HPLC characterization of two resins used in removable prosthodontics: ProBase® hot and ProBase® cold

Abstract

Introduction: Denture base acrylic resins release residual monomers as a result of an incomplete polymerization [1]. Due to its toxic effects on cells and constant contact with the oral mucosa, it is important to analyze the composition of these resins [2]. Organic solvents can mimic the erosive and acidic action of food and beverages and to penetrate resins’ polymeric matrix [3]. According to ISO 10993-5 (1999), to ensure the release of monomers, specimens must remain for at least 24 hours in contact with the solvent. High Performance Liquid Chromatography (HPLC) is the most efficient method to identify these components [3]. The aim of this study is to identify the monomers released by two denture base acrylic resins. Materials and methods: Specimens of self-cured resin ProBase® Cold and heat-polymerized resin ProBase® Hot were prepared according to the manufacturer’s instructions and placed in contact with an organic solvent by the sink-in method. The elution of Hydroxyethyl Methacrylate (HEMA), Methyl Methacrylate (MMA), Triethylene Glycol Dimethacrylate (TEGDMA) and Urethane Dimethacrylate (UDMA) monomers was evaluated by HPLC 0 hours (t0) and 24 hours (t24) after placing the samples in an oven at 37 °C. Results: The four studied monomers were found in both resins’ structures. Self-cured resin ProBase®Cold released higher concentrations of residual monomers compared to heat-polymerized resin ProBase® Hot (ρ = 0.021). TEGDMA and UDMA monomers were not released by acrylic resin ProBase® Hot at t0. Discussion and conclusions: t0 was evaluated in order to study the monomer release once the acrylic denture is placed into the patient’s mouth, at the dentist appointment. The results agree with Bayraktar et al. who stated that self-curing resins release higher ammounts of residual monomers when compared with heat polymerized acrylic resins [4]. Given the toxic effects of each monomer, we may assume that using acrylic resin ProBase® Hot on acrylic dentures is more beneficial to the patient when compared to ProBase® Cold.