro-computed tomography (μCT) translational application in endodontics has occurred. The purpose of the study was to assess the applications of a new method to measure dentin mineral density (DMD) and to compare between 2 levels of energy sources. Two sets of standardized porous solid hydroxyapatite (HA) phantoms, with mineral densities of 0.25 g/cm 3 and 0.75 g/cm3, respectively were embedded in aluminum foil. The μCT homogeneity and noise in the HA phantoms were analyzed using 50 kV and 100 kV energy sources. DMD of 66 extracted human teeth was measured at the cemento-enamel junction (CEJ), mid-root, and apical levels. Assessment included linearity between the energy source and the DMD measurement. The quality of the images obtained from the 2 energy sources was compared and analyzed statistically. HA phantom rods and validation methods showed that 100 kV provided a more accurate measurement of the DMD in all groups tested. The 100 kV 3D reconstructed µCT images displayed a more defined details of the dentin structure. A statistically significant difference was found between 100 and 50 kV (p < 0.05) in all measured areas except for the mid-root. Using micro-computed tomography is a practical and non-destructive method to measure dentin density. 100 kV energy source provides clearer and more consistent images., (© 2023. The Author(s).)

Dentin hypersensitivity is an oral health concern affecting a large percentage of the world's adult population. Occlusion of the exposed dentinal tubules is among the treatment options available, and silver diammine fluoride (SDF) is an occluding agent used for interrupting or dampening the stimulus of the dental pulp nerves that produce pain. In addition to dentin permeability testing, the evaluation of desensitizing agents occluding dentinal tubules strongly relies on microscopic techniques, such as scanning electron microscopy (SEM). Limitations of SEM are that it provides only surface images that lack detailed information on the depth of penetration and amount of material present within the treated specimen, and it is prone to sample preparation artifacts. Here, we present high-resolution X-ray computed tomography (nano-CT) as a potential method for investigating dentin specimens with occluded tubules. We studied human dentin treated with SDF as an exemplary dentinal occlusion treatment option. We evaluated the silver deposits formed on the dentin surface region near the dentinal tubules and in the tubular regions using cross-section SEM, Energy Dispersive X-ray (EDX) analysis, and nano-CT. The resulting images obtained by SEM and nano-CT had comparable resolutions, and both techniques produced images of the tubules' occlusion. Nano-CT provided three-dimensional images adequate to quantitate tubule size and orientation in space. Moreover, it enabled clear visualization of dentinal tubules in any virtual plane and estimation of the amount and depth of occluding material. Thus, nano-CT has the potential to be a valuable technique for evaluating the occluding effects of virtually any material applied to dentinal tubules, supporting deciding between the best occluding treatment options., (© 2023. Springer Nature Limited.)

This study evaluated the drilling path (mm) and the dentin wear (mm 3 ) of two instruments used during guided endodontic access. Twenty mandibular incisors with calcified canals were selected using cone-beam computed tomography (CBCT) and fixed in articulated models. Preoperative CBCT scans were performed in combination with intraoral scanning, and the images were reconstructed in the Blue Sky Bio software for access planning and printing the guides. The access cavity was drilled with 1.0-mm-diameter bur (DSP) and 0.8-mm-diameter bur (Munce). Postoperative CBCT was performed, and the images obtained preoperative and postoperative were superimposed for the analyses. Data were analysed by a t-test and linear regression (α = 0.05). No difference was found in the drilling path (p = 0.422). However, the Munce bur had higher dentin wear than the DSP bur (p = 0.011). A positive linear correlation (R 2  = 0.859) was found between the factors., (© 2022 Australian Society of Endodontology Inc.)

The aim of this study was to compare four different instrument kinematics in oval canals. Distal root of sixty extracted first mandibular molars with single oval canal were allocated randomly to four groups (n = 15) namely protaper universal [PTU] (Rotary), self-adjusting file [SAF] (Adaptive), TruShape [TS] (Rotary) and WaveOne [WO] (Reciprocating). The percentage of untouched and touched surfaces of the root canal was evaluated using micro-computed tomography (MCT). Pre- and post-instrumentation weight was assessed using digital microbalance for determining the amount of dentin removed and apical extrusion of debris. The results were tabulated, and their mean difference was statistically analysed using one-way ANOVA and Tukey's HSD test. PTU and SAF exhibited significantly less mean percentage of untouched surface compared to TS. TS files removed less dentin and extruded less debris in long oval canals., (© 2023 Australian Society of Endodontology Inc.)

