Optimization of Plasmonic Gold Nanoparticle Concentration in Green LED Light Active Dental Photopolymer.

Katalin Bukovinszky,Sándor Kökényesi,Péter Petrik,Attila Bonyár,Melinda Szalóki,Sándor Kéki,Lajos Daróczi,Csaba Hegedűs,István Csarnovics,Benjámin Kalas

doi:10.3390/polym13020275

Katalin Bukovinszky, Sándor Kökényesi + Show 8 more

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https://doi.org/10.3390/polym13020275

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Abstract

Gold nanoparticles (AuNPs) display surface plasmon resonance (SPR) as a result of their irradiation at a targeted light frequency. SPR also results in heat production that increases the temperature of the surrounding environment, affecting polymerization. The aim was to investigate the SPR effect of AuNPs on a dimethacrylate-based photopolymer system. The tested composites were designed to overlap the illumination required for the polymerization and the plasmon effect. The 5 nm-sized dodecanethiol capped AuNPs were applied in different concentrations in the matrix that were irradiated with green light (λ = 532 nm), where the Irgacure 784 photoinitiator also absorbs the light. The plasmonic effect was investigated for the refractive index change by surface plasmon resonance imaging (SPRi) supplemented by ellipsometry. Moreover, optical transmission and transmission electron micrographs (TEM), diametral tensile stress (DTS), and confocal Raman spectroscopy was performed to determine the degree of conversion (DC) at 1.0, 1.4, and 2.0 mW/cm2 light intensities. It was found that the optimal conditions were at 0.0208 wt% AuNPs concentration and 1.4 mW/cm2 light intensity at which the refractive index change, DTS, and DC data were all maximal. The study confirmed that AuNPs are applicable to improve the polymerization efficiency of dental composite resin.

Highlights

As outlined in the Introduction, our aim was to improve the mechanical properties of dental resins by applying gold nanoparticles, as nanoplasmonic materials embedded into a resin matrix
The plasmonic effect of the nanoparticles was achieved by green LED light illumination, and the photopolymerization reactions in the presence and absence of AuPNs were monitored
We showed that the cross-link density does not necessarily change if we increase the light intensity, showing that Irgacure 784 could work successfully at narrow intensities which means the intensity of light is probably not a determinant factor for the results

Summary

Introduction

The challenge is to create a resin matrix with low polymerization shrinkage and better depth of cure or degree of conversion along with improved mechanical properties, aesthetics, and biocompatibility [3]. As they are photosensitive materials, the successful photocuring process requires an efficient initiator molecule and adequate light energy with compatible wavelength. The tertiary amine used can add uneven yellow discoloration to the cured restoration These disadvantages of CQ motivated the researchers to find alternative initiator molecules. Acylphospine oxide derivates such as diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (lucirin TPO), phenylbis (2,4,6-trimethylbensoyl) phosphine oxide (BAPO), and the pale yellow liquid 1-phenyl and 1,2 propenedione (PPD) have been suggested as an alternative photoinitiator in dental composites [1,4]

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