Exceptional bone remodeling over composite restoration in the management of external root resorption: A case report.

A 65-year-old Caucasian male was referred to an endodontic specialist practice in a private clinic in December 2019 for the management of an asymptomatic, radiolucent lesion located at the cervical level of the distal root of his right lower first molar, noticed during a routine periapical radiograph. After an accurate evaluation with cone-beam computed tomography (CBCT), the subgingival lesion was diagnosed as a supracrestal external cervical resorption (ECR), with a circumferential spread ⩽90°, confined to dentine without pulp involvement. The lesion was treated with the following sequence: (1) a full flap accessed the ECR, (2) the granulomatous tissue was removed from the root area, (3) the cavity was refreshed and filled with a well-refined and polished resin composite, (4) the flap was sutured at the cemento-enamel junction. A mandibular CBCT scan was performed before treatment, right after treatment, and 3 years postoperatively. Compared to the 3-year posttreatment CBCT scan, the immediate posttreatment one, revealed the absence of bone loss and an unexpected coronal bone remodeling with new bone formation over the treated lesion.

Antimicrobial Silk Fibroin Methacrylated Scaffolds for Regenerative Endodontics.

INTRODUCTION: Recognizing the necessity of novel disinfection strategies for improved bacterial control to ultimately favor tissue regeneration, this study developed and characterized antibiotics-laden silk fibroin methacrylated (SilkMA) scaffolds for regenerative endodontics. METHODS: SilkMA-based solutions (10% w/v) containing clindamycin (CLI) or tinidazole (TIN) (0 - control; 5, 10, or 15% w/w) or the combination of both drugs (BiMix CLI/TIN 10%) were electrospun and photocrosslinked. Morphology and composition were assessed using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Additionally, swelling and degradation profiles were also determined. Cytotoxicity was evaluated in stem cells from apical papilla (SCAPs). Antibacterial efficacy was tested using direct and indirect contact assays against Aggregatibacter actinomycetemcomitans/Aa, Actinomyces naeslundii/An, Enterococcus faecalis/Ef, and Fusobacterium nucleatum/Fn. E. faecalis biofilm inhibition on dentin discs was specifically evaluated for BiMix-laden scaffolds. Data were statistically analyzed with a significance level of 5%. RESULTS: SEM revealed that all scaffolds had similar characteristics, including fiber morphology and bead absence. FTIR showed the incorporation of CLI and TIN into the fibers and in BiMix scaffolds. Antibiotic-laden scaffolds exhibited lower swelling capacity than the control and were degraded entirely after 45 days. Scaffolds laden with CLI, TIN, or BiMix throughout all time points did not reduce SCAPs' viability. CLI-laden scaffolds inhibited the growth of Aa, An, and Ef, while TIN-laden scaffolds inhibited Fn growth. BiMix-laden scaffolds significantly inhibited Aa, An, Ef, and Fn in direct contact, and their aliquots inhibited An and Fn through indirect contact, with additional biofilm inhibition against Ef. CONCLUSIONS: BiMix-laden SilkMA scaffolds are cytocompatible and exhibit antimicrobial effects against endodontic pathogens, indicating their therapeutic potential as a drug delivery system for regenerative endodontics.

Patient-related predictors of post-operative pain following root canal treatment: A structural model analysis.

AIM: The pathways to post-operative pain are complex and encompass factors that extend beyond the treatment protocol employed. This study aimed to identify patient-related predictors of post-operative pain following root canal treatment. METHODOLOGY: A total of 154 patients received a single-visit root canal treatment for asymptomatic necrotic mandibular molars. Before treatment, dental anxiety, dental fear and sense of coherence (SOC) were measured as predictors for each patient using validated questionnaires. Other measured predictors included gender, age, previous negative experiences at the dental offices and prior root canal treatment. Post-operative pain was assessed using the Numeric Rating Scale at multiple time-points over 30 days. Structural equation analysis was employed to evaluate the direct and indirect effects of patient-related predictors on a theoretical model of post-operative pain. The irrigant solution was also included in the model, as it was the only aspect that varied in the treatment protocol (sodium hypochlorite 2.5% and 8.25%). RESULTS: Dental anxiety (coefficient 0.028; p < .01), dental fear (coefficient 0.007; p = .02) and irrigant solution (coefficient 0.004; p = .03) exerted a direct effect on post-operative pain. SOC exerted an indirect effect on post-operative (coefficient 0.006; p = .01) through dental anxiety and dental fear. Moreover, previous negative experiences (coefficient 0.048; p = .04) exerted an indirect effect on post-operative pain through dental anxiety. CONCLUSIONS: Dental anxiety, dental fear, previous negative experiences and SOC are patient-related predictors of post-operative pain following root canal treatment. These factors should be taken into consideration in clinical practice, as patients with these characteristics may be at an increased risk of experiencing post-operative pain.

