Apical Foramen Research Articles

Tertiary Lymphoid Structure in Dental Pulp: The Role in Combating Bacterial Infections.

Tertiary lymphoid structure (TLS) is associated with various pathologies, including those of cancers and chronic infections. Depending on the organ, multiple factors regulate the formation of TLS. However, the role of TLS in immune response and the molecules that drive its formation remain uncertain. The dental pulp, includes a few immune cells surrounded by rigid mineralized tissue, and opens to the outside through the apical foramen. Owing to this special organization, the dental pulp generates a directional immune response to bacterial infection. Considering this aspect, the dental pulp is an ideal model for comprehensively studying the TLS. In the present study, single-cell RNA sequencing of healthy and inflamed human dental pulp reveals known markers of TLS, including C-C motif chemokine ligand 19 (CCL19), lysosome-associated membrane glycoprotein 3 (LAMP3), CC chemokine receptor 7 (CCR7), and CD86, present in inflamed dental pulp. Compared with the healthy pulp, types and proportions of immune cells increase, along with enhanced cellular communication. Multiple immunofluorescence staining reveals that typical TLS emerges in dental pulp with pulpitis, consistent with the high expression of CC chemokine ligand 3 (CCL3), which may be a key driver of TLS formation. Moreover, TLS is also observed in a mouse model of pulpitis. These findings collectively offer insights into the formation and function of TLS in response to infection.

ProDesign Logic Files Effect on Apical Foramen Wear and Shape Transformation After Foraminal Enlargement.

This study aimed to evaluate the effect of ProDesign Logic files 45.01 and 50.01 on apical foramen wear and shape transformation after foraminal enlargement at tooth length (TL) and 1 mm beyond. Sixty freshly extracted single-rooted lower human premolars teeth were distributed randomly into five groups (n = 12): Group 1 (40.05 WL) (control): No foraminal enlargement, Group 2 (45.01 TL): Specimens underwent foraminal enlargement with 45.01 Prodesign Logic file at TL; Group 3 (45.01 TL + 1): Specimens underwent foraminal enlargement with 45.01 Prodesign Logic file at 1 mm beyond TL; Group 4 (50.01 TL): Specimens underwent foraminal enlargement with 50.01 Prodesign Logic file at TL; Group 5 (50.01 TL + 1): Specimens underwent foraminal enlargement with 50.01 Prodesign Logic file at 1 mm beyond TL. Scanning electron microscopy was used to evaluate apical foramen variations and shape alterations. Data were analyzed by Student's t-test, Kruskal-Wallis, and Mann-Whitney test. Significant differences (p < 0.01) were observed among all tested groups compared to the control group in terms of the average worn area of the apical foramen. Foraminal enlargement led to significant shape transformation, resulting in round-shaped foramina. ProDesign Logic 45.01 and 50.01 files at TL causes notable wear and round-shaped foramina.

Regenerative Endodontic Procedures With Minced Pulp Tissue Graft in Mature Permanent Teeth: A Clinical Study

IntroductionRegenerative endodontic procedures (REPs) using cell-based approaches have emerged as novel treatment modalities. This clinical study aimed to present the outcomes and explore factors influencing REPs with minced pulp tissue (MP) grafts in a mature tooth. MethodsSix healthy male patients aged 20–27 requiring nonsurgical root canal treatment were enrolled in this study. MP tissue obtained from third molars was introduced into the instrumented, disinfected, and blood-filled root canal. The canal was sealed with bioceramic cement, and the coronal access cavity was restored. ResultsFollow-ups for 6 cases ranged from 19 to 42 months. Radiographically, all the teeth showed favorable outcomes. Among the 6 teeth, 2 showed neither intracanal calcification nor recovery in sensibility tests, and one had no intracanal calcification with an inapplicable sensibility test evaluation. In 2 teeth, intracanal calcification was observed in the apical third; however, there was no recovery in the sensibility tests. One tooth exhibited intracanal calcification in the apical third and showed recovery in the sensibility tests. Considering these outcomes and clinical variables, the size of the apical foramen and the composition of the transplanted pulp tissue were identified as tentative influencing factors. ConclusionsThis study on simplified cell-based therapy using autologous MP for pulp/dentin regeneration in adult teeth not only enhances our understanding of REPs but also suggests its potential as an alternative treatment option to conventional endodontic treatment.

