Mandibular Molars Research Articles

CBCT evaluation of the shaping characteristics of five different file systems in mesial canals of mandibular first molars – An ex vivo study

Cone-Beam Computed Tomography (CBCT) has revolutionized endodontic research by providing detailed 3D imaging, crucial for assessing the shaping characteristics of endodontic file systems. In the challenging mesial canals of mandibular first molars, where complex anatomy often complicates treatment, CBCT offers precise evaluation of how different file systems shape these canals. This ex vivo study compares five distinct file systems, analysing their ability to maintain the original canal curvature and ensure effective cleaning. The study aims to identify the most effective file systems, potentially improving clinical outcomes in endodontic therapy. This ex vivo study compared the shaping characterstics of five Ni-Ti rotary File Systems, File Univesal X7 Edge Endo, Bassilogic ProDesign Logic, Gen Endo Coltene Whaledent Pvt. Ltd., Endo Star E3 Azure Basic, Mani Jizai using Cone Beam Computed Tomography (CBCT). One hundred extracted human permanent mandibular first molars with mesial root curvature angles ranging from 20-30 degrees were divided into five groups (n=20 each). The teeth were imaged using CBCT with CS9300 equipment, set at 84 kV, 5 mA, and a 10.8-second exposure, achieving a resolution of 90 microns and a slice thickness of 76 microns to obtain a pretreatment outline of the root canals. All scans were reoriented along the x, y, and z axes. Canal transportation and root canal volume were evaluated at 0.0, 1.0, 2.0, 3.0, 4.0, and 5.0 mm intervals. The mean differences in volume and area were analyzed using one-way ANOVA to determine the variance between the five different file groups. Gen Endo File System did the least modifications in the Canal Area and Volume. Within the parameters of this study it was concluded that GEN ENDO Files did the least modifications in canal anatomy as compared to other groups.

Evaluation of success rate and marginal bone loss in dental implants subjected to early loading with a follow up of one year

Dental implants (also known as oral or endosseous implants are considered to be an important contribution to dentistry as they have revolutionized the way by which missing teeth are replaced with a high success rate. Implant success is evaluated by various implant health parameters along with patient satisfaction. : The aim of this study was to evaluate and compare the success rate and marginal bone loss in dental implants subjected to early loading versus conventional loading and also to find out the clinical viability of early loading in day-to-day practice, especially in the Armed Forces.This study was done with a split mouth design.Fifteen patients of either sex in the mean age of 22 to 52 years with bilateral missing first mandibular molar, fulfilling the inclusion criteria were selected and divided into two groups. In Group 1, subjected to early loading, (fifteen sites) the provisional prostheses were fabricated and cemented in occlusal contact with the opposing dentition within 8 weeks of implant placement. In Group 2 (fifteen sites) 15 implants were to be subjected to conventional loading after six months.Two implants were lost in group 1 and one implant in group 2 during the study. The difference in Periotest values of Group-1 and Group-2 was not significant (p value > 0.005). The Peri crestal bone level in both (early loading and conventional loading) groups were within the acceptable limits and difference between the groups was not significant (p value >0.005).Based on the results of the study, it can be concluded that early loading is a viable treatment modality and can be routinely employed for rehabilitation of partially edentulous arches. Meticulous diagnosis and treatment planning, precise clinical and laboratory protocols are critical in long term success of prostheses.

