Effect of Dentine Conditioning on Adhesion of RM-Glass Ionomer Cements

Abstract

Objective: Recently, a new resin modified glass ionomer cement (RM-GIC) adhesive was introduced with manufacturer’s instructions suggesting phosphoric acid etching for dentine surface treatment which has been regarded as not ideal. This study aimed to investigate the use of phosphoric acid as a surface treatment when bonding RM-GIC adhesives Method: Caries-free human teeth were used as the bonding substrate. Three RM-GICs were tested: Fuji Bond LC (FJ: GC Corp, Japan), Riva Bond LC (RB: SDI, Aust) and Ketac Nano (KN:3M-ESPE, USA). Surface treatment was either 37% phosphoric acid for 5 sec or 10% polyacrylic acid (PAA) for 10 sec, or following manufacturer’s recommended methods, Fuji Bond LC: Cavity Conditioner (10 sec) and Ketac Nano: Ketac Nano priming agent (15 sec). Teeth were finished with 600-grit SiC paper, the surface treated then bonded with one of the RM-GICs and stored for 24 h. Teeth were sectioned (cross-sectional area approx. 1mm2) and subjected to microtensile bond testing. Five teeth were tested for each adhesive-treatment combination (15 sticks prepared from each tooth). ANOVA and Tukey’s post hoc test were used to analyse results.

Result: The use of phosphoric acid etch for FJ (24.8 MPa) and RB (25 MPa) produced the highest strengths but were not statistically better than PAA (FJ: 21.9 MPA; RB 22.4 MPa) or Cavity Conditioner (FJ:21 MPa), P>0.05. KN showed statistically lower bond strengths for phosphoric acid (17.2 MPa), PAA (15.6) and the primer (14 MPa), P<0.05 compared with the FJ or RB. Failure mode showed no specific trend with surface treatment method.

Conclusion: It would seem for RM-GICs a very short etch with phosphoric acid does not have an adverse effect on bond strengths in the short-term, but is no better than using 10% PAA. Long-term adhesion tests are needed to further clarify which surface preparation method is best.