Effect of Steam Autoclaving on the Tensile Strength of Resin Cements Used for Bonding Two-Piece Zirconia Abutments
The purpose of this study was to evaluate the effects of steam autoclave sterilization on the tensile strength of two types of resin cements used to bond customized CAD/CAM zirconia abutments onto titanium bases. Forty sets of zirconia abutments cemented to screwed titanium bases of implants analogs were divided into 4 groups (n = 10). Two groups were treated with a conventional chemically activated resin cement (ML, Multilink Ivoclar Vivadent) and the other two groups with a self-adhesive dual resin cement (RelyX U200, 3M ESPE). One group from each cement was submitted to steam autoclaving. The autoclave sterilization cycle was performed after 72 hours of cementation for 15 minutes at 121°C and 2.1 Kgf/cm2. The samples were subjected to tensile strength testing in a universal testing machine (200 Kgf, 0.5 mm/min), from which the means and standard deviations were obtained in Newtons. Results showed (via ANOVA and Tukey's test; α = 0.05) that in the absence of steam autoclaving, no difference was observed in tensile strength between the cements tested: ML: 344.87 (93.79) and U200: 280 (92.42) (P = .314). Steam autoclaving, however, significantly increased tensile strength for the ML: 465.42 (87.87) compared to U200: 289.10 (49.02) (P < .001). Despite the significant increase in the ML samples (P = .013), autoclaving did not affect the tensile strength of the U200 samples (P > 0.05). The authors concluded that steam autoclaving increases the mean tensile strength of the chemically activated cement compared to the dual-cure self-adhesive cement. The performance of both cements evaluated was similar if the sterilization step was disconsidered.
Figure 1. Abutment-Amplified cemented cylinder (P-I Branemark Philosophy). Figure 2. Relationship between the thickness of the Ti base ring and the Zr abutment.
(A) Schematic outline of the device used for the test. a: Metal device that was turned internally, so that the portion of the analog and the zirconia abutment would pass through it (this device is connected to the load cell); b: another device was made by hollowing a steel cylinder so the groove in the apical portion of the implant analog would fit and remain fixed (this device is attached to the base of the universal test machine); c: device screwed into a metal apparatus to secure the zirconia abutment in position; d: zirconia abutment; e: implant analog. (B) Tensile test moment.
Figure 4. (a) Illustration of the resin cement fully adhered to the zirconia abutment. (b) Implant analog without resin cement. Figure 5. (a) Ilustration of the zirconia abutment without resin cement. (b) Resin cement fully adhered to the titanium base. Figure 6. (a and b) Illustration showing the mixed fracture mode of the resin cement in the zirconia abutment and adhered to the titanium base.
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