Abstract
This study assessed the influence of rapid 3 s light curing on the new generation of bulk-fill resin composites under the simulated aging challenge and depths up to 4 mm. Four bulk-fill materials were tested: two materials designed for rapid curing (Tetric PowerFill—PFILL; Tetric PowerFlow—PFLW) and two regular materials (Filtek One Bulk Fill Restorative—FIL; SDR Plus Bulk Fill Flowable—SDR). Three-point bending (n = 10) was used to measure flexural strength (FS) and flexural modulus (FM). In the 3 s group, two 2 mm thick specimens were stacked to obtain 4 mm thickness, while 2 mm-thick specimens were used for ISO group. Specimens were aged for 1, 30, or 30 + 3 days in ethanol. The degree of conversion (DC) up to 4 mm was measured by Raman spectroscopy. There was no difference between curing protocols in FS after 1 day for all materials except PFLW. FM was higher for all materials for ISO curing protocol. Mechanical properties deteriorated by increasing depth (2–4 mm) and aging. ISO curing induced higher DC for PFLW and FIL, while 3 s curing was sufficient for PFILL and SDR. The 3 s curing negatively affected FM of all tested materials, whereas its influence on FS and DC was highly material-specific.
Highlights
The use of dental bulk-fill composites in restorative dental medicine has been increasing in recent years due to the simplicity of their application in thick 4–5 mm layers and clinical performance similar to conventional composites [1,2]
Higher radiant exitance combined with short exposure time commonly resulted in a lower degree of conversion (DC), hardness, flexural strength (FS), and modulus (FM), in contrast to the higher exposure times combined with lower radiant exitance of the curing unit [4,5,6]
The present study aimed to examine the DC, FS, and flexural modulus (FM) of a new generation of bulk-fill composites at 0–2 mm and 2–4 mm depths cured with ultra-short very highradiant exitance light and compare them to ISO-recommended curing on 2 mm thick specimens
Summary
The use of dental bulk-fill composites in restorative dental medicine has been increasing in recent years due to the simplicity of their application in thick 4–5 mm layers and clinical performance similar to conventional composites [1,2]. It has been claimed that the curing time can be reduced to only 3 s with the prerequisite high radiant exitance of photopolymerization devices of 3000 mW/cm or higher [3]. The exposure reciprocity hypothesis claims that the light exposure time can be reduced if the radiant exitance (mW/cm2) is increased, as long as the energy density (J/cm2) is the same. This concept has been heavily criticized in past studies [4,5,6]. In high-viscosity materials, the filler particles decelerate this reaction, so the consequences are not as clearly visible as in low-viscosity materials
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