Abstract
Objective The aim of this study was to evaluate the influence of different light-curing units (LCUs) with distinct tip diameters and light spectra for activating bulk-fill resins. Materials and Methods The specimens ( n = 10) were made from a conventional composite (Amaris, VOCO) and bulk-fill resins (Aura Bulk Fill, SDI; Filtek One, 3M ESPE; Tetric Bulk Fill, Ivoclar Vivadent) with two diameters, 7 or 10 mm, × 2 mm thickness. Following 24 hours of specimen preparation, the degree of conversion (DC) was evaluated using the Fourier-transform infrared unit. Knoop hardness (KHN) readings were performed on the center and periphery of the specimens. Data were assessed for homoscedasticity and submitted to one-way and three-way analysis of variance followed by the Tukey's and Dunnett's tests, depending on the analysis performed (α = 0.05). Results LCUs and specimen diameter significantly affected the DC. The Tetric Bulk Fill provided increased DC results when light-cured with Valo (54.8 and 53.5%, for 7 and 10 mm, respectively) compared with Radii Xpert (52.1 and 52.9%, for 7 and 10 mm, respectively). No significant differences in KHN results were noted for the conventional resin composite ( Amaris ) compared with LCUs ( p = 0.213) or disc diameters ( p = 0.587), but the center of the specimen exhibited superior KHN ( p ≤ 0.001) than the periphery. Conclusion The light spectrum of the multipeak LCU ( Valo ) significantly increased the DC and KHN of the bulk-fill resin composite with additional initiator to camphorquinone ( Tetric Bulk Fill ) compared with the monowave LCU ( Radii Xpert ). The tip size of the LCUs influenced the performance of some of the resin composites tested.
Highlights
Resin-based composites (RBCs) are widely used materials for Classes I and II restorations with failure rates of 1.8% after 5 years and 2.4% after 10 years.[1]
The higher power of the cordless light-emitting diodes (LED) units during the cycle was individually checked for five light cycles of 20 seconds using a power meter (Nova, Ophir Spiricon, Logan, Utah, United States), the average of the five cycles was divided by the tip area, calculated from the optical diameter, as measured with a digital caliper (CD6CS, Mitutoyo, Kanagawa, Japan), to obtain the irradiance (►Table 1).[13]
Tetric Bulk Fill exhibited increased degree of conversion (DC) compared with conventional resin composite for both diameters and light-curing unit (LCU) evaluated
Summary
Resin-based composites (RBCs) are widely used materials for Classes I and II restorations with failure rates of 1.8% after 5 years and 2.4% after 10 years.[1]. Beyond decreasing the clinical time of the restorative procedure, bulk-fill resin composites are used in single increments of up to 4 or 5 mm thickness because they present lower polymerization shrinkage and lower residual shrinkage stress.[5]
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