Dentine acid-etch technique

The acid-etch technique of Buonocore cannot be easily applied to dentine, because the process alters the surface of dentine unfavourably. It removes the mineral phase, and leaves behind a coUagen-rich structure that is soft, and which tends to collapse when dried with air. The matted collagen fibre surface that is thereby formed forms weak bonds with organic substances, and this results in low values of bond strengths. These typically lie in the range 5-10MPa [3]. 

Glass-ionomer cements have taken a major place in dental treatments as restorative filling materials and also in a range of more adhesive applications due to their ability to bond to both dentine and composite fillers. Acid-etching techniques are well established for the bonding of resins to enamel. 

A combination of modified features of the last-named two bonding systems is realized in an adhesive applieation known as the Kanca technique, in which dentin and enamel pre-treatment by phosphorie acid etching is followed by the consecutive layering of NTG-GMA, PMDM, and HEMA-bis-GMA adhesive resins, onto which the restorative is placed by conventional manipulation. Low microleakage, and composite shear bond strengths to enamel/dentin at the 18-MPa level, have been reported [54]. 

The clinical technique can also affect the performance of dental adhesive systems. Significant reduction in the degree of conversion and mechanical properties of adhesive systems was observed when solvents were not properly evaporated [23-26]. The application of simplified-step adhesive systems to an excessively wet dentin surface may lead to phase separation and a hydrophobic-poor and hydro-philic-rich zone may be formed, lowering the stability of the adhesive interface [13]. Acidic monomers remain active when poorly polymerized resulting in continuous etching of the underlying dentin [27]. 

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