Microrobotics in endodontics: A perspective.

Microorganisms are the primary aetiological factor of apical periodontitis. The goal of endodontic treatment is to prevent and eliminate the infection by removing the microorganisms. However, microbial biofilms and the complex root canal anatomy impair the disinfection process. Effective and precise endodontic therapy could potentially be achieved using advanced multifunctional technologies that have the ability to access hard-to-reach surfaces and perform simultaneous biofilm killing, removal, and detection of microorganisms. Advances in microrobotics are providing novel therapeutic and diagnostic opportunities with high precision and efficacy to address current biofilm-related challenges in biomedicine. Concurrently, multifunctional magnetic microrobots have been developed to overcome the disinfection challenges of current approaches to disrupt, kill, and retrieve biofilms with the goal of enhancing the efficacy and precision of endodontic therapy. This article reviews the recent advances of microrobotics in healthcare and particularly advances to overcome disinfection challenges in endodontics, and provides perspectives for future research in the field.

Periapical healing following endodontic microsurgery with collagen-based bone-filling material: A randomized controlled clinical trial.

AIM: To evaluate two- and three-dimensionally the effect of resorbable collagen-based bone-filling material on periapical healing of endodontic lesions with four-wall defects following endodontic microsurgery (EMS). METHODOLOGY: This parallel, randomized controlled superiority clinical trial involved 86 lesions with the strictly endodontic origin and four-wall defect morphology. EMS procedures were performed by calibrated postgraduate residents. Before flap closure, osteotomies were randomized to the control or treatment group. In the control group, the flap was repositioned with no material added. In the treatment group, a collagen-based bone-filling augmentation material was placed into the osteotomy. Clinical and radiographic examinations were completed after 12 months. Periapical healing was evaluated by blinded evaluators using periapical (PA) radiographs according to Molven's criteria and cone beam computed tomography (CBCT) scans according to PENN's 3D criteria. Cortical plate healing was scored according to the RAC/B index. The data were analysed using Fisher's exact test, Logistic regression models and Chi-squared test. The significance level was predetermined at p < .05. RESULTS: Sixty-six cases were evaluated at the 12-month follow-up, with 30 and 36 cases in the control and treatment groups, respectively. Only the asymptomatic cases (control = 26, treatment = 32) were included in the radiographic evaluation. Twenty-three cases (88.5%) in the control and 28 (87.5%) cases in the treatment group demonstrated complete healing on PA radiographs (p = 1.000). On CBCT, 10 (38.4%) and 21 (65.6%) cases had completely healed in the control and treatment groups, respectively (p = .095). The re-establishment of the buccal cortical plate was detected in 12 (46.2%) and 22 (68.8%) cases in the control and treatment groups, respectively (p = .243). CONCLUSION: Within the limitations of the present study, the use of collagen-based bone-filling material had no statistically significant effect on the periapical healing of endodontic lesions with four-wall defect following EMS at the 12-month follow-up when evaluated by PA radiographs or CBCT scans. However, the observed higher percentage of a re-established cortical plate in the treatment group could suggest a clinical benefit that is of interest after surgical endodontic treatment.

Mouse Mandibular Retromolar Taste Buds Associated With a Mucus Salivary Gland.

We have characterized a recently rediscovered chemosensory structure at the rear of the mandibular mucosa in the mouse oral cavity originally reported in the 1980s. This consists of unorganized taste buds, not contained within troughs, associated with the ducts of an underlying minor salivary gland. Using whole-mount preparations of transgenic mice expressing green fluorescent protein under the promoter of taste-signaling-specific genes, we determined that the structure contains taste bud clusters and salivary gland orifices at the rear of each mandible, distal to the last molar and anterior to the ascending ramus. Immunohistochemical analysis shows in the retromolar taste buds expression of the taste receptors Tas2R131 and T1R3 and taste cascade molecules TrpM5, PLCß2, and GNAT3, consistent with type II taste cells, and expression of GAD1, consistent with type III taste cells. Furthermore, the neuronal marker, calcitonin gene-related peptide, in retromolar mucosa tissue wrapping around TrpM5+ taste buds was observed. RT-PCR showed that retromolar taste buds express all 3 mouse tas1r genes, 28 of the 35 tas2r genes, and taste transduction signaling genes gnat3, plcb2, and trpm5, making the retromolar taste buds similar to other lingual and palate taste buds. Finally, histochemistry demonstrated that the mandibular retromolar secretory gland is a minor salivary gland of mucous type. The mandibular retromolar taste structure may thus play a role in taste sensation and represent a potential novel pharmacological target for taste disorders.

