Effect of composition and complexity of dentin-bonding agents on operator variability--analysis of gap formation using confocal microscopy.

The variability of gap formation due to different operators and bonding agents around dentin-bonded composites in cylindrical cavities (internal diameter, 3 mm; depth, 1 mm; n = 210) was evaluated in vitro. Seven dentists evaluated two experimental bonding systems (A & B) and one commercial product (C) by each treating 10 teeth with each system. One of the investigators restored all cavities with composite (Z100, 3M ESPE) and removed excess material to expose the cavity margins. After storage in water for 1 wk, the maximum gap-width was measured using a confocal microscope and statistically analysed. The relative gap-widths (%) for the three bonding systems were not statistically different. Means +/- SD were 0.18 +/- 0.06, 0.19 +/- 0.08, and 0.20 +/- 0.06 for groups A, B, and C, respectively. The variation caused by the operator-material interaction was significant. When the operator's variability (SD) within the different materials was examined, group C displayed a significantly lower variability than the other two. It was concluded that the operator variable is a more important consideration than the material variable. The self-etching system performed better than the more complex A and B systems when variability rather than gap size was considered.