The clinical outcomes of vital intact teeth close to large cystic lesions of endodontic origin: A prospective clinical study.

AIM: To evaluate the indication of the endodontic treatment for vital intact teeth with the root apex involved in large radicular cystic lesions of endodontic origin. METHODOLOGY: This prospective cohort study enrolled healthy participants with radicular cysts of endodontic origin and with the root apex of vital intact teeth involved in the bone defect, as determined by cone beam computed tomography (CBCT). Thirty-two sound vital teeth were analysed by thermal (TPT) and electric pulp tests (EPT) before surgery (T0) and 1 week (T1), 2 weeks (T2), 3 months (T3) and 6 months (T4) post-surgery. Student's t-test (p < .05) was used to compare the EPT values at baseline and T4. anova (p < .05) was used to analyse the EPT variations for all maxillary and mandibular teeth. McNemar test (p < .05) was used to compare the results according to variation in EPT values gathering by variation, no variation and no response. RESULTS: At T1, 75 and 65.7% of teeth responded positively whilst 25 and 34.3% did not respond to EPT and TPT, respectively. The variation of the EPT values between T0 and T1 was observed for 50.0% of teeth, whilst no variation was noticed in 25.0% of teeth. At T4, 90.6 and 87.5% of teeth responded positively whilst 9.4 and 12.5% did not respond to EPT and TPT, respectively. At T4, variation of the EPT values between T0 and T4 was observed for 28.1%, whilst no variation was noticed in 62.5% of teeth. There were no statistical differences in EPT results between T0 and T4 (p > .05), but significant differences were observed for EPT values between T1 and T4 (p < .05), and between mandibular and maxillary teeth. The pulp sensibility of maxillary teeth worsened after surgery, before reverting progressively to T0 values, whilst no statistically significant differences were observed for mandibular teeth at the different time points. CONCLUSIONS: These data support the inconsistence of the prophylactic endodontic treatment in healthy vital teeth with apex involvement in large cystic lesions of endodontic origin. Post-surgery follow-up with TPT and EPT is recommended to assess pulp status.

Endodontic microsurgery virtual reality simulation and digital workflow process in a teaching environment.

INTRODUCTION: Computer simulations are stimulating increased attention in dentistry. Augmented reality superimposes a virtual scenario over an existing reality and allows interaction with it. Virtual reality (VR) simulates a fully immersive situation permitting the user to experience the full environment in real time. Haptic technology provides tactile and realistic force feedback for the user to experience the immersive situation as if they were really there. Preclinical training is important to gain familiarity with difficult surgical techniques and to implement interpersonal skills. Developing a valid assessment of surgical simulation is challenging. This paper wants to present a newly realized VR simulation in endodontic microsurgery through the developmental digital workflow, the demonstration of a haptic VR scenario and student self-assessment and self-reflection feedback. METHODS: The volumes were exported in a stereolithography format to prepare and optimize in terms of shape and shade for the VR simulation. The graphics and touchable haptic solid were created using Virteasy Editor, which allows the transformation of 3D surfaces into graphical and volumetric haptic solids depending on their material (enamel, dentine, pulp and bone). Users were asked to execute the osteotomy and root-resection preparation. The assessment criteria were determined, and the feedback statements were created by a questionnaire with fixed answers. Objective and qualitative criteria for assessing the preparation were obtained from the literature. RESULTS: This study provides proof that it is possible to provide reliable and clinically relevant qualitative feedback with a VR simulator. CONCLUSION: VR simulation offers an innovative approach with all the benefits of clinical experience. It permits you to save your own progress and review the assessment at any time.

Micro-CT evaluation of rotary and reciprocating glide path and shaping systems outcomes in maxillary molar curved canals.

The shaping outcomes after instrumentation with rotary and reciprocating glide path and shaping systems were evaluated through micro-computed tomography (Micro-CT). Thirty extracted maxillary first molars were selected. Mesio-buccal canals were randomized into two groups (n = 15): rotary system ProGlider and ProTaper Next X1, X2 (PG-PTN) and reciprocating system WaveOne Gold Glider and WaveOne Gold Primary (WOGG-WOG). Specimens were micro-CT scanned before, after glide path and after shaping. Increase in canal volume and surface area, percentage of removed dentin from the inner curvature, centroid shift and canal geometry variation through ratio of diameter ratios (RDR) and ratio of cross-sectional areas (RA) were measured in the apical and coronal levels and at the point of maximum curvature. The number of pecking motions needed to reach the working length (WL) was recorded. One-way ANOVA and post hoc Turkey-Kramer tests were used (p < 0.05). Post-glide path analysis revealed that in the coronal third, RDR was more favorable to PG and centroid shift was lower for WOGG in the apical third. Post-shaping analysis showed a reduced removal of dentin and a more favorable RA for PTN at point of maximum curvature. The number of pecking motions up to WL resulted in different between groups both for glide path and shaping phases. Despite a higher dentin removal for reciprocating instruments at the point of maximum curvature, both systems seemed to produce well-centered glide path and shaping outcomes. Rotary and reciprocating systems seemed able to respect the original canal anatomy.

