Interaction of Two Self-etch Adhesives with Dentin Using FESEM, TEM, and µTBS

Objectives: To study the interaction of two self-etch adhesives with dentin. Methods: Six third molars were used for µTBS. Middle dentin was exposed with a diamond saw. Teeth were assigned to two adhesives: Adper Prompt (ADP, 3M ESPE), and Prompt L-Pop (PLP, 3M ESPE) and restored with Filtek Z250 in increments of 2 mm each. The crowns were sectioned in X and Y directions to obtain sticks with a cross section of 0.7±0.2 mm². Each stick was fractured in tension under an Instron 4204 testing machine at a crosshead speed of 1 mm/min. Statistics was computed using t-test, p<0.05. For FESEM and TEM, four dentin disks with a thickness of 800 µm were restored and sectioned in two halves. One half was fixed and processed for FESEM (demineralized with 6NHCL for 30 s and deproteinized with 2.5% NaOCl for 10 min), while the other half was fixed, processed, and sectioned with an ultramicrotome for TEM analysis. Results: µTBS in MPa ± S.E.M. (spontaneous failures included): ADP=28.8±3.2 (n=96); PLP= 27.8±3.3 (n=86, no statistical differences between means (p=0.764). FESEM and TEM: The adhesives penetrated the dentin tubules and resulted in sealed interfaces. The depth of hybridization was: ADP=0.9-1.2 µm; PLP=1.9-2.9 µm. Conclusion: ADP and PLP resulted in statistical similar dentin bond strengths. The ultrastructural evaluation showed that the self-etch adhesives used in this study formed an acid-resistant hybridized area. Supported by 3M ESPE.