Microhardness of bulk-fill vs. conventional resin composites polymerized with different curing times in different thicknesses

Year 2025, Volume: 5 Issue: 3, 189 - 195, 31.12.2025

Ekin Dermanli Elif Ozturk

https://doi.org/10.61139/ijdor.1829950

https://izlik.org/JA92DG59DG

Abstract

Objective: This study aimed to evaluate and compare the Vickers hardness values of two resin composites at both their top and bottom surfaces.
Methods: A bulk-fill resin composite and a conventional composite material were used in this investigation. For each material, five disc-shaped specimens were fabricated with a diameter of 10 mm and thicknesses of either 2 mm or 4 mm. The samples were polymerized from the top surface for either 20 or 40 seconds, resulting in a total of eight experimental groups. Each specimen underwent three Vickers hardness measurements on both its upper and lower surfaces. Microhardness was assessed using a Vickers hardness tester applying a 300-g (2.94 N) load for a dwell time of 15 seconds. The resulting data were evaluated using the Kruskal–Wallis test with Bonferroni adjustment for multiple comparisons.
Results: Significant differences were found between the hardness values measured at the top and bottom surfaces in all groups (p<0.05), with the exception of the conventional composite cured for 40 seconds at a 2-mm thickness, where no statistically significant difference was detected (VH_top = 98.1, VH_bottom = 94.4, p>0.05). For both materials, extending the curing time resulted in a statistically significant increase in microhardness at both surfaces (p<0.05). While changes in composite thickness did not influence the top surface hardness (p>0.05), increasing thickness led to reduced hardness values at the bottom surface (p<0.05).
Conclusions: The thickness of the material was found to affect the bottom surface microhardness in both the bulk-fill and conventional composites. Additionally, extending the curing duration led to higher microhardness values at both the top and bottom surfaces of the evaluated materials.

Keywords

resin , composite , bulk-fill , depth of cure , microhardness

Ethical Statement

Not applicable

Supporting Institution

No funding resource is associated with this study.

Project Number

1

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