Minimally invasive guided endodontic microsurgery with Zekrya bur: A 48-month follow-up case report.

Endodontic microsurgery guided by navigation systems represents a precise and minimally invasive approach for retreatment of apical periodontitis following failed conventional endodontic therapy. Accurate localization and minimal access to the root apex are paramount for successful outcomes and preservation of anatomical structures. Workflow considerations, such as three-dimensional (3D) virtual planning and endodontic guidance represent new crucial aspects for addressing complex cases. This clinical case report presents the successful reintervention of a complex case using a Zekrya bur, operative microscopy, cone beam computed tomography and biocompatible materials. After a 48-month follow-up, complete healing of the treated area was observed. This minimally invasive technique, employing a simple instrument widely available globally, underscores the potential for efficient and predictable outcomes in complex endodontic microsurgical retreatment.

Anti-inflammatory potential of casein enzymatic hydrolysate/gelatin methacryloyl scaffolds for vital pulp therapy.

OBJECTIVES: To synthesize casein enzymatic hydrolysate (CEH)-laden gelatin methacryloyl (GelMA) fibrous scaffolds and evaluate the cytocompatibility and anti-inflammatory effects on dental pulp stem cells (DPSCs). MATERIALS AND METHODS: GelMA fibrous scaffolds with 10%, 20%, and 30% CEH (w/w) and without CEH (control) were obtained via electrospinning. Chemo-morphological, degradation, and mechanical analyses were conducted to evaluate the morphology and composition of the fibers, mass loss, and mechanical properties, respectively. Adhesion/spreading and viability of DPSCs seeded on the scaffolds were also assessed. The anti-inflammatory potential on DPSCs was tested after the chronic challenge of cells with lipopolysaccharides (LPS), followed by treatment with extracts obtained after immersing the scaffolds in α-MEM. The synthesis of the pro-inflammatory cytokines IL-6, IL-1α, and TNF-α was measured by ELISA. Data were analyzed by ANOVA/post-hoc tests (α = 5%). RESULTS: CEH-laden electrospun fibers had a larger diameter than pure GelMA (p ≤ 0.036). GelMA scaffolds laden with 20% and 30% CEH had a greater mass loss. Tensile strength was reduced for the 10% CEH fibers (p = 0.0052), whereas no difference was observed for the 20% and 30% fibers (p ≥ 0.6736) compared to the control. Young's modulus decreased with CEH (p < 0.0001). Elongation at break increased for the 20% and 30% CEH scaffolds (p ≤ 0.0038). Over time, DPSCs viability increased across all groups, indicating cytocompatibility, with CEH-laden scaffolds exhibiting greater cell viability after seven days (p ≤ 0.0166). Also, 10% CEH-GelMA scaffolds decreased the IL-6, IL-1α, and TNF-α synthesis (p ≤ 0.035). CONCLUSION: CEH-laden GelMA scaffolds facilitated both adhesion and proliferation of DPSCs, and 10% CEH provided anti-inflammatory potential after chronic LPS challenge. CLINICAL RELEVANCE: CEH incorporated in GelMA fibrous scaffolds demonstrated the potential to be used as a cytocompatible and anti-inflammatory biomaterial for vital pulp therapy.

Dissimilar Sequelae Caused by Single Dental Trauma: A Case Report with Long-Term Follow-up.