Statement of Problem: Mandibular second molars have variable root, pulp chamber floor, and radicular groove morphologies, potentially affecting residual dentin thickness and post placement suitability. However, an identification of the danger zones is lacking., Purpose: The purpose of this in vitro study was to investigate the residual dentin thickness in the danger zone of mandibular second molars after virtual fiber post placement by using a simulation method based on microcomputed tomography (μCT)., Material and Methods: A total of 84 extracted mandibular second molars were scanned using μCT and classified according to root morphology (separate or fused) and pulp chamber floor morphologies (C-shaped, non-C-shaped, or no pulp chamber floor). Fused-root mandibular second molars were further classified based on the radicular groove type (V-, U-, or Ω-shaped). All specimens were accessed, instrumented, and rescanned with μCT. Two types of commercial fiber posts were also scanned. Clinical fiber post placement was simulated in all prepared canals by using a multifunctional software program. The minimum residual dentin thickness of each root canal was measured and analyzed by using nonparametric tests to identify the danger zone. Perforation rates were calculated and recorded., Results: Larger fiber posts decreased minimum residual dentin thickness (P<.05) and increased perforation rate. In regard to mandibular second molars with separate roots, the distal root canal exhibited a significantly higher minimum residual dentin thickness than the mesiobuccal and mesiolingual root canals (P<.05). However, no significant difference in minimum residual dentin thickness was found between the different canals in fused-root mandibular second molars with C-shaped pulp chamber floors (P<.05). Fused-root mandibular second molars with Ω-shaped radicular grooves had a lower minimum residual dentin thickness than those with V-shaped radicular grooves (P<.05) and demonstrated the highest perforation rate., Conclusions: The morphologies of the root, pulp chamber floor, and radicular groove were correlated with residual dentin thickness distribution in mandibular second molars after fiber post placement. A comprehensive understanding of mandibular second molar morphology is essential for determining the suitability of post-and-core crown restorations after endodontic treatment., (Copyright © 2023 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Aim: The present study aimed to determine and compare the dentine thickness around the root canals of maxillary molars with fusion using micro-computed tomography (micro-CT)., Methodology: A total of 120 fused maxillary molars having more than a single canal with distinct canal orifices near the cementoenamel junction were selected from a pool of extracted maxillary molars, which were scanned on a micro-CT device (SkyScan 1172, Bruker-microCT). The minimum dentine thickness around the root canals in furcal direction was measured using CTAn software (v.1.18.8 Bruker-microCT) at each millimetre. The specimens were grouped according to their fusion type, and dentine thickness around the canals was compared. The data were statistically analysed using anova and post hoc Tukey-Kramer tests following an assessment of the normality of their distribution with the Kolmogorov-Smirnov test (p < .05)., Results: Dentine thickness showed a statistically significant decrease at 2 mm apical to the orifice level irrespective of fusion type. The minimum dentine thickness values were detected around the second mesiobuccal canal as 0.30 mm at 6 mm below orifice. Dentine thickness around the mesiobuccal canal was significantly greater in fusion type 1 than those of types 2 and 3 (p < .05), while those of distobuccal and palatal canals were significantly thinner in type 3 fusion compared with type 1 or 6 (pDentine thickness showed a statistically significant decrease at 2 mm apical to the orifice level  irrespective of fusion type. The minimum dentine thickness values were detected around the second mesiobuccal canal as 0.30 mm at 6 mm below orifice. Dentine thickness around the mesiobuccal canal was significantly greater in fusion type 1 than those of types 2 and 3 ( CONCLUSION: Minimum dentine thickness values at the danger zone of distobuccal and palatal canals change according to the fusion type in fused maxillary second molars., (© 2023 British Endodontic Society. Published by John Wiley & Sons Ltd.)

Background: The objective was to investigate the radiopacity of 11 commercial posterior restorative materials by establishing their mean gray values (MGVs) and comparing them with dental hard tissues., Methods and Materials: Five-disc specimens were prepared for each of the following materials: Cerasmart 270 CAD/CAM block A3LT (CS), Amalgam (A), Ketac Molar A3 (KM), Cention-N A2 (CN), G-aenial Universal Flo AO2 (GO2) and A2 (G2), Ever-X Flow Dentine (EXD) and Bulk (EXB) shades, Equia Forte HT Fil A2 (EF2) and A3 (EF3), and Equia Fil A3 (E3). Freshly extracted maxillary premolar teeth were used as a control. The MGVs of specimens and a 10-step aluminum stepwedge (Al) were measured with Adobe Photoshop. ANOVA and Dunnett T3 tests were used to assess the significance of the differences (α=0.05)., Results: Statistically significant differences were revealed between some of the groups. Amalgam had the highest radiopacity. The radiopacity of dentin and CS were close to that of 1 mm Al. G2, KM, GO2, EXB, and EXD showed higher mean radiopacity than dentin. Enamel had a radiopacity equivalent to 2 mm Al. CN, EF2, and E3 had higher mean radiopacity than enamel., Conclusions: All materials met the ISO requirements. Alkasite and reinforced glass ionomer restoratives demonstrated higher mean radiopacity than the posterior flowable composites. Material shades did not affect the radiopacity., (©Operative Dentistry, 2023.)

Introduction: Age estimation is an important forensic resource in human identification. Amongst the different methods of dental age estimation, root dentin transparency (RDT) is considered a reliable parameter, as well as an indicator of chronological age at time of death in human adult remains. The aim of this study was to estimate the age of individuals using the Bang and Ramm method and to derive a new formula suitable for age estimation in the Peruvian population by assessing the length and percentage length of RDT., Materials and Methods: The sample consisted of 248 teeth collected from 124 deceased individuals, between the ages of 30 and 70 years. RDT length was digitally measured from sectioned and photographed teeth. Linear and quadratic regressions were made to derive Peruvian formulae and the new formulae were applied to another group of samples (n=30)., Results: Data showed a significant correlation (p<0.01) between chronological age and translucency length (Pearson´s correlation=0.775) and percentage length (Pearson´s correlation=0.778). Linear and quadratic regressions for obtaining Peruvian formulae showed that quadratic equations expressed greater determination coefficients. Comparisons between estimated age using Peruvian formulae showed that dental age from percentage of length of RDT a higher percentage of estimates with errors <± 05 and <± 10 years. The accuracy of the new Peruvian formula using the percentage of length of RDT (MAE=7.83) can be considered acceptable., Conclusion: As shown in the results, age estimation using the Peruvian formula derived from the percentage of length of RDT has proven to be more accurate than estimates using the Bang and Ramm method. Thus, it could be used in age estimation for Peruvian individuals, as it is the most accurate methods and provides a larger number of acceptable estimates.

