Preparation of a new type of giomers and their thermal characterization by photopyroelectric calorimetry

Abstract

Giomers represent a new concept in restorative dentistry, based on novel pre-reacted glass technology, where special glass-ionomer fillers are included in the resin matrix. A series of resin matrices based on 2,2-bis(2-hydroxy-3-methacryloxypropyl), bis-GMA (phenylpropane), and 1,6-bis(methacryloxy-2-ethoxy-carbonyl-amino)—UDMA (2,4,4-trimethylhexane) as base monomers and triethyleneglycol dimethacrylate (TEGDMA)/2-hydroxyethyl methacrylate (HEMA) as diluting monomers, have been prepared and investigated together with commercial Beautifil II giomer and three adhesives (one commercial and two experimental). The photopyroelectric (PPE) calorimetry in both front and back (BPPE) detection configurations was applied to measure the dynamic thermal parameters of the investigated materials. The BPPE configuration, together with the frequency scanning procedure, was used to directly measure the thermal diffusivity of the primer and the bounding materials, as well as the UDMA/HEMA and TEGDMA/bis-GMA mixtures. The results indicate that the values of the thermal parameters of the materials prepared in our laboratory (6.95 × 10⁻⁸ m² s⁻¹ < α < 12.93 × 10⁻⁸ m² s⁻¹) are close to those of the corresponding commercial materials (11.63 × 10⁻⁸ m² s⁻¹ < α < 12.01 × 10⁻⁸ m² s⁻¹). For the commercially available giomer (Beautifil II), the values of the thermal diffusivity (α = 8.19 × 10⁻⁸ m² s⁻¹) and effusivity (e = 960 W s^1/2 m⁻² K⁻¹) indicate a good thermal biocompatibility of the material.