Micro-computed tomographic evaluation of endodontic ledge position in relation to canal curvatures.

BACKGROUND: Endodontic ledge (EL) formation is the most common complication of endodontic treatment. Although various etiological factors have been identified, canal curvature is the most significant variable correlated with EL formation. The aim of this micro-computed tomographic (micro-CT) study was to evaluate EL position in the mesial canals of the lower molars in relation to the degree of canal curvature. METHODS: Forty intact mandibular first molars with independent mesial canals with 20°-40° primary mesio-distal curvature, 10°-30° buccal-lingual canal curvature and 4 < r ≤ 8 mm main curvature radius were selected. Working length was measured with a K-File #10 and a high resolution pre-operative micro-CT analysis was performed. Ledges were created at the point of maximum canal curvature using stainless steel K-Files #30-35, alternating irrigation with 5% NaOCl and 10% EDTA. A post-operative high-resolution micro-CT analysis was then completed. Pre- and post-operative images were analyzed. The angle (α) formed between the vector passing through the geometric center of the EL and the center of the original canal lumen and the line joining the centers of the mesio-buccal and mesio-lingual canal orifices was calculated, and a descriptive statistical analysis was achieved. The α angle values were analyzed in relation to canal curvature using Kruskal-Wallis and post hoc Dunn's tests. The level of significance was set at P < 0.05. RESULTS: The α angles appeared inversely proportional to canal curvatures in the buccal-lingual and mesio-distal projections. The mean α angle was 36.4° (standard deviation 10.64; 95% confidence interval 34.1-40.9). CONCLUSION: Within the limitations of this study, endodontic ledges develop in the opposite direction to the three-dimensional canal curvature and their position is influenced by the degree of curvature. Clinically, the α angle values may be related to the recommended direction to manage endodontic ledges.

Endodontic Treatment of a Molar with Peculiar Anatomy: Case Study with CBCT and 3D Printed Model.

AIM: The aim of the study was to achieve the endodontic treatment of a second maxillary molar with abnormal anatomy through cone-beam computed tomography (CBCT) analysis and three-dimensional (3D) printing. BACKGROUND: A patient arrived referring recurrent abscesses, spontaneous pain, and the difficulty to eat properly; a diagnosis of tooth necrosis was made. The periapical X-ray showed an abnormal anatomy of the tooth. CASE DESCRIPTION: The preoperative analysis of the tooth morphology was performed through CBCT analysis. The 3D scans were reconstructed through a dedicated software application (Mimics) to visualize the abnormal anatomy and detect the root canal morphology. Moreover, a 3D printed model was created to plan the clinical stage. Canal shaping was achieved with ProGlider and ProTaper Next techniques, and the root canal filling was performed with a carrier-based technique. CONCLUSION: The limits of this case were the low definition of the CBCT owned by the patient and the difficulties during the scouting of the canals due to the abnormal endodontic space complicated by narrow and flat canals. The software reconstruction allowed a 3D high-definition preclinical analysis of the tooth anatomy. CLINICAL SIGNIFICANCE: Both digital analysis and printed models based on CBCT scans seemed fundamental to preclinically understand the abnormal endodontic anatomy.

Influence of surface coating sealer on resin composite water absorption and discoloration: An in vitro study.

