Development of novel resin modified glass ionomer cements (RMGICs) with reduced water uptake for use in cementing fixed prosthodontics

Abstract

Resin modified glass ionomer cements (RMGICs) comprise GIC and a polymerisable resin monomer, commonly 2-hydroxyethyl methacrylate (HEMA). Therefore, they have the advantages of a resin (e.g. improved strength), together with those of GICs (e.g. fluoride release). However, RMGICs possess some limitations, these being a high water uptake thus leading to expansion, due to the incorporation of the resin, which has subsequently led to fractures of some all-ceramic crowns. Moreover, release of unconverted monomers (HEMA) from RMGICs was associated with decreasing their biocompatibility. The goals of this study were i) to develop novel cements with lower water uptake and dimensional changes compared to commercial RMGICs through incorporating alternative monomers (resin) that are known for their lower water uptake compared to HEMA, ii) to develop control materials that mimic the compositions of commercial materials, iii) to assess the physical, mechanical and biological properties of the new cements and compare them with the commercial and home material counterparts. To achieve the above goals, two commercial materials (Fuji Plus, GC and RelyX Luting, 3M-ESPE) were included in this study. Two control liquids were prepared based on the composition of the two commercial materials (using the materials MSDS and FT-IR). Eight novel liquid compositions were also developed replacing HEMA (partially or fully) with THFM and/or HPM, where the powder used was the same powder as their commercial counterparts. All materials underwent various experiments and investigations. These included water absorption, dimensional changes, polymerisation shrinkage and exotherm, working and setting times, FT-IR analyses, HPLC for detecting leachants, mechanical properties and cell viability studies. All novel materials demonstrated lower water uptake and dimensional changes compared to their commercial and home counterparts. They showed comparable properties with respect to the other properties investigated (e.g. polymerisation shrinkage and handling properties). Two compositions (F3 and F4, based on Fuji Plus formulation) showed improved biocompatibility. This study improved some of the main limitations associated with RMGICs (high water uptake and dimensional change), which will widen the applications of these products.