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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: 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]