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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. [ABSTRACT FROM AUTHOR]

Purpose: To three-dimensionally evaluate the interfacial gap of bulk-fill resin composites applied in deep Class-I restorations with different layering techniques and curing modes. Materials and Methods: Ninety-six (n = 96) samples were prepared with standardized deep Class-I cavities and adhesive procedures. Four materials were tested: SDR (SDR), SonicFill2 (SF), Admira Fusion X-Tra (AFXT), Filtek Supreme XTE (FS). Four subgroups (n = 6) were created according to layering and curing techniques: 2+2mm increments with soft start curing (SG1), 2+2 mm with conventional curing (SG2), a 4-mm increment with soft start curing (SG3), a 4-mm increment with conventional curing (SG4). All samples underwent micro-CT scans; afterwards, voids surrounding the restorations automatically underwent a thresholding procedure (Mimics, Materialise; Geomagic Studio 12, 3D Systems) to analyze the 3D interfacial gap. Statistical analysis was performed using three-way ANOVA with Tukey’s test (significance p < 0.05). Results: Statistically significant differences were reported between materials, layering techniques and their interaction. No statistically significant differences were reported for polymerisation mode. Bulk-fill materials showed average interfacial gap volumes ranging from 0.031 mm³ to 0.200 mm³, while FS showed volumes ranging from 0.416 mm³ to 1200 mm³. Conclusions: All bulk-fill materials performed statistically significantly better than did FS (p < 0.05), with no statistically significant differences between them. Curing mode did not influence interfacial gap volume in any group (p > 0.05), while bulk-filling vs layering influenced the volume of interfacial gaps only in the FS group, which performied better when incrementally applied. Regarding gap localisation, the floor of the cavity was the area with the highest likelihood of gaps in all samples. [ABSTRACT FROM AUTHOR]

Purpose: The management of complicated crown-root fractures is challenging for endodontic restoration. The present case describes a patient who sustained trauma to the maxillary right central incisor. Materials and Methods: Clinical and radiographic examination showed a complicated crown-root fracture and incomplete root development with periapical radiolucency and inadequate endodontic treatment with overfilling. Orthograde retreatment with MTA apical closure combined with a microsurgical approach to remove of extruded material was performed. Coronal sealing was accomplished with a direct adhesive restoration and marginal relocation. Results: A 5-year follow-up showed complete healing of the periapical lesion and correct preservation of function and esthetic parameters. Conclusion: A modern minimally invasive treatment protocol allows the maximum conservation of residual dental tissues. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the immediate and aged bond strength and interfacial nanolaekage of different adhesives and protocols on dental elements prepared with diamond burs and Er:YAG laser. Materials and Methods: Forty molar crowns were flattened and a standardized smear layer was created. Teeth were divided into two main groups according to the dentin cutting technique: 1. Er:YAG laser for 30 s at 30 Hz repetition rate, 250 mJ energy per pulse, and water spray irrigation set at level 8; and 2. diamond bur. Each group was then divided into subgroups according to the adhesive protocol: SG1: dentin etching for 15 s followed by universal adhesive application (All Bond Universal, Bisco); SG2: universal adhesive application (All Bond Universal); SG3: two-step self-etch adhesive application (Clearfil SE Bond 2, Kuraray Noritake); SG4: etching followed by 3-step etch-and-rinse adhesive application (Optibond FL, Kerr). After curing the adhesives, resin composite buildups of 4 mm were made and specimens were sectioned to obtain 1-mm-thick sticks in accordance with the μTBS test technique. Sticks were stressed to failure at baseline and after 6 months of storage in artificial saliva. Three teeth per group were prepared for nanoleakage interfacial analyses. Data were statistically analyzed with three-way ANOVA and Tukey's post-hoc test (p < 0.05).Results: A significant difference in bond strengths was found for treatment, aging, and adhesive protocol. Nanoleak age analysis showed higher marginal infiltration in Er:YAG-treated groups both at baseline and after aging. Conclusions: Surfaces prepared with diamond burs presented higher bond strengths than did those prepared with Er:YAG laser. Adhesive protocols and aging could influence the adhesive-dentin interface. Further studies are necessary to validate the results obtained. [ABSTRACT FROM AUTHOR]