Objectives: To compare autogenous dentin nanoparticles with allograft bone grafts in the treatment of stage III periodontitis., Method: The randomised study was conducted at the Department of Oral Medicine and Periodontology, Faculty of Oral and Dental Medicine, Kafrelsheikh University Hospital, Egypt, from January 2021 to January 2022, and comprised adult patients of either gender with stage III periodontitis. Each patient's bilateral intrabony defect was randomly treated with an allograft on one side and a graft made of dentin nanoparticles on the testside. Each patient'sremoved tooth was ground into these nanoparticles. Both groups had their probing pocket depth and clinical attachment loss evaluated at baseline and six months aftersurgery. Additionally, digital periapical films were collected in both groups at baseline and six months after therapy to assess vertical bone loss. Data was analysed using SPSS 20., Results: Of the 20 patients, 8(40%) were males and 12(60%) were females with overall mean age 31.00±4.06 years(range: 18-50 years). Of the 40 sites, 20(50%) each were in test and control groups. Compared to baseline values, both groups showed significant improvement in probing pocket depth, clinical attachment loss and vertical bone loss post intervention (p<0.05). There was no significant difference between the postoperative outcomes of the two groups(p>0.05)., Conclusions: Autogenous dentin nanoparticles were found to be an effective and promising biomaterial for bone regeneration in intrabony defects., Clinical Trial: NCT05258006 link: https://clinicaltrials.gov/ct2/show/NCT05258006, Registration date of the Trial 10/2/2022.

Aim: To compare the effect of polymerization of resin-modified glass ionomer cement and dual-cure resin cement on the crystalline structure and to correlate it clinically with postoperative sensitivity., Settings and Design: The evaluation of crystalline strain in the dentin slabs was done using Synchrotron X-ray diffraction. The post operative sensitivity was measured clinically using Schiff's sensitivity scale., Materials and Methods: A total of 44 extracted and noncarious premolars were collected. Dentin slabs of dimensions 2 mm × 2 mm × 1.5 mm were prepared from the buccal aspect of the extracted teeth. The dentin slabs were then divided into two groups, Group A dual-cured resin cement and Group B resin-modified glass ionomer cement was applied. The dentin slabs first underwent synchrotron X-ray diffraction before and after the application of cement. Forty-two patients who were undergoing complete metal fixed prostheses on vital posterior abutments were selected. In this, 21 vital abutments were included in each group. Tooth preparation and fabrication of complete metal prostheses were done in the conventional manner and cemented using the 2 luting cements in Groups A and B, respectively. Dentinal hypersensitivity was measured using Schiff 's scale, postcementation, after 1 week and 1 month., Statistical Analysis: Independent t-test was done for comparing the two cements in two cements in terms of lattice strain. Mann-Whitney U-test was done for comparing the cements with respect to dentinal hypersensitivity. Spearman's correlation coefficient was used for clinical correlation between dentinal hypersensitivity and crystalline strain., Results: The lattice strain generated in dual cure resin cement was higher than that in resin-modified glass ionomer cement and was statistically significant. Postcementation hypersensitivity was higher in dual-cured resin than resin-modified glass ionomer cement but was not statistically significant in the follow-up visits. Spearman's correlation coefficients did not reveal any significant clinical correlation between lattice strain and dentinal hypersensitivity., Conclusion: Dual cure resin cements generate greater lattice strain as compared to resin modified glass ionomer cements.

