Adhesive strength of self-adhesive resins to lithium disilicate ceramic and dentin: effect of dentin chelating agents.

The aim of this study was to test the effect of different chelating agents on microtensile bond strength (MTBS) of self-adhesive resin cements to dentin. The occlusal surfaces of extracted human mandibular molars (N = 80) were cut horizontally to expose sound dentin. The teeth were randomly divided into four groups (n = 20 per group) and dentin surfaces were conditioned according to one of the following methods: group C: no treatment (control group); group CH: 0.2 % chitosan; group E: 17 % ethylene diamine tetra acetic acid (EDTA) and group P: 25 % polyacrylic acid (PAA). Lithium disilicate glass ceramic (e.max CAD) blocks were cemented to conditioned dentin surfaces with self-adhesive cements (RelyX Unicem or Clearfil SA) and photo-polymerized. Specimens were stored in distilled water at 37 °C for 24 h and thermocycled for 6,000 times. The beams were obtained from bonded ceramic-cement-tooth assemblies and were subjected to the MTBS test (1 mm/min). Failure types were analyzed and selected beams were examined under scanning electron microscope. Data (MPa) were analyzed using two-way ANOVA and Tukey's test (P < 0.05). While cement type significantly affected the MTBS results (P < 0.05), no significant difference was observed between the dentin chelating agents (P = 0.785). Interaction terms were not significant (P = 0.114). Control group with no dentin conditioning presented significantly lower results with both cements (RelyX Unicem: 8.1 ± 1.9(a), Clearfil SA: 8 ± 1.6(a)) than those of conditioned groups (19.3 ± 4.2(b)-24.5 ± 5.2(b)) (P < 0.05). Failure types were predominantly adhesive in all groups. Chitosan (2 %), EDTA (17 %) or PAA (25 %) could all be used as dentin chelating agents in conjunction with self-adhesive resin cements tested.