The shaping ability of WaveOne Gold, TRUShape and XP-endo Shaper systems in oval-shaped distal canals of mandibular molars: A microcomputed tomographic analysis.

AIM: To compare the shaping ability of a heat-treated centric reciprocating file system (WaveOne Gold), a heat-treated eccentric rotary multifile system (TRUShape 3D Conforming Files), and a heat-treated expandable one-file rotary system (XP-endo Shaper) extending its activation time, in preparing oval-shaped root canals in extracted mandibular molars by means of microcomputed tomography (micro-CT) analysis. METHODOLOGY: Thirty moderately curved oval-shaped distal roots of mandibular molars were selected. The normality of canal length, curvature angle, volume, surface area, structure model index, and aspect ratio were confirmed. The samples were randomly divided into three groups (n = 10). Micro-CT scans were taken before and after canals were instrumented using WaveOne Gold (size 35, .06 taper), or TRUShape (size 30, .06v taper), both following the manufacturer's instructions, or XP-endo Shaper following a new protocol with extended activation time. The mechanical preparation time for each sample was recorded. Pre- and postoperative images were analysed for the percentage of unprepared canal areas and the percentage of removed dentine. Data were compared between groups using the statistical analyses one-way ANOVA and Tukey tests (p < .05). RESULTS: The percentage of unprepared canal areas was significantly higher with WaveOne Gold (% 11.5 ± 4.0) and TRUShape (% 12.4 ± 5.8) compared with XP-endo Shaper (% 5.2 ± 2.6) (p < .05). XP-endo Shaper removed significantly more dentine (3.3 ± 1.5 mm3 ) than WaveOne Gold (1.8 ± 0.8 mm3 ) and TRUShape (1.9 ± 0.8 mm3 ) (p < .05). No significant differences were seen for mechanical preparation time between WaveOne Gold (79 ± 31 s), TRUShape (104 ± 41 s) and XP-endo Shaper (71 ± 23 s) (p > .05). CONCLUSIONS: The comparison of three recognized root canal filing systems has shown that with similar preparation times, the XP-endo Shaper removed more dentine (mm3 ) leaving less unprepared canal wall area (%) than WaveOne Gold and TRUShape when preparing oval-shaped root canals of extracted mandibular molars.

Comparing the incidence of postoperative pain after root canal filling with warm vertical obturation with resin-based sealer and sealer-based obturation with calcium silicate-based sealer: a prospective clinical trial.

OBJECTIVE: This prospective clinical study compares postoperative pain after single-visit, non-surgical root canal treatment of teeth with irreversible pulpitis using two different root canal filling techniques. MATERIAL AND METHODS: All cases were treated by endodontic residents with a standardized protocol (minimum apical size 35) and filled with one of the two techniques: warm vertical compaction technique (WVT) with gutta percha and epoxy resin-based sealer (AH Plus Jet Root Canal Sealer, Dentsply Maillefer, York, PA, USA) or sealer-based filling technique (SBT) with single cone gutta percha and calcium silicate-based sealer (EndoSequence BC Sealer, Brasseler, Savannah, GA, USA). Surveys were given to participating patients to record pain intensity on a numeric rating scale (NRS, 0-10) at 4, 24, and 48 h postoperatively. Statistical significance was set at 0.05 level. RESULTS: One hundred ninety-four surveys were distributed over eighteen months. Ninety-two patients returned the survey (41 WVT and 51 SBT), of which 38% were asymptomatic irreversible pulpitis cases. The NRS values reduced over time for both techniques. No statistical difference was found between the two groups at the three time points assessed (p > 0.05). Postoperative pain was related to age, gender, presence of preoperative pain, and sealer extrusion (p < 0.05), however not related to preoperative periapical symptoms (percussion/palpation), dental arch, root type, and experience of the provider (p > 0.05). CONCLUSIONS: The intensity of postoperative pain for the two obturation techniques was equivalent at evaluated time points. CLINICAL RELEVANCE: The obturation technique does not influence postoperative pain. After endodontic treatment of symptomatic irreversible pulpitis teeth, the pain subsides in 48 h regardless of the technique. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT04462731.