Introduction: This ex vivo study aimed to evaluate the shaping abilities and preservation of dentin with traditional and modern instruments after using sizes 25 and 40 in oval canals of mandibular incisors with conservative access., Method: Thirty mandibular incisors with single straight oval canals were selected and assigned into 2 groups (n = 15) according to the instrument system used during preparation, Slim Shaper (SS) plus Apical Shaper (AS) and Protaper Gold (PG). The samples were subjected to micro-computed tomography before and after preparation with sizes 25 and 40. The shaping parameters evaluated included canal volume and surface area, amount of unprepared root canal walls, and reduction in pericervical dentin., Results: Canal volume and surface area were significantly increased after enlargement with each instrument size (P < .01). The percentage of unprepared areas showed a significant intragroup decrease after using PG F2 and F4 or SS 3 and AS (P < .05). Intergroup comparison showed no significant differences. Pericervical dentin was reduced in all groups. The intragroup comparison only revealed a significant reduction (P < .01) between PG F2 and F4. In addition, a significant decrease in pericervical dentin (P < .05) was observed between PG F4 40/.06 and AS 40/.03. No significant differences were observed between PG F2 25/.08 and SS 3 25/.04., Conclusion: Increasing the instrumentation size from 25 to 40 significantly reduces the percentage of unprepared areas regardless of the system used. In addition, using a modern system with a regressive taper allows the maintenance of pericervical dentin without compromising shaping efficacy in the apical third of the mandibular incisors with oval canals and conservative access., (Copyright © 2023 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Background: Mandibular first molars appear to be the most commonly tooth subjected to a root canal treatment, therefore a better understanding of the anatomy critical zones for resistance of this teeth may decrease the treatment's failure rate. So, this study was conducted to evaluate the dentin thickness of the danger zone in mesial roots of mandibular first molars using cone beam computed tomography in an Iranian population., Methods: In this cross-sectional study, 210 Cone Beam Computed Tomography acquisition of the mandibular first molars were collected from a radiology center in Qazvin. The dentin thickness of the mesial roots (mesiobuccal and mesiolingual canals) was measured from the furcation to 5 mm below. The relationship between the dentin thickness in the danger zone and parameters, like age, gender, placement side, root length, the curvature of the canal, canal type, presence of middle mesial canal, and distance between the orifices of the mesial canals was investigated. Frequency, mean and standard deviation for variables were calculated, and data analysis was done by SPSS using simple and multiple linear regression and Pearson correlation coefficient. Also, two-sample t -test was used to compare mesiobuccal and mesiolingual on two sides. The significant level was also considered at ( p < 0.05)., Results: The average minimum thickness of danger zone dentin was found to be 0.885 ± 0.259 mm in the mesiobuccal canal and 0.906 ± 0.206 mm in the mesiolingualcanal. Also, the minimum thickness of dentin in the mesiobuccal and mesiolingual canals in the range of 0 to 1 mm from the furcation was more than in other areas. There was no significant relationship between the minimum dentin thickness of the danger zone with gender, placement side, root length, canal type, and mesial canal entrance distance. But with increasing age, the thickness of dentin in the danger zone in the mesiolingualcanal increased significantly ( p = 0.008). It was also observed that with the increase in the curvature of the canal, the thickness of the dentin in the danger zone in the mesiobuccal canal decreased (moderately curved ( p = 0.008), severely curved ( p = 0.046)). In addition, the thickness of the dentin in the mesiobuccal and mesiolingual canal was less in the samples with the middle mesial canal ( p = 0.047, 0.044)., Conclusions: Less dentin thickness in the danger zone in the mesial roots of mesiolingual mandibular first molars was seen in younger patients in mesiolingual canal, with a greater degree of canal curvature in the mesiobuccal canal and teeth with a middle mesial canal. Therefore, it is suggested that large taper instruments should be used with more precision to prevent complications., Competing Interests: The authors declare no conflict of interest. Luca Testarelli is serving as one of the Editorial Board Members and Guest Editors of this journal. We declare that Luca Testarelli had no involvement in the peer review of this article and has no access to information regarding its peer review. Full responsibility for the editorial process for this article was delegated to Marco Tatullo., (© 2023 The Author(s). Published by IMR Press.)

The occlusion of dentinal tubules has become a rapid and effective method for treating dentin hypersensitivity. Accurate evaluation of dentin occlusion is critical to illustrate the efficacy of oral care products and to optimize dental therapy in the clinics, which is limited by the conventional two-dimensional (2-D) characterization methods. Here, we demonstrate the visualization of the dentin occlusion via three-dimensional (3-D) characterization using a focused ion beam-scanning electron microscopy (FIB-SEM) tomography. Using the "Slice and View" approach, the material used for occluding dentin tubules is imaged with a very high-resolution voxel (10 nm × 10 nm × 20 nm) from 2-D SEM images and then reconstructed into a 3-D volume, which presents the mode of action of toothpaste for treating dentin hypersensitivity. Meanwhile, quantitative analysis of the depth of occlusion is successfully obtained. This work validates the feasibility of FIB-SEM tomography in the analysis of dentin occlusion within the complicated networks of dentine tubules at the nanoscale, and provides a novel approach to facilitate the research and development of oral care products., (© 2023. The Author(s).)

The aim of this study was to evaluate the existence of preoperative dentinal defects among differently preserved dentoalveolar bone-blocks (frozen vs. embalmed) and to investigate the effect of varying apical forces (low: <4 N, high: 4-8 N) during root canal preparation on microcrack formation using micro-computed tomography (micro-CT). Thirteen embalmed and seven frozen bone-blocks containing 1-3 single rooted teeth were collected. The teeth were evenly divided into three groups (n = 10): FLow (frozen, <4 N), ELow (embalmed, <4 N), EHigh (embalmed, 4-8 N). After working length determination all specimens were scanned preoperatively. Root canal preparation was performed using nickel-titanium instruments sizes 25/.06 and 40/.06 (F6 SkyTaper; Komet, Lemgo, Germany). A postoperative scan was performed and image stacks were co-registered. All cross-sectional images were screened to identify the presence of dentinal defects. The results were expressed as the percentage of teeth/slices presenting dentinal defects. The statistical analyses were performed with Kruskal-Wallis-Test and Mann-Whitney-U-Test (α = 5%). Embalmed specimens presented a significantly higher percentage of slices with preoperative microcracks (p<0.05) than frozen specimens. No significant difference between groups was observed regarding the induction of microcracks (p>0.05). Root canal preparation does not induce microcracks in dentoalveolar bone-blocks from donors of old age, irrespective of the preservation method and the apically directed forces., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Haupt et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Introduction: The purpose of this study was to evaluate and compare 2 different access cavity designs in combination with 2 popular single-file preparation systems to see which combination preserves dentin, more specifically pericervical dentin, best. The minimum remaining dentin thickness and dentin volumes were evaluated pre- and postinstrumentation., Methods: Sixty extracted human mandibular molars were selected and randomly divided into 2 different access cavity design preparation groups: traditional access cavities (n = 30) and conservative access cavities (n = 30). Within each cavity preparation design group, the 30 teeth were divided into 2 instrumentation groups (WaveOne Gold Primary; Dentsply Sirona, Ballaigues, Switzerland [n = 15] and TruNatomy Prime, Dentsply Sirona [n = 15]). Samples were scanned using micro-computed tomographic imaging before and after access cavity preparation as well as after final endodontic instrumentation. The pericervical remaining dentin thickness and dentin volume changes were evaluated and compared., Results: Conservative access cavity designs resulted in more favorable remaining dentin thickness. The least amount of mean dentin volume loss was also recorded in the conservative access cavity preparation groups regardless of the preparation instrumentation., Conclusions: In terms of the remaining pericervical dentin thickness and dentin volume reductions, the authors conclude that conservative access cavity designs preserve dentin best., (Copyright © 2022 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

