Effects of Monomer Composition of Urethane Methacrylate Based Resins on the C=C Degree of Conversion, Residual Monomer Content and Mechanical Properties.

Andrea Maria Chisnoiu,Radu Marcel Chisnoiu,Alexandra Roman,Georgiana Florentina Gheorghe,Andrada Soanca,Codruta Sarosi,Marioara Moldovan,Stanca Cuc,Miuta Filip,Ancuta Trifoi,Timea Gherman

doi:10.3390/polym13244415

Abstract

(1) Background: This study investigated the influence of Bis-GMA, TEGDMA, UDMA, and two different polyethylene glycol (PEG)-containing, UDMO-based co-monomers on the Young’s modulus and flexural strength, degree of methacrylate C=C double bond conversion and residual monomer elution of experimental dental resins. (2) Methods: Urethane methacrylate-based monomer was synthesised via a radical chain growth polymerization mechanism using PEG in order to improve the mechanical properties. Dental resins were formulated using Bis-GMA, UDMA, or UDMO as base monomers combined with TEGDMA as a dilution monomer and DMAEM + CQ as the photo-initiator system. Degree of conversion (DC), mechanical properties, and residual monomer content of light-activated methacrylate resin formulations were evaluated and statistically analysed by ANOVA and a Tukey’s test. (3) Results: PEG-containing UDMO resins had lower Young’s modulus and elastic strength than UDMA-derived resin for all irradiation times. The highest DC (67,418%) was observed for the PEG-containing UDMO-based resin formulation when light cured for 40 s. For all samples, DC increased with the photo-polymerization time. The amount of residual monomer decreased after increasing the light-curing period from 20 to 40 s, resin with UDMO content 0.01 mol of PEG having the smallest amount of free eluted monomer. (4) Conclusions: A strong structure–property relationship exists in photo-cured dimethacrylate-based dental resins. The time and quantity of the photochemical initiation system can influence the physical–mechanical properties of the resins but also the monomers in their composition.

Highlights

The use of composite resins as restorative materials based on dimethacrylic monomers is one of the most important attempts in the field of dentistry [1]
The organic matrix is typically based on dimethacrylate resins [2,3], while fillers vary depending on size, shape, and morphology, each offering different properties depending on the properties that the dental resin must provide [4]
To overcome the disadvantages of low monomer mobility and reactivity resulting in decreased Degree of conversion (DC) and crosslinking density, bisphenol A-glycidyl methacrylate resin (Bis-GMA) has been partially replaced with the low viscosity and more flexible UDMA, and it was diluted with dimetacrilat de trietilen glicol Triethylene glycol dimethacrylate (TEGDMA) [6,7,8]

Summary

Introduction

The use of composite resins as restorative materials based on dimethacrylic monomers is one of the most important attempts in the field of dentistry [1]. The most commonly used monomer in dental composites is bisphenol A-glycidyl methacrylate resin (Bis-GMA) [5]. Bis-GMA is characterized as a long, rigid molecule with reactive double carbon bonds on both ends, a highly viscous monomer due to its hydroxyl groups, which increase its polarity and cause strong intermolecular interactions. The degree of conversion of the C=C double bonds is correlated with the most important characteristics of the materials, such as mechanical properties, volumetric shrinkage, wear resistance, water absorption, and monomer elution [10]

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