Microtensile Dentin-bond Strength Study of Rigid Rod Polymer Modified Primers

Objectives: This study evaluated the effect of solvent-monomer-ratio and optional addition of initiator-activator system to the experimental rigid rod polymer (RRP) modified primer on microtensile dentin-bond strength (µTBS). RRPs are based on long stiff molecules (eg. polyphenylenes), which can act as reinforcing nanoscale fiber fillers after being dissolved with solvent. Methods: Primers with different solvent proportions were fabricated by dissolving RRP (Parmax, 1240, Mississippi PolymerTechnologies Inc., USA) into dichloromethane (DCM) and optionally further mixing it with monomers, activator and initiator; bis[2-(methacryloyloxy)-ethyl]phosphate (BMEP) and 3(methacryloyloxy)propyltrimethoxysilane (MPS) dimethylaminoethyl methacrylate (DMAEMA) and camphorquinone (Table). A commercial etch-and-rinse adhesive (Voco Solobond Plus) was used as a control. Primers were applied onto human dentin prior composite resin build-up was light-polymerised incrementally. After 48 hours in water at 37°C the teeth were sectioned and the specimens were then tested with the microtensile tester. Fracture surface analysis was performed. Results: Increase of the solvent-monomer ratio and addition of RRP into primers increased uTBS (3-way ANOVA, p=0.05). Adding activator and initiator into primer did not increase bond strength. Most of the failures in all groups were mixed type failures (adhesive-cohesive). Conclusions: Experimental primer of low viscosity (ratio 5:1) showed comparable results with the control primer-adhesive system.

ANOVA was performed (p=0.05). Superscript letter indicates homogenous subsets in one-way ANOVA (Tukey) (p=0.05).