The management of the deep carious lesion with reversible pulpitis is a dilemma for the dentist. The current study compared selective removal to soft dentine (SRSD) and full pulpotomy (FP) for treating proximal deep carious lesions in teeth with reversible pulpitis. Visual-tactile examination and bitewing radiographs were used to determine the depth of carious lesion, and American Association of Endodontists recommendations were used to formulate pulp diagnosis. Sixty mandibular molar teeth from healthy patients between the ages of 16-35 years and a diagnosis of proximal deep carious lesion with reversible pulpitis were included. Teeth were randomly allocated to two study groups. SRSD group (n = 30): soft dentine was preserved over the pulpal aspect. A hard-setting calcium hydroxide cement liner and resin-modified glass ionomer cement base were applied over the remaining soft carious dentine. FP group (n = 30): complete caries removal followed by mineral trioxide aggregate FP was performed. The teeth in both groups were restored with composite resin restoration. The established criteria for outcome assessment of SRSD and pulpotomy were used. Accordingly, only asymptomatic teeth with no radiological evidence of periapical rarefaction were considered successful at the 12-month follow-up. Two-sample t test, Pearson χ2 test/Fisher's exact test, and percentage agreement were used for statistical evaluation. According to the per-protocol analysis, the success rate of both SRSD and FP treatment was 95.45% and 95.65%, respectively, and the actual difference between the two treatments was 1% (95% CI: [-10, 9]). The data suggests that both treatments (SRSD and FP) appear to have a good success rate (&gt;95%) when used to manage permanent mandibular molar teeth with proximal deep carious lesion and reversible pulpitis. As SRSD is a noninvasive procedure, it should be favored over FP in these instances., (© 2023 S. Karger AG, Basel.)

This study sought to 1) investigate the spatial distribution of mineral density of dog dentin using µ-CT and 2) characterize the relationship between the elastic modulus and mineral density of dog dentin using nanoindentation and µ-CT. Maxillary canine teeth of 10 mature dogs were scanned with a µ-CT then sectioned in the transverse and vertical planes and tested using nanoindentation. Spatial distribution of mineral density and elastic modulus was quantified. Results demonstrated significant spatial variation in mineral density and elastic modulus. Mineral density and elastic modulus generally increased from the dentin-pulp interface to the dentino-enamel junction and from the crown base to the crown tip. Significant site dependent correlations between mineral density and elastic modulus were determined (0.021 > R 2  > 0.408). The results of this study suggest that while mineral density is a mediator of elastic modulus, other mediators such as collagen content may contribute to the mechanical behavior of dog dentin., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The aim of this prospective cohort study was to assess the radiographic progression of underlying dentin shadows (UDS) on the occlusal surfaces of permanent posterior teeth of adolescents and young adults over 1-2 years and to identify possible risk factors. A total of 149 UDS lesions (from 101 individuals) were included at baseline. Each participant had to present at least one UDS to be considered eligible for the study. Data collection included the application of a questionnaire, clinical examination, and bilateral bitewing radiographs, performed at baseline and after 1-2 years. The association between possible predictors and UDS progression (defined radiographically as an increase in the radiographic score from baseline to follow-up) was assessed using Weibull regression models. Hazard ratios (HRs) and their 95% confidence intervals (CIs) were estimated. A total of 81 individuals (mean age: 24.0, standard deviation: 8.03) were reexamined after 1-2 years (742 occlusal surfaces, of which 118 were UDS). The overall progression rate was 8.6% after 1-2 years, being 12.6% for UDS without baseline radiolucency and 20% for UDS with baseline radiolucency. The risk analysis showed that UDS without radiolucency at baseline had a similar likelihood of progression (adjusted HR = 1.71, 95% CI = 0.68-4.32, p = 0.26) while UDS with radiolucency at baseline were more likely to progress (adjusted HR = 2.96, 95% CI = 1.06-8.26, p = 0.04) than the reference category (sound occlusal surfaces without radiolucency). These estimates were adjusted for caries prevalence, tooth type, and arch. This study showed low progression rates of UDS after 1-2 years. The presence of radiolucency at baseline was found to predict UDS progression., (© 2023 S. Karger AG, Basel.)