Comparison of canal transportation and centering ability of manual K-files and reciprocating files in glide path preparation: a micro-computed tomography study of constricted canals.

BACKGROUND: Optimum Glide Path (OGP) is a new reciprocating motion aiming to perform efficient glide path preparation in constricted canals. The aim of this study was to investigate and compare manual and OGP movement in terms of canal transportation and centering ability in glide path preparation of constricted canals. METHODS: Thirty constricted mesial root canals of mandibular molars, with initial apical size no larger than ISO#8, were selected and negotiated with #6-#8 K-files under the microscope. Canals were randomly divided into two experimental groups: Group 1 (MAN, n = 15): Glide path was established by using #10-#15 stainless steel K-files manually; Group 2 (OGP, n = 15): #10-#15 Mechanical Glide Path super-files were used with OGP motion (OGP 90°, 300 rpm). Each instrument was used to prepare only 2 canals (as in one mesial root). Canals were scanned before and after glide path preparation with micro-computed tomography (micro-CT) to evaluate root canal transportation and centering ratio at 1, 3 and 5 mm levels from the root apex. File distortions and separations were recorded. Paired t-test was used to statistically evaluate the data (P < .05). RESULTS: Group 2 showed a significantly lower transportation value than group 1 at 1-mm and 3-mm levels (P < .05), however the difference at 5-mm level was not significant. There was no significant difference regarding the centering ratio between the groups. Six #10 K-files were severely distorted in group 1, while no file separation or distortion was found in group 2. CONCLUSIONS: OGP motion performed significantly less canal transportation (apical 3 mm) and file distortion during glide path establishment in constricted canals comparing to manual motion, while the centering ability between the two was similar. CLINICAL RELEVANCE: OGP reciprocating motion provides a safer and efficient clinical approach compared to traditional manual motion in glide path establishment with small files in constricted canals.

Dentists' clinical decision-making about teeth with apical periodontitis using a variable-controlled survey model in South Korea.

BACKGROUND: This study, by using a variable-controlled survey model, sought to compare clinical decisions made by dentists with different clinical backgrounds in South Korea regarding teeth with apical periodontitis and to identify factors that influenced decision-making. METHODS: A questionnaire with 36 questions about identical patient information, clinical signs, and symptoms was filled out by participants. Each question referred to a radiograph that had been manipulated using computer software in order to control tooth-related factors. Participants were instructed to record their demographic information and choose the ideal treatment option related to each radiograph. Simple and multivariable logistic regression analyses (p < .05) were used to investigate factors related to the decision to extract the tooth. We divided factors into dentist-related factors (gender, years of experience, and professional registration) and tooth-related factors (tooth position, coronal status, root canal filling status, and size of the periapical radiolucency). Dentists were categorized into three groups, based on professional registration: general dental practitioners (GDPs), endodontists, and other specialists. Simple logistic regression analysis (p < .05) was used to evaluate the tooth-related factors influencing extraction, depending on the dentists' specialty. RESULTS: Participants mostly preferred saving the teeth over extraction. This preference was highest among the endodontists, followed by other specialists and GDPs. Extractions were significantly preferred for molars, teeth with previous root canal fillings, and those with apical lesions greater than 5 mm. CONCLUSIONS: This study suggests that dentists' decision-making regarding teeth with apical periodontitis was associated with their work experience and specialty and influenced by tooth position, root canal filling status, and size of the apical lesion. CLINICAL RELEVANCE: This survey revealed that clinical decision-making related to teeth with apical periodontitis was affected by dentists' specialty and work experience and by tooth-related factors, such as tooth position, root canal filling status, and size of the apical lesion.

Canal transportation and centering ratio after preparation in severely curved canals: analysis by micro-computed tomography and double-digital radiography.

