The Effect of Resin Type and Placement Technique on the Hardness of Resin-Based Composites Polymerized with LED and UV Light-Curing Units

TL;DR

This study examines how different resins and placement methods affect the hardness of dental composites cured with LED or UV light.

Contribution

The study identifies how resin type and placement technique influence composite hardness under different curing methods.

Findings

The hardness of resin-based composites varies significantly depending on the resin type and placement technique.

Tetric Flow RBC failed to polymerize with both LED and UV light-curing units on either surface.

Bulk placement technique showed higher hardness on the bottom surface when using UV light-curing units for certain resins.

Abstract

The aim of this in vitro study is to evaluate the effect of resin type and placement technique on the hardness of resin-based composites (RBCs). A total of 300 samples consisting of five RBCs (Filtek Z250 microhybrid, Filtek P60 packable, Tetric Ceram hybrid, Admira ORMOCER, and Tetric Flow flowable RBCs) were prepared. Each RBC was placed into Teflon molds with a 4 mm diameter and 2 or 8 mm depths with standard, bulk and incremental techniques and was polymerized by second-generation LED (Hilux Ledmax 1055, 229.153 mW/cm2) and UV (ELC-410, 26.106 mW/cm2) light-curing units (LCUs) in standard mode (n = 10). The Vickers hardness number (VHN) was measured from the top and bottom surfaces of the RBCs. Data were statistically analyzed with a one-way ANOVA. Multiple comparisons were made using the Tukey, Scheffe, and t-tests (p < 0.05). The VHN of the RBCs polymerized with LED and UV LCUs varied between 110.33 and 25.16 and between 104.86 and 34.20, respectively. The Tetric Flow RBC did not polymerize with the LCUs on either surface. The RBCs placed using the bulk technique could not polymerize with the UV LCU on the top surface, except for the Filtek P60 RBC, but showed a higher VHN on the bottom surface. These significant findings highlight that the hardness is specific to the RBC material and placement technique.

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