IADR Abstract Archives
Effect of Photo-Initiators on Elution and Conversion of Adhesives
Method: We used Scotchbond Universal (‘SBU-CQ/amine_4.0’, 3M ESPE), containing about 2wt% camphorquinone (CQ) and 2wt% ethyl-4-dimethylamino benzoate (EDMAB), an experimental version ‘SBU-TPO_2.1’containing 2.1wt% 2,4,6-trimethylbenzoyldiphenylphosphine oxide or TPO, and 4 experimental LUB adhesives (Kuraray), namely ‘LUB-CQ/amine_0.7’, ‘LUB-CQ/amine_4.0’, ‘LUB/-TPO_0.7’ and ‘LUB/-TPO_2.0’, with the photo-initiator respectively consisting of 0.35wt% CQ and 0.35wt% EDMAB, 2.0wt% CQ and 2.0wt% EDMAB, 0.7wt% TPO, and 2.0wt% TPO. Each adhesive was applied to 12 mid-coronal human dentin discs, covered by a glass slide and light-cured for 10 sec (Bluephase 20i, ‘high mode’, Ivoclar-Vivadent). Eight specimens were immersed immediately in 1ml absolute ethanol for 24h (37°C), after which the concentrations of Bis-GMA and HEMA were determined using high-performance liquid chromatography (Zorbax Eclipse column XDB-C18, HPLC, Agilent 1200). DC was measured using the 4 remaining specimens by micro-Raman spectroscopy (Senterra, Bruker), with DC calculated as the ratio of peak intensities of the aliphatic 1640 cm-1 and aromatic 1610 cm-1peaks in cured and uncured materials.
Result:
At high photo-initiator concentration (2%), DC of the adhesives was alike, but elution of especially HEMA differed. At low concentration (0.7%), TPO was more efficient than CQ/Amine. DC correlated with elution of Bis-GMA (R²=0.812, p=0.01421) and elution of HEMA (R²=0.766, p=0.02257).
BisGMA and HEMA elution and degree of conversion of the adhesive formulations.
Elution (%) |
SBU-CQ/Amine_4.0 |
SBU-TPO_2.1 |
LUB-CQ/Amine_0.7 |
LUB-CQ/Amine_4.0 |
LUB-TPO_0.7 |
LUB-TPO_2.0 |
Bis-GMA |
4.2(1.0)C,D |
3.3(1.1)C,D |
10.3(1.7)B |
2.1(0.6)D |
3.6(1.0)CD |
4.0(1.3)C,D |
HEMA |
9.5(1.9)B |
2.5(0.9)D,E |
25.4(2.4)A |
5.7(2.4)C |
9.3(3.1)B |
5.6(2.5)C,E |
DC |
84.3(4.8)II |
83.4(2.1)II |
69.8(3.7)III |
90.6(2.1)I |
83.8(2.6)II |
91.2(3.1)I |
Different superscripts indicate significant difference (ANOVA, Tukey’s HSD, p<0.05)
Conclusion: The kind and concentration of photo-initiator affects the elution of Bis-GMA and HEMA and the degree of conversion. CQ/amine should be employed in a higher concentration than TPO.