PURPOSE: To evaluate the in vitro efficacy of surface coating sealer (SCS) in reducing the amount of water absorption and stain formation in resin composites. METHODS: To evaluate the amount of water sorption, 40 stainless steel round molds (n=10 per composite) were filled with Filtek Supreme XTE; Venus Diamond; Clearfil Majesty ES-2; Gradia Direct Anterior. Groups were further divided into two subgroups (n=5) according to the presence/absence of SCS (Easy Glaze). Their masses were measured at baseline and reweighed at 1, 4, 12, and 20 weeks. For staining evaluation, 48 resin composite discs, 2 mm-thick, were obtained with the same composites and SCS was applied on a single surface of each sample. After baseline color assessment, samples were immersed in vials containing 5 mL of six different staining solutions. Color evaluation was performed again after 1, 4, 12, and 20 weeks. Three-way ANOVA was performed to evaluate differences in weight gain and color changes (P< 0.05). RESULTS: A significant protective action of SCS (P< 0.001), but not of the composites (P= 0.366) was found. Differences in weight and color change were not influenced by the resin composite, but only by the presence of the coating on the surface of the samples. SCS are well-established materials for polishing and protecting composite restorations from water sorption and color changes. Different staining solutions can still produce different effects on resin composite. CLINICAL SIGNIFICANCE: Surface coating sealers are able to reduce water uptake and discoloration from resin composites, thus leading to less degradation of composite restorations over time.

Influence of dentin pretreatment with synthetic hydroxyapatite application on the bond strength of fiber posts luted with 10-methacryloyloxydecyl dihydrogen phosphate-containing luting systems.

The aim of this in vitro study was evaluate the effect of application of synthetic hydroxyapatite on fiber post bond strength to radicular dentine. Forty, single-root teeth were endodontically treated and an 8 mm post space was prepared. Specimens were randomly placed in four groups (n = 10 in each) and treated using the following fiber post luting procedures: group 1, 17% EDTA + Panavia SA; group 2, 17% EDTA + Teethmate Desensitizer + Panavia SA; group 3, All-Bond Universal + Duo-Link Universal; and group 4, All-Bond Universal + Teethmate Desensitizer + Duo-Link Universal. Fiber posts were luted in the post space and light-cured for 120 s using a light-emitting diode (LED) lamp. After 7 d of storage at 37°C, the teeth were cut into 1-mm-thick slices, which were subjected to a push-out test until failure using a universal testing machine. Two specimens per group were prepared for scanning electron microscopy analysis. An energy-dispersive X-ray spectroscopy detector was used for elemental analysis of the specimen surface. The results were statistically analyzed using one-way anova. The fiber post bond strength was statistically significantly increased after the application of Teethmate Desensitizer to post space walls, either with a 10-MDP-containing self-adhesive cement or with a universal adhesive. Scanning electron microscopy and EDAX analysis showed that Teethmate Desensitizer created a calcium phosphate precipitate over post space dentinal tubules, which significantly improved the bond strength of the fiber post luted with 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP)-containing adhesive systems.

Influence of operator experience on non-carious cervical lesion restorations: Clinical evaluation with different adhesive systems.

PURPOSE: To evaluate the influence of operator experience on adhesive technique and to assess the clinical performances of two different adhesive systems. METHODS: 90 cervical lesions in 42 subjects, with a mean age of 52.4 years (range between 32-63) were selected. Lesions were divided into two groups according to operator experience (n = 42 restorations performed by a skilled operator, n = 48 restorations performed by five unexperienced operators) and further divided into two subgroups according to the adhesive system used: three-step etch-and-rinse (Optibond FL) or one step self-etch (G-Bond). Adhesives were applied according to manufacturers' instructions. Subjects underwent follow-up at 12, 24, and 36 months and restoration retention, enamel and dentin marginal integrity, marginal discoloration, caries occurrence, post-operative sensitivity, and preservation of tooth vitality were evaluated according to USPSH criteria. ANOVA test was performed to evaluate the influence of the adhesive system, the operator experience, and aging on restorations. RESULTS: Operator experience (expert vs. inexperienced), aging time (12, 24, or 36 months), and the adhesive system (self-etch vs. etch-and-rinse) all affected the results statistically, as did the interaction between the adhesive system and operator experience.

Influence of multi-step etch-and-rinse versus self-etch adhesive systems on the post-operative sensitivity in medium-depth carious lesions: An in vivo study.