The aim of this study was to conduct a three-dimensional (3D) evaluation of radiographic changes after indirect pulp capping (IPC) with silver diamine fluoride (SDF) with or without potassium iodide (KI) and resin-modified glass ionomer cement (RMGIC) in deep carious young permanent molars using cone-beam computed tomography (CBCT). 108 first permanent molars with deep occlusal cavitated caries lesions, in forty-nine 6- to 9-year-old children, were randomly allocated to one of 3 groups (n = 36) and treated with SDF+KI, SDF, and RMGIC as IPC materials. CBCT scans were taken at 0 and 12 months to assess tertiary dentin formation (volume and grey level intensity), increase in root length, and pathological changes such as secondary caries, periapical radiolucency, internal resorption, and obliteration of the pulp. The 3D image analysis procedures were performed using ITK-SNAP and 3D Slicer CMF. Comparisons were made using analysis of variance with a fixed effect for treatment and random effects for patient and patient-by-treatment to account for within-patient correlations. A two-sided 5% significance level was used. There were no significant differences among the three groups regarding tertiary dentin volume (p = 0.712) and grey level intensity (p = 0.660), increase in root length (p = 0.365), prevention of secondary caries (p = 0.63), and periapical radiolucency (p = 0.80) in the analysed 69 CBCT scans. The study did not find differences among the groups regarding quality and quantity of tertiary dentin formed, increase in root length, absence of secondary caries, and other signs of failure as shown by CBCT. Clinical Significance: The results show no significant differences in radiographic outcomes (quality and quantity of tertiary dentin formed, increase in root length, absence of secondary caries, and other signs of failure) when using SDF+KI, SDF, and RMGIC in IPC. The results of this study can help guide treatment decision-making regarding use of SDF and SDF+KI as IPC materials in deep cavitated lesions., (© 2023 S. Karger AG, Basel.)

Objectives: This in vitro research aimed to quantitatively evaluate the enamel and dentin tissue removal and the residual adhesion surface area (RAS) after different margin designs and locations for indirect partial restorations (IPR)., Methods: A human molar was scanned using a Micro-CT and the STL file obtained was used to 3D-print 50 resin-tooth replicas. IPR standardized preparations were performed. The specimens were randomly assigned to 5 groups (n = 10), according to preparation and margin location to the dental equator (DE): 1) Rounded shoulder above the DE (SA); 2) Hollow chamfer above the DE (CA); 3) Butt joint above the DE (BJ); 4) Rounded shoulder below the DE (SB); 5) Chamfer below the DE (CB). Then, the tooth replicas were scanned and each STL file was aligned and superimposed to the original STL model file. Data of enamel and dentin volume removal and RAS were assessed and statistically analyzed (one-way ANOVA and Kruskal-Wallis tests for the two dental substrates respectively). Significance was set at p<0.05., Results: Differences in dental tissue reductions were related to the margin location. Above the equator, SA, CA, and BJ performed comparably (p>0.05). Below the equator, CB was significantly more conservative in enamel reduction than SB (p<0.05) and showed the highest enamel adhesive surface exposure among the tested preparations (p<0.05)., Conclusions: When the preparation margin is placed above DE, BJ determines a greater exposure of dentin, reducing the adhesive surface in enamel. Below DE, SB seems to be more aggressive in terms of tissue removal compared to CB., Clinical Significance: The results of this in vitro study suggest that in teeth requiring partial restoration with the margin below the dental equator, a chamfer preparation would be more conservative than a shoulder preparation. When above the equator, preparations with flat designs would expose more dentine providing a worse substrate for adhesion., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

Aim: To evaluate the effects of progressive root canal enlargements on the unprepared surface area and remaining dentine thickness of three-rooted maxillary first premolars with different root configurations., Methodology: Thirty three-rooted maxillary first premolars with three root configurations (n = 10) were selected and scanned in a micro-CT device. The root canals were sequentially enlarged with rotary instruments sizes 30.02 (step 1), 30.04 (step 2) and 30.06 (step 3). After each step, a new scan was taken. Analysed parameters included morphometric measurements (length, volume and surface area), number of static voxels and minimal dentine thickness. Statistical analyses were performed with one-way anova post hoc Tukey tests and paired sample t-test at a significance level of 5%., Results: No statistical differences were observed amongst groups regarding the morphometric parameters and static voxels (p > .05). The minimal dentine thickness of the distobuccal root significantly changed depending on the root configuration (p < .05), whilst no differences were observed in the other roots (p > .05). A great variation in the position of the minimal dentine thickness was observed after preparation. Overall, mean percentage reduction in dentine thickness was higher in the buccal roots than in the palatal root (p < .05). In the mesiobuccal and distobuccal root, the number of slices with minimal dentine thickness lower than 0.05 mm increases 2 to 3 times and 3 to 4 times, respectively, from steps 1 to 3., Conclusions: Instruments sizes 30.02 and 30.04 can be safely and effectively used to enlarge the buccal and palatal canals of three-rooted maxillary first premolars., (© 2022 British Endodontic Society. Published by John Wiley & Sons Ltd.)