Three-dimensional finite element analysis of maxillary molar distalization treated with clear aligners combined with different traction methods

BackgroundThis study aimed to analyze the effects of maxillary molar distalization using clear aligners with different intramaxillary and intermaxillary traction via the three-dimensional (3D) finite element method.MethodsA 3D finite element model consisting of the maxilla, mandible, dentitions, periodontal ligaments (PDLs), attachments, and clear aligners was constructed. Five groups were established based on different traction modalities: group 1 (control group); group 2 (orthodontic mini-implants (OMIs) were implanted between the maxillary first molars and the second premolars on the buccal side); group 3 (OMIs were implanted in the infrazygomatic crest area between the maxillary first and second molars on the buccal side); group 4 (OMIs were implanted between the maxillary first molars and the second premolars on the palatal side); and group 5 (class II elastics were utilized between the maxillary canines and the mandibular first molars). OMIs were implanted 4 mm away from the alveolar crest in each experimental group. A force of 1.5 N was applied to each experimental group. The 3D displacement of the target teeth and stress distribution around the PDLs were analyzed.ResultsGroup 4 exhibited the least amount of torque change in the upper anterior teeth and the highest displacement of the maxillary second molars. Group 3 showed smaller changes in anterior teeth torque and higher molar distalization efficiency compared to group 2. Group 5 showed adverse effects such as anterior teeth extrusion and mandibular anchorage loss.ConclusionOMIs implanted on the palatal side have advantages in preserving anterior teeth anchorage and improving the efficiency of molar distalization compared to those positioned on the buccal side. OMIs implanted in the infrazygomatic crest area between the first and second molars on the buccal side demonstrate benefits in the aforementioned aspects when compared to OMIs implanted between the first molars and the second premolars on the buccal side.

An Evaluation of London's Intermediate Minor Oral Surgery Service

ABSTRACTBackgroundOral surgery as a speciality has traditionally experienced significant demands, representing one of the largest volume and cost of referrals from primary to secondary care. The IMOS service was created with the objective to increase the efficiency and accessibility of oral surgery services to the public, as well as reduce pressures within hospital settings.AimsTo assess: The quality of the service provided. The waiting times. If the service met needs. Patient‐reported outcome and experience measures. MethodA random sample of patients referred to London Tier 2 IMOS providers were selected, 10 from each provider, totalling 180. They were evaluated to ascertain waiting times, treatment delivered, quality of documentation and level of complexity, level 1, 2, and 3. Patient‐Reported Experience Measures (PREMs) and Patient Reported Outcome Measures (PROMs) were also carried out to assess satisfaction.Results38.3% of referrals were classed as Level 1 and the remaining Level 2 and Level 3 were 60% and 1.67%, respectively. 37.2% of patients were seen within 0–49 days, and 72.3% of patients were seen and treated within 18 weeks. 90.8% of these cases were non‐surgical, 17.9% involved mandibular 3rd molar extractions, of which 46.6% were surgical.313 PREMs and 321 PROMs were collected, the experience survey revealed over 98.7% of patients felt anxiety and pain were managed well, with any concerns addressed. PROMs showed that 94.3% of patients did not require further calls or assistance post‐treatment. 72.4% of patients felt recovery was completed within 3 days of the treatment. 1.87% of patients required further assistance such as for dry socket and infection.ConclusionThe London IMOS service is an economical, safe and effective environment to provide minor oral surgery to the vast majority of patients, who would have otherwise been seen in secondary care. Development of pan London triage and communication pathways will further enhance the service and ensure smooth and efficient patient journeys.

Detection of three-rooted mandibular first molars on panoramic radiographs using deep learning

