decyl phosphoric acid (MDP) monomers. The dilemma for the clinicians remains whether <strong>to</strong> follow the manufacturers’ instructions <strong>of</strong> the <strong>cement</strong>s during <strong>cement</strong>ing the FPDs made <strong>of</strong> zirconia or modify the instructions and follow the instructions <strong>of</strong> some manufacturers that suggest separate surface-conditioning pro<strong>to</strong>cols. Therefore, the objectives <strong>of</strong> this study were <strong>to</strong> evaluate (1) the bond strength <strong>of</strong> four <strong>resin</strong> materials with various chemical compositions following the manufacturers’ instructions only and (2) <strong>to</strong> test their durability under dry and thermally aged conditions. The tested hypothesis was that thermocycling would decrease the bond strength <strong>of</strong> all <strong>resin</strong>s. Materials and methods Disc-shaped (diameter=15 mm, thickness=2 mm) Y-<strong>TZP</strong> ceramics (LAVA, 3M ESPE, Seefeld, Germany) were embedded in polyethylene molds using polymethylmethacrylate (PMMA; Condular AG, Wager, Switzerland) with one side <strong>of</strong> the disc exposed for adhering the <strong>cement</strong> (Fig. 1). They were ground finished up <strong>to</strong> 1,200-grit silicone carbide abrasive under water cooling and ultrasonically cleaned in distilled water for 3 min. The discs were randomly divided in<strong>to</strong> eight groups depending on the <strong>cement</strong> type and the ageing condition <strong>to</strong> be applied (N=80, n=10/per group; Table 1). Four types <strong>of</strong> <strong>resin</strong> materials were chosen: a light-polymerized (Panavia F 2.0, Kuraray, Medical Inc., Osaka, Japan), self-adhering (Multilink Ivoclar Vivadent, Schaan, Liechtenstein) and chemically polymerized <strong>cement</strong> (SuperBond, Sun Medical, LTD, Tokyo, Japan) where the <strong>resin</strong> composite (Quadrant Posterior Dense, Cavex, Harlem, The Netherlands) acted as the control material. Fig. 1 The Y-<strong>TZP</strong> disc specimen was embedded in the PMMA with the <strong>cement</strong>ation surface exposed. Cement was applied incrementally, not exceeding 2 mm, <strong>to</strong> the surface using polyethylene molds (inner diameter=3.6 mm, height=5 mm) and polymerized accordingly Table 1 Testing groups considering the types <strong>of</strong> <strong>resin</strong> <strong>cement</strong>s and the s<strong>to</strong>rage conditions (dry vs thermocycling—TC) Type <strong>of</strong> <strong>resin</strong> <strong>cement</strong> S<strong>to</strong>rage condition a Panavia F 2.0 b Multilink c Superbond d Quadrant Posterior Dense e Shear bond test The specimens were placed in the jig <strong>of</strong> the universal testing machine (Zwick ROELL Z2.5 MA 18-1-3/7 Ulm, Germany), and load was applied <strong>to</strong> the adhesive interface until failure occurred (crosshead speed=1.0 mm/min). The maximum force <strong>to</strong> produce fracture was recorded (N/mm 2 = MPa) using the corresponding s<strong>of</strong>tware. Statistical analysis Dry Gr1 TC Gr2 Dry Gr3 TC Gr4 Dry Gr5 TC Gr6 Dry Gr7 TC Gr8 Clin Oral Invest Testing groups a Dry condition—Shear test was performed immediately after <strong>cement</strong>ation; TC condition—6,000 cycles between 5 and 55°C in deionized grade 3 water. The dwelling time at each temperature was 30 s, and the transfer time from one bath <strong>to</strong> another was 2 s (Willytech, Gräfelfing, Germany). b (1) Conditioning the ceramic using chair-side air-particle abrasion device with 50 μm Al 2O 3 for 15 s making circular movements from a distance <strong>of</strong> 10 mm; (2) rinsing the surface for 20 s with water and air drying for 5 s; (3) mixing equal amounts <strong>of</strong> paste A and B from the Panavia F 2.0 with a <strong>cement</strong> spatula for 20 s; (4) application <strong>of</strong> the mixed <strong>cement</strong> in the polyethylene mould on<strong>to</strong> the ceramic surface incrementally; (5) light polymerization (light output=500 mW/cm 2 ) <strong>of</strong> each increment for 20 s (Astralis ® 5, Ivoclar Vivadent AG, Schaan, Liechtenstein). c (1) Rinsing the surface for 20 s with water and air drying for 5 s; (2) applying Monobond-S on the ceramic surface with a microbrush, waiting 60 s and air drying; (3) application <strong>of</strong> the mixed <strong>cement</strong> in the polyethylene mould on<strong>to</strong> the ceramic surface incrementally (Ivoclar Vivadent AG, Schaan, Liechtenstein). d (1) Rinsing the surface for 20 s and air drying for 5 s; (2) applying the Porcelain Liner M <strong>to</strong> the surface with a microbrush; (3) Mixing four drops <strong>of</strong> Quick Monomer, one drop <strong>of</strong> Catalyst S and one small scoop <strong>of</strong> the <strong>cement</strong> powder with a brush; (4) application <strong>of</strong> the mixed <strong>cement</strong> in the polyethylene mould on<strong>to</strong> the ceramic surface incrementally; (5) waiting for polymerization for 6 min (Sun Medical Co., LTD, Moriyama, Japan). e (1) Rinsing the surface for 20 s and air drying for 5 s; (2) application <strong>of</strong> the mixed <strong>cement</strong> in the polyethylene mould on<strong>to</strong> the ceramic surface incrementally; (3) light polymerization (light output=500 mW/cm 2 )<strong>of</strong> each increment for 40 s (Astralis ® 5, Ivoclar Vivadent AG, Schaan, Liechtenstein; Cavex, Haarlem, The Netherlands). Two-way analysis <strong>of</strong> variance (ANOVA) and post-hoc multiple comparisons were used <strong>to</strong> analyze the data (SPSS for Windows Version 10.05; SPSS, Chicago, IL) with the shear bond strength as the dependent variable. p values less
Clin Oral Invest than 0.05 were considered <strong>to</strong> be statistically significant in all tests. Multiple comparisons were made using Tukey’s adjustment test. Results Bond strength results were significantly affected by the s<strong>to</strong>rage condition (p
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