Self-adhesive resin cements should ease the placement of dental restorations. The purpose of this study was to evaluate their shear bond strength to enamel and dentin. Sixty molars were randomly assigned to 12 test groups (each n = 10), and the approximal surfaces were ground flat to get an enamel and dentin surface with a diameter of at least 4 mm. Ceramic specimens were bonded to the surfaces with either Variolink/Syntac Classic (VSC), Panavia F2.0 (PAF), RelyX Unicem (RLX), Maxcem Elite (MCE), iCem (IC), or an experimental self-adhesive resin cement (EXP). The shear bond strength (crosshead speed: 1 mm/min) was measured after 24-h storage in NaCl (37 degrees C). The fracture modes were determined with a stereomicroscope (magnification, 8-50-fold). VSC had the highest shear bond strength within the enamel groups (42.9 +/- 9 MPa) and IC the lowest (10.5 +/- 4.2 MPa, p < 0.001). The highest dentin shear bond strength was determined for VSC (39.2 +/- 8.9 MPa, p < 0.001) and the lowest for EXP (7.8 +/- 3.9 MPa, p < 0.001). Self-adhesive resin cements fractured mainly between resin and enamel or dentin. The shear bond strength of self-adhesive resin cements was inferior compared to conventional composite resin cements.

No abstract

SUMMARYThis study evaluated the shear bond strength of self-etch adhesives to enamel and the effect of additional phosphoric acid etching.Seventy sound human molars were randomly divided into three test groups and one control group. The enamel surfaces of the control group (n=10) were treated with Syntac Classic (SC). Each test group was subdivided into two groups (each n=10). In half of each test group, ground enamel surfaces were coated with the self-etch adhesives AdheSe (ADH), Xeno III (XE) or Futurabond NR (FNR). In the remaining half of each test group, an additional phosphoric acid etching of the enamel surface was performed prior to applying the adhesives. The shear bond strength was measured with a universal testing machine at a crosshead speed of 1 mm/minute after storing the samples in distilled water at 37°C for 24 hours. Fracture modes were determined by SEM examination. For statistical analy-© Operative Dentistry, 2008, 33-2, 155-162 Clinical RelevanceWhen using self-etch adhesives to bond composite materials to enamel, there is concern about the ability to achieve bond strengths comparable to approved etch-and-rinse systems. An additional phosphoric acid etching can improve the shear bond strength of self-etch adhesives to enamel.

The purpose of this study was to analyze the push-out strength of two fiber post systems/resin cements (RelyX Unicem/RelyX Fiber Post (RLX) and Variolink II/DT Light SL (VL)) depending on the root canal filling (RF). One hundred sixty extracted human teeth were divided into four groups: gutta-percha/AH Plus (GP), gutta-percha/Guttaflow (GF), pre-existing root canal filling (PRF), and without root canal filling (WRF). After root canal treatment, fiber posts were inserted using either RelyX® or Variolink II®/Excite DSC®. Half of the specimens were thermocycled (TC, 5,000 cycles, 5-55°C). All specimens were subjected to the push-out test (crosshead speed 1 mm/min). Three-way ANOVA showed a significant influence of either the RF or the resin cement/post system (p < 0.001). The highest bond strength was measured for VL-WRF without TC (16.5 ± 6.4 MPa). TC had no significant influence within the RLX groups. For groups PRF and WRF, significant differences were documented between VL and RLX (PRF 16.3 ± 6.0 vs 7.0 ± 2.4 MPa, p = 0.001; WRF 16.5 ± 6.4 vs 8.0 ± 5.0, p = 0.004) before TC. No differences were found after TC. The fracture mode analysis for VL showed mainly adhesive fractures between post and cement. For RLX, mixed fractures between post and tooth and between tooth and cement were predominantly determined. The adhesion of resin cements/post systems could be dependent on the type of RF. Higher bond strength values were found for the conventional ("etch and rinse") adhesive than for the "self-adhesive resin cement."