Does tin pre-treatment enhance the bond strength of adhesive systems to enamel?

Objectives: The study investigated the modification of composite-to-enamel bond strength by pre-treatment of enamel with a concentrated, acidic SnCl2-solution. Methods: Six groups of flat human enamel specimens (n = 44 per group) were treated as follows: OB-H: H3PO4 etching, Optibond FL application (primer + adhesive; manufacturer's instructions); OB-S: SnCl2 pre-treatment, Optibond FL application (primer + adhesive); OB-HS: H3PO4 etching + SnCl2 pre-treatment, Optibond FL application (primer + adhesive); CF-N: Clearfil SE application (primer + bond; manufacturer's instructions); CF-H: H3PO4 etching, Clearfil SE application (primer + bond); CF-S: SnCl2 pre-treatment, Clearfil SE application (primer + bond). Enamel specimens were then built up with resin composite (Clearfil Majesty Esthetic) and stored (100% humidity, 37 degrees C, 1 week). mu TBS-measurement and failure mode analysis of one-half of the specimens were performed immediately after storage, while the other half was analysed after a thermocycling procedure (8500 cycles; 5 degrees C and 55 degrees C; dwell time 30 s). Additional specimens were prepared for SEM- and EDX-analysis. Results: Highest values were measured for OB-H before and after thermocycling, lowest values for CF-N. Compared to OB-H treatment, OB-S treatment reduced mu TBS before/after thermocycling by 23%/28% and OB-HS treatment by 8%/24% (except for OB-SH before (n. s.), all p <= 0.001 compared to OB-H). In the Clearfil SE treated groups pre-treatment increased mu TBS significantly compared to CF-N (before/after: CF-H: + 46%/+70%; CF-S: + 51%/42%; all p <= 0.001). Conclusion: Pre-treatment with H3PO4 or SnCl2 markedly increased the mu TBS of Clearfil SE to enamel. However, thermocycling partly reduced the gain in mu TBS obtained by SnCl2 pretreatment. Clinical significance: The application of an acidic and highly concentrated SnCl2 solution is a good option to increase the mu TBS between enamel and a resin composite mediated by an adhesive system containing the multifunctional monomer MDP. (C) 2013 Elsevier Ltd. All rights reserved.