Immediate care and accurate diagnosis are essential for treating dental trauma. This report presents a 7-year-old boy suffered a bicycle accident with direct trauma to the mouth and extrusive luxation of teeth #11 and #21. The emergency treatment was performed within the first hour. Clinical examinations showed that both teeth exhibited 3 mm extrusion from comparing their incisal edges to their neighboring teeth, had edematous gingiva, showed grade 3 mobility and were painful to percussion. Radiographic exams showed incomplete root formation, widened periodontal spaces along their entire lengths and absence of bone or root fractures. The treatment consisted of immediate repositioning and semi-rigid splinting. After 15 days, tooth #11 exhibited no clinical signor symptom and tooth #21 was diagnosed with pulp necrosis, with an acute dentoalveolar abscess and intraoral edema. Immediate endodontic treatment was initiated (intracanal dressing with calcium hydroxide paste). At 30 days, another pulp sensibility test was performed on tooth #11, which had a negative response. In the same visit, the intracanal dressing of tooth #21 was replaced. The Ca(OH)2 medication was replaced every 6 months until the formation of an apical barrier. The final dressing consisted of gutta-percha and Grossman's sealer and was placed two and a half years after the first dressing appointment. The extrusive luxation resulted in two different sequelae: complete root obliteration in tooth #11 and anomalous root development after the formation of an apical barrier in tooth #21. The patient received orthodontic treatment after 6 years from the initial treatment with no negative outcome. After 18 years follow-up, both teeth were stabilized with no symptom or sign. It's important to follow the evolution of every trauma case continuously because the sequelae can be unpredictable.

Comparing the Efficiency of Single versus Dual Ultrasonic Devices for Metallic Post Removal in Endodontic Retreatment: A Clinical Study.

Introduction: Ultrasonic vibration for metallic post removal seems to be a unanimous choice between endodontists and general practitioners for providing the best results and having the highest safety. This study compared the time required by ultrasonic vibration for removing metallic post (MP) when 1 or 2 ultrasonics devices are used. Materials and Methods: One hundred and fifteen teeth with MPs from 105 patients, indicated for nonsurgical endodontic retreatment were divided into 2 groups according to the number of ultrasonic devices used (G1-1 device) and (G2-2 devices). In G1, the MP was worn with a transmetal bur, alongside the wear of the cement line (around 2 mm deep). Then, an ultrasonic tip attached to an ultrasonic unit, with a power of 100% was activated at the level of the post, with constant water spray at a level of 1 mm above the axial surface of the tooth. The position of the tip was changed between buccal and lingual surfaces every 10 seconds until the MP was removed. In G2 the same procedures were performed as described in G1, but two ultrasonic tips were activated simultaneously at buccal and lingual surfaces until the MP was removed. The vibration time necessary for removing each MP was recorded using a chronometer. Results: The mean time was 131.10±29.68 seconds (mean±standard error of the mean) for MP removal using one ultrasonic device, and 24.86±6.88 seconds for two devices. The time required for MP removal using two ultrasonic devices was significantly less than when using one ultrasonic device (P<0.001). Conclusion: The technique with 2 ultrasonic devices proved to be more efficient than the one using only 1 ultrasonic device.

Apical Periodontitis in Vital and Nonvital Teeth: Clinical and Radiographic Features.

Apical periodontitis (AP) is a common inflammatory condition predominantly caused by the response of the immune system to microbial invasion within the root canal system. Contrary to conventional perception, AP may occur in vital teeth with inflamed pulp; adding complexity to diagnosis and treatment. AP, due to its frequent lack of symptoms and reliance on radiographic evaluation for detection, often presents diagnostic challenges. In addition, AP pathogenesis involves complex interactions between microbial virulence and host immune response at the cellular and molecular levels. Comprehensive diagnostic procedures, including patient history, clinical examination, and radiographic evaluation, are essential for early detection and necessary intervention, with the recognition of clinical signs and symptoms underscoring the importance of regular dental evaluations. The current review primarily discusses the radiographic and clinical features of AP in vital and non-vital teeth; introducing a new taxonomic classification to improve diagnostic precision and treatment outcomes. Moreover, it proposes different treatment categories/options for the management of AP, based on pulp status as well as clinical and radiographic findings; emphasizing vital pulp therapy and root canal treatment for vital and non-vital teeth with AP, respectively. Furthermore, the global and regional epidemiology of AP is presented, along with its association with systemic health conditions; e.g., cardiovascular diseases, diabetes mellitus, and adverse pregnancy outcomes. Moreover, future research directions are advocated to improve the efficacy and predictability of diagnosis and treatments; paving the path for clinicians in early detection, accurate diagnosis, and effective management of AP to enhance oral health outcomes.

