Self-etching Adhesives on Enamel and Dentin: A FEI-SEM Study

The self-etching adhesives vary in their acidity by virtue of the composition and concentration of polymerizable acidic resin monomers. The application of self-etching systems on enamel has been a controversial issue boot on prismatic and aprismatic enamel. Objectives: The aim of this study was to examine the interfacial ultramorphology on enamel and dentin by the use of a replica system. Materials and Method: 6 specimens of prismatic and aprismatic enamel and 6 specimens of dentin were selected. Three self-etching adhesives were used: XENO III (Dentplay), SE Bond (Kuraray) and Tyrian (Bisco). All systems were applied following manufacturers’ instructions. A thin layer of composite was cured for 20 s onto the adhesive layer. Specimens were treated with HCl 6N for 3 days and with NaOCl 5% for 2 days. After each step, specimens were rinsed in deionized water. Specimens were coated with platinum particles and inspected by high resolution SEM (FEISEM). Results: The morphology of enamel replicas revealed different patterns of surface roughness related to the different aggressiveness of the etching primers. All three systems resulted less effective on aprismatic than prismatic enamel. SE Bond appeared to be the least effective on prismatic/aprismatic enamel creating an heterogeneous etching pattern. Tyrian and in particular XENO III resulted to be more aggressive and an homogeneous enamel etching pattern was observed. Application on dentin revealed formation of hybrid layer by all three self-etching adhesives. Differences were observed in resin tag length (Xeno III and Tyrian approx. 15µm, SE Bond approx. 4µm), number, morphology and length of lateral branches. Conclusions: These morphological data confirmed a correlation between acidic potential and etching patterns produced by self etching systems. In particular Xeno III and Tyrian seems to be more effective than SE Bond on enamel, while similar hybrid layer morphology was found on dentin.