Effectiveness of two self-etchings bonded clinically in caries affected dentin with homogeneous smear layer

To examine the interface of two self-etchings in carious affected dentin (CAD), under clinical conditions. Materials and Methods. Class I cavities were prepared in 21 carious premolars, refining them by the use of a fine diamond bur in order to create similar smear layer interference. The mild self-etching Clearfil SE Bond (CSE), pH = 2.0, and the strong Tyrian SPE-One Step Plus (TSO), pH = 0.5, were applied followed by a composite. Teeth were extracted and processed for TEM. The primer’s osmolarity of the self-etchings was also calculated using a microosmometer. Results. CSE hybrid layer retained smear layer residues and scattered crystallites as an effect of the mild acidity. A high presence of hydroxyapatite still protected the affected fibres within the hybrid layer. CSE primer demonstrated values of 3220mOsm/kg. TSO interdiffusion showed strong demineralization. Resin
tags were not formed in the dentinal tubules which remained obstructed by crystals.However, dissolution of peritubular dentin and
porosities were observed in the intertubular regions.The osmolarity of TSO was 8200mOsm/kg. Conclusion. Increasing the acidity
and osmolarity of the self-etchings increases interference in the homogeneous reinforcement of CAD, which may predispose the
hybrid layer to instability and hydrolytic degradation overtime.