Optimized protocol for collecting root canal biofilms for in vitro studies

Endodontic retreatment is often necessitated by several factors, including the persistence of microorganisms in the root canal system (RCS). Their complex organization in biofilms increases their pathogenic potential, necessitating new disinfection strategies. This study aimed to standardize a new in vitro protocol for collecting biofilm from the RCS. Thirty-four bovine incisors were used in the study, divided into two experimental groups with two collection steps each: (a) biofilm collection protocol and (b) absorbent paper points protocol. Twelve specimens from each group were selected for counting colony-forming units (CFUs), while eight specimens were prepared for scanning electron microscopy (SEM). Two additional specimens served as sterilization controls to ensure that experiments were free of contamination. The coronal region was removed and standardized at 15 mm. After preparation with ProTaper up to F5, the apical foramen was sealed with composite resin, and the roots were stabilized with acrylic resin in 1.5-mL Eppendorf tubes. The specimens were sterilized and inoculated with Enterococcus faecalis NTCT 775 every 24 h for 21 days. After this period, each group underwent biofilm collection protocols, and CFU and scanning electron microscopy (SEM) data were analyzed. The Shapiro–Wilk test was performed to assess the normality of log-transformed data, and the results indicated a normal distribution for all groups, allowing parametric testing. The Levene test was used to evaluate the equality of variances. The proposed biofilm collection method yielded significantly higher CFU counts compared with the absorbent paper points method, particularly when analyzed on a log₁₀ scale. An independent samples t-test confirmed a statistically significant difference between the two methods (p < 0.0001). The proposed protocol achieved an efficiency rate of 95.85 % ± 1.15 %, whereas the absorbent paper points protocol yielded a lower efficiency of 5.46 % ± 1.37 %. Therefore, the biofilm collection protocol proposed in this study proved to be more effective for biofilm removal from the RCS.

Comparative Evaluation of Dentinal Microcrack Formation During Root Canal Preparation Using Different Rotary Files: An In Vitro Study

Background:The success of endodontic treatment depends on completely removing all vital and necrotic pulp tissue, microorganisms, and microbial toxins from the root canal. During the cleaning and shaping process, the canal is shaped through the interaction between instruments and the dentin walls. These interactions can create several temporary stress points within the dentin, which may lead to the development of dentinal defects, craze lines, or microcracks. As a result, the techniques employed for shaping root canals carry the risk of starting crack formation, which, under functional pressure, could progress into complete fractures. This study was aimed to compare and evaluate the incidence of dentinal microcrack formation during root canal preparation using ProTaper Universal, ProTaper Gold, NeoEndo Flex and Hyflex EDM files. Materials and Methods: A total of 95 freshly extracted single rooted premolars with single straight canal were selected and stored in normal saline. Each specimen was examined using dental operating microscope to exclude cracked samples. Specimens then decoronated using a diamond disc and water as a coolant to a standardized length of 14 mm. Canal patency was determined by passing 10 K file passively and the working length was established 1 mm short of the file length at which the file become visible at the apical foramen. Canal was then enlarged upto15 k size file. Teeth samples were then divided into 5 groups having 19 teeth each. Group 1: Control Group (Uninstrumented teeth), Group 2 : Protaper Universal, Group 3 : Protaper Gold, Group 4 : NeoEndo Flex ,Group 5 : Hyflex EDM. After completion of cleaning and shaping procedure (to a standard apical diameter of 25), canal was rinsed with distilled water. Root was then horizontally sectioned at 3 mm, 6 mm and 9 mm from the apex with diamond disc at low speed under water cooling. All the sections were evaluated under stereomicroscope for presence of cracks and images were recorded. Cracks were observed as lines extending from the root canal lumen to the dentin or from the outer surface into the dentin. Results: All the file systems used in this study showed dentinal microcracks. ProTaper Universal exhibited the highest percentage of dentinal defects, while Hyflex EDM displayed the lowest among the file systems used (ProTaper Universal, ProTaper Gold, NeoEndo Flex and Hyflex EDM). The defects were present more in the apical third (3 mm) as compared to 6 mm (middle third) and 9 mm (coronal third) sections