This study aimed to develop a deep learning system for the detection of three-rooted mandibular first molars (MFMs) on panoramic radiographs and to assess its diagnostic performance. Panoramic radiographs, together with cone beam computed tomographic (CBCT) images of the same subjects, were retrospectively collected from 730 patients, encompassing a total of 1444 MFMs (367 teeth were three-rooted and the remaining 1077 teeth were two-rooted). Five convolutional neural network (CNN) models (ResNet-101 and − 50, DenseNet-201, MobileNet-v3 and Inception-v3) were employed to classify three- and two-rooted MFMs on the panoramic radiographs. The diagnostic performance of each model was evaluated using standard metrics, including accuracy, sensitivity, specificity, precision, negative predictive value, and F1 score. Receiver operating characteristic (ROC) curve analyses were performed, with the CBCT examination taken as the gold standard.Among the five CNN models evaluated, ResNet-101 demonstrated superior diagnostic performance, and the AUC value attained was 0.907, significantly higher than that of all other models (all P < 0.01). The accuracy, sensitivity, and specificity were 87.5%, 83.6%, and 88.9%, respectively. DenseNet-201, however, showed the lowest diagnostic performance among the five models (all P < 0.01), with an AUC value of 0.701 and an accuracy of 73.2%. Overall, the performance of the CNNs diminished when using image patches containing only the distal half of MFMs, with AUC values ranging between 0.680 and 0.800. In contrast, the diagnostic performance of the two clinicians was poorer, with AUC values of only 0.680 and 0.632, respectively. In conclusion, the CNN-based deep learning system exhibited a high level of accuracy in the detection of three-rooted MFMs on panoramic radiographs.

Comparison of cyclic fatigue resistance of three different single-file systems after clinical use

BackgroundNickel titanium (NiTi) rotary files have drastically altered the treatment protocol in endodontics, allowing for faster and easier preparation and more thorough irrigation of the root canal system. Despite the advantages of the NiTi files, instrument separation still remains a major concern. The aim of this study was to compare the cyclic fatigue resistance of three different single-file NiTi systems after clinical use: WaveOne Gold (WOG, Dentsply Maillefer, Ballaigues, Switzerland), One Curve (OC, Micro Mega, Besancon, France), and Reciproc Blue (RPC Blue, VDW, Munich, Germany).MethodsA total of 120 patients requiring endodontic treatment to first or second mandibular molars, were randomly divided into three groups (patient n = 40) and root canals were prepared with WOG, OC or RPC Blue. Each group consists of 2 subgroups: first use (file n = 10, patient n = 10) and third use of file (file n = 10, patient n = 30). In control group, files were subjected to cyclic fatigue test without use (file n = 10). Cyclic fatigue resistance of files was assessed by groove method. The data was evaluated by two-way ANOVA, Games & Howell post hoc and Weibull reliability analyses (p < .05).ResultsRPC Blue files showed the highest failure time value in all groups. In third use group, OC and RPC Blue files showed significantly higher failure time values compared to WOG files (p < .05). In general, RPC Blue files show the highest values in terms of number of cycles to fracture (NCF) in all groups, while OC and WOG files follow RPC Blue files respectively. There was statistically significant difference among groups considering the fragment length (p < .05).ConclusionsWithin the limitations of this study, RPC Blue files exhibited highest cyclic fatigue resistance after clinical use.

Distalization Methods for Maxillary Molars Utilizing Temporary Anchorage Devices (TADs): A Narrative Review

Class II malocclusions, characterized by the mesial positioning of the maxillary molars relative to the mandibular molars, are among the most frequently encountered orthodontic issues. One of the widely adopted non-extraction approaches for addressing this malocclusion is maxillary molar distalization, which has been utilized for decades to create space within the dental arch. Historically, extraoral appliances such as headgear were commonly employed. However, with technological advancements, intraoral distalization devices, particularly those incorporating temporary anchorage devices (TADs), have gained prominence due to their compact size, not being visible externally, and improved patient acceptance. These appliances offer significant advantages, including being less invasive compared with extraction-based camouflage treatments, being more readily accepted by patients due to the absence of extraction spaces, and not requiring the complex biomechanical principles involved in extraction-based methods. TADs have revolutionized distalization techniques by providing superior anchorage control, reducing treatment duration, and offering a straightforward, patient-friendly application. The purpose of this comprehensive narrative review is to focus specifically on intraoral distalization techniques utilizing TADs, summarizing their efficacy and outcomes in the management of Class II malocclusions as reported in clinical studies over the past three decades.

