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Purpose: To assess the bond strength and the hybrid layer (HL) micro-morphological characteristics at the cement-dentin interface (CD-i) between root canal walls and two adhesive resin cements [self-etch (SERc) and self-adhesive (SARc)] in root-canal-treated (RCT) and naturally aged retreated teeth (RCR-T)., Materials and Methods: Vital (n = 16) and RCT (n = 16) teeth were, respectively, endodontically treated or retreated. Fiber posts were luted either with SERc (Clearfil Universal Bond Quick + DC Core Plus) or SARc (iCEM). Samples were then sectioned into 1 mm thick slices perpendicular to the fiber post and submitted to push-out bond strength test. Vital (n = 4) and RCT (n = 4) first maxillary molars were also selected and prepared to evaluate CD-i morphology through confocal laser scanning microscopy (CLSM). Three-way analysis of variance (ANOVA) and Tukey post-hoc tests were assessed to statistically analyze the obtained data (p 0.05)., Results: Bond strength was significantly jeopardized in retreated teeth and in the root apical half, while the cements had no significant influence. Most failures occurred between dentin and resin cement. HL thickness was also hindered in retreated teeth. iCEM produced a thinner HL compared to SERc. Resin tag formation was significantly hampered in the root apical half., Conclusions: SARc performed as well as SERc on aged RCT radicular dentin. Clinicians can rely on simplified one-step luting systems when adhesion is required in unfavorable substrates such as the root canal post space of aged RCT teeth.

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.

Purpose: To evaluate interfacial gap and fracture resistance of endodontically treated maxillary premolars, restored with different glass-fiber reinforced materials., Materials and Methods: Eighty-four extracted intact premolars were endodontically treated and MOD cavities prepared. Specimens were divided into 7 groups (n = 12 for each) as follows: sound teeth (G1); no restoration (G2); direct composite restoration with fiber-reinforced composite (everX Posterior GC) (G3); direct composite restoration (Filtek Supreme XTE, 3M Oral Care; "FSXTE") (G4); a horizontal layer of high-viscosity flowable composite (G-ænial Flow, GC) was placed on the pulp chamber floor, 10 mm x 3 mm glass fibers (everStick NET, GC) were inserted into the cavity (G5); same procedure as in group 5 except the direct restoration was made incrementally with FSXTE (3M Oral Care) (G6); composite overlays were placed (G7). Specimens were scanned with micro-CT to evaluate 3D interfacial gaps before and after chewing simulation using Mimics software to calculate voids between restoration and tooth (dentin and enamel). These data (in mm3) were collected for statistical analysis. Thereafter, specimens were loaded to fracture using a universal testing machine. Maximum breaking loads were recorded in Newton (N). The data obtained were analyzed using two-way ANOVA and post-hoc Tukey's test (p < 0.05)., Results: ANOVA showed that horizontal glass-fiber insertions statistically significantly reduced interfacial gaps after chewing simulation. No differences in fracture resistance were found between Filtek Supreme XTE and everX Posterior; moreover, glass-fiber insertion did not significantly improve fracture resistance in either case. Composite overlays achieved significantly better fracture toughness than did direct restorations., Conclusions: For the direct restoration of endodontically treated premolars, the insertion of glass fibers into direct composite restorations was unable to guarantee a significant increase in the fracture resistance or a significant change in the fracture pattern. However, it significantly reduced interfacial gap volume after cycling fatigue.

