Nanoindentation hardness study of dental composite filling materials
Abstract
Background: Short fiber-reinforced composites (SFRCs) offer a promising alternative for restoring deep cavities with high
volume factor. The aim of this study was to evaluate the surface hardness of flowable SFRC using nanoindentation, applying
different restorative techniques.
Materials and Methods: Composite specimens were prepared in four groups (n = 18 / group), each representing a different
restorative technique: layered conventional composite, layered SFRC, bulk-fill SFRC, and bulk-fill composite. The
hardness of the specimens was measured on their top, side, and bottom surfaces using a nano indenter, both before
and after water storage. All specimens were prepared in standardized moulds simulating deep Class I cavities. Nanoindentation
was performed in 19 locations per sample using a Berkovich diamond tip, following the ISO 14577 standards.
Results: The bulk-fill composite group showed significantly lower hardness values across all measurement levels. In
contrast, both the layered and bulk-fill SFRC groups demonstrated higher or comparable surface hardness values to the
layered conventional composite group. Water storage reduced surface hardness in all groups, but the effect was more
pronounced in the bulk-fill composite group.
Conclusions: Based on our results, flowable SFRC can be applied using either a layered or bulk-fill technique without
significant differences in mechanical properties. This material may be particularly advantageous for restoring deep cavities
with high volume factor, as it provides adequate surface hardness at both coronal and apical levels.
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