Application of artificial intelligence-based detection of furcation involvement in mandibular first molar using cone beam tomography images- a preliminary study

BackgroundRadiographs play a key role in diagnosis of periodontal diseases. Deep learning models have been explored for image analysis in periodontal diseases. However, there is lacuna of research in the deep learning model-based detection of furcation involvements [FI]. The objective of this study was to determine the accuracy of deep learning model in the detection of FI in axial CBCT images.MethodologyWe obtained initial dataset 285 axial CBCT images among which 143 were normal (without FI) and 142 were abnormal (with FI). Data augmentation technique was used to create 600(300 normal and 300 abnormal) images by using 200 images from the training dataset. Remaining 85(43 normal and 42 abnormal) images were kept for testing of model. ResNet101V2 with transfer learning was used employed for the analysis of images.ResultsTraining accuracy of model is 98%, valid accuracy is 97% and test accuracy is 91%. The precision and F1 score were 0.98 and 0.98 respectively. The Area under curve (AUC) was reported at 0.98. The test loss was reported at 0.2170.ConclusionThe deep learning model (ResNet101V2) can accurately detect the FI in axial CBCT images. However, since our study was preliminary in nature and carried out with relatively smaller dataset, a study with larger dataset will further confirm the accuracy of deep learning models.

Investigation of the association between COX-2 polymorphisms and external apical root resorption in orthodontically treated patients.

To evaluate the association between single nucleotide polymorphisms (SNPs) in cyclooxygenase-2 (COX-2) and external apical root resorption (EARR) after orthodontic treatment. This study analyzed the orthodontic records of patients from Regensburg University Hospital and two collaborating private practices. EARR was analyzed in the maxillary central incisors and first mandibular molars using pre- and post-treatment cephalometric and panoramic radiographs, respectively. Genomic DNA was obtained from salivary oral cells. Two SNPs in COX-2, rs5275 (3 prime untranslated region variant) and rs689466 (upstream transcript variant, downstream transcript variant), were genotyped using real-time Polymerase chain reaction (PCR). The linear regression models were fitted to assess the effects of the evaluated SNPs at a significance level of 5%. A total of 143 biologically unrelated patients (mean age: 13.5 ± 4.5 years) were included in the study. The F-test showed that only the regression for EARR in the mandibular molars in the dominant model for rs5275 G allele had a good fit (F = 3.50, P = 0.034). The model showed that individuals carrying at least one G allele for rs5275 had a 17% increase in EARR in the molars compared to common AA homozygotes (exp(B) = 1.17; 95% CI: 1.04, 1.32; P = 0.010). Although an effect of the G allele (rs5275) was detected, this effect did not explain much of the variability in EARR (adjusted R2 = 0.04). The results suggested that patients carrying the polymorphic form of the rs5275 were more likely to have EARR in the mandibular molars; therefore, COX-2 could have an effect on EARR. The knowledge of the genetic background concerning EARR after orthodontic treatment would aid in clinical practice to screen for associated genetic factors and potentially aid its prevention and management, considering that patients' genetic profiles would soon be available.

Mandibular Molar with Mid Mesial Root Canal: A Case Report

The aim of this case report was to illustrate how crucial it is to understand the core structure of root canals, aimed at the effectiveness of endodontic therapy. One of the primary reasons endodontic therapy fails has been identified as a lack of understanding of anatomic variants and their features in various teeth. The authors of this paper examine the significance of identifying and treating mandibular first molars with numerous root canals, to assess frequency of such cases, and to element endodontic treatment of patients

Photoactivated rose bengal-doped TiO2 nanoparticles modified fifth-generation adhesive on the survival rate of Streptococcus mutants and mechanical properties of tooth-colored restorative material to carious dentin.