Guided Endodontic Treatment of Mandibular Incisor with Pulp Canal Obliteration following Dental Trauma: A Case Report.

Root canal obliteration is caused by hard tissue apposition and is often associated with teeth with a history of trauma, orthodontic movement, caries reaction, restorative procedures near the pulp chamber, and teeth of elderly patients. Preoperative planning of root canal treatment should be thorough and include an assessment of the patient's signs and symptoms in addition to the evaluation of complementary examinations. In a 27-year-old patient with dyschromia of the lower central incisor, a history of dental trauma, and a positive response to vertical percussion, an initial periapical radiograph was obtained that showed calcification of the canal and presence of a periapical lesion. The patient presented with pain on chewing, a positive response to palpation and a vertical percussion test. The diagnosis was symptomatic apical periodontitis. A cone-beam computed tomography scan was requested and a surface scan was performed to establish a static guide. The root canal was accessed in the middle third of the root and the canal was located using a minimally invasive approach. The root canal was treated conventionally. Results obtained showed the success of the treatment after a 3-year clinical and radiographic follow-up. Therefore, the use of an endodontic guide in cases of calcified canals significantly reduces the clinician's working time and offers a more predictable approach to the treatment of these pathologies.

Reducing Apical Bacterial Extrusion: The Impact of Reciproc File Size and Irrigation Technique.

Introduction: This study used different irrigation techniques to compare the levels of apical bacterial extrusion during the preparation of root canals with a reciprocating instrument widely used in endodontics, the Reciproc files 25/0.08 and 40/0.06. Materials and Methods: The irrigation techniques employed were conventional syringe irrigation and passive ultrasonic irrigation (PUI); the latter, with one or two activation cycles. Seventy extracted mandibular human premolars were contaminated with Enterococcus faecalis for 5 days and were distributed into 6 experimental groups (n=10), and the remaining specimens were used as positive and negative control groups (n=5). Group 1: instrumentation performed with Reciproc 25/0.08 and conventional syringe irrigation; Group 2: instrumentation performed with Reciproc 25/0.08 along with PUI for one minute after instrumentation (PUI-1); and Group 3: instrumentation performed with Reciproc 25/0.08 along with PUI for one minute before and after instrumentation (PUI-2). Groups 4, 5 and 6 were instrumented with Reciproc 40/0.06, and irrigation was performed similar to the previous groups, in the aforementioned order. Each root canal was irrigated with saline solution. Extruded debris was collected in microtubes. The contents of the microtubes were homogenized, diluted, and spread on Brain Heart Infusion agar. After 48 hours, the number of colony-forming units was determined for each sample. For statistical analysis, the Kruskal-Wallis test followed by the Dunn's tests were used (α=0.05). Results: The CFU/mL count indicated that the instrumentation with Reciproc 25/0.08 was associated with the highest bacterial extrusion, mainly when PUI was performed (P<0.05). Conclusion: All the instrumentation techniques caused bacterial extrusion through the apical foramen; however, the largest file size of the Reciproc 40/0.06 groups was associated with less apical bacterial extrusion.

Dental Pathophysiology of Odontogenic Sinusitis: Endodontic Infections.

Bacterial odontogenic sinusitis (ODS) arises from maxillary dental issues or oral procedures, and affects at least the maxillary sinuses, with or without other paranasal sinus involvement. It has been historically underreported, in contrast to more recent findings attributing 25-40% of chronic maxillary sinusitis to dental causes. Endodontic infections represent one of the most common causes of ODS. Endodontic factors like root canal infection and microbial proximity to sinus cavities play pivotal roles. Host immunological responses further shape disease severity and progression. This article aims to explore the complexity of endodontic infections that cause ODS, elucidating anatomical, microbial, and immunological aspects.

Prevalence of Isthmi and Root Canal Configurations in Mandibular Permanent Teeth Using Cone-Beam Computed Tomography.

