Characteristics of the sorption of water and an ethanol/water solution by light‐cured copolymers of 2‐hydroxyethyl methacrylate with dental dimethacrylates

Abstract

This work concerns the synthesis of copolymers of 2-hydroxyethyl methacrylate (HEMA) and the dimethacrylates bisphenol A glycol dimethacrylate, bisphenol ethoxylated dimethacrylate, urethane dimethacrylate, and triethylene glycol dimethacrylate (50/50 mol/mol) because of their potential use in contemporary dentine adhesives. Copolymerization was carried out at room temperature with visible light (k max 5 470 nm), with the system camphorquinone/N,N-dimethylaminoethyl methacrylate being used as the photoinitiator. The behavior of these copolymers under oral conditions is of great concern. Thus, the sorption/desorption kinetics of water and a 75 vol % ethanol/water solution (which is an oral/food simulating liquid) by these copolymers were studied. The maximum amount of sorbed/desorbed liquid, solubility, and diffusion coefficient of each liquid were determined. The amount of sorbed liquid and solubility of the copolymers depended on both the structure of the copolymer and the nature of the solvent. The amount of water sorbed by the copolymers and their diffusion coefficients were much lower than those of the HEMA homopolymer but closer to those of the homopolymers of the dimethacrylate comonomers. All the copolymers sorbed a higher amount of the ethanol/water solution than water.

Diffusion coefficients of water and leachables in methacrylate-based crosslinked polymers using absorption experiments

“…This shows that the loss of leachables is the only factor contributing to this peak. Similar findings have been reported by other investigators [9]. …”

“…The diffusion coefficients of water were found to range from 1.06 to 3.15 ×10 −8 cm 2 /s. These values are similar to those reported in the literature for other methacrylate based dentin adhesives [9, 8]. The diffusion coefficients of leachables were found to be generally an order of magnitude smaller than the diffusion coefficients of water.…”

“…The unreacted hydrophobic components in the polymer diffused in a negligible amount into the aqueous solution during the time of absorbance experiments [23, 24]. Sideridou et al have also reported [9] that a significant amount of hydrophobic monomer (BisGMA) still remained in the resins even after the second water sorption following a sorption-desorption cycle.…”

“…The dentin adhesive resins were prepared using 15 candidate co-monomers along with HEMA (2-hydroxyethyl methacrylate) and BisGMA (Bisphenol A glycerolate (1 glycerol/phenol) dimethacrylate). In the past, similar mass change measurements have been performed to determine the diffusion coefficient of water in polymers and dentin adhesives [8, 13, 14, 9, 15, 16]. In these references, one-dimensional diffusion using Crank’s solution for the fractional solute absorption was applied to disc specimens.…”

Dynamic thermo-mechanical properties of various flowable resin composites

“…However, ideally, one might expect a restorative material to present the same structural, mechanical and physical characteristics of dentin (7). Yet the E’ modulus of dentin at 37°C and at 1 Hz was measured as being 15 GPa (8): in our study all the materials present values well below this at 35°C and 40°C, consistent with the results of other studies (7,9,10), indicating, in theory, that flowable resins are actually incapable of fully serving as dentin substitutes and the need to restrict them to small-volume restorations. Indeed, the greater the difference between the elasticity modulus of dentin and that of the material, the higher the risk of interface destruction appears to be (11,12).…”