PURPOSE: To evaluate the influence of a three-step etch-and-rinse versus a two-step self-etch adhesive system on immediate post-operative sensitivity. METHODS: In total, 204 subjects with one posterior tooth affected by a primary carious lesion were recruited. The subjects were randomly divided into two groups, based on the two multi-step adhesive systems used: Group A (All Bond 3) and Group B (Clearfil Protect Bond). The same skilled operator carried out the restorations using a nano-hybrid composite (Venus Diamond) in oblique stratification. Each increment was light-cured for 20 seconds with a LED lamp (Translux Power Blue). Subjects received a three-level thermal sensitivity questionnaire for post-operative sensitivity ratings. The evaluations were recorded daily for 7 days. Scores were analyzed using the McNemar test and postoperative trends were analyzed with the Friedman test (P < 0.05). All (100%) enrolled subjects completed the follow-up visits. There was no statistically significant difference between the two groups in post-operative sensitivity trends. In both groups, increased post-operative sensitivity was found at D1, which then decreased significantly during the observation period. RESULTS: The results of this in vivo study showed that both of the tested adhesives, etch-and-rinse or self-etch, provided effective dentin sealing, preventing subjects from experiencing post-operative sensitivity in the treatment of medium-depth cavities.

Fiber-post bond strength in canals obturated with a cross-linked gutta-percha core obturator.

The aim of this in-vitro study was to evaluate the bond strength of fiber posts cemented in a root canal filled using various root-canal obturation techniques. A total of 33 monoradicular samples, treated endodontically, were randomly assigned to three groups according to the root-canal obturation technique: group 1, continuous-wave technique; group 2, plastic-obturator-core technique; and group 3, cross-linked gutta-percha obturator-core technique. Fiber posts were luted in each sample and each was sectioned perpendicular to the post axis. The push-out test was performed using a universal machine and the maximum failure load was recorded in MPa mm(-2) . Several samples were randomly chosen for scanning electron microscopy evaluation. The mean debris and dentinal tubule-opening scores were calculated separately in the coronal and apical portions. Bond strength was significantly higher in group 1 than in groups 2 and 3. Debris scores were significantly higher in the apical portion of groups 2 and 3 than in group 1. Within the limitations of this study it can be affirmed that thermoplasticized alpha gutta-percha seemed to worsen the cleaning of post-space walls and hence reduced fiber-post bond strength.

Effects of Etching Time and Ethanol Wet Bonding on Bond Strength and Metalloproteinase Activity in Radicular Dentin.

(1) Background: The objective of this in vitro study was to evaluate the impact of different etching times and ethanol pre-treatments on the immediate bond strength of a hydrophilic multi-mode universal adhesive (Clearfil Universal Bond Quick, Kuraray, UBQ) and on the consequent gelatinolytic activity of metalloproteinases (MMPs) on radicular dentin. (2) Methods: Sixty single-root teeth were selected and divided into four groups according to the adhesive protocol applied for fiber post cementation: (G1) 15 s H3PO4 application + UBQ; (G2) 30 s H3PO4 application + UBQ; (G3) 15 s H3PO4 application + ethanol pre-treatment + UBQ; (G4) 30 s H3PO4 + ethanol pre-treatment + UBQ. After adhesive procedures, fiber posts were luted into the post space with a dual-curing cement (DC Core, Kuraray) and light-cured for 40 s. To perform the push-out test and nanoleakage analyses for both coronal end apical areas, 1 mm slices were prepared, following a 24 h storage period in artificial saliva. Additionally, an in situ zymographic assay was conducted to explore endogenous MMP activity within the radicular layer. Results were statistically analyzed with ANOVA and Tukey post hoc tests. Statistical significance was set at p < 0.05. (3) Result: ANOVA revealed a statistically significant difference in push-out bond strength related to the pre-treatment variable but did not highlight any significance of etching time. Specimens pre-treated with ethanol wet bond application showed higher bond strength (p < 0.01). In situ zymography quantification analyses revealed that all tested groups, independently of etching time end ethanol pre-treatment, activated MMP gelatinolytic activity. A significant increase in MMP activity was detected for the 30 s etching time. However, ETOH pre-treatment significantly reduced MMP activity within the adhesive interface (p < 0.01). (4) Conclusions: The tested adhesive showed similar results regardless of the etching time protocol. The gelatinolytic activity of MMPs was observed in all the groups. Further investigations and extended follow-ups are required to validate the results of the present study in vivo.

Confocal laser scanning evaluation of the influence of ledges on root canal disinfection.