While root canal anatomy in Middle Eastern populations is well-studied, research on isthmi in mandibular permanent teeth from this region is limited. This retrospective study used cone-beam computed tomography (CBCT) to examine isthmi prevalence and location, as well as root canal morphologies (per Vertucci's classification) in mandibular permanent teeth from a subpopulation in Ardabil, Iran. The study is aimed at enhancing our understanding of dental anatomical variations in Middle Eastern populations. A total of 3566 teeth from 384 CBCT scans were evaluated in this retrospective study. Mandibular teeth were evaluated on sagittal, coronal, and axial sections regarding the presence of isthmus and root morphology (Vertucci's classification). CBCT scans of 197 males (51.3%) and 187 females (48.7%) were evaluated, with a mean age of 41.1 ± 11.4 years. Isthmi were most prevalent in molar mesial roots, typically located in the middle third for anterior teeth and first premolars and cervical third for posterior teeth. While gender did not play a significant role, the presence of an isthmus in the mesial root of the left second molars was associated with a younger mean patient age (p < 0.05). Root morphology varied across tooth types. Central and lateral incisors predominantly showed Vertucci's Types I and III. Canines and premolars were mostly Type I, with some variation. Molar mesial roots frequently exhibited Types IV and II, while distal roots were predominantly Type I. Statistically significant differences were found between morphology and gender in the first left premolar (Type I more common in women; Type V in men; p < 0.001) and in the right canine (Type I more prevalent in men; Types III and V more prevalent in women; p < 0.001). The results revealed wide variations in root canal morphology and a relatively high prevalence of isthmi in the study population. Our findings suggest a potential difference in tooth anatomy based on sex and a relationship between age and the presence of isthmi.

[Effectiveness of curcumin as photodynamic therapy for endodontic procedures: a narrative review]. / Efectividad de la curcumina como terapia fotodinámica para los procedimientos de endodoncia: una revisión narrativa.

Introduction: Endodontic therapy is performed by biomechanical preparation and intracanal medication; however, residual bacteria can be compromised due to their ability to adhere to the root canal walls. Therefore, photodynamic therapy has gained popularity because of its good ability to prevent and eradicate microbial infections by using a light-activated dye. Objective: Analyze and to update the information on the effect of curcumin in photodynamic therapy in root canal treatment. Material and Methods: A literature search was carried out in PubMed/MEDLINE, Scopus, Ebsco, Science Direct, and LILACS databases using the keywords "curcumin", "turmeric", "photodynamic", "photochemotherapy", "photoradiation", "photoactivated disinfection", "root canal disinfection", "root canal therapy", "endodontics" in both Spanish and English, from 2018 to 2023. Results: Information from the last five years was collected with the aim of updating the study topic. 749 articles were examined using inclusion and exclusion criteria, of which only 50 met these criteria and were analyzed. Current studies show the effects of therapy on the contamination of the root canal biofilm with E. faecalis, demonstrating that photoactivated curcumin promotes the disruption of the biofilm and reduction of Colony-Forming Units. Conclusions: Curcumin as a photosensitizer demonstrates a potential antibacterial effect significantly decreasing the viability of microbial cells and the vitality of biofilms.

[Acute apical abscess and associated factors in patients during the covid-19 pandemic in a health center in Acapulco, Mexico.] / Absceso apical agudo y factores asociados en pacientes durante la pandemia de covid-19 en un centro de salud de acapulco, méxico.

Objective: To estimate the prevalence of acute apical abscess and identify associated factors in patients of a health center from Acapulco, Mexico. Material and methods: Epidemiological study that collected clinical records of patients during the period of october 2021. Sociodemographic and housing information was collected, as well as personal pathological and non-pathological history and a record of the diagnosis of the periapical lesion based on its clinical characteristics issued by the operator on duty. Through multivariate analysis, a factor associated with acute apical abscess was identified with the odds ratio and its 95% confidence interval as estimators of the strength of association with CIETmap statistical software. Results: The 37% (32/87) of patients were diagnosed with the infection. In terms of gender, females were the most affected with a proportion of 56% (18/32). The most common cause was caries with 72% (23/32). The right upper second premolar was the most affected tooth with 25% (8/32). One associated factor was identified, age 36 to 62 years (ORa=3.54; CI95%a=1.27 -16.62). Conclusion: The morbidity rate of the infection was moderate, and it is a common pathology in stomatological emergency consultations, so it is important for the professional in charge of the area to manage it clinically. It will be important to implement oral health education strategies aimed at different age groups to raise awareness of the cariogenic process and its consequences.

