Adhesive Monomer Conversion on Various Substrates

Methods: Six groups of 10-12 specimens each were prepared using the one-step self-etch adhesives Clearfil S³ Bond Plus (C-S³P, Kuraray) and Scotchbond Universal (Sc-U, 3M ESPE) and.

Group 1: The adhesive was applied according to manufacturer’s instructions to a glass slide, then covered by another glass slide and light-cured.

Group 2: Same as Group 1, but applied to a glass plate pre-heated to 37°C.

Group 3: The adhesive was applied to mid-coronal human dentin discs, covered by a glass slide and light-cured.

Group 4: Same as Group 3, but applied to dentin discs pre-heated to 37°C.

Group 5: Same as Group 3, but dentin was dehydrated in an oven at 37°C and under vacuum.

Group 6: Same as Group 1, but the adhesive was mixed with 10wt% dentin powder obtained by grinding human dentin (A 10, IKA).

The specimens were cured for 10 sec (Bluephase 20i, Ivoclar-Vivadent) and stored at 37°C for 24 h. DC was measured by ATR FTIR (Vertex 70, Bruker). DC was calculated as the ratio of peak intensities of the aliphatic 1640 cm^-1 and aromatic 1610 cm^-1peaks in cured and uncured materials.

Results: Mean DC (SD) of the adhesives tested following the 6 different protocols

Groups with the same superscript are not significantly different (ANOVA, Tukey’s HSD, p<0.05)

Conclusions: The hydration state of dentin had a more profound effect on DC of the adhesives tested than the dentin temperature. Pre-heating glass or dentin may have a positive effect on monomer conversion, though this is adhesive dependent.