Effect of Application Deviations on Dentin Sealing of a Universal Adhesive: Permeability and Nanoleakage

The objective of this study was to evaluate the effect that deviations from the recommended protocol of a universal adhesive system, applied to dentin according to the self-etch (SE) and the etch-and-rinse (ER) techniques, has on permeability and nanoleakage.

Permeability: 60 extracted non-carious human third molars (N = 60) were sectioned to obtain 0.7-mm-thick dentin disks. The specimens were randomly assigned to three subgroups and treated with a universal adhesive system (Prime&Bond Active Universal) using the SE and ER techniques: (1) following the manufacturer's instructions with 5 seconds drying (MFR DRY 5S), (2) following the MFR DRY 10S, and (3) reduced application time of the adhesive to 5 seconds (APPL 5S). Nanoleakage: 12 additional 0.7-mm-thick dentin disks were prepared, treated and divided into six groups. They were immersed in 50 wt% ammoniacal silver nitrate and processed according to conventional methods for the analysis of nanoleakage under transmission electron microscopy.

The results were statistically analyzed by two-way analysis of variance and post-hoc Bonferroni's test.

Significant differences in permeability reduction were observed among the treatment groups (0.001). The results obtained for APPL 5S were significantly lower than the results obtained for both the MFR DRY 5S (p = 0.003) and MFR DRY 10S (p = 0.001).

The reduced application time to 5 seconds creates imperfect dentin tubule sealing, which may explain clinical reports of postoperative sensitivity and early degradation of the resin-dentin interface.