Comparative Evaluation of Accuracy of Two Apex Locators with Different Irrigants: An In-Vitro Study

Aim: The aim of this in-vitro study will be to evaluate and compare the accuracy of two apex locators in the presence of various irrigants. Methods and Material: The study will be conducted on 80 extracted straight, single-rooted permanent human teeth with mature apices. The teeth will be decoronated. Access cavity preparations will be done and working length will be established with 10 K file or 15 k-file into the canal until its tip emerged through the major apical foramen at ×10 magnification under a stereomicroscope. All the samples selected will be divided into four groups on the basis of irrigants used. Group 1 will be dry without irrigants, used as control, in Group 2 saline will be used as irrigant, in Group 3 sodium hypochlorite will be used as irrigant and in Group 4 chlorehexidine will be used as irrigant. Each group again will be subdivided into two groups on the basis of two different apex locators used (Root ZX Mini J. Morita) and CanalPro (Coltene). All the samples will be embedded in gelatin filled polyurethane bottles to simulate the periodontium. Statistical analysis used: Subsequently, the data will be statistically analysed using one-way analysis of variance (ANOVA) and paired t-test. Results: In this study, group 2 canal pro apex locator is accurate and sodium hypochlorite irrigant shows maximum variation. Conclusions: Canalpro showed accurate values than Root ZX and sodium hypochlorite showed more variations

Preparation, structure, osteogenic differentiation ability, and biosafety of bioglass for root canal disinfection

In this paper, SiO2-P2O5-Ca(Sr/Zn)O-Na2O-F system glasses with varying CaO:SrO and CaO:ZnO ratios were prepared by traditional melting method, which combined the remineralization properties of bioglass with the special functions of Zn2+ and Sr2+. The evolution of glass composition and its thermal properties, network structure, and biological properties was investigated by DSC, FTIR, and biological experiment. The results showed that all the extracts of glass powder could promote the osteogenic differentiation of human periodontal ligament cells (HPDLCs). Among them, the two kinds of glass containing 6 wt% SrO and only 2 wt% ZnO had the greatest potential to accelerate the bone tissue reconstruction. Hematoxylin-eosin (HE) staining histological results showed that 3 months after the two kinds of glass were implanted in the animal model of periapical inflammation, the bone matrix formed a good seal in the apical foramen, and new bone and capillaries were formed in the apical area, which has a clinical application and transformation prospect.

Cytotoxic Effect of Two Different Concentrations of Sodium Hypochlorite: An In-Vitro Study.

Introduction The endodontic treatment of primary teeth presents considerable complications due to their distinct anatomical properties. In order to achieve a successful endodontic treatment, certain factors must be assessed. These factors include a precise diagnosis, thorough cleaning, and a reliable disinfection protocol. Although sodium hypochlorite (NaOCl) has been effective as an irrigation agent in primary teeth, it is important to recognize that higher concentrations of NaOCl might possibly inflict toxic harm on the periapical environment if they penetrate the tooth's apical foramina. Since primary teeth are important, pediatric dentists must choose an appropriate NaOCl concentration for root canal irrigation, as higher concentrations can be toxic. Thus, the current investigation examined the cytotoxicity of two different NaOCl concentrations at various volumes. Methods To evaluate the cytotoxicity potential, a culture ofnauplii (brine shrimp) was prepared and subjected to testing. For the test, 5, 10, 20, and 40 µL of 1% and 3% NaOCl were added to the brine shrimp culture at different concentrations, and saline was used as a control. After a span of 24 hours, the total number of alive nauplii was duly noted. Results After 24 hours, nauplii showed no mortality in the control group. For 1% NaOCl, mortality ranged from 10% to 20% across volumes, with no significant differences (p = 0.193). In contrast, 3% NaOCl caused significantly higher mortality: 20% at 5 µL, 30% at 10 and 20 µL, and 60% at 40 µL (p = 0.007). Tukey's analysis revealed no significant differences for 1% NaOCl (p > 0.05) but significant differences for 3% NaOCl at 40 µL (p < 0.05). Conclusion Based on the results of the present study, it was observed that a 1% NaOCl solution exhibited a lower level of toxicity in comparison to a 3% NaOCl solution. These findings highlight the importance of using lower concentrations of NaOCl for endodontic irrigation in pediatric dentistry to reduce the risk of tissue damage and ensure safer outcomes for young patients.

