Conversion and Tack-Curing of Light-Cured Veneer Luting Agents

Light attenuation and excess handling of light-cured luting agents create problems in bonding veneer restorations. The aim of the present study was to assess the curing capacity of light-cured veneer luting agents (VLA) [Choice 2 (CH2), G-Cem Veneer (GCV), Panavia LC Veneer (PNV), PermaCem LC Veneer (PMS), and Variolink Esthetic LC (VEV)] under lithium disilicate veneers, in the presence or absence of touch-cure primers (Adhese Universal Bond DC for VEV, G Premio Bond + DCA Activator for GCV, and V5 Tooth Primer V5 for PNV) and to evaluate material setting under two tack-curing irradiation modes (contact, distant). The methods used were ATR-FTIR spectroscopy and Vickers hardness (VHN) tests (<i>n</i> = 5/product and test). According to the results, all materials cured under the ceramic demonstrated significantly lower DC% from the controls, with a ranking of VEV, CH2 > GCV, PMS, PNV. The primers improved DC% by 4-13% only in the veneer groups. Tack-curing in contact mode demonstrated conversion and hardness values ranging from 37% to 78% and 31% to 57% of the controls respectively, corresponding to a vitreous state. For the distant mode, very low conversion values were found (0-7% of the controls), with untraceable indentations. It can be concluded that low translucency veneers reduce conversion of VLAs, which can be improved by using touch-cure activators. Tack-curing, as instructed, creates vitrified materials, resulting in difficult removal of set excess, which implies the need for better standardization of the procedure.