Objectives: The aim of this study was to define the morphological bonding of the F2000 Restorative System (3M Dental Product) to enamel and dentin. For this purpose, high resolution scanning electron microscope (SEM) in conjunction with a tensile bond strength analysis was used to correlate the morphological findings to the bonding potential. Scotchbond 1 (SB1) adhesive system was utilized as a control.
Materials and methods: Teeth were prepared in vivo and prepared as: (1) F2000 PA for 15s, (2) F2000 PA for 30s, (3) 35% phosphoric acid for 15s and SB1 and (4) 35% phosphoric acid for 30s and SB1. All teeth were then restored with the F2000 compomer restorative material, extracted, sectioned and analyzed by means of a field emission in-lens SEM (FEISEM). The conditioning/etching patterns of the two adhesive systems were also evaluated in vitro on dentin disks in order to show high resolution details of every single step of the bonding procedure.
Results: FEISEM images showed a repetitive pattern of the enamel crystals with several microporosities after the 30s application of F2000 PA; moreover a good adaptation of the adhesive resin on the conditioned enamel was observable. FEISEM analysis of the dentin surface revealed no evidence of a smear layer after the application of F2000 PA for 30s. Residual smear plugs were partially obliterating the tubule orifices when F2000 PA was used, while they were completely absent after etching with 35% phosphoric acid. The total etching technique revealed open tubules and resin tags formation after the application of SB1.
Conclusions: The one step etching/priming/bonding procedure of the F2000 PA showed favorable results at ultra-structural level when applied on both the enamel and the dentin surface for 30s (as per manufacturers' instructions), but the bond strength analysis showed higher values of bonding of the F2000 compomer when the SB1 adhesive agent (after etching with 35% phosphoric acid) was used (7.7+/-2.2 vs 19.0+/-4.4MPa).