Degree of conversion of two-step etch-and-rinse adhesives: In situ micro-Raman analysis Chiara Ottavia Navarra a , Lorenzo Breschi a,b, *, Gianluca Turco a , Marina Diolosa ` a , Luca Fontanive a , Lucia Manzoli c , Roberto Di Lenarda a , Milena Cadenaro a a Department of Medical Sciences, University of Trieste, Piazza dell’Ospitale, 1, I-34125 Trieste, Italy b IGM, Unit of Bologna, C.N.R. – IOR, Bologna, Italy c Department of SAU&FAL, University of Bologna, Bologna, Italy 1. Introduction The clinical performance of present day adhesives has significantly improved, allowing adhesive restorations to be placed with a high predictable level of clinical success. The versatility of adhesive dentistry has prompted the steady development of new bonding agents, with the aims of simplifying their clinical application, shortening side-chair clinical time, and reducing the technique sensitivity of procedures. In accordance with their application mode, dentine bonding systems can be divided into etch-and-rinse and self-etch (or etch-and-dry) adhesives. 1,2 Because the adhesive mixture should be able to prime and bond simulta- neously to the hydrophilic collagen network, high concentra- tions of hydrophilic monomer and solvents characterize the formulations of two-step etch-and-rinse adhesives. 3 In- creased hydrophilicity of monomers favours phase separation j o u r n a l o f d e n t i s t r y x x x ( 2 0 1 2 ) x x x – x x x a r t i c l e i n f o Article history: Received 8 February 2012 Received in revised form 2 May 2012 Accepted 3 May 2012 Keywords: Two-step etch-and-rinse adhesives Degree of conversion Micro-Raman spectroscopy Hybrid layer a b s t r a c t Objectives: DC of three commercial two-step etch-and-rinse adhesives across the dentine– adhesive interface was investigated using micro-Raman spectroscopy. The hypothesis tested was that no difference in DC would exist among the adhesives tested. Methods: Adper Scotchbond 1XT (3M ESPE), Prime&Bond NT (Dentsply DeTrey), and Ambar (FGM) were applied on human dentine disks (n = 9). Composite increments of 2 mm were then applied on the adhesive surface. Raman spectra were collected along the dentine– adhesive interface. The relative intensities of the peaks associated with the mineral (PO 4 3 at 960 cm 1 ) and the adhesive (C C at 1640 cm 1 ; phenyl C C at 1610 cm 1 ) were used to identify the adhesive within the hybrid layer and calculate its DC. Results: Adper Scotchbond 1XT and Ambar showed similar DC (79  7% and 77  7%, respectively), while a lower DC was found for Prime&Bond NT (70  7%; p < 0.05). Conclusions: The hypothesis tested was rejected because differences were found among the adhesives tested. The difference in DC among the three adhesive systems can be attributed to different monomer compositions and solvents. Further studies are needed to correlate DC with other mechanical properties of these adhesives. Clinical significance: Insufficient polymerization of an adhesive can result in a weak hybrid layer, and the presence of unreacted monomers may result in degradation of the polymeric network, decreasing the strength and longevity of the bond. In the present study, Adper Scotchbond 1XT and Ambar performed significantly better than Prime&Bond NT. # 2012 Elsevier Ltd. All rights reserved. * Corresponding author at: Department of Medical Sciences, University of Trieste, Piazza dell’Ospitale, 1, I-34125 Trieste, Italy. Tel.: +39 0403992192; fax: +39 0403996128. E-mail address: lbreschi@units.it (L. Breschi). JJOD-1897; No. of Pages 7 Please cite this article in press as: Navarra CO, et al. Degree of conversion of two-step etch-and-rinse adhesives: In situ micro-Raman analysis. Journal of Dentistry (2012), http://dx.doi.org/10.1016/j.jdent.2012.05.001 Available online at www.sciencedirect.com journal homepage: www.intl.elsevierhealth.com/journals/jden 0300-5712/$ – see front matter # 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jdent.2012.05.001