OBJECTIVES: This study compared canal transportation and centering ratio produced after instrumentation with a single heat-treated reciprocating system, WaveOne Gold (WOG; Dentsply Sirona, Tulsa, OK, USA) and a single heat-treated rotary instrument, XP-endo Shaper (XPS; FKG, La Chaux-de-Fonds, Switzerland), using micro-computed tomographic (micro-CT) imaging, and evaluated the ability of double-digital radiography (DDR) to detect canal transportation. MATERIALS AND METHODS: Mesial root canals of mandibular molars with severe curvature (25-70°) were randomly assigned to either WOG or XPS groups for preparation. Centering ratio was measured by micro-CT imaging, while canal transportation was measured by micro-CT and DDR methods at 3, 5, and 7 mm from the apex. Data were statistically compared between groups using the t test (α = 5%). RESULTS: The micro-CT method showed that XPS's shaping ability regarding the centering ability (P = 0.030) and canal transportation (P = 0.028) was significantly better than WOG only at the 7-mm level. The DDR technique detected no difference in canal transportation between groups at any level (P > 0.05); however, a significant difference between evaluation methods was detected at the 5-mm level in the WOG group (P = 0.023). CONCLUSIONS: Micro-CT technique revealed a significantly better centering ability and less canal transportation with XPS compared to WOG. The DDR technique was not capable of detecting the significant difference between the tested groups. CLINICAL RELEVANCE: Root canal curvatures may lead to procedural errors during endodontic treatment. Thus, differences on the shaping ability of single heat-treated reciprocating and rotary systems should be known.

Effect of thermomechanical aging on bond strength and interface morphology of glass fiber and zirconia posts bonded with a self-etch adhesive and a self-adhesive resin cement to natural teeth.

STATEMENT OF PROBLEM: Information regarding the effect of thermomechanical aging (TMA) on the bond strength of luting cements to root canal dentin and endodontic posts is limited. PURPOSE: The purpose of this study was to investigate the effect of TMA on the bond strength of fiber and zirconia posts bonded to root canal dentin with 2 different resin cements with microtensile and scanning electron microscopic evaluation. MATERIAL AND METHODS: Eighty extracted single-rooted human premolars were endodontically treated and restored with either a glass fiber post (FP) or a zirconia post (ZP) with 2 commercially available resin luting cements. The teeth were divided into 2 main groups. In the first group, posts (n=40) were bonded with a self-etch adhesive cement (SEAC). In the second group (n=40), posts were bonded using a self-adhesive cement (SAC). During the first aging phase, all specimens in each group were stored in distilled water for 30 days at 37°C. During the second phase, half of the specimens in each group were subjected to the TMA. The test groups were as follows: FP/SEAC, FP/SEAC+TMA, ZP/SEAC, ZP/SEAC+TMA, FP/SAC, FP/SAC+TMA, ZP/SAC, and ZP/SAC+TMA. The bond strength was measured with a microtensile test. Data were analyzed by 3-way analysis of variance and the Tukey honest significant different test (α=.05). RESULTS: FP/SEAC at 30 days was higher than in the other groups. However, bond strength values were significantly reduced in this group after TMA (P<.001). CONCLUSIONS: Bond strength values and physical properties of SEAC with higher filler content were more affected by the TMA than those of SALC. According to scanning electron microscopic observation, TMA also affected the micromorphologic interface between the posts and the resin cements as well as between the resin cements and the root canal dentin.

Systemic Corticosteroid Uses in Endodontics-Part 1: Managing Postoperative Pain.

INTRODUCTION: This study aimed to systematically search and review all available literature regarding systemic (oral or locally injected) corticosteroids in endodontics to assess their effect on postoperative pain. METHODS: A search was conducted using PubMed, Cochrane Library, Embase, Scopus, Dentistry & Oral Science, and ProQuest. Randomized controlled trials enrolling participants undergoing endodontic treatment and assessing the presence of pain and pain scores at 6, 12, and 24 hours postoperatively were included. We synthesize the effect measures using risk ratios (RRs), standardized mean differences (SMDs), and their corresponding 95% confidence intervals (CIs). Meta-analysis was performed using the random-effects inverse variance method. The level of significance was set at P < .05. The certainty of the evidence was evaluated using Grading of Recommendations, Assessment, Development and Evaluation approach. RESULTS: A total of 2303 participants from 29 trials were included. Patients who received corticosteroids were significantly less likely to report pain at 6 hours (RR = 2.5; 95% CI, 1.74-3.61; P < .00001), 12 hours (RR = 2.10; 95% CI, 1.53-2.90; P < .00001), and 24 hours (RR = 1.77; 95% CI, 1.38-2.28; P < .00001) postoperatively. Furthermore, they reported lower pain intensity at 6 hours (SMD = - 0.82; 95% CI, -1.17 to -0.48; P < .00001), 12 hours (SMD = - 0.63; 95% CI, -0.75 to -0.51; P < .00001), and 24 hours (SMD = - 0.68; 95% CI, -0.90 to -0.46; P < .00001) postoperatively. CONCLUSIONS: Moderate certainty evidence indicates that the use of systemic corticosteroids likely results in a moderate to large reduction in postoperative endodontic pain.

