Evaluating EDTA as a Substitute for Phosphoric-Acid-Etched Enamel and Dentin

Matrix metalloproteinases (MMPs) available after acid-etching can degrade un-encapsulated collagen within the hybrid layer.  Applying 2% chlorhexidine (CHX) after acid-etching prevents activation of MMPs. Neutral ethylenediamine-tetra-acetic acid (EDTA) may prevent release of MMPs.  Objectives: To determine if EDTA conditioning can replace phosphoric-acid-etching (PAE) of enamel and dentin which has been treated with CHX.  Methods:   Sixty caries free molars were mounted in acrylic resin and randomly divided into four groups (n=15).  Occlusal surfaces were reduced exposing flat enamel (E) surfaces which were treated by actively rubbing 17% EDTA for 15, 30 or 60seconds.  The fourth group was phosphoric-acid-etched (15s), rinsed (15s), lightly dried and lightly scrubbed with 2% CHX (60s).  Two applications of Optibond Solo Plus were applied, air-dried after each application (10s) and light-cured (20s).  Columns of Filtek Z250 resin 2.5mm in height and 2.38mm in diameter were bonded and light-cured (40s).  Specimens were stored (48h) in 100% humidity followed by immersion in de-ionized water (24h).  Specimens were shear tested until failure in an Instron (crosshead speed of 0.05mm/min).  After shear testing the occlusal surfaces were reduced to expose dentin (D) and bonding protocols repeated for testing dentin shear bond strength. Results: Mean shear bond strengths (MPa) were as follows: E/EDTA/15s 12.7, E/EDTA/30s 12.3, E/EDTA/60s 15.1, E/PAE/CHX 15.7, D/EDTA/15s 13.3, D/EDTA/30s 14.3, D/EDTA/60s 13.6, D/PAE/CHX 20.2.  Data was skewed and analyses performed on log-transformed values with two-way ANOVA.  There were significant differences between enamel and dentin (p<0.0001), and within enamel (p<0.007) and dentin groups (p<0.0001).  All EDTA treated dentin groups were significantly weaker than phosphoric-acid-etched chlorhexidine treated dentin which was statistically stronger than all other enamel and dentin groups.  Only EDTA(60s) treated enamel was not significantly different than phosphoric-acid-etched enamel.  Conclusions:   EDTA should not be used to condition enamel and dentin when using OBSP.