Objective: To determine the degree of conversion (DC) of adhesives containing 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO) or camphorquinone(CQ)-amine initiators.
Materials and Methods: Commercial G-aenial Bond (GC), G-aenial Bond with 2wt% TPO or CQ-amine (Sigma-Aldrich), Scotchbond Universal (3M ESPE) and EXL 759 (3M ESPE), the same composition as Scotchbond Universal except for 2.1wt% TPO, were used. G-aenial Bond was used as self-etch, Scotchbond Universal and EXL 759 both as self-etch and etch-and-rinse adhesives. Mid-coronal dentin discs (n=5 per group) were cut from intact human molars. One drop of G-aenial Bond was applied to each disc, left for 10 s and gently air blown for 10 s. One drop of Scotchbond Universal or EXL 759 was rubbed into dentin for 20 s and gently air blown for 5 s. Following the etch-and-rinse approach, dentin discs were etched with 35% phosphoric acid for 15 s, rinsed and blot-dried prior to adhesive application in the same manner as described above. In each group, the adhesive was covered with a glass slide and cured using a Bluephase 20i LED unit (Ivoclar Vivadent) for 10 s. DC was determined using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR; Vertex 70, Bruker). The data were statistically analyzed using ANOVA with the Tukey`s post-test (α=0.05).
Results: The commercial G-aenial Bond showed higher conversion (91.4±2.7%) than the TPO- (71.1±7.0%) and CQ-containing G-aenial Bond (74.7±4.7%) (p<0.05), which had similar DC (p>0.05). DC was higher for EXL 759 with TPO than for Scotchbond Universal when applied as self-etch adhesives (64.7±5.6% versus 50.0±4.4%, p>0.05). Significantly higher DC was found for Scotchbond Universal (77.1±3.0%) and EXL 759 with TPO (72.0±1.9%) following the etch-and-rinse versus the self-etch approach (p<0.05).
Conclusions: TPO improved conversion of Scotchbond Universal “self-etch” but had no effect on the DC of G-aenial Bond and Scotchbond Universal “etch-and-rinse”.