Effect of Surface Treatment and Polymerization on Residual Monomer Content

Objectives: The aim of this investigation was to evaluate the residual monomer content in a composite resin luting cement after being applied to dental ceramic and metal surfaces which were subjected to various surface treatment methods. Methods: Composite resin luting cement RelyX ARC (3M ESPE, USA) was used on feldspathic ceramic (Ceramco, Dentsply, USA) and metal (Vautid, Germany) substrate. A total of 36 test specimens were grouped according to the type of substrate (ceramic and metal), surface treatment method (Air particle abrasion with 50 ìm Al2O3, diamond bur, acid etching with 9.5 % hydrofluoric acid and 36 % phosphoric acid) and polymerization method (light and self-cured). Acid etching to metal substrates were omitted due to their inefficiency on the metal surface. The weight of the test samples were measured before surface treatment, following surface treatment, application of luting cements and three-day-storage in a tetrahydrofurane solution. In addition, residual monomer contents of the test samples were determined by Shimadzu's (LC-2010) modular high performance liquid chromatograph (HPLC) system (Shimadzu Corporation, Kyoto, Japan) following three-day-storage. Results: For all groups, higher amounts of total residual monomers were obtained with self-curing (18-64 %-wt) than light-curing (2-8 %-wt) and residual Bis-GMA (1-48 %-wt) was measured to be higher than TEGDMA (1-16 %-wt). The highest total residual monomer contents were obtained with diamond bur treated and self-cured specimens (29 %-wt) for metal groups and with phosphoric acid etched and self-cured specimens (64 %-wt) for ceramic groups. Conclusion: There were significant differences in residual monomer contents of the tested composite resin luting cement. Residual monomer content of composite resin cement decreased with light-curing.