Objective. The purpose of this ex vivo study was to compare the trueness of traditional and digital workflows and to analyze the interfacial fit of CAD/CAM restorations on gypsum and 3D-printed casts (3DC). Methods: Forty patients underwent indirect posterior adhesive restorations. After tooth preparation, both traditional and chairside procedures were followed. Obtained models were scanned to generate STL files of the intraoral impression (IOS), the conventional cast (RS), and the 3D-printed cast (3DCS). Superimposition of the casts was performed to evaluate trueness. Then, for each preparation, two identical CAD/CAM restorations were milled and luted on RS and 3DC. Micro-CT scan was performed to evaluate 3D interfacial fit. Results. Surface trueness analysis showed no significant differences among groups (p > 0.05), with average trueness ranging from 11.56 to 17.01 µm. Micro-CT analysis showed significant differences between gypsum casts (average ranging from 135.78 to 212.31 µm) and 3DC (average ranging from 57.63 to 144.55 µm) for both marginal and internal fit. Conclusions. In adhesive restorations manufacturing, digital and conventional procedures generate casts that are not significantly different. Marginal fit of adhesive restorations is similar to conventional crown design and clinically acceptable. It is assumable that a direct digital workflow could benefit from the usage of 3DC. [ABSTRACT FROM AUTHOR]

