Abstract
Objective: To evaluate the effect of shade and curing mode on cure efficiency of two dual-cure resin cements. Material and Methods: Two shades (A2 and TRANS) of two different dual-cure resin cements (G-CEM, GC Dental and SET PP, SDI) were submitted to different curing modes: light curing through a 2 mm thick ceramic disc (IPS Empress Esthetic, A2, Ivoclar Vivadent) for 20 s (16 J/cm2), 40 s (32 J/cm2) or 80 s (64 J/cm2) performed immediately or with 1 or 5 min of delay. Fourier transform infrared spectroscopy (FT-IR) was used to evaluate the degree of conversion (DC) after 48 h. For the statistical analysis, data were submitted to three-way analysis of variance, followed by Tukey’s test for multiple comparisons (p=0.05). Results: Shade influenced DC (%) for the dual-cure resin cements tested (p=0.00001). TRANS shade showed lower DC (%) for both cements when there was no delay before light-curing (p=0.00001). Curing mode also influenced DC (%) for the dual-cure resin cements tested: radiant exposure greater than 32 J/cm2 and delaying light-curing for 1 to 5 min increased the DC (%) for both dual-cure resin cements evaluated. Conclusions: One min delay prior to light curing improved the cure efficiency and may be a more clinically acceptable approach to increase the degree of conversion of dual-cure resin cements.
Highlights
Dual-cure resin cements have been widely used in clinical practice [1], especially when photo-activation can be impaired by low light absorption due to the distance from the luting area to the light source, as in fiber posts cementation [2,3,4], or due to light scattering by the thickness and opacity of indirect restorations [5,6,7,8].Effective light curing of resin cements depends on photon absorption in order to excite the photo-initiators and initiate polymerization; photo-absorption depends on the capacity of light flux through the overlying material [5,6]
The lower degree of conversion (DC) mean values for TRANS shade dualcure resin cements compared to the A2 shade is most likely due to a lower camphorquinone concentration or the addition of a different photo-initiator in order to reduce the yellowish color caused by camphorquinone [17]
Five minutes delay prior to light curing significantly improved degree of conversion. This agrees with recent studies that demonstrated delaying before light curing improves the degree of conversion of dual-cure resin cements [19,20]; One min delay prior to light curing improved the degree of conversion compared to no delay and may be a more clinically acceptable approach to increase the degree of conversion
Summary
Dual-cure resin cements have been widely used in clinical practice [1], especially when photo-activation can be impaired by low light absorption due to the distance from the luting area to the light source, as in fiber posts cementation [2,3,4], or due to light scattering by the thickness and opacity of indirect restorations [5,6,7,8].Effective light curing of resin cements depends on photon absorption in order to excite the photo-initiators and initiate polymerization; photo-absorption depends on the capacity of light flux through the overlying material [5,6]. Dual-cure resin cements have been widely used in clinical practice [1], especially when photo-activation can be impaired by low light absorption due to the distance from the luting area to the light source, as in fiber posts cementation [2,3,4], or due to light scattering by the thickness and opacity of indirect restorations [5,6,7,8]. Low light absorption by light-cured resin cements can adversely affect degree of conversion and chemicalmechanical properties and marginal integrity leading to clinical failure [11]. Dual-cure resin cements help to compensate for problems caused by light flux attenuation in photo-activation. An effective curing mode protocol to achieve satisfactory adhesive cementation is still not established [12]
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