Influence of Photoinitiator and Light-Curing Source on Bond Strength of Experimental Resin Cements to Dentin

Abstract

This study evaluated the bond strength (BS) of experimental resin cements formulated with different photoinitiators when activated by two kinds of light-curing units (LCUs) through a ceramic material. Seven resin blends with different camphorquinone (CQ) and/or phenylpropanedione (PPD) concentrations (weight) were prepared: C5: 0.5% CQ; C8: 0.8% CQ; P5: 0.5% PPD; P8: 0.8% PPD; C1P4: 0.1% CQ and 0.4% PPD; C4P1: 0.4% CQ and 0.1% PPD; C4P4: 0.4% CQ and 0.4% PPD. Two LCUs were used: one quartz-tungsten-halogen (QTH - 850 mW/cm²) and one light-emitting diode (LED - 1300 mW/cm²). The microtensile bond strength of each blend was assessed. Data were submitted to two-way ANOVA and Tukey's test (α=0.05). The BS values did not exhibit significant differences for LCUs, regardless of the photoinitiator type. Three cements showed significant differences: P5 and C5 had higher BS with QTH, and C4P1 with LED. For QTH, P5 showed the highest and C1P4 the lowest BS. For the LED, C4P1 showed the highest BS of all the cements. The results indicated that PPD was a viable alternative in the formulation of photocured resin cements, reducing or eliminating CQ that is yellowish without impairing the bond strength. Furthermore, both LED and QTH were effective in curing resin cements that contain PPD or CQ.

Microtensile Bond Strength and Microhardness of Composite Resin Restorations Using a Sonic-Resin Placement System

“…The output power (mW) of LED curing unit was measured with a power meter (Ophir Optronics Inc., Danvers, MA, USA) with a value of 538 mW. The light irradiance (mW/cm²) with a value of 1400 mW/cm 2 was determined by dividing the output power by the tip area that was measured by calculating the area by formula πr 2 , where r was measured with a digital caliper (Mitutoyo, Tokyo, Japan) (13).…”

Influence of Different Concentration and Ratio of a Photoinitiator System on the Properties of Experimental Resin Composites

“…The elastic modulus was measured as the slope of the strain x strain curve in the linear portion, using the following equation: E=L1D 3 …”

“…When constant weight was obtained (two days of no weight change) this value was recorded as m 2 and the samples were returned into the desiccators. The entire mass reconditioning cycle was repeated and the constant mass (two days of no weight change) was recorded as m 3 . The values for water sorption (WS) and solubility (WSB), in micrograms per cubic millimeters, were calculated using the following equations:…”

“…Light absorption raises CQ to an excited state that interacts with a tertiary amine, forming a triplet exciplex that disintegrates into free radicals. These radicals initiate the polymerization of methacrylates, which success conducts on obtaining a reliable bond and good polymerization (3). The concentration of CQ and amine, as well as the CQ/amine ratio, play important roles in the polymerization efficiency and ultimately in the physical and mechanical properties of resin composite materials (4)(5)(6).…”

Influence of Photoinitiator System on Physical-Chemical Properties of Experimental Self-Adhesive Composites

“…The CQ absorbs light with a wavelength between 400 and 500 nm, with visible range maximum absorption peak at 468 nm (7). It presents an intense yellow coloration and requires a co-initiator molecule to optimize the polymerization reaction, which unfortunately may suffer oxidation with time, leading to higher intrinsic discoloration.…”