Assessment of the antimicrobial, micro tensile bond strength (μTBS), and degree of conversion (DC) of fifth-generation adhesive modified using photoactivated 0.5% rose bengal (RB) and photoactivated RB-doped titanium dioxide nanoparticles (TiO2NPs) in different concentrations (2% and 5%) as compared with the unmodified adhesive bonded to the carious affected dentin (CAD). Forty mandibular molars with caries progression up to the middle third of the dentin, as per the International Caries Detection and Assessment System (ICDAS) score of 4 and 5 were included. Specimens were divided into four groups based on etch and rinse adhesive (ERA) modification group 1: unmodified ERA, group 2: photoactivated 0.5% RB photosensitizer (PS) modified ERA, group 3: photoactivated RB-doped 2 wt% TiO2NPs adhesive, group 4: photoactivated RB-doped 5 wt% TiO2NPs adhesive. Followed by adhesive and composite restoration on the CAD surface. All the specimens were thermocycled and an assessment of μTBS and failure pattern analysis was performed. The antibacterial potency of RB and RB-doped TiO2NPs (2% and 5%) followed by their activation using visible light against Streptococcus mutans (S.mutans) were tested. The survival rate of S.mutans was assessed using the Kruskal-Wallis test. The analysis of μTBS involved the use of ANOVA, followed by a post-hoc Tukey honestly significant difference (HSD) multiple comparisons test. Group 1 (Unmodified ERA) (0.52 ± 0.31 CFU/mL) treated samples unveiled the highest means of bacterial survival and lowest μTBS (11.32 ± 0.63 MPa). Nevertheless, group 4: photoactivated RB-doped 5 wt% TiO2NPs adhesive displayed the lowest outcomes of S.mutans survival (0.11 ± 0.02 CFU/mL) and highest bond strength (18.76 ± 1.45 MPa). The photoactivated RB-doped 2 wt% TiO2NPs in adhesive demonstrated promising enhancements in both μTBS and antibacterial efficacy against S.mutans. However, it is noteworthy that this modification led to a decrease in the DC of the adhesive. RESEARCH HIGHLIGHTS: Unmodified ERA-treated samples unveiled the highest bacterial survival and the lowest μTBS. Photoactivated RB-doped 5 wt% TiO2NPs adhesive displayed the lowest S.mutans survival rate and highest bond strength. DC decreased with an increase in concentration of TiO2.

Umbilical cord mesenchymal stem cells improve bone regeneration in diabetes mellitus animal model with apical periodontitis

BackgroundPrevious studies revealed diabetes mellitus subjects tend to have persistent apical periodontitis. Regenerative stem cells therapy through endodontic procedure is hoped to be a solution. This study assessed bone regeneration in diabetic rats with apical periodontitis through histopathological analysis of osteoblasts and immunohistochemical analysis of runt-related transcription factor 2 (Runx2) and Osterix. MethodsDiabetes mellitus and apical periodontitis was induced on 20 rats. Apical periodontitis was induced on mandibular right first molars under anesthesia. The teeth were left open for 7 days following access cavity and pulp extirpation, then the rats’ teeth were endodontically treated and randomly allocated into 4 groups (5 rats per group). The first and second groups was ended at 30 days (C30) and 60 days (C60) and labelled as control. The third and fourth groups was given umbilical cord mesenchymal stem cells and ended at 30 days (T30) and 60 days (T60). The osteoblasts, Runx2 and Osterix were analyzed. ANOVA and Tukey HSD tests were used for analysis. Differences with p values < 0.05 were considered significant. ResultsThe number of osteoblasts in the apical area in control groups (C30 and C60) and treatment groups (T30 and T60) showed a significant increase (p < 0.05). The expressions of Runx2 and Osterix in osteoblasts showed a significant increase among the control (C30 and C60) and treatment groups (T30 and T60) (p < 0.05). ConclusionUmbilical cord mesenchymal stem cells improve bone regeneration in diabetic animal model with apical periodontitis, in terms of osteoblasts, Runx2 and Osterix.