Significance: The increase in root caries is a serious problem as society ages. Root caries is diagnosed by inspection and palpation, which are qualitative. A method to objectively and quantitatively evaluate the progress of root caries in a clinical setting is strongly desired. The root caries could be diagnosed by measuring hardness because dentin becomes softer as the caries progresses. Vickers hardness has been customarily used as an indicator of tooth hardness. However, this method cannot be used to in vivo teeth because the teeth must be dried prior to measurement to make the indentation. A hardness meter using an indenter with light for tooth monitoring (HAMILTOM) is proposed as an optical device. HAMILTOM could measure hardness of teeth in wet condition as a dark area while applying a load to dentins without drying. Therefore, HAMILTOM may realize hardness measurements of in vivo teeth in a clinical setting quantitatively., Aim: The aim of our study is to demonstrate the optical dentin hardness measuring device HAMILTOM using bovine dentin with different demineralization times and to evaluate the correlation between the dark areas measured by HAMILTOM and the Vickers hardness measured by the Vickers hardness tester., Approach: The samples were 20 bovine dentins. They were demineralized by a lactic acid solution with different times and divided into groups 1 and 2 of 10 samples each. In both groups, the dark areas and Vickers hardness were measured for each sample. Group 1 was used to obtain a calibration curve to calculate Vickers hardness from the dark area. Group 2 was used to validate the calibration curve obtained from the dentin samples of group 1., Results: The areas appearing black without a total internal reflection of the indenter measured by HAMILTOM increased as the demineralization time increased. Additionally, the Vickers hardness of group 2 calculated by the dark areas of group 2 and the calibration curve obtained in group 1 and the Vickers hardness of group 2 measured by the Vickers hardness tester were strongly correlated with a determination coefficient of 0.99., Conclusions: The results demonstrate that HAMILTOM may be a suitable alternative to the conventional method. Unlike the conventional method, which cannot be used for in vivo teeth, HAMILTOM holds potential to quantitatively evaluate the progress of caries in in vivo teeth.

Objective: The tufts of human dental enamel are structures located at the enamel-dentin junction and whose origin has not been clearly established. Although studies have highlighted their protein content and hypomineralization, none has been able to shed light on their 3D structure. The aim of this study was to reveal the whole structure using high-resolution conventional microtomography., Design: Ten adult mandibular first and second molars and two primary mandibular first molars were sectioned and scanned with microcomputed tomography with a resolution between 4.7 and 5 micrometers. By determining the threshold discriminating dentin and tufts, we were able to reconstruct 3D meshes., Results: We revealed the exact pattern of the tufts in adult molars and discovered their distribution, their dynamics, and the existence of a regular undulation, forming a particular angle of approximately 30 degrees with the dentin surface. A spatial frequency of approximately 160 micrometers would be compatible with the variation in the orientation of groups of dental enamel rods. In contrast, the present setting is not sufficient to extract similar information for primary teeth., Conclusions: Enamel tufts have a specific pattern, with an oriented draped form and are regularly spaced. The possible connection between these undulations and the Hunter-Schreger bands (diazonias and parazonias) needs to be studied., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Objectives: Preservation of pulpal vitality in immature permanent teeth with deep carious lesions is essential to enable further root development and apical closure. This systematic review aimed to evaluate the evidence regarding the efficacy, presented clinical and radiographic success, and bacteriological outcomes of techniques and materials used for deep caries management in vital immature permanent teeth., Data: Randomised controlled trials evaluating Vital Pulp Therapy (VPT) for deep caries in immature permanent posterior teeth without history of irreversible pulpitis, and a follow up period of ≥12 months were included. Study characteristics and outcomes of all included studies were summarized. Cochrane's Risk-of-bias tool 2.0 was used to assess the quality of eligible studies. Meta-analyses using a random effects model was performed., Sources: Electronic databases PubMed, Medline, Embase, LILACS, CENTRAL and Cochrane Library were searched, followed by a manual search., Study Selection: Twelve papers were included into the review. Overall success rates were 98%, 93.5%, 93.6% for direct pulp cap (DPC), indirect pulp cap (IPC) and pulpotomy (PP) respectively. Regardless of VPT technique, there were no significant differences between clinical and radiographic success rates. Completion of root development was achieved in more than 83% of the cases in all VPT techniques., Conclusions: All treatment modalities for PP were equally efficient with high overall success rates. Biodentine showed high success rates regardless of technique. No significant differences were found in the clinical and radiographic success rates between various follow-up intervals. There are no clear conclusions regarding superiority of either VPT technique on apical closure., Clinical Significance: This manuscript systematically evaluates the evidence and summarises all available data on each vital pulp therapy technique and materials used in treatment of deep caries in immature permanent teeth with vital pulps. The limitations in the current scientific literature and recommendations for future research are also highlighted., (Copyright © 2022. Published by Elsevier Ltd.)

The aim of this study was to investigate the influence of moisture content in frozen and embalmed human cadavers on the detection of dentinal microcracks using micro-computed tomography (micro-CT). The group of embalmed specimens included three mandibular and two maxillary segments each containing one tooth. The group of frozen cadavers consisted of two frozen mandibular bone-blocks with two teeth and one mandibular segment containing one tooth. The final number of teeth for each preservation method was n = 5. All specimens were scanned with eight different moisture conditions: 48 h wet, 2 h dry, 48 h wet, 24 h dry, 48 h wet, 1 wk dry, 48 h wet, 1 wk dry. Micro-CT images were screened for the presence of dentinal microcracks. Statistical analysis was performed by nonparametric analysis of variance (α = 5%). Only few microcracks were observed in wet and in 2 h dried bone-blocks with no significant differences (p = 0.63 and p = 0.23, respectively). There was a significant and steady increase of microcracks within the groups of dried specimens as follows: 2 h dry < 24 h dry < first wk dry < second wk dry (all p < 0.008). Preservation method had no significant influence on the visibility of microcracks (p = 0.98). Identification of dentinal microcracks on micro-CT images is influenced by moisture content of cadaveric bone-blocks irrespective of the preservation method., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The aim of this study was to measure the initial and remaining dentin thickness in the danger zone of the second mesiobuccal (MB2) canal of maxillary first molars after rotary instrumentation using cone beam computed tomography (CBCT) imaging. After determining initial dentin thickness, each sample was subjected to a standardized protocol of rotary instrumentation files: ProTaper Gold Sx Orifice Opener (maximum depth of 7 mm); Vortex Blue 15.04, 20.04, 25.04, ProTaper Gold S1, S2, F1, F2, and finally Vortex Blue 30.06. Subsequent CBCT measurements were made to compare changes in remaining dentin thickness in comparison to initial presentation. Preoperative dentin thickness in the danger zone had a mean of 0.82 ± 0.17mm. Significant levels of dentin removal in the danger zone were noted after all instrumentation groups when compared to the pre-instrumentation mean (Sx P < 0.001, 25.04 P < 0.0006, F2 P < 0.0001, 30.06 P < 0.0001). It was concluded that a thin area of dentin exists along the distal wall of the MB2 (danger zone) from the furcation to 4 mm apically., (© 2021 Australian Society of Endodontology Inc.)

