Ultrastructural examination of one-step self-etch adhesive bonded primary sound and caries-affected dentin.

PURPOSE: To examine the ultrastructure and silver nanoleakage of the resin-dentin interfaces in sound and caries-affected primary tooth dentin bonded with a 4-META one-step self-etch adhesive.
METHODS: Each of five sound and carious primary molars was bonded with Hybrid Bond. Resin-dentin interfaces were observed with TEM micrographs obtained from silver-impregnated, unstained and undemineralized sections of bonded sound and caries-affected primary dentin, and stained and demineralized sections of bonded sound and caries affected primary dentin without silver impregnation.
RESULTS: For sound dentin, silver nanoleakage was observed extensively in the patent dentin tubules, within the dentin beneath the hybrid layer, within the hybrid layer in some specimens, and as water trees that partially protruded into the overlying adhesive layer. The hybrid layer was about 1 microm thick. Smear plugs in the dentin tubules and smear on the ground dentin protruded in the hybrid layer. Remnants of demineralized smear were observed overlying the adhesive layer. For caries-affected dentin, the hybrid layer was obscure. Dentin tubules were occluded with mineral deposits. There were no water trees or nanoleakage in the adhesive layer or hybrid layer. However, smear remnants were observed in the adhesive layer and large silver deposits were observed in the highly porous underlying caries-affected dentin.