Non surgical Endodontic Management of Dens Invaginatus: A case report

Dens invaginatus is a dental germ aberrant development caused by enamel invagination. It is distinguished by enamel and dentin invagination, which forms a lumen within the diseased tooth that can reach as deep as the apical foramen. Diagnosing and treating these illnesses might be challenging due to their canal morphology. Understanding dental anatomy and deviations is essential for successful endodontic therapy.Early and correct diagnosis is critical in determining the most effective treatment for such cases. This case report describes on such successful rehabilitation of case of dens invagiatus Oehler’s type II with open apex.

Sinus membrane thickness of healthy endodontically treated maxillary molars

ObjectiveThe study aimed to investigate the sinus membrane thickness (SMT) adjacent to healthy endodontically-treated maxillary molars with or without protruded apical foramen into the sinus cavity using cone-beam computed tomography (CBCT).Materials and methodsImages of 207 non-smoker patients aged 18–40 were retrospectively analyzed, 140 were endodontically treated, and 136 were without endodontic treatment. Patients with any sinus pathology, teeth that have symptoms, or poor root filling were excluded. Study groups consisted of Group EM-I (endodontically treated and protruded apical foramen), Group EM-C (endodontically treated and contacted apical foramen), and similarly without endodontic treatment; Group M-I and Group M-C. SMT upon the mesial, distal, and palatal roots was measured. One-way ANOVA and Student’s t-tests were performed.ResultsGroup EM-I had the thickest sinus membrane compared to other groups (p = 0.013). SMT values were 2.37–2.60 mm in Group EM-I, and 1.34–1.58 mm in other groups. Thickening (> 2 mm) percentages were 33.45% in Group EM-I and between 4.25 and 8.25% in other groups. No statistical difference was detected between first and second molars and genders (p > 0.05).ConclusionWhen the apical foramen protruded into the sinus cavity, the conventional root canal treatment caused a minimal (between 2.37 mm and 2.60 mm) sinus membrane thickening with a rate of 33.45% based upon CBCT examinations.

Cytotoxic effect of 1% and 3% Sodium hypochlorite as irrigation agent in primary teeth on human red blood cells: an in vitro study

Background and objectives. The endodontic treatment of primary teeth presents significant challenges due to their unique anatomical characteristics. To ensure a successful treatment, it is essential to evaluate a few factors. These factors include accurate diagnosis, disinfection protocol, intracanal medicaments, and irrigation solutions. While Sodium hypochlorite (NaOCl) has gained success as an irrigation agent in primary teeth, it is important to note that higher concentrations of NaOCl can potentially cause toxicity to the periapical environment if they pass through the tooth's apical foramina. Thus, this study compared the cytotoxicity of two different concentrations of sodium hypochlorite at varied volumes on red blood cells (RBC). Materials and methods. In order to evaluate the cytotoxicity potential, fresh human blood was collected from a single healthy individual and subjected to testing. For the test, 10 µL, 20 µL, 30 µL, 40 µL and 50 µL of 1% and 3% NaOCl were added to the RBC. The tubes were gently mixed and incubated at 37°C for 30 minutes. A UV-visible spectrophotometer was used to calculate the absorbance of the supernatant at a wavelength of 540 nm. Results. There was no significant difference in 1% sodium hypochlorite at different volumes with a p value &gt;0.05 using Tukey's post hoc test. However, there was a significant difference between the volumes of 3% sodium hypochlorite at 40 and 50 µg/ml with a p value of 0.004 and 0.001 respectively. Conclusions. According to the current study's findings, 1% sodium hypochlorite solution exhibited less toxicity than 3% sodium hypochlorite.

Increase Toll-like receptors 2 and 4 in apical periodontitis of rats with chronic liver disease.

