ABSTRACT: Can CQ completely be replaced by Alternative Initiators in Dental-Adhesives?

Objectives: Despite good clinical acceptance, photoinitiating systems based on camphorquinone and amines raise concerns in terms of yellowing, aging, toxicity, or degradation in low pH conditions. This study aimed to prove whether CQ could be successfully replaced by alternative initiators in adhesive systems. Further, the efficiency of a prototype dual-wavelength LED (=Light Emitting Diode) curing unit was analyzed.

Methods: In two commercial adhesive systems –Excite and Heliobond/Ivoclar-Vivadent- CQ was completely replaced by Lucirin-TPO. The commercial adhesives and their experimental counterpart were evaluated after curing for 10s and 20s with two dual-wavelength LED (P=Prototype/Ivoclar-Vivadent, Schaan, Lichtenstein; U=Ultralume5/Ultradent, South Jordan, USA) and one regular LED unit (B=Bluephase/ Ivoclar-Vivadent), by applying the curing unit at two distances of 0 mm and 5 mm. Degree of cure (DC) and mechanical properties (HV=Vickers hardness, E=Modulus of elasticity) were assessed after 24h storage in distilled water at 37°C.

Adhesive	Exposure	E	HV	DC-Height	DC-Area*
Excite	P-10s	4.0^bcd(0.2)	24.3^e(1.5)	87.0^ef(0.9)	90.8^ef(0.6)
Excite	P-20s	4.2^fg(0.1)	24.3^e(1.1)	86.6^ef(0.7)	90.9^ef(0.5)
Excite	B-10s	4.1^cdefg(0.1)	21.9^cd(1.5)	71.8^ab(12.4)	78.0^ab(11.4)
Excite	B-20s	4.1^bcdef(0.3)	23.2^cde(1.8)	72.1^abc(9.4)	78.2^bc(9.1)
Excite	U-10s	4.1^bcdef(0.3)	22.6^cd(1.7)	85.4^ef(2.6)	89.9^ef(2.8)
Excite	U-20s	4.2^fg(0.1)	24.5^e(1.5)	90.1^ef(1.0)	93.6^f(0.7)
Excite	P-10s-5mm	4.0^bcd(0.1)	19.8^b(1.4)	80.7^de(2.8)	84.5^bcde(2.5)
Excite	P-20s-5mm	4.0^bcd(0.1)	21.8^c(1.9)	85.0^ef(1.3)	87.5^ef(1.0)
Excite	B10s-5mm	3.3^a(0.8)	17.7^a(3.7)	66.6^a(2.5)	70.0^a(2.6)
Excite	B20s-5mm	4.0^bcd(0.3)	22.2^cd(0.8)	76.0^bcd(1.9)	79.4^bcd(1.8)
Excite	U10s-5mm	3.9^b(0.2)	21.8^c(1.2)	83.1^def(1.1)	86.1^cdef(1.3)
Excite	U20s-5mm	4.0^bcde(0.1)	22.0^cd(1.6)	85.1^ef(2.8)	87.9^ef(2.6)
Excite-exp	P-10s	4.2^fg(0.01)	22.5^cd(1.5)	86.7^ef(1.1)	91.3^ef(0.8)
Excite-exp	P-20s	4.3^g(0.1)	23.3^cde(1.4)	87.6^ef(1.3)	92.1^ef(1.4)
Excite-exp	U-10s	4.2^efg(0.1)	23.4^de(2.3)	84.3^def(4.6)	89.0^ef(4.2)
Excite-exp	U-20s	4.2^fg(0.1)	24.8^e(0.8)	87.3^ef(1.9)	92.0^ef(2.0)
Excite-exp	P-10s-5mm	3.9^bc(0.2)	21.9^cd(1.4)	82.8^def(1.5)	88.7^ef(1.3)
Excite-exp	P-20s-5mm	4.1^bcdef(0.2)	23.2^cde(1.2)	82.8^def(0.2)	88.8^ef(0.8)
Excite-exp	U-10s-5mm	4.1^defg(0.1)	23.2^cde(1.6)	80.5^cde(0.1)	85.9^bcdef(0.2)
Excite-exp	U-20s-5mm	4.2^fg(0.1)	23.3^cde(1.5)	82.3^def(0.6)	86.9^def(0.3)

Conclusion: Experimental data showed that the CQ-amine system could be completely replaced by Lucirin-TPO when dual-wavelength LED units were used for photoactivation.