Tooth preservation and "the treatable or hopeless tooth": Re-thinking a concept / Zahnerhaltung und «Der behandlungsunwürdige oder hoffnungslose Zahn¼: Ein Konzept, das man überdenken sollte?

The masticatory organ is at the center of dental practice. Tooth loss, regarded as an organ failure, is a core dispute in our profession, as it more often than not does not happen spon-taneously but is influenced by the dentist's treatment plan. Despite the prosthetic possibili-ties of tooth replacement, efforts should be made to preserve as many teeth as possible. Decisions between tooth preservation and extraction are complex and have far-reaching consequences. This article discusses this problem using a clinical case study of a 43-year-old female patient with pronounced localized periodontitis. After a comprehensive diagnosis and treatment planning, a daring regenerative therapy was carried out to try to preserve the tooth. The case shows that even seemingly hopeless teeth can be successfully treated syn-chronously using modern therapeutic approaches. Initial literature data supports the possi-bility of preserving severely compromised teeth in the long term in compliant patients. An integrative treatment approach based on individual patient factors and modern regenerative techniques may well be a viable alternative to tooth extraction and prosthetic restoration, albeit not inexpensive and uncomplicated. This communication emphasizes the need for precise diagnostics, a comprehensive treatment plan, and honest communication with pa-tients about the prospects of success and possible risks, and highlights the strengths of con-sistent tooth preservation.

Anatomical characteristics of different tooth groups. Effect on in-office bleaching treatment

AIM: The objective of the present study was to investigate the association between the anatomical characteristics of different tooth groups and the diffusion and bleaching effect of hydrogen peroxide (H2O2). MATERIALS AND METHODS: Computed tomography (CT) images from five patients were used to assess the hard tissue thickness and pulp volume (PV) of four tooth groups: lower (mandibular) incisors (LI), upper (maxillary) incisors (UI), canines (C), and premolars (PM). Additionally, 80 bovine tooth disks were divided into four groups (n = 20) to match the thickness of each tooth group studied. All the specimens were exposed to a 35% H2O2 bleaching gel, with 50 µL applied for 45 min during the first, second, and third sessions. Diffusion was evaluated using the peroxidase enzyme method. Color change analyses (∆E, ∆E00, and ∆WID) were performed after the three application sessions and 7 days after the bleaching treatment using a spectrophotometer. RESULTS: The PM group showed greater thickness and PV, followed by the C, UI, and LI groups (P 0.001). The LI group had six times greater H2O2 diffusion compared with the PM group (P 0.001), while the PM group exhibited a PV nine times larger than the LI group. Furthermore, the LI and UI groups achieved color saturation with one fewer session than the C and PM groups. CONCLUSIONS: Specific tooth groups have anatomical characteristics that interfere with bleaching treatment in terms of the diffusion and whitening effect of H2O2. Furthermore, the diffusion capacity of H2O2 was inversely proportional to the thickness of the tooth groups.

CBCT based investigation of frequency of Middle Mesial Canal in Mandibular First Molars of Saudi Sub-population.

Objective: One key factor in determining endodontic treatment outcome is the clinicians' comprehension of tooth anatomy, as missed canals may harbor bacteria ultimately leading to apical periodontitis. The study aimed to investigate the prevalence of middle mesial canal (MMC) in Mandibular first molars (MFMs) of Saudi subpopulation. Methods: The cross-sectional retrospective study was conducted at Qassim University Dental College from June to August 2023. Overall, 302 CBCT images with 604 bilateral lower first molars were examined by two calibrated assessors. The existence of MMC was noted. The data were coded, and analysis was done in SPPS-24. The reliability of inter-evaluator and intra-evaluator agreement for detecting MMC were estimated using Cohen's kappa. Results: The patients' average age was 30.95±11.61years. The sample's female to male ratio was 1:1.75. The overall frequency of MMC was 14.2%. The differences in the frequency of MMC on the basis of gender, quadrants and age groups were found to be insignificant. Inter-evaluator and intra-evaluator reliability was noted to be 0.78 and 0.74, depicting acceptable reliability. Conclusions: The MMC is an uncommon occurrence with rare bilateral presentation in MFMs of Saudi population. Endodontists performing endodontic treatment in such subjects should mindfully investigate inter mesiobuccal- mesiolingual canals area for locating, negotiating, and managing any present MMC's.

