Shear Bond Strength of Three Resin-modified-glass-ionomers Following Six Surface Treatments

Resin-modified-glass-ionomers (RMGI) bond to dentin via resin (micromechanical) and ionomer components (chemical).  Cavity Conditioner (CC) containing polyacrylic acid and 17% ethylenediamine-tetra-acetic acid (EDTA) remove smear layers allowing chemical bonding.  Self Primer (SP), Ketac Primer (KP) and Optibond Solo Plus (OBSP) contain resinous components for micromechanical bonding.  Objectives: To determine best combination of RGMI and dentin conditioner.  Methods: 285 caries-free third molars mounted in acrylic resin were reduced exposing dentin.  Teeth were assigned to 19 groups (n=15) depending upon surface treatments:  Smear layer (SL) intact (negative control), CC, EDTA, SP, KP and acid-etching (15s) followed by two applications of OBSP.  Filtek Z250 composite resin bonded to dentin with OBSP served as the positive control.  Conditioning and bonding agents were used according to manufacturers’ instructions.  Copper band matrices (5mm in diameter, 2mm in height) were affixed to dentin.  After conditioning, Fuji II LC (F), Riva LC (R), Ketac Nano LC (KN) or Z250 were placed in matrices and light-cured (40s).  Specimens were stored (24h) in de-ionized water (37ºC), shear tested in an Instron (crosshead speed of 0.05mm/min.)  Results: mean shear bond strengths recorded in MPa were as follows: R/OBSP 15.5^A; Z250/OBSP 14.6^A; KN/OBSP 12.1^AB; F/OBSP 12.1^AB; F/SP 9.4^ABC; F/KP 9.4^ABC; F/EDTA 7.9^BCD; KN/SP 7.7^BCD; R/SP 6.2^CDE; F/CC 5.0^DEF; KN/EDTA 4.8^DEF; R/EDTA 3.9^EF; KN/KP 3.7^EF; R/CC 3.6^F; R/KP 3.6^F; KN/CC 1.7^G   Data was analyzed on a log-transformed scale using two-way ANOVA and Tukey’s HSD.  Groups not sharing the same superscripts were statistically different (p<0.05).  Significant interactions between RMGIs and conditioners were dependent upon RMGI (p<.0001).  OBSP provided highest strengths for all RMGIs which were not statistically different from the positive control.  Conclusions: Resin components (micromechanical) play a larger role than ionomer components (chemical) in RMGI bonding.