The aim was to analyse the influence of an apical ledge on root canal disinfection. Forty-four single-rooted teeth were micro-CT scanned and inoculated with Enterococcus faecalis. In Group S shaping was performed with ProTaper Next (PTN) up to X3 at working length (WL). In Group L an apical ledge was created with K-Files #40 and shaping completed up to PTN X3. NaOCl 5% and EDTA 10% irrigant solutions were alternated. Confocal laser scanning microscope (CLSM) and viability staining were used to analyse the proportions of dead (red) and live (green) bacteria and penetration ability inside dentinal tubules. Data were analysed with the Mann-Whitney test with Bonferroni correction (p < 0.05). In Group L the amount of red fluorescence resulted significantly lower, and penetration ability was decreased in the apical and middle portion (p < 0.05). The presence of an apical ledge may negatively influence the disinfection both in the apical and middle third.

Endodontic Treatment of Chronic Apical Periodontitis Ameliorates Systemic Inflammation and Restores Impaired Cellular Responses to Insulin in an In Vitro Model.

INTRODUCTION: A growing body of research supports an association between periapical inflammation and an increased risk of developing systemic diseases. There is currently no scientific evidence to support a causal effect of inflammation on the onset of insulin resistance (IR) in patients with apical periodontitis (AP). The aim of this in vitro study was to evaluate any association between AP and levels of serum inflammatory factors potentially associated with the onset of IR, and to investigate the effect of root canal treatment (RCT) on these systemic inflammation markers and on the response in vitro to insulin. METHODS: A total of 27 control subjects and 27 patients with AP were enrolled. Patients with AP underwent RCT and were followed-up 6 and 12 months post-treatment. Enzyme-linked immunosorbent assays were used to evaluate serum levels of proinflammatory cytokines interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor (TNF)-α. The response in vitro to insulin was assessed by measuring glucose consumption in a human pancreatic epithelioid carcinoma cell line treated with sera from healthy and AP subjects. RESULTS: At baseline AP was associated with significant higher levels of IL-1, IL-6, and IL-8 in the serum of untreated (AP) patients vs controls (P < .001). Glucose consumption decreased in pancreatic cells incubated with baseline serum from patients with AP, in a manner proportional to total cytokines amount. Notably, endodontic treatment was associated with reduced levels of cytokines (P < .001) and improved response to insulin in AP group (P < .001). CONCLUSIONS: Our findings suggest that AP may promote inflammatory-driven IR in an in vitro model, and that RCT may ameliorate inflammatory mediators in vivo and the cellular response to insulin in vitro.

Influence of adhesive techniques on fracture resistance of endodontically treated premolars with various residual wall thicknesses.

STATEMENT OF PROBLEM: The choice of restorative method is commonly based on the cavity configuration and the residual number of cavity walls. However, the residual wall thickness could be a valuable clinical parameter in the choice of restoration for endodontically treated teeth. PURPOSE: The fracture resistance of endodontically treated premolars was compared with different wall thicknesses restored with direct composite resin with and without cuspal coverage and with and without fiber post insertion. MATERIAL AND METHODS: This study included 104 intact human maxillary premolars extracted for periodontal or orthodontic reasons. Standardized mesio-occluso-distal cavities were prepared with different palatal wall thicknesses (1.5, 2, and 2.5 mm) and a buccal wall thickness of 2 mm. Teeth were restored with or without a fiber post and with or without cuspal coverage. Specimens were subjected to thermocycling (3000 cycles, 5 to 55°C) and embedded in polymerized acrylic resin. Teeth were submitted to cyclic fatigue followed by a static fatigue test with a universal testing machine; a compressive force was applied 30 degrees to the long axis of the teeth until fracture. The results were statistically analyzed by 3-way ANOVA (α=.05). RESULTS: Residual wall thickness (P=.004), the type of adhesive restoration (P<.001), and fiber post insertion (P<.001) significantly influenced the fracture resistance of endodontically treated premolars. CONCLUSIONS: In specimens with a cavity wall thickness >2 mm, direct intracuspal composite resin restorations supported by a fiber post achieved comparable fracture resistance. With a residual wall thickness <2 mm, only cuspal coverage with or without a fiber post provided satisfactory fracture resistance.

Working length variation during multiple-visit endodontic treatment: An observational study.

This study investigated variation in working length during multiple-visit endodontic treatment. Patients (N = 106) with pulpitis or pulp necrosis, with or without apical periodontitis, were included. During the first appointment, glide path was performed with ProGlider and shaping with ProTaper Next. Working length was detected four times. Working length was then re-recorded prior to filling during the second appointment and a 0.5 mm threshold was selected as the minimum clinically meaningful variation. A logistic regression model was used to evaluate the impact of tooth anatomy, preoperative pulp status, apical periodontitis and lesions of endodontic origin on working length variation. Working length varied between first and second appointments in 34% of patients. The presence of apical periodontitis was the only variable significantly associated with variation in working length (p = 0.011). These data suggest that working length should be re-checked prior to root canal filling to prevent procedural errors.