Evaluation of colour change, marginal adaptation, fracture strength, and failure type in maxillary and mandibular premolar zirconia endo-crowns.

OBJECTIVES: The objective of this in vitro study was to evaluate the effects of different preparation designs on the mean colour change (ΔE*), marginal adaptation, fracture resistance, and fracture types of maxillary and mandibular premolar endocrowns (ECs). METHODOLOGY: A total of 40 extracted maxillary and mandibular premolars were treated endodontically, and each type was subdivided according to the remaining axial height (remaining walls on all surfaces; 2-4 mm) and 2 mm inside the pulp chamber. Specimens were immersed in coffee for 14 days, ΔE* was determined, marginal adaptation was observed, fracture forces test was conducted, and the samples were examined visually at 10× magnification to evaluate failure type and identify fracture origin. The data were entered and analyzed using Statistical Package for Social Sciences, and significance between and within groups was evaluated through ANOVA. The p-value ≤ 0.05 was considered statistically significant. RESULTS: The ΔE* values of the maxillary premolar with 2 mm axial height were the highest (6.8 ± 0.89 units), whereas the lowest value was observed in the mandibular premolar with 4 mm axial height (2.9 ± 0.53 units). Significant differences (p < 0.05) in teeth and design were observed. The marginal adaptation of the mandibular premolar with 4 mm axial height was the highest (30.20 ± 1.53 µm), whereas the lowest marginal adaptation was observed in the maxillary premolar with 2 mm axial height (14.38 ± 0.99 µm), and the difference was statistically significant (p < 0.05). The maximum fracture force was observed in maxillary premolars with 2 mm axial height (2248.15 ± 134.74 N), and no statistically significant difference (p = 0.07) was observed between maxillary and mandibular premolars at 4 mm axial height. CONCLUSION: The recorded ΔE* values of the ECs were within clinically acceptable values or slightly higher, and the marginal adaption values were within acceptable and recommended clinical values in µm. EC preparation with 2 mm axial height in both arches recorded the highest fracture forces. Type III (split fracture) failure was recorded as the highest in the maxillary and mandibular premolar ECs with different axial wall heights.

Multimethod Analysis of a Novel Multi-coloured Heat-treated Nickel-Titanium Rotary System: Design, Metallurgy, Mechanical Properties, and Shaping Ability.

INTRODUCTION: This study aimed to compare a new multicolored rotary system with four heat-treated rotary instruments using the multimethod approach. METHODS: Three-hundred instruments of RCS Rainbow, Rotate, RaCe EVO, OneCurve, and ProTaper Ultimate systems were evaluated regarding their design (stereomicroscopy, scanning electron microscopy, and 3D surface scanning), metallurgy, and mechanical performance (cyclic fatigue, torsional resistance, bending and buckling resistance, and cutting ability). Unprepared surfaces after canal preparation of maxillary molars were evaluated using micro-computed tomography. Kruskal-Wallis and one-way analysis of variance post hoc Tukey tests were used for statistical comparisons (α = 5%). RESULTS: Instruments exhibited variations in active blade length, number of spirals, and cross-sectional designs. RCS Rainbow showed specific phase transformation temperatures, highest bending (400.5gf) and buckling (286gf) resistance values, and lowest mean angle of rotation (529°) (P < .05). OneCurve exhibited superior cutting ability (8.4 mm) and longer time to fracture (112s). RaCe EVO displayed the lowest time to fracture (51s), maximum torque (1.2 N.cm), buckling (174gf), and bending resistance (261gf) values (P < .05). ProTaper Ultimate showed the highest torque (1.6 N.cm) and angle of rotation (611°) (P < .05), while its bending load (262gf) was comparable to RaCe EVO (P > .05). Rotate instrument showed intermediate values in the mechanical tests. No difference was observed regarding the unprepared canal surfaces (P > .05) CONCLUSIONS: RCS Rainbow demonstrates a trade-off between flexibility and other mechanical properties. Its dimensions exceeded those of other instruments, affording it higher torque resistance, yet concurrently reducing its flexibility, angle of rotation, and cutting ability. OneCurve stands out as a well-balanced choice by integrating geometric design and mechanical performance.