The purpose of this study is to investigate the effect of different application methods on the adaptation to dentin and porosity properties of calcium silicate based materials. This study included 72 maxillary canine teeth that had been extracted for various reasons. Following the root canal treatment, root, end resections were performed on the specimens. After the apicectomy, 3 mm deep cavities were created. All materials were mixed according to the manufacturer's instructions. Retrograde cavities were filled with RetroMTA [Group 1a-1c], Biodentine [Group 2a-2c] and BioAggregate [Group 3a-3c]. Placement techniques were applied for each material by using incremental, bulk technique and ultrasonic activation, respectively. The samples were scanned with the SkyScan 1272 μCT system. Porosity values were higher in bulk fill and incremental placement techniques than ultrasonic technique when using MTA and BioAggregate ( p  < 0.05), but Biodentine showed no statistically significant difference ( p  > 0.05) on using different placement techniques. The ultrasonic activation technique is beneficial to improve the condensation quality of MTA and BioAggregate. Biodentine showed better results regardless of different application techniques.

BACKGROUND Since 3-dimensional cone beam computed tomography (CBCT) started to be used in dentistry, mineral density can now be examined with computer software from the data on the images obtained. Detailed and clear images at different slice intervals can be obtained with CBCT, and mineral density can be measured from the image data on a computer with a Hounsfield unit (HU) scale. In addition to the broad opportunities presented by CBCT, this feature has presented a wider perspective to researchers. MATERIAL AND METHODS In this study, the CBCT images obtained from patients with the genetic disorder of ectodermal dysplasia were compared with the images of a control group to determine differences in mineralization of the teeth and to show that these could be compared by measuring the mineral density of dentin and enamel tissues using the HU scale on data from CBCT images. This opens new opportunities for cognitive and implementation research. RESULTS In the study, CBCT images of 14 ectodermal dysplasia and 14 control group cases previously obtained for various reasons were used. Mineral density measurements were made from 4 different regions of the teeth of the ectodermal dysplasia and control groups (incisor edge of the crown, the center buccal, cervicale line, and apex of the teeth), and the groups were compared. CONCLUSIONS The aim of this study was to provide a new overview of the feasibility and suitability of mineralization measurement of dentin and enamel dental tissues with CBCT in ectodermal dysplasia and control groups.

Aim: To describe the radicular dentine thickness in mandibular first premolars presenting C-shaped root canals, to identify the canal walls with less thickness as potential danger zones. In addition, to describe the internal and external anatomical characteristics of these teeth and associate them with the dentine thickness., Methodology: A total of 70 mandibular first premolars presenting C-shaped root canals were examined. Their internal morphology was analysed using Vertucci's and Fan's criteria, and their external morphology was analysed using the ASUDAS score. Besides, the dentine thickness around the root canals was two/three-dimensionally determined at five root planes and quantified in the distal and the mesial aspects., Results: According to Fan's, ASUDAS, and Vertucci's classifications, the most common canal configurations were category C3, grade 3, and type V, respectively. In Vertucci's type III anatomy, the mesial root wall of the lingual canal showed significantly less dentine thickness than the distal wall in the middle plane (p = .031). Similarly, in Vertucci's type V anatomy, significantly less dentine thickness was observed in the mesial root wall of the buccal and lingual canals in the middle plane (p < .001) and the buccal canal in the middle-apical plane (p = .014) than the distal root wall of these canals. In teeth with ASUDAS grade 3 and 4 scores, significantly less dentine thickness was observed in the mesial in comparison with the distal root wall of these canals. These differences were demonstrated in the middle and middle-apical planes (p < .001) of grade 3 teeth and the middle-apical plane (p < .001) of grade 4 teeth. In these root planes, the Ver1-AS3 and VerV-AS3 combinations presented a 4-times greater risk of presenting walls with a critical dentine thickness of 0.6 mm (odds ratio [OR] = 4, p = .025) than the combinations Ver1-AS2, VerV-AS2, VerV-AS4, and VerIII-AS3., Conclusions: The root canal system configuration of mandibular first premolars with C-shaped canals showed a wide range of anatomical variations. The lowest dentine thickness was located in the mesial wall of the canals in the middle and apical root thirds of Vertucci's type III and V anatomies and in teeth with deep radicular grooves scored as ASUDAS grades 3 and 4. In the middle and middle-apical planes, the presence of the combinations Ver1-AS3 and VerV-AS3 showed a high risk of presenting a critical dentine thickness of 0.6 mm. Therefore, these root canal walls with less dentine thickness represent potential instrumentation danger zones in mandibular first premolars with C-shaped canals., (© 2022 British Endodontic Society. Published by John Wiley & Sons Ltd.)