Systemic Corticosteroid Uses in Endodontics-Part 2: Enhancing the Success of Local Anesthesia.

INTRODUCTION: Chronic inflammation in irreversible pulpitis leads to heightened sensitivity of nociceptive receptors, resulting in persistent hyperalgesia. This poses significant challenges in achieving effective anesthesia for patients with irreversible pulpitis. Various anesthetic techniques and pharmacological approaches have been employed to enhance the success of local anesthesia. Recently, the preemptive use of anti-inflammatory agents, specifically corticosteroids, has gained attention and shown promising results in randomized controlled trials. This systemic review and meta-analysis aimed to evaluate the impact of systemically administered corticosteroids on enhancing anesthetic success in patients undergoing endodontic treatment. METHODS: A comprehensive search was conducted across multiple databases including PubMed, Cochrane Library, Embase, Scopus, Dentistry & Oral Science, and ProQuest. Additionally, the references of primary studies and related systematic reviews were manually searched for additional relevant publications. The primary outcome assessed was the success of anesthesia, and the effect measure was risk ratio using the random-effects inverse variance method. Statistical significance was set at P < .05. The certainty of the evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluation approach. RESULTS: Twelve studies involving 917 participants were analyzed to determine the frequency of successful anesthesia. The corticosteroid group demonstrated a significantly higher number of patients achieving successful anesthesia (risk ratio = 1.66; 95% confidence interval, 1.34-2.06;P < .00001). However, heterogeneity within the pooled data analysis was observed (I2 = 57%, P = .007). CONCLUSIONS: Moderate certainty evidence indicates that preemptive use of systemic corticosteroids enhances the success of local anesthesia, specifically inferior alveolar nerve block, in cases of irreversible pulpitis.

Increased Purinergic Signaling in Human Dental Pulps With Inflammatory Pain is Sex-Dependent.

An enhanced understanding of neurotransmitter systems contributing to pain transmission aids in drug development, while the identification of biological variables like age and sex helps in the development of personalized pain management and effective clinical trial design. This study identified enhanced expression of purinergic signaling components specifically in painful inflammation, with levels increased more in women as compared to men. Inflammatory dental pain is common and potentially debilitating; as inflammation of the dental pulp can occur with or without pain, it provides a powerful model to examine distinct pain pathways in humans. In control tissues, P2X3 and P2X2 receptors colocalized with PGP9.5-positive nerves. Expression of the ecto-nucleotidase NTPDase1 (CD39) increased with exposure to extracellular adenosine triphosphate (ATP), implying CD39 acted as a marker for sustained elevation of extracellular ATP. Both immunohistochemistry and immunoblots showed P2X2, P2X3, and CD39 increased in symptomatic pulpitis, suggesting receptors and the ATP agonist were elevated in patients with increased pain. The increased expression of P2X3 and CD39 was more frequently observed in women than men. In summary, this study identifies CD39 as a marker for chronic elevation of extracellular ATP in fixed human tissue. It supports a role for increased purinergic signaling in humans with inflammatory dental pain and suggests the contribution of purines shows sexual dimorphism. This highlights the potential for P2X antagonists to treat pain in humans and stresses the need to consider sex in clinical trials that target pain and purinergic pathways. PERSPECTIVE: This article demonstrates an elevation of ATP-marker CD39 and of ATP receptors P2X2 and P2X3 with inflammatory pain and suggests the rise is greater in women. This highlights the potential for P2X antagonists to treat pain and stresses the consideration of sexual dimorphism in studies of purines and pain.

Nanozyme-Shelled Microcapsules for Targeting Biofilm Infections in Confined Spaces.