Purpose: Epidemiological data showed that 16%-30% of 7- to 21-year-old patients have experienced dental trauma. Direct restorations can achieve good esthetic and functional results with significant conservation of dental tissues. This approach is far more in agreement with modern, less-invasive restorative concepts, especially in young patients. The aim of the study was to describe functional and esthetic parameters of a direct restorative treatment with a 5-year follow-up. Case Report: The 11-year-old male patient was referred to the Endodontic Department of the University of Turin Dental School for a traumatic episode involving the maxillary right central incisor. Clinical and radiographic examination showed the presence of complicated crown-root fracture and incomplete root development with periapical radiolucency and inadequate endodontic treatment with overfilling. Orthograde retreatment was executed, obtaining an apical seal with a 3-mmlayer of white MTA (ProRoot MTA, Tulsa Dental). Afterwards, the excess material and the expected fibrous tissues were removed with apical microsurgery, performed with microscopic vision (OPMI Pro Ergo, Carl Zeiss). Since the flap was raised, the coronal fracture margin was exposed and marginal relocation was carried out using flowable composite. After two weeks, a direct restoration was placed using a wax-up to plan and manage the treatment. A silicon index was created to serve as a guide for the direct composites. Additive restorations were then performed following a standardized clinical procedure: rubber-dam isolation, etch-and-rinse adhesive application, and fabrication of direct additive restorations using Clearfil-Majesty ES2 (Kuraray) with an incremental layering technique with the help of silicon guides. Dentin and enamel shades were then layered to complete the direct restorations. Finally, teeth were finished and polished with diamond bur and soft flex disks. Results: The 5-year follow-up showed complete healing of the periapical lesion and correct preservation of function and esthetic parameters. Conclusion: Nanofilled composite resins and the use of new adhesives positively influence the longevity of the direct composite restorations, which have become a reliable approach with the maximum conservation of sound tooth structure in the era of the modern minimally invasive dentistry. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this in vitro study was to evaluate the effect of three different CAD/CAM processed materials on the interfacial gap, wear, and fracture resistance of endodontically treated molars. Materials and Methods: 48 maxillary molars were selected and endodontically treated. On each specimen a standardized MOD cavity was prepared. Specimens were then divided in two groups (n = 24 each) according to the build-up technique employed: G1) build-up with a bulk fill composite material (Admira Fusion X-Tra, Voco); G2: fiber post-supported buildup. Then, a 2-mm-thick standardized overlay preparation exposing enamel margins was performed. Specimens were scanned with Cerec Omnicam (Denstply Sirona) and the indirect restoration was milled with Cerec MXCL. Each group was divided into 3 subgroups (n = 8 each) according to the CAD/CAM material employed: SG1) Grandio-Bloks (Voco); SG2) Cerasmart (GC); SG3) Celtra Duo (Dentsply). Each overlay, once completed, was luted following a standardized procedure. All specimens were scanned with micro-CT at high-resolution scans (voltage 100kV, current 80A, source-to-object distance 80 mm, source-to-detector distance 220 mm, pixel binning 292, exposure time/projection 3 s). Then, specimens of each group were subjected to mechanical fatigue testing in a dual-axis chewing device (CS-4.4, SD Mechatronik). A force of 5 kg was applied using a ceramic steatite ball for 500,000 cycles. After fatigue, micro-CT scanning was performed to evaluate the interfacial gap. Replicas were obtained for external gap evaluation with SEM. Micro-CT images, before and after cycling load, were analyzed with Geomagic Software and Mimics to evaluate interfaces gap progression before and after mechanical load. Statistical analysis was performed with two-way ANOVA. Results: The interfacial gap was not significantly influenced by the build-up technique (p = 0.061). SG2 and SG3 showed a smaller gap (p = 0.001) and a higher fracture resistance rate (p = 0.0001). No differences were found between SEM and 3D gap evaluation. Conclusion: Interfacial gap and fracture resistance could be influenced by the CAD/CAM material employed to restore endodontically treated molars. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this in vitro study was to evaluate the effect of different direct restoration techniques on endodontically treated anterior teeth, with or without fiber posts, analyzing interfacial adaptation, wear, and fracture resistance. Materials and Methods: 36 extracted single-rooted anterior teeth were selected. Endodontic treatment was carried out in all samples. After 24 h of storage in water at 37°C, samples were divided into 3 groups according to the cavity design: 1) endodontic access; 2) endodontic access + 1 class-III cavity; 3) endodontic access + 2 class-III cavities. Samples were then divided into 3 subgroups (n = 4) according to the restoration technique: SB1) direct composite restoration (DCR); SB2) DCR supported by a fiber post (Rebilda Post, Voco); SB3) DCR supported by vertical fibers (Rebilda Post GT, Voco). All specimens were scanned with x-ray computed microtomography (micro-CT Skyscan, Bruker), with the following parameters: 100 kV, 100 μA, Al-Cu filter, 10 μm pixel size, rotation step 0.1 degree, 6 h total scan duration. Then, specimens of each group were subjected to mechanical fatigue testing in a dual-axis masticatory simulator (CS4.4, SD Mechatronik). A force of 50 N was applied using a ceramic steatite ball with a diameter of 4 mm as an antagonist for 100,000 cycles at a frequency of 1 Hz, downward speed 16 mm/s, 2-mm sliding movement starting from the palatal cingulum towards the incisal edge, with an initial angle of 45 degrees. After fatigue testing, micro-CT scanning was performed again to evaluate the interfacial behavior and wear resistance. Micro-CT images before and after cyclic loading were analyzed with Mimics (segmentation) and Geomagic Software (alignment and analysis) to evaluate composite wear and interface gap progression before and after mechanical loading. Finally, a static fracture test with a universal testing machine (Instron) was performed to measure the fracture resistance of the samples after fatigue tests (4-mm-diameter metal cone at a constant speed of 0.5 mm/min and an angle of 30 degrees). Statistical analysis was performed with two-way ANOVA to evaluate the effect of cavity configuration and restoration of wear, interfacial gap, and fracture resistance. Results: Gap progression and volume are significantly related to the build-up technique (p < 0.001) as well as to the cavity configuration (p = 0.032). Two-way ANOVA showed that both the variable cavity (p = 0.0020) and the variable material (p = 0.0013) significantly influence the fracture resistance. No other significant interactions were shown by ANOVA (p = 0.5130). Conclusion: Endontically treated anterior teeth should be restored with composite restorations supported by fiber structures, especially in the case of loss of both marginal ridges. Further studies are needed to better understand the influence of fiber post on interfacial adaptation, wear, and fracture resistance over time. [ABSTRACT FROM AUTHOR]

This study evaluated the effectiveness of chemical-based adhesive techniques on promoting immediate and aged bond strength between zirconia and luting cement. A total of 128 discs of zirconia were divided into 4 groups (n = 32) according to the adhesive treatment: tribochemical silica-coating followed by silane (Silane Primer, Kerr) and bonding (Optibond FL, Kerr), Signum Zirconia Bond (Hereaus), Z-Prime Plus (Bisco), and All-Bond Universal (Bisco). Composite cylinders were cemented on the zirconia sample with Duo-Link Universal (Bisco). Eight specimens per group were subjected to 10,000 thermocycles and subsequently bond strength was tested with shear-bond strength test. ANOVA test showed that artificial aging significantly affected the bond strength to zirconia. Bonferroni test highlighted a significant influence of adhesive treatment (Signum) on bond strength after thermocycling. It was concluded that 10-MDP-based bonding systems showed no improvement in initial bond strength compared with tribochemical treatment. All chemical bonding techniques tested in this study were influenced by thermocycling. [ABSTRACT FROM AUTHOR]