Objectives: To evaluate retrospectively the longevity of endodontically treated teeth restored with direct resin composite without cusp coverage, with or without the insertion of fibre posts. The null hypothesis was that direct restorations with fibre posts perform better than those without fibre posts., Methods: Patients recruited for this study were treated in the Department of Cariology and Operative Dentistry, University of Turin, between 2008 and 2011. In total, 247 patients with 376 root treated posterior teeth, restored with direct resin composite, were recalled for a control visit. Only second-class cavities were considered. Two groups were defined based on the absence (Group A) or presence (Group B) of fibre post. Failures and complications, such as periodontal failure, endodontic failure, tooth extraction, root fracture, post fracture, post debonding, replacement of restoration, crown displacement, and coronal-tooth fracture, were noted. Functional restoration quality was evaluated following the modified USPHS criteria. Data were evaluated statistically with ANOVA., Results: Group A consisted of 128 patients with 178 restorations (88 premolars, 90 molars) with a median follow-up of 34.44 months. Group B consisted of 119 patients with 198 teeth (92 premolars, 106 molars) with a median follow-up of 35.37 months. Direct restorations with fibre posts were statistically significantly more functional (95.12% success) than those without fibre posts (80% success) because of less marginal discolouration, better marginal integrity, and higher restoration integrity., Conclusions: The null hypothesis was accepted because direct post-endodontic restorations with fibre posts performed better than restorations without posts after 3 years of masticatory function., Clinical Significance: An evaluation of the longevity of post endodontic direct restoration would seem to enhance the fiber post insertion within a composite restoration to reduce clinical failures., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2013 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

Objectives: The aim of this study was to investigate the influence of post placement on fracture resistance of endodontically treated mandibular molars restored with adhesive overlay restorations., Methods: Endodontically treated human molars with two- and one-wall cavities either underwent or did not undergo fibre post insertion within composite build-up before cementation of indirect composite onlay restorations. The specimens were thermocycled, exposed to cyclic loading, and submitted to the static fracture resistance test. Fracture loads and mode of failure were evaluated., Results: Statistical analysis revealed that specimens with fibre posts demonstrated similar failure loads (p=0.065) but more favourable fracture patterns compared with specimens without fibre posts. No difference was found between two- and one-wall cavities., Conclusions: Within the limitations of this study, the insertion of fibre posts did not improve support under indirect composite overlays., Clinical Significance: When restoring heavily broken down endodontically treated mandibular molars with an indirect overlay composite restoration, the fibre post inserted within the composite build-up do not provide any increase in fracture resistance., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

In endodontically treated teeth, cuspal coverage plays a fundamental role in reducing the risk of fracture. However, the adhesive techniques with or without fiber post increased the possibilities in restoring root-filled teeth. The aim of this study was to determine the effect of the fiber post and/or post length and/or cuspal coverage on the fracture resistance of endodontically treated maxillary premolars. Seventy intact single-rooted maxillary premolars were selected and divided in seven groups of ten each: "intact teeth" (control), "inlay without fiber post" (G1), "inlay with long fiber post" (G2), "inlay with short fiber post" (G3), "onlay without fiber post" (G4), "onlay with long fiber post" (G5), and "onlay with short fiber post" (G6). Except for intact teeth, all specimens were prepared with a mesio-occluso-distal (MOD) cavity, endodontically treated and restored with or without long or short post, with or without cusp coverage. All specimens were thermal-cycled, exposed to a cyclic loading, and then submitted to the static fracture resistance test. Fracture loads and mode of failure were evaluated. A statistically significant difference in fracture resistance was found between group 1 and the other groups (p < 0.001). χ2 test showed statistically significant differences in the patterns of fractures between the groups (p < 0.001). The highest number of favorable fractures was observed in groups 3 and 4. Similar fracture resistance was detected in maxillary premolars endodontically treated with MOD cavity preparations, restored with either direct resin composite with fiber post or cusp capping. The "short post" direct restoration may be a valid alternative in the restoration of root-filled premolars.

Polymerase chain reaction (PCR) followed by reverse dot blot was used to detect Enterococcus faecalis leakage through mineral trioxide aggregate (MTA) apical obturations of pulpless teeth with open apices. Prepared root canals of 34 extracted teeth were given a standard apical foramen opening and received orthograde apical obturation with MTA; three groups had 1-, 2-, or 3-mm thickness. Sterilized specimens were inoculated with E. faecalis and incubated in sterile medium. DNA extracted from the specimens was amplified by polymerase chain reaction, which yielded a specific segment of E. faecalis 16S rDNA. On day 10 of incubation, no specimens were contaminated. On day 50, almost 17% of specimens were contaminated, with no statistically significant difference between groups (Chi-square = 0.48; df = 2; p = 0.787). Therefore, MTA provides an adequate seal even in cases of orthograde apical obturation of pulpless teeth with open apices.