Micromorphological analysis of the interaction between a one-bottle adhesive and mineralized primary dentine after superficial deproteination

It has been claimed that resin monomers may incompletely penetrate into demineralized collagen network, which could form a weak hybrid layer. In consequence, it has been proposed that removal of the exposed collagen network could improve adhesion to dentine. The interface between a water/ethanol-based one-bottle adhesive (Single Bond, 3M) which is devoid of acid monomers, and deproteinated surface of primary dentine was evaluated by SEM. Dentine disks were obtained from 20 primary teeth. Two disks were used to standardize the application time of sodium hypochlorite (NaOCl) for getting an effective deproteination. The remaining 18 disks were equally divided into two groups and treated as follows: control group (CG) 35% phosphoric acid (PA) for 15s; treated group/deproteination (TG) 35% PA for 15s+10% NaOCl for 3 min. Single Bond and Z250 (3M) were placed on all disks according to the manufacturer's instructions. The 18 resin-dentine disks were fractured to obtain hemi-disks and processed for SEM. The examination of the CG specimens showed a typical hybrid layer and the presence of numerous tags with few and short microtags. The TG specimens, which did not present hybrid layer, also exhibited numerous tags, with few and short microtags. Some areas between the tags showed fibrillar-like projections, which appeared to be mineralized collagen fibrils, which were incorporated into the adhesive. Thus, our results suggest that some chemical interaction may occur between mineralized dentinal collagen and the adhesive used.