Dynamic Navigation System vs. Free-Hand Approach in Microsurgical and Non-Surgical Endodontics: A Systematic Review and Meta-Analysis of Experimental Studies.

(1) Background: A Dynamic Navigation System (DNS) is an innovative tool that facilitates the management of complex endodontic cases. Despite the number of advantages and limitations of this approach, there is no evidence-based information about its efficiency in comparison with that of the traditional method in endodontics. (2) Objectives: We aimed to explore any beneficial effects of the DNS and compare the outcomes of DNS vs. free-hand (FH) approaches for non-surgical and microsurgical endodontics. (3) Methods: A literature search was conducted in August 2023 to identify randomized, experimental, non-surgical, and microsurgical endodontic studies that compared the DNS with FH approaches. The procedural time (ΔT, s), substance loss (ΔV, mm3), angular deviation (ΔAD, °), coronal/platform linear deviation (ΔLD_C, mm), and apical linear deviation (ΔLD_A, mm) were recorded and analyzed. Quality and risk of bias assessments were conducted according to the Quality Assessment Tool For In Vitro Studies. A meta-analysis was performed using mean difference and standard deviation for each outcome, and heterogeneity (I2) was estimated. p < 0.05 was considered significant. (4) Results: One-hundred and forty-six studies were identified following duplicate removal, and nine were included in the systematic review and meta-analysis. The overall risk of bias was classified as low. The DNS was found to be more accurate and efficient than the FH approach was, resulting in a significantly shorter operation time (p < 0.00001) and less angular (p ≤ 0.0001) and linear deviation (p ≤ 0.01). For substance loss, the advantage of the DNS was significant only for microsurgery (p = 0.65, and p < 0.005, for non-surgical and microsurgical procedures, respectively). A reduced risk of iatrogenic failure using the DNS was observed for both expert and novice operators. (5) Conclusions: The DNS appears beneficial for non-surgical and microsurgical endodontics, regardless of the operator's experience. However, appropriate training and experience are necessary to access the full advantages offered by the DNS.

Does Curing Delay Affect the Bond Strength of Fiber Post with Self-Adhesive Cements?

PURPOSE: To evaluate the effect of three different curing protocols based on different ratios of self-curing and light-curing periods on the bond strength and nanoleakage of fiber posts luted with dual-curing self-adhesive cements. MATERIALS AND METHODS: A total of 48 single-root teeth were endodontically treated and obturated, and an 8-mm post space was prepared with dedicated drills. Specimens were randomly divided into two groups according to the self-adhesive cement employed: group 1 (G1) = PANAVIA SA Plus (Kuraray Noritake), and group 2 (G2) = Bifix SE (VOCO). The specimens were further divided into three subgroups (n = 8 each) according to the light-curing protocol applied: no light-curing (SG1), 20 seconds of light-curing 20 seconds after cement injection (SG2), and 20 seconds of light-curing 120 seconds after cement injection (SG3). Slices of 1-mm thickness were prepared for the pushout test and nanoleakage analyses of the coronal and apical regions after 24 hours of storage in artificial saliva. Results were statistically analyzed with three-way ANOVA and Tukey post hoc tests. Statistical significance was set for P < .05. RESULTS: Three-way ANOVA analysis showed that the factors of cement (P = .02) and curing protocol (P < .001) had a significant influence on bond strength. Tukey post hoc test reported that light-curing 120 seconds after injection showed higher bond strength compared to both no light-curing and photoactivation after 20 seconds. CONCLUSION: To achieve the highest bond strength with self-adhesive cements, photoactivation with a 120-second delay after mixing is required. There is no difference between light-curing immediately and light-curing 20 seconds after mixing.

Effects of Different Fiber-Reinforced Solutions on Fracture Strength and Pattern in Endodontically Treated Molars.