Bacterial infections in irregular and branched confinements pose significant therapeutic challenges. Despite their high antimicrobial efficacy, enzyme-mimicking nanoparticles (nanozymes) face difficulties in achieving localized catalysis at distant infection sites within confined spaces. Incorporating nanozymes into microrobots enables the delivery of catalytic agents to hard-to-reach areas, but poor nanoparticle dispersibility and distribution during fabrication hinder their catalytic performance. To address these challenges, a nanozyme-shelled microrobotic platform is introduced using magnetic microcapsules with collective and adaptive mobility for automated navigation and localized catalysis within complex confinements. Using double emulsions produced from microfluidics as templates, iron oxide and silica nanoparticles are assembled into 100-µm microcapsules, which self-organize into multi-unit, millimeter-size assemblies under rotating magnetic fields. These microcapsules exhibit high peroxidase-like activity, efficiently catalyzing hydrogen peroxide to generate reactive oxygen species (ROS). Notably, microcapsule assemblies display remarkable collective navigation within arched and branched confinements, reaching the targeted apical regions of the tooth canal with high accuracy. Furthermore, these nanozyme-shelled microrobots perform rapid catalysis in situ and effectively kill biofilms on contact via ROS generation, enabling localized antibiofilm action. This study demonstrates a facile method of integrating nanozymes onto a versatile microrobotic platform to address current needs for targeted therapeutic catalysis in complex and confined microenvironments.

Endodontic treatments on permanent teeth in pediatric patients aged 6-12 years old.

Backgroud/purpose: The prevalence of carious lesions and traumatic injury in individuals between ages 6 and 12 is high. This study aimed to characterize pediatric patients aged 6-12 treated in the endodontic clinic and investigate the prevalence and patterns of their provided endodontic treatments. Materials and methods: Clinical and radiographic records of patients (ages 6-12) referred to the postgraduate Endodontics clinic from June 2017 to June 2020 were reviewed. Demographics, pre-and post-operative conditions, type of endodontic treatment, and behavioral management were collected. Results: A total of 6350 teeth from 6089 patients were treated in this period, and 425 teeth (6.7%) from 405 patients were included. Ages 9-11 were the most commonly treated age group. Significantly more lower molars (41.9%) and upper anterior teeth (36.7%) were treated (P < 0.05). The majority of teeth were diagnosed with pulp necrosis (39.5%), and the most common periapical diagnosis was normal apical tissues (39.8%), then symptomatic apical periodontitis (38.8%). The most common etiological factor was caries (63.5%). Two hundred six teeth (48.5%) were treated with root canal therapy, 161 teeth (37.9%) with vital pulp therapy, 46 teeth (10.8%) with apexification or regenerative endodontic procedure, 12 teeth (2.8%) with non-surgical retreatment. A statistically high number of patients (87.8%) tolerated the endodontic procedures without any sedation (P < 0.0001). Conclusion: Pediatric patients aged 6-12 compose around 7% of the population treated at the postgraduate Endodontics clinic, reflecting the high demand for endodontic treatment in a pediatric mixed dentition population.

XP-endo Finisher effectively reduces hard-tissue debris accumulated in root canals with isthmus after preparation with a reciprocating file system.

This study compared the accumulated hard-tissue debris (AHTD) after preparation with WaveOne Gold (WOG) to XP-endo Shaper (XPS), without and with a supplementary step using XP-endo Finisher (XPF) using clinically applicable irrigation. Twenty-four mesial roots with two canals and single foramen were micro-CT-scanned and matched. Scans were also taken after preparation with WOG or XPS, and after XPF. Irrigation with 2.5% NaOCl (total: 17 ml per canal) and 17% EDTA (2.5 ml per canal) was performed using a 30ga Max-I-Probe needle placed up to the working length. Morphological parameters were calculated and compared within and among groups. XPF significantly reduced unprepared area within XPS and WOG groups, and AHTD within WOG (p < 0.05). There were no significant differences between WOG and XPS after preparation and after XPF (p > 0.05). In conclusion, WOG and XPS produced a similar volume of AHTD, but the supplementary step with XPF decreased the AHTD in the WOG group.