Efficient Retrieval of Separated Endodontic Instruments: A Case Series Using the TS Infinite Loop System in the Coronal, Middle Thirds

Instrument separation during endodontic treatment presents a significant challenge, often leading to compromised treatment outcomes. This case series focuses on the successful retrieval of separated instruments from the root canal system using the TS Infinite Loop System. Three clinical cases involving separated instruments in the mesiobuccal canals of mandibular molars are presented, demonstrating the procedural approach and techniques used for retrieval. A combination of ultrasonic troughing and the TS Infinite Loop System enabled precise removal of fractured instruments without unnecessary dentin removal or canal enlargement. This series highlights the efficacy, precision, and potential of the TS Infinite Loop System as a reliable tool for managing instrument retrieval in challenging clinical scenarios.

Comparison of Fracture Resistance Force (Load-to-fractured Test) and Failure Type of 3D-printed Stainless Steel Crowns and Preformed Stainless Steel Crowns in Primary Molars: An In Vitro Study.

This study aims to compare the fracture resistance force (FRF) and failure types of three-dimensional (3D)-printed stainless steel crowns (SSCs) and preformed SSCs in primary molars. Forty-eight over-retained and extracted mandibular second deciduous molars were divided into two groups: one receiving 3D-printed crowns and the other preformed crowns. Fracture resistance testing was performed using a universal mechanical testing machine, and failure types were analyzed post-testing. Fracture resistance testing revealed a significant difference between 3D-printed and preformed SSCs (p < 0.05), with 3D-printed crowns exhibiting a mean FRF of 3953.82 N compared to 742.94 N for preformed crowns. Additionally, Mann-Whitney U tests and Chi-squared tests were utilized to examine variations within and across the groups. Analysis of shear bond strength showed that 3D-printed crowns demonstrated superior adhesive performance compared to preformed crowns, with mean shear bond strength values of 3953.82 N and 742.94 N, respectively. Both groups A and B showed unrepairable failure modes. The study concludes that 3D-printed SSCs offer distinct advantages over preformed options, including tailored fit, enhanced mechanical properties, and improved longevity. These findings underscore the potential of 3D printing technology to revolutionize pediatric dental restoration practices. Integrating 3D printing into pediatric dental practice holds promise for optimizing treatment outcomes and improving long-term oral health in children. The superior fracture resistance and adhesive performance of 3D-printed crowns suggest their potential to enhance restoration viability and reduce the need for subsequent interventions. Giridharan DL, Gopal S. Comparison of Fracture Resistance Force (Load-to-fractured Test) and Failure Type of 3D-printed Stainless Steel Crowns and Preformed Stainless Steel Crowns in Primary Molars: An In Vitro Study. Int J Clin Pediatr Dent 2024;17(10):1129-1134.

Comparative Analysis of Marginal Fit and Fracture Resistance in CAD-CAM Lithium Disilicate and Pre-processed Composite Endocrowns: An In Vitro Study.

This study aimed to determine the optimal finish line and material criteria for optimal marginal fit and fracture resistance in endocrowns. The impact of two preparation designs on endocrowns made from computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate and pre-processed CAD/CAM composite was compared. In a randomized 3-arm trial involving 42 mandibular molars, two marginal configurations (with and without chamfer finish lines) were evaluated for each material group. Marginal fit was assessed pre- and post-cementation using scanning electron microscope, and fracture resistance was tested with a universal testing machine. Student t-test was used to compare within group differences and ANOVA with Tukey test was used to compare intergroup differences. The significance level was set at 0.05. Edelweiss CAD/CAM blocks demonstrated the least marginal gap pre- and post-cementation, and superior fracture resistance compared to lithium disilicate and HIPC composite resin. Finish lines significantly affected marginal adaptation in all groups. Fracture resistance differences between designs within the same group were not statistically significant. The CAD/CAM composite proved effective for endocrown restorations, with finish lines impacting marginal adaptation but not fracture resistance. Edelweiss CAD/CAM blocks showed superior performance in both aspects, suggesting their suitability for such restorations. The study highlights the clinical significance of using Edelweiss CAD/CAM blocks for endocrown restorations, demonstrating superior marginal fit and fracture resistance. Clinicians can enhance restoration longevity by selecting appropriate materials and preparation designs, particularly the use of finish lines, to optimize marginal adaptation without compromising fracture resistance. How to cite this article: Singh MV, Sarfaraz H, Lampl S, et al. Comparative Analysis of Marginal Fit and Fracture Resistance in CAD-CAM Lithium Disilicate and Pre-processed Composite Endocrowns: An In Vitro Study. J Contemp Dent Pract 2024;25(8):732-739.

