The effect of a leucite-containing ceramic filler on the abrasive wear of dental composites

Errors in light-emitting diodes positioning when curing bulk fill and incremental composites: impact on properties after aging

Objectives

This study aimed to evaluate the effect of improper positioning single-peak and multi-peak lights on color change, microhardness of bottom and top, and surface topography of bulk fill and incremental composites after artificial aging for 1 year.

Materials and Methods

Bulk fill and incremental composites were cured using multi-peak and single-peak light-emitting diode (LED) following 4 clinical conditions: (1) optimal condition (no angulation or tip displacement), (2) tip-displacement (2 mm), (3) slight tip angulation (α = 20°) and (4) moderate tip angulation (α = 35°). After 1-year of water aging, the specimens were analyzed for color changes (ΔE), Vickers hardness, surface topography (Ra, Rt, and Rv), and scanning electron microscopy.

Results

For samples cured by single-peak LED, the improper positioning significantly increases the color change compared to the optimal position regardless of the type of composite (p < 0.001). For multi-peak LED, the type of resin composite and the curing condition displayed a significant effect on ΔE (p < 0.001). For both LEDs, the Vickers hardness and bottom/top ratio of Vickers hardness were affected by the type of composite and the curing condition (p < 0.01).

Conclusions

The bulk fill composite presented greater resistance to wear, higher color stability, and better microhardness than the incremental composite when subjected to improper curing. The multi-peak LED improves curing under improper conditions compared to single-peak LED. Prevention of errors when curing composites requires the attention of all personnel involved in the patient's care once the clinical relevance of the appropriate polymerization reflects on reliable long-term outcomes.

Examination of composite resins with electron microscopy, microhardness tester and energy dispersive X-ray microanalyzer

This study was conducted to examine the ultrastructures of eight recently improved light-cure restorative composite resins with scanning and transmission electron microscopes (SEM and TEM). Additionally, Vickers hardness, volume/weight fraction of filler, and chemical composition were analyzed. Composite resins selected for evaluation were Beautifil II, Clearfil AP-X, Clearfil Majesty, Estelite sigma, Filtek Supreme, Filtek Z250, Solare, and Synergy. SEM and TEM images revealed a great diversity in ultrastructure, and Vickers hardness test showed significant differences amongst all the composite resins (except between Clearfil Majesty and Estelite sigma, and between Filtek Supreme and Filtek Z250). By means of EDX, similar elements such as C, O, and Si were detected, but the concentration was different in every composite resin. Results obtained in this study served to validate that the methods employed in this study SEM and TEM at high magnification--were useful in examining the ultrastructures of composite resins. It was also found that the ultrastructure, size of filler particles, volume/weight fraction of filler, and chemical composition of the composite resins had an effect on Vickers hardness. Given the great diversity of ultrastructures amongst the composite resins, which stemmed from the different revolutionary technologies used to manufacture them, further studies are warranted in the search of clinical applications that optimally match the differing properties of these materials.