The aim of this study was to evaluate the influence of liver fibrosis (LF) on the expression of Toll-like receptors (TLR) 2 and 4 in apical periodontitis (AP) in Wistar rats. Forty Wistar rats were allocated in the following groups (n = 10): C-control; AP-apical periodontitis; LF-liver fibrosis; AP + LF-rats with AP and LF. LF and AP were induced by established methodologies. Histological, bacteriological, and immunohistochemical analyses were performed according to pre-established scores. For comparisons between AP and AP + LF groups, the Mann-Whitney test was used (P < .05). The livers of the LF and AP + LF groups showed generalized portal inflammatory infiltrate and collagen fibers confirming the presence of LF. Histopathological analysis in the maxilla of the AP + LF group showed areas of necrosis comprising the entire dental pulp and periapical tissue surrounded by a more intense inflammatory infiltrate than observed in the AP group (P = 0.032). A significant number of specimens in the AP + LF group showed microorganisms beyond the apical foramen adhered to the extraradicular biofilm, demonstrating greater invasion compared to the AP group (P = .008). Immunohistochemical analysis showed a large number of cells immunoreactive for TLR2 and TLR4 in the AP + LF group, compared to the AP group (P < 0.05). Liver fibrosis favors the inflammation and contamination of microorganisms in apical periodontitis and triggers the expression of TLR2 and TLR4, modulating innate immunity response in periapical lesions.

Endodontic Management of Mandibular Second Molar with Middle Distal Canal

Mandibular second molar is often associated with variations in root canal morphology. Despite the intricate association, the occurrence of middle distal canal in endodontic literature is limited, with an incidence of 0.2% to 3%. Therefore, this study presents a case report describing a clinical situation in mandibular second molar that shows four canals, opening into different apical foramens. A 30-year-old male patient came to the Rumah Sakit Gigi dan Mulut of Universitas Sumatera Utara with the main complaint of intermittent pain in the lower right tooth persisting for two days. The results of clinical examination of the lower right second molar labeled as #47, showed a temporary filling, while radiography indicated widened periodontal ligament space and termination of lamina dura. After receiving informed consent, root canal therapy was carried out, and a direct resin composite onlay was selected for final restoration. To locate and treat hidden and unusual anatomy, dentists are often required to possess a comprehensive understanding of internal dental anatomy and use modern instruments, such as the dental operating microscope and ultrasonic tips. In certain clinical, direct resin composite onlay restorations can represent a valid alternative to traditional indirect restorations. In conclusion, this study shows that a comprehensive understanding of the potential variances in the internal anatomy of human teeth is essential to achieving successful outcomes in endodontic therapy.

Comparative evaluation of the efficacy of 1% and 3% Sodium hypochlorite in reducing the microbial counts in primary teeth root canals using Bioluminometer – A randomized clinical trial

PurposeSodium hypochlorite (NaOCl) is commonly used to irrigate primary teeth during pulpectomy. Although high concentrations of NaOCl are effective, they pose a risk of toxic damage to periapical tissues if NaOCl penetrates through the apical foramen. Therefore, low concentrations of NaOCl are preferred to mitigate this risk. However, concerns persist regarding the antibacterial efficacy of low concentrations of NaOCl compared to high concentrations. The objective of this study was to assess and compare the efficacy of 1% and 3% NaOCl irrigation in reducing bacterial load within primary teeth root canals. Materials and methodsThis clinical study involved forty participants divided into two groups. Group 1 (n = 20) received canal irrigation with 1 % NaOCl solution, while Group 2 (n = 20) received canal irrigation with 3 % NaOCl solution. Microbial samples were collected from the root canal using a paper point before and after irrigation. The samples were aseptically transferred to ultra-snap tubes and then analyzed using a Bioluminometer. The results were recorded. ResultsBoth groups exhibited a decrease in bacterial count after irrigation. The mean colony count post irrigation for 3 % NaOCl was 258.05 ± 28.61, and for 1 % NaOCl it was 267.60 ± 30.56. However, no statistically significant difference was observed upon intergroup comparison. ConclusionThis study shows that 1% NaOCl is equally effective as 3% NaOCl in reducing bacterial count in root canals. Thus, using 1% NaOCl as an irrigant is appropriate in clinical practice.

Effect of apical foraminal enlargement on postoperative pain and inflammatory markers in asymtomatic single-rooted mandibular teeth with apical periodontitis - An in vivo randomized controlled trial.