Influence of different kinematics on shaping ability and accumulated hard tissue debris: an ex vivo study.

To determine the shaping ability, the amount of accumulated hard tissue debris (AHTD) and untouched area is generated by different kinematics through micro-CT. Thirty-two mesial roots of mandibular molars with Vertucci type IV were pre-scanned through micro-CT evaluation and randomized to one of the four experimental groups according to the kinematics tested: Continuous Rotation (CR), Reciprocation (REC), Optimum Torque Reverse (OTR) and Jeni motion. The root canal preparation was performed with HyFlex EDM (Coltène/Whaledent AG) up to OneFile. After each file used, irrigation was performed with 2mL 5.25% NaOCl for 1min. The final rinse was performed with 1ml of 5.25% NaOCl followed by a 1ml of 17% EDTA and, 1ml of distilled water. Then, the samples were scanned and the images, before and after preparation, were superimposed and analyzed to determine the AHTD, untouched areas, canal transportation, centering ability, and shaping time. Data were statistically analyzed using Kruskal-Wallis test and Dunn post hoc with p < 0.05. No significant differences were detected among the tested kinematics in terms of untouched areas, AHTD, canal transportation and shaping time (p > 0.05). Significantly more untouched areas were detected in the coronal third compared to the middle (p = 0.0301) and apical ones (p = 0.0399) under continuous rotation. Moreover, a significantly higher centering ratio in the middle third compared to the apical was observed for Jeni motion (p = 0.0207). The tested kinematics showed similar untouched areas, AHTD, shaping ability and shaping time. All motions determined an appropriate mechanical preparation; yet, none of them was able to prepare all canal walls and keep the root canals completely free from hard tissue debris.

Cone-beam computed tomographic investigation of the association between impacted mandibular third molars and the development of distal caries in adjacent second molars in a Chinese population

To investigate the association between impacted mandibular third molars (IMTMs) and the prevalence of distal caries in adjacent mandibular second molars (MSMs) in a Chinese population, a retrospective analysis was conducted using cone-beam computed tomography (CBCT) images obtained from routine dental practice for various diagnostic purposes. The impaction patterns of the mandibular third molars were recorded using Winter's classification and Pell and Gregory's classification. The occurrence and severity of distal caries in MSMs were also documented. Chi-square tests and logistical regression analyses were used to assess the association between distal caries in the MSM and variables. A total of 552 scans were included, and the frequency of IMTMs was 64.5 % (647/1003). According to Winter's classification, the most common type of impaction was mesioangular impaction (45.5 %), followed by horizontal (31.2 %) and vertical impaction (17.5 %). Based on Pell and Gregory's classification, level B impaction (54.9 %) and class II impaction (57.5 %) were the most frequent. Compared to the non-impaction group, the frequency of distal caries in the MSMs for the impaction group was significantly higher (19.5 % [126/647] vs. 3.5 % [12/346]; p < 0.01). The prevalence of carious lesion in MSMs associated with IMTMs increased with age, peaking in the 31–35 years age group, followed by a decrease in the 36–40 years age group, and then rising again in patients aged above 40 years. Logistical regression analyses confirmed that the pattern of IMTMs significantly associated with distal caries in MSMs, and mesioangular angulation of IMTM (OR = 11.22), position A (OR = 8.37), a type I ramus relationship (OR = 2.70), and the 18–25 age group (OR = 2.62) were identified as significant risk factors (all p < 0.01). In conclusion, the present study demonstrates that the pattern of IMTMs contributes to the development of distal caries in adjacent MSMs. Clinicians should carefully consider these factors when evaluating the need for prophylactic extraction of IMTMs to prevent distal caries in MSMs.

