SEM EVALUATION OF THE RESIN-DENTIN INTERFACE WITH PROPRIETARY BONDING AGENTS IN HUMAN-SUBJECTS

Laboratory studies on dentin bonding do not replicate physiological reality. This study examined with SEM the attachment produced in vivo under clinical conditions. Forty-four cavities were prepared in buccal/ lingual surfaces of 16 premolar teeth scheduled for extraction and assignedrandomly for treatment with: All-Bond 2 (Bisco) (A) with and (B) without dentin etch, (C) Scotchbond 2 (3M), (D) Scotchbond Multi-Purpose (3M), and (E) controls, using Enamel Bond (Kulzer) with dentin etch. After atraumatic extraction, restorations were split transversely by freeze-fracture and acid-treated. SEM examination of A revealed significant areas of gap-free attachment, with evidence of an acid-resistant hybrid layer (5-8 mu m), often with resin tags of various lengths. Resin-reinforced collagen fibers were seen. Gap formation was coincident with lack of bonding resin layer over primed dentin. Attachment with B was less effective; a hybrid layer was infrequently seen and few resin tags. Pooled bonding resin at internal line angles appeared to favor an effective bond. Treatment C resulted in large areas of detachment, leaving an adherent primed dentin layer with short resin tags. Treatment D revealed significant areas of gap-free attachment and evidence of a hybrid layer. Controls (E) showed total bond failure. Attachment with A and D was secure, restorations remaining in situ even after freeze-fracture. This study confirmed that brief acid pre-treatment of dentin, allowing diffusion of resin-dentin primers, appeared conducive to development of an effective bond in vivo, similar to that reported in vitro.