This study aims to assess the effect of apical foraminal enlargement on inflammatory markers and pain in patients with asymptomatic single-rooted mandibular teeth with apical periodontitis. The study included 60 patients based on inclusion and exclusion criteria. Before beginning root canal treatment (RCT), a blood sample was obtained from the antecubital fossa to evaluate the inflammatory markers, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR). Access opening was done and initial irrigation was done. Working length (WL) was determined with an electronic apex locator and verified with a radiograph. In the control group, the determined WL was maintained, while in the experimental group, the WL was set till the apical foramen. Biomechanical preparation was done in both groups till F2 or F3 based on the initial apical file, followed by final irrigation and obturation based on the master apical file size. Patients were given a Visual Analog Scale to record pain sensations at 24, 48, and 72 h postoperative. After 72 h, patients were recalled for follow-up appointments, and blood was taken from the antecubital fossa again to evaluate inflammatory markers. The resultant findings for the reduction in inflammatory markers before and after RCT with or without foraminal enlargement were statistically analyzed using the Student's t-test. The pain was statistically examined with one-way "analysis of variance" and Tukey's post hoc test for inter-group comparison of pain. The level of significance was set at P < 0.05. The statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) Version 23 for Windows (SPSS Inc., Chicago, IL, USA). As pain in the control groups is zero before and after RCT, statistical analysis is not required as the overall pain score is zero. The P values of the CRP and ESR of the control group were 0.02 and 0.03, respectively, which indicates it is significant whereas the P values of the ESR and CRP of the experimental group were 0.0002 and 0.0008 which indicates it is highly significant. Results indicate that the experimental group is more effective compared to the control group in reducing inflammatory markers. Pain in the control group after RCT was zero at the end of 24, 48, and 72 h. In the experimental group, where RCT was done with apical foraminal enlargement, mild pain was present at the end of 24 h which gradually decreased at the end of 48 h and no pain was reported at the end of 72 h. Reduction in inflammatory markers was more effective in RCT with apical enlargement than without apical enlargement. RCT with apical enlargement caused mild pain in the patients immediately after treatment which gradually decreased over time.

Exploring the Interface: A Case Series on Endoperio Lesions.

Endoperiodontal lesion is a result of pathological/inflammatory connections between pulpal and periodontal tissues via open structures like apical foramina, dentinal tubules, and lateral accessory canals. This case series deals with endoperio lesions in which regenerative treatment is performed post-root canal treatment (RCT). Post 6 months, results suggested uneventful healing with gain in clinical attachment level.

Mental foramen and apical foramen: A dangerous anatomical proximity.

The study evaluated the spatial position of the mental foramen (MF) using 300 cone-beam computed tomography. The spatial position was analyzed with the horizontal location and relative location (distance between apical foramen and MF). The horizontal location was assessed through three positions (positions 1, 2, and 3). The relative location was determined with the x, y, and x coordinates of the root apex of mandibular premolars and the MF. Student's t-test and chi-square were performed. The most common horizontal location (52%) was position 2, which means between the premolars (p < 0.05). The relative location of the MF to the root apex of the second premolar was closer than the first premolar (p < 0.05). The distance between the root tip of the second premolar and the MF was 5.27 mm, with a minimum value of 1.87 mm. Clinicians should be aware of the possible neural results to the mental nerve of an endodontic infection and the extrusion of irrigation solutions.

A systematic review of the impact of apical patency on postoperative pain

Background and aims: Apical patency (AP), a technique in endodontics, involves keeping a small opening in the apical foramen during root canal instrumentation. However, there has been a debate about its effect on postoperative pain. To clarify this issue, this systematic review aimed to study the literature and determine the impact of AP on postoperative pain after endodontic procedures. Methods: A systematic search was conducted across multiple databases, including PubMed/MEDLINE, Scopus, Web of Science, and Cochrane Library, up to November 2, 2023. Studies on the relationship between AP and postoperative pain in endodontic treatments were included in this research. Relevant articles were independently screened, and data were extracted based on our study aims. Results: Eleven randomized controlled trial studies met the inclusion criteria. The findings indicated that among the included studies, six demonstrated no differences between the AP and non-AP (NAP) groups in terms of postoperative pain scores. In addition, four studies reported a decrease in operative pain in the AP group compared to the NAP group, and only one study showed that AP increases postoperative pain. However, conflicting evidence was observed in a subset of studies; there were no significant differences between the AP and NAP groups in terms of the postoperative pain scores. Conclusion: Compared with NAP, AP does not intensify the postoperative pain in teeth with vital and necrotic pulp.

