dental materials 22 ( 2 0 0 6 ) 963–972 available at www.sciencedirect.com journal homepage: www.intl.elsevierhealth.com/journals/dema Polymerization efficacy of simplified adhesive systems studied by NMR and MRI techniques T.G. Nunes a,∗ , F.C.P. Garcia b , R. Osorio c , R. Carvalho b , M. Toledano c a Departamento de Engenharia de Materiais/IST, Av. Rovisco Pais, 1, 1049-001 Lisboa, Portugal b University of S ˜ ao Paulo, Bauru School of Dentistry, Brazil c Departamento de Estomatolog´ ıa, Universidad de Granada, Spain article info Article history: Received 8 June 2005 Received in revised form 19 October 2005 Accepted 27 October 2005 Keywords: Dentin adhesive systems Self-etching Photo-polymerization HEMA Solvent evaporation Nuclear magnetic resonance Stray-field magnetic resonance imaging abstract Objective. To ascertain the efficacy of polymerization of self-etching dental adhesives in dif- ferent solvent evaporation conditions. Material and methods. Four self-etching adhesive systems were studied. Two of them are clas- sified as mild two-step self-etching adhesives (Clearfil SE Bond, Protect Bond) and the other two are strong one-step systems (Xeno III, ADP-Prompt-L-Pop). The influence of temperature and duration of the air-drying period on photo-polymerization was followed by: gravimetry, 1 H solid-state NMR spectroscopy and stray-field MRI. The evolution of proton magnetization with irradiation time was recorded and correlated with volumetric polymerization shrink- age and extent of reaction; evaporation and hardening effects were identified. Results. Main variables determining water-solvent evaporation of the tested adhesives are: (1) water/HEMA relative concentration, (2) presence of photoinitiator compounds in the primer (SEB) and (3) presence of ethanol (XENO). SEB shows the highest extent of photo- polymerization of the tested adhesives. The lowest volumetric contraction was obtained for APLP and XENO and the attempt to remove the solvents did not increase the extent of polymerization significantly. Conclusions. Temperature increase following photo-polymerization reaction is dominant towards the effect of the drying step for solvent evaporation in self-etching systems. Attempts to remove the solvents did not increase the extent of polymerization, so other problems are impairing the polymerization of one-step adhesives. Clinical significance. The use of tested one-step adhesives is discouraged as the attained low extent of polymerization may lead to low bond strength, high susceptibility to degradation and also will favor a continuing etching effect on the underlying dentin. © 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. 1. Introduction The durability of resin–dentin bonds is a key issue if resin com- posites are to be successfully used over long time periods [1]. Self-etching systems have been proposed as suitable adhesive agents for dentin bonding and this appears to be a promising ∗ Corresponding author. Tel.: +351 21 8418103; fax: +351 21 8418101. E-mail address: Teresa.Nunes@ist.utl.pt (T.G. Nunes). approach for reducing technique sensitivity in dentin bond- ing. These systems must diffuse by demineralising through the smear layer and into sound underlying dentin, forming a hybrid layer (resin–infiltrated dentin) and leaving this intact dentin sealed [2]. When testing self-etching systems a high correlation has been encountered between degree of cure 0109-5641/$ – see front matter © 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.dental.2005.10.008