Interfacial Characterization of a New Universal Dentin Adhesive

Objective: To study the dentin-resin interface and nanoleakage of a novel universal adhesive.

Method: Dentin – 12 human molars (middle dentin) were assigned to 6 groups: (1) Group CSE – Clearfil SE Bond (Kuraray), a 2-bottle self-etch adhesive (self-etch control); (2) Group OSL – OptiBond SOLO Plus (OSL, Kerr), a 2-bottle etch&rinse adhesive applied on etched moist dentin (etch&rinse control); (3) Group OSL-d - OSL applied on etched dried dentin; (4) Group SBU-SE - Scotchbond Universal Adhesive (SBU, 3M ESPE), a 1-bottle universal adhesive, applied as a self-etch adhesive; (5) Group SBU-ER – SBU applied as an etch&rinse adhesive on etched moist dentin; (6) Group SBU-ERd - SBU applied as an etch&rinse adhesive on etched dried dentin. Specimens were restored and processed for FESEM evaluation. For nanoleakage assessment, 42 sound molars were randomly assigned to the same experimental groups with an additional group 7 (selective enamel-etching, SBU-En). Buccal and lingual class V preparations were restored with Filtek Z250 and processed with 50% ammoniacal silver nitrate.  After sectioning, specimens were observed under a stereomicroscope to evaluate the depth of silver penetration (0-4). The scores were compared using Mann-Whitney test (p<0.05). Selected specimens were processed for backscattered FESEM to evaluate the nanoleakage pattern into the resin-dentin interface.

Results: SBU-SE and CSE formed a continuous dentin-resin interface with a 0.2μm-0.3μm thick hybrid layer (HL). Air-drying did not affect the HL for SBU-ERd. OSL-d resulted in an inconsistent HL with areas of debonding. SBU-SE and SBU-En resulted in statistically lower silver infiltration than all other groups. These two adhesives virtually prevented nanoleakage in all specimens. CSE and OSL were ranked in the intermediate subset. OSL-d, SBU-ER, and SBU-ERd resulted in significantly greater silver penetration than the remaining groups.

Conclusion: SBU-SE and CSE form a very similar resin-dentin interface/HL. SBU-SE and SBU-En (selective enamel-etching) seal dentin margins.