The Influence of Cone Beam Computed Tomography-Derived 3D-Printed Models on Endodontic Microsurgical Treatment Planning and Confidence of the Operator.

INTRODUCTION: Currently, there are no studies evaluating the impact of 3-dimensional (3D) printed models on endodontic surgical treatment planning. The aims of this study were: 1) to determine if 3D models could influence treatment planning; and 2) to assess the effect of 3D supported planning on operator confidence. MATERIALS: Endodontic practitioners (n = 25) were asked to analyze a preselected cone beam computed tomography (CBCT) scan of an endodontic surgical case and answer a questionnaire that elucidated their surgical approach. After 30 days, the same participants were asked to analyze the same CBCT scan. Additionally, participants were asked to study and to perform a mock osteotomy on a 3D printed model. The participants responded to the same questionnaire along with a new set of questions. Responses were statistically analyzed using chi square test followed by either logistic or ordered regression analysis. Adjustment for multiple comparison analysis was done using a Bonferroni correction. Statistical significance was set at ≤0.005. RESULTS: The availability of both the 3D printed model and the CBCT scan resulted in statistically significant differences in the participants' responses to their ability to detect bone landmarks, predict the location of osteotomy, and to determine the following: size of osteotomy, angle of instrumentation, involvement of critical structures in flap reflection and involvement of vital structures during curettage. In addition, the participants' confidence in performing surgery was found to be significantly higher. CONCLUSIONS: The availability of 3D printed models did not alter the participants' surgical approach but it significantly improved their confidence for endodontic microsurgery.

Surgical management of lateral lesions with intentional replantation in single-rooted mandibular first premolars with radicular groove: 2 case reports.

BACKGROUND: The authors' aim was to describe 2 endodontically treated mandibular first premolars with apical and mesiolingual radiolucencies on radiographs with different approaches that were resolved with intentional replantation. CASE DESCRIPTION: In case 1, a 58-year-old man reported biting sensitivity on endodontically treated mandibular first premolar with good quality restorations. A periapical radiograph (PAX) and cone-beam computed tomography (CBCT) image revealed 2 low-density areas located at the apical and mesiolingual aspects of the root. A radicular groove accessory canal was noted on the mesial root surface during intentional replantation. The patient has been asymptomatic. At a 3-year follow-up, complete healing was observed on PAX and CBCT images. In case 2, a 40-year-old woman reported pinching pain of her mandibular right quadrant that returned a few months after initial root canal treatment. Radiographs revealed periapical radiolucency at the apexes of the mandibular first premolar with a missed lingual canal. Nonsurgical retreatment was performed in 2 visits with calcium hydroxide dressing. Two months later, endodontic microsurgery was performed owing to ongoing symptoms. In addition, CBCT images showed extensive bone loss on the mesiolingual aspect of the root. Intentional replantation was performed 2 weeks later because she had intolerable pain. A radicular groove accessory canal was observed on the mesial root surface during the procedure. The patient reported substantial relief of pain. The radiolucencies healed by the 25-month follow-up as observed on PAX and CBCT images. PRACTICAL IMPLICATIONS: Intentional replantation is recommended in mandibular first premolars with a mesiolingual lesion that cannot be accessed easily with endodontic microsurgery and after conservative retreatment has been performed.

Possible Causes for Failure of Endodontic Surgery - A Retrospective Series of 20 Resurgery Cases.

OBJECTIVE: This study aimed to evaluate unsuccessful endodontic surgery cases for possible causes for treatment failure and evaluate if a nonsurgical retreatment (NSRTX) approach could have been a better alternative to resurgery. METHODS: Analyses of clinical and cone-beam computed tomography (CBCT) images, periapical radiographs, and chart documentation determined study parameters. Preoperative factors were age, sex, tooth type, signs and/or symptoms, presence of periapical radiolucency, previous root canal treatment, timeline since previous endodontic surgery, presence of posts, cores, and restorations. The intra-operative factors were microsurgical classification, previous techniques, and current techniques utilized. Postoperative factors were signs and/or symptoms, time to follow-up, and healing status. The accessibility of the root canal system and the quality of the existing root filling were used to evaluate NSRTX as an alternative to resurgery. RESULTS: A total of 1073 surgical cases from 2011-2019 were reviewed. In 14 patients, 20 cases matched the inclusion criteria and allowed for data extraction. The mean time since the previous surgery was 2.9+-2.1 years, with a mean follow-up of 9.1+-5.8 months after the resurgery. Possible reasons for failure identified were: insufficient root-end filling (leaking, off-axis preparation, lack of depth, overfill) n=12/20, 60.0%; missed anatomy (main and lateral canals, isthmus) n=9/20, 45.0%; incomplete resection n=6/20, 30.0%. In 18/20 cases (90.0%), resurgery appeared to be indicated for 2/20 cases (10.0%). Therefore, NSRTX may have been a potential alternative. CONCLUSION: Further evidence for possible causes of failure of endodontic surgery was provided, which were primarily iatrogenic. The evaluation of CBCT and high magnification intra-operative images proved beneficial for identifying critical issues for all investigated cases.