AI-driven segmentation of the pulp cavity system in mandibular molars on CBCT images using convolutional neural networks

ObjectiveTo develop and validate an artificial intelligence (AI)-driven tool for automated segmentation of the pulp cavity system of mandibular molars on cone-beam computed tomography (CBCT) images.Materials and methodsAfter ethical approval, 66 CBCT scans were retrieved from a hospital database and divided into training (n = 26, 86 molars), validation (n = 7, 20 molars), and testing (n = 33, 60 molars) sets. After automated segmentation, an expert evaluated the quality of the AI-driven segmentations. The expert then refined any under- or over-segmentation to produce refined-AI (R-AI) segmentations. The AI and R-AI 3D models were compared to assess the accuracy. 30% of the testing sample was randomly selected to assess accuracy metrics and conduct time analysis.ResultsThe AI-driven tool achieved high accuracy, with a Dice similarity coefficient (DSC) of 88% ± 7% for first molars and 90% ± 6% for second molars (p > .05). The 95% Hausdorff distance (HD) was lower for AI-driven segmentation (0.13 ± 0.07) compared to manual segmentation (0.21 ± 0.08) (p < .05). Regarding time efficiency, AI-driven (4.3 ± 2 s) and R-AI segmentation (139 ± 93 s) methods were the fastest, compared to manual segmentation (2349 ± 444 s) (p < .05).ConclusionThe AI-driven segmentation proved to be accurate and time-efficient in segmenting the pulp cavity system in mandibular molars.Clinical RelevanceAutomated segmentation of the pulp cavity system may result in a fast and accurate 3D model, facilitating minimal-invasive endodontics and leading to higher efficiency of the endodontic workflow, enabling anticipation of complications.

Influence of implant depth and scanning rod length on accuracy of digital impression for mandibular posterior single-tooth implant restoration

To study the influence of implant depth and scanning rod lengths on the accuracy of digital impression for single-tooth implant restoration of the mandibular posterior teeth. Five standard dental cast models with missing right mandibular first molar (46) were prepared with the subgingival implant depths of 0, 1, 3, 5 and 7 mm. ITI RC and ITI RC H11 scanning rods were connected to the replacement body and placed into the seating tract for scanning. The reference data were obtained using a 3D dental scanner, and the experimental data were obtained by 10 scans of each model using a digitized intraoral scanner. Geomagic Wrap 2021 was used to analyze the model data to test the trueness and precision of the models. The trueness did not differ significantly among the groups (P > 0.05). The implant depth of 1 mm achieved the highest impression precision (66.81±2.45 μm), and the depth of 0 mm resulted in a significantly lower precision (95.60±3.04 μm) than the depth of 1 and 3 mm. Starting from the subgingival depth of 1 mm, the precision of the scan decreased progressively with the increase of the implant depth. At the subgingival implant depth of 5 or 7 mm, the use of an extended rod significantly improved the scan precision. For single-tooth implant restoration of the mandibular posterior teeth, the implant depth can substantially affect the accuracy of digital impression, which decreases as the implant depth increases. For a deep implant, the use of a longer scanning rod can improve the scanning accuracy.

Comparative Analysis of Canal Centering and Transportation: Edgefile X7 vs HyFlex EDM in Moderately Curved Mesiobuccal Root Canals of Mandibular Molars

Comparative Analysis of Canal Centering and Transportation: Edgefile X7 vs HyFlex EDM in Moderately Curved Mesiobuccal Root Canals of Mandibular Molars