Biomechanical impact of different isthmus positions in mandibular first molar root canals: a finite element analysis.

This study used image-based finite element analysis (FEA) to assess the biomechanical changes in mandibular first molars resulting from alterations in the position of the root canal isthmus. A healthy mandibular first molar, characterized by two intact root canals and a cavity-free surface, was selected as the subject. A three-dimensional model for the molar was established using scanned images of the patient's mandibular teeth. Subsequently, four distinct finite element models were created, each representing varied root canal morphologies: non-isthmus (Group A), isthmus located at the upper 1/3 of the root (Group B), middle 1/3 of the root (Group C), and lower 1/3 of the root (Group D). A static load of 200 N was applied along the tooth's longitudinal axis on the occlusal surface to simulate regular chewing forces. The biomechanical assessment was conducted regarding the mechanical stress profile within the root dentin. The equivalent stress (Von Mises stress) was used to assess the biomechanical features of mandibular teeth under mechanical loading. In Group A (without an isthmus), the maximum stress was 22.2MPa, while experimental groups with an isthmus exhibited higher stresses, reaching up to 29.4MPa. All maximum stresses were concentrated near the apical foramen. The presence of the isthmus modified the stress distribution in the dentin wall of the tooth canal. Notably, dentin stresses at specific locations demonstrated differences: at 8mm from the root tip, Group B: 13.6MPa vs. Group A: 11.4MPa; at 3mm from the root tip, Group C: 14.2MPa vs. Group A: 4.5MPa; at 1mm from the root tip, Group D: 25.1MPa vs. Group A: 10.3MPa. The maximum stress in the root canal dentin within the isthmus region was located either at the top or bottom of the isthmus. A root canal isthmus modifies the stress profile within the dentin. The maximum stress occurs near the apical foramen and significantly increases when the isthmus is located closer to the apical foramina.

Influence of Different Apical Foramen Morphologies on the Accuracy of Four Electronic Foramen Locators.

The aim of this study was to evaluate the accuracy of the Root ZX II (RZX), Raypex 6 (RAY), EPex Pro (EPEX), and CanalPro (CNP) electronic foramen locators (EFLs) in different foraminal morphologies (fully formed foramen, immature foramen with parallel walls, and immature foramen with divergent walls); this article also evaluated the influence of different penetration levels (0.0 mm and -1.0 mm). Thirty single-rooted human premolars were accessed and had their cervical/middle thirds prepared with SX ProTaper files. The apical foramens (AF) were standardized to 250 µm and the initial root canal length (RCL1) was measured under 16x magnification with aid of a digital caliper. Using the alginate model, electronic measurements (EM) were taken 1.0 mm up to AF (EM1/-1) and at AF (EM1/0), always using adjusted hand K-files. The root apexes were then cross-sectioned 3.0 mm from the foramen; then, new RCL (RCL2) and electronic measurements were performed (EM2/-1 and EM2/0.0). Finally, retropreparations were performed with instruments SX ProTaper files introduced 4.0 mm in the apicocervical direction. Then new RCL (RCL3) and electronic measurements (EM3/-1 and EM3/0) were performed. Values were tabulated and tested for normality using the Shapiro-Wilk test, which yielded nonparametric distributions of the data. Data were subjected to the Kruskal-Wallis and Dunn tests to estimate possible differences between devices as a function of foramen morphology and/or apical limit. The significance level was set at 5.0%. In general, the EFLs were accurate in determining the RCL. Statistically significant differences were observed between EPEX and RAY at 0.0, when measuring the divergent AF canals (p < 0.05). Regarding the different foramen morphologies in each EFL, RZX and EPEX showed no interference (p > 0.05), whereas RAY and CNP had lower accuracy levels at 0.0 with divergent AF (p < 0.05). The four devices evaluated are accurate to determine the RCL in the conditions tested. The apical limit of penetration did not have significant influence on their accuracy. Conversely, the presence of divergence in the AF walls negatively influenced de RAY and CNP precisions at the foraminal level.