PURPOSE: To evaluate the fracture strength of endodontically treated molars filled with different composite resins with vs without fiber reinforcement. MATERIALS AND METHODS: A total of 60 intact mandibular molars were selected and endodontically treated. A standardized mesio-occlusal-distal cavity was prepared with cervical margins 1 mm above the cementoenamel junction and oral and buccal walls with 1.5-mm thickness. Universal adhesive was used in all specimens in etch-and-rinse mode. Specimens were divided into four groups (n = 15 each) according to restoration technique: group CSM = adhesive overlay with hybrid ceramic; group EXP = direct restoration with short fiber-reinforced composite; group ESU = direct restoration with nanohybrid composite; and group EST = direct restoration with nanohybrid composite reinforced with horizontal bidirectional glass fibers placed over the pulpal chamber floor. After 7 days of storage in water, samples were loaded until fracture using a universal testing machine. The maximum breaking loads were recorded in Newtons, and statistical analysis was then conducted with two-way ANOVA and post hoc Tukey test. Fragments were analyzed using scanning electron microscopy. RESULTS: Mean fracture resistance values were: CSM = 1,428.91 ± 316.90 N; EXP = 1,874.57 ± 299.47 N; ESU = 1,557.44 ± 355.65 N; and EST = 1,870.27 ± 145.11 N. The CSM and EXP groups showed the highest strength values when compared to the other groups. The variable fiber insertion did not significantly alter the fracture resistance. The origin of the fracture was always located on the occlusal surface, mainly in the major contact loading area. CONCLUSION: The use of fiber-reinforced composite showed great improvement in fracture resistance, similar to a cuspal coverage restoration. However, only short fiber-reinforced composites showed a favorable fracture pattern. Int J Prosthodont 2023;36:603-611.

Wear Behaviour of Polymer-Infiltrated Network Ceramics, Lithium Disilicate and Cubic Zirconia against Enamel in a Bruxism-Simulated Scenario.

The present study aimed to evaluate the wear rate of polymer-infiltrated network composites and ceramics against enamel in a bruxism-simulated scenario. Ninety-six (n = 96) molars were divided into six groups (n = 16) according to their occlusal material: group 1-a polymer-infiltrated network ceramic (PINC); group 2-a second polymer-infiltrated network ceramic (PINC2); group 3-nanohybrid resin-based composite (CO); group 4-cubic zirconia (ZR); group 5-lithium disilicate (LS); and group 6-sound enamel (EN). A laser scanner was used to digitalize all of the occlusal surfaces before and after a fatigue test, which was conducted with a chewing simulator set at 80 N and semicircular movement in order to simulate bruxist movement and loads. Statistical analysis of volume loss was performed with a one-way ANOVA and post hoc Bonferroni test. ZR had significantly inferior wear to PINC (p ≤ 0.01) and CO (p = 0.04). LS wore the antagonist enamel significantly more than PINC, CO, PINC2 and EN (p ≤ 0.01). On the other hand, ZR wore the antagonist enamel significantly more than CO (p ≤ 0.01) and PINC2 (p = 0.05). In conclusion, PINCs better preserved antagonist enamel at the expense of a higher wear of their own. LS causes significantly higher enamel wear compared with PINCs. ZR caused significantly higher enamel wear compared with CO and PINC2, but it was wear-resistant.

Micro-Computed Tomography Evaluation of Minimally Invasive Shaping Systems in Mandibular First Molars.

The aim of this study was to compare the shaping ability of a modified ProTaper Next technique (PTNm) with that of TruNatomy (TN) in lower molars mesial curved canals using micro-computed tomography (Micro-CT). Sixty mesial canals of first mandibular molars were randomly assigned between two groups (n = 30). After canal scouting with K-File #10, glide path and shaping were carried out with TN or PTNm systems. The PTNm sequence consists of ProGlider, followed by ProTaper Next X1 and apical finishing with NiTiFlex #25 up to working length (WL) to ensure adequate apical cleaning. Samples were scanned using micro-CT and pre- and post-shaping volumes were matched to analyse geometric parameters: the volume of removed dentin; the difference of canal surface; centroid shift, minimum and maximum root canal diameters; cross-sectional areas; the ratio of diameter ratios (RDR) and the ratio of cross-sectional areas (RA). Measurements were assessed 2 mm from the apex and in relation to the middle and coronal root canal thirds. Data were analysed using ANOVA (p < 0.05). No statistically significant differences were found between the groups for any parameter at each level of analysis, except for RA at the coronal level (p = 0.037). The PTNm system showed the tendency to enlarge more in the coronal portion with a lower centroid shift at apical level compared with TN sequence (p > 0.05). Both PTNm and TN sequences demonstrated similar maintenance of original anatomy during the shaping of lower molar mesial curved canals.