Effect of sodium hypochlorite on conventional and heat-treated nickel-titanium endodontic rotary instruments - An in vitro study.

BACKGROUND/PURPOSE: Sodium hypochlorite (NaOCl) is a highly alkaline solution which exhibits antimicrobial properties. However, it causes corrosion to endodontic rotary files. This study investigated the effect of NaOCl on the metal surface of five different unused endodontic rotary files in vitro. MATERIALS AND METHODS: Two non-heat-treated nickel-titanium (NiTi) files, ProTaper, BioRace, and three heat-treated NiTi files, VortexBlue, TRUShape, and EdgeFile X7 files, were immersed in 4% NaOCl for 5, 10, and 20 min, and 1, 6 and 24 h. The corrosion susceptibility was evaluated by visual inspection and scanning electron microscopy (SEM). RESULTS: In the TRUShape group, the black particulate matter was mostly formed at the file's curvature and shaft. A large amount of precipitate accumulated in the EdgeFile group. The extent and prevalence of surface defects were found to be consistently higher in EdgeFile X7 instruments than in any other instruments. EdgeFile X7 and TRUShape files exhibited a greater corrosive tendency to NaOCl than BioRace, ProTaper, and VortexBlue not only under visual inspection, but also under SEM analysis after prolonged immersion (1, 6, 24 h) in 4% NaOCl. However, shorter immersion periods (5, 10, 20 min) showed little surface corrosion across all experimental groups. CONCLUSION: Within the limitations of this study, EdgeFile X7 and TRUShape files exhibit greater corrosive tendencies to NaOCl in vitro than BioRace, ProTaper, and VortexBlue files after prolonged immersion in 4% NaOCl. However, shorter immersion periods, which more closely approximate clinical conditions during single root canal therapy, may not show surface corrosion across all experimental groups.

Micro-Computed Tomographic Analysis of the Shaping Ability of XP-Endo Shaper in Oval-Shaped Distal Root Canals of Mandibular Molars.

OBJECTIVE: To compare the shaping ability of the XP-endo Shaper (XPS) system to the ProTaper Next (PTN) system in oval-shaped distal root canals. METHODS: From 12 mandibular molars, distal roots with moderately curved single oval canals were randomly assorted to be instrumented with XPS (experimental group) or PTN (control group) and then scanned using micro-computed tomography [Scan 1]. The root canals of the XPS samples were prepared following the manufacturer's instructions using 15 insertions (XPS15) and rescanned [Scan 2]. An additional 10 insertions to the working length were applied, totalling 25 insertions (XPS25), and the roots were rescanned again [Scan 3]. PTN samples were prepared up to the X3 instrument (PTNX3) and rescanned [Scan 2]. The dentine removed and the unprepared areas were assessed. Data were analysed using a t-test with significance at α=0.05. RESULTS: XPS25 was associated with a significantly greater dentine removal than XPS15 over the entire root canal length and in all three-thirds of the root canal (P<0.05). XPS25 significantly removed more dentine than PTNX3 in only the coronal third (P<0.05). XPS25 was also associated with a significantly smaller percentage of unprepared areas than XPS15 overall and in the coronal third (P<0.05). PTNX3 was associated with a significantly larger percentage of unprepared areas than XPS15 and XPS25 overall and in the coronal and middle thirds (P<0.05). CONCLUSION: Ten additional movements with XPS significantly improved instrumentation capacity, reducing the percentage of untouched surface areas but also removing more dentine.