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    Adhesion of veneering composite to metal-free CAD/CAM materials: effect of surface conditioning and adhesive resin type
    (Taylor & Francis Ltd, 2023) Onugoren, Nazik Irem; Demirci, Fatih; Tatar, Numan; Eyuboglu, Tan Firat; Ozcan, Mutlu
    ObjectivesThis study aimed to investigate the adhesion of veneering composite to metal-free computer-aided design/computer-aided manufacturing (CAD/CAM) materials with different compositions after surface conditioning and application of adhesive resins.Materials and MethodsA total of one hundred and sixty specimens were divided into four groups (n = 40) manufactured either from polyetheretherketone (PEEK; KERAstar PEEK), polyetherketoneketone (PEKK; Pekkton), fiber-reinforced composite (FRC; Trinia), or high-impact polymer composite (COMP; Bredent HIPC) CAD/CAM discs. Each group was then randomly subdivided into four different subgroups of adhesive systems (n = 10) as Visiolink (Bredent), Single Bond Universal (3M), G-Premio BOND (GC), and OptiBond Universal (Kerr). The shear bond strength (SBS) of each specimen with veneering composite material was tested with a universal testing machine following thermocycle aging (5000 times). The modes of failure resulting from the tests were determined with scanning electron microscope (SEM), dispersive spectroscopy (EDS), and analytical imaging. The data were statistically analyzed with two-way ANOVA and Bonferroni post hoc tests (alpha = 0.05).ResultsThe highest SBS values among all groups were found for the COMP material (20.28 +/- 2.08 MPa) with OptiBond Universal adhesive, while the lowest for the PEEK material (10.33 +/- 2.47 MPa) with G-Premio BOND. The most common failure mode for the PEEK and PEKK specimens was adhesive failure, for the FRC and COMP groups mixed failures were common.ConclusionsBond strength values of at least 10 MPa were achieved for all tested between metal-free CAD/CAM materials and adhesive resin application.
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    Effect of passive air exposure and light contact duration on the bond strength and mechanical properties of universal adhesives
    (Elsevier Sci Ltd, 2025) Ocal, Fikri; Onugoren, Nazik Irem; Dayi, Burak; Sarici, Tuba
    Objective This study aimed to evaluate the effects of passive air exposure (no active drying) and light contact time (under D65 light simulating daylight) on adhesive performance. Methods Five universal adhesives (G-Premio Bond [GC], Clearfil Universal Bond [Kuraray], Prime & Bond Universal [Dentsply], OptiBond Universal [Kerr] and Gluma Bond Universal [Kulzer]) were applied to dentin samples after different passive air exposure times (0, 5, 15, 30 s) under standard D65 artificial daylight. Micro-tensile bond strength (mu TBS), fracture distance (Delta L), and elastic modulus (E) were measured. Morphological evaluation of the adhesive interfaces and fracture patterns was performed using scanning electron microscopy (SEM). Statistical analysis included two-way ANOVA to assess the main effects and interactions of adhesive type and exposure time, followed by one-way ANOVA or Kruskal-Wallis tests for group-specific comparisons. Post hoc tests (Tukey, Bonferroni, or Games-Howell) were applied when appropriate. Correlation and regression analyses were also performed. Statistical significance was set at p < 0.05. Results Passive air contact and light exposure significantly affected the mechanical performance of the adhesives. The GPB 30 s group showed the highest bond strength, while the elastic modulus decreased significantly (p = 0.028). The CUB 15 s group exhibited one of the highest elastic modulus values, but the adhesive fracture rate was high in the fracture type (p = 0.007). Correlation analyses showed a strong negative relationship between elastic modulus and fracture distance (r = -0.559/-0.834). SEM images revealed that air bubbles had a negative effect on bond strength. Significance of the study This study guides on the optimal application time for clinical applications by evaluating the effects of air and light exposure time on bonding mechanisms in universal adhesive systems. The findings suggest that adhesive application protocols should be precisely optimized.