Infiltration/evaporation‐induced shrinkage of demineralized dentin by solvated model adhesives

Abstract

During dentin bonding, solvated adhesive comonomers are applied to watersaturated decalcified dentin matrices. When alcohol-solvated hydrophilic or hydrophobic methacrylate monomers are applied, they chemically remove water and cause matrix shrinkage during comonomer infiltration. Evaporation of solvent induces further shrinkage. The purpose of this work was to compare the shrinkage of water-saturated dentin matrices infiltrated with ethanol-or methanol-solvated 2-hydroxyethyl methacrylate (HEMA), 2,2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl] propane (BisGMA), or triethyleneglycol dimethacrylate (TEGDMA) at 90/10, 70/30, 50/50, and 30/70 mass fraction % alcohol/ monomer before and after evaporation of alcohol. Thin (ca 0.2 mm) disks of human midcoronal dentin were demineralized and placed in a well beneath the contact probe of a linear variable differential transformer (LVDT). The height of the matrix was measured before and after random application of one of the twelve alcohol/monomer mixtures. Matrix height was measured during infiltration and during solvent evaporation. Between trials, residual monomer was extracted using ethanol. These studies were repeated on specimens in which 100% alcohol was used to substitute for water in the matrix. Both studies revealed that matrices shrink 30 -50% but that pretreatment of matrices with alcohol prevents BisGMA phase separations from occurring. Wet bonding with ethanol instead of water permits infiltration of relatively hydrophobic alcohol/monomers.

Bonding efficiency and durability: current possibilities

“…216 This technique also prevents phase separation of hydrophobic resin monomers in the presence of water, 217,218,219 since the latter is completely replaced by ethanol prior to the application of the ethanolsoluble monomers. 220,221 Additionally, the elimination of residual water seems to contribute to decrease or even eliminate hydrolytic enzymatic degradation of collagen fibrils, 212,222 thereby increasing bond durability and stability. 213 However, this technique is very sensitive, time consuming and requires the application of many steps to achieve the desired dehydration, which becomes inappropriate.…”

Effects of Resin Hydrophilicity on Dentin Bond Strength

“…With ethanol filling the interfibrillar spaces, the dental matrix becomes much more hydrophobic. As ethanol replaces water, some interpeptide hydrogen bonding (H-bonding) develops, within collagen, that stiffens the matrix enough to minimize its shrinkage (Eddleston et al, 2003;Garcia et al, 2005;Becker et al, 2006). This should lead to better infiltration of hydrophobic dimethacrylates into ethanol-saturated matrices, than into water-saturated matrices.…”

Effects of polar solvents and adhesive resin on the denaturation temperatures of demineralised dentine matrices

“…When they are rehydrated, there is a rapid loss in stiffness, indicating that it is reversible and due to weak, noncovalent forces 20 . An interesting new model was developed that directly measures changes in the dimensions of water-saturated demineralised dentine matrices when they are dried, using a contact LVDT probe [22][23][24][25][26][27] . Using solvents with known solubility parameters (δ) for hydrogen bonding forces (δ h ), as "liquid energy probes" 28 , solvents with δ h values below 18 (J/cm 3 ) ½ could not expand dried collapsed demineralised dentine matrices 23,25 .…”