Adsorption of 4-Methacryloxyethyl Trimellitate Anhydride (4-META) on Hydroxyapatite and its Role in Composite Bonding

Abstract

The adsorption of 4-methacryloxyethyl trimellitate anhydride (4-META) was studied from ethanol and dichloromethane onto synthetic hydroxyapatite (containing about 1.5 monolayers of physisorbed water) in order to study its role in restorative composite bonding to teeth. The adsorption isotherm of 4-META was S-shaped and reversible from ethanol, and followed the Langmuir plot at lower concentrations. The isotherm was irreversible from dichloromethane, and a constant amount of adsorbate was removed from the solutions above a certain concentration. The irreversibly adsorbed compound was completely removed by washing with ethanol. Therefore, the bonding between teeth and the restorative resin containing 4-META as a coupling agent is micromechanical and not chemical in nature. An analysis of isotherms showed that the benzene rings of the adsorbate molecules lie flat on the surface for both solvents. The molecules adsorbed from ethanol rotate about the solvent-modified (esterified) or unmodified carboxylic anhydride moieties with methacrylate hydrocarbon groups which are folded upward. However, the molecules adsorbed from dichloromethane remain fixed to the surface without rotation, and their methacryloxyethyl groups are folded over the rings. The diametral tensile strength of a BIS-GMA polymer with adsorbate-covered apatite was approximately equal to that of the composite filled with untreated apatite.

Comparative Study on Adhesive Performance of Functional Monomers

“…The chemical bonding capacity of 4-MET is weaker, and it is doubtful that 4-MET, even within a short application time, is capable of chemically bonding to hydroxyapatite. This confirms the rather weak adsorption of 4-META from ethanol and dichloromethane onto synthetic hydroxyapatite reported in a study by Misra (1989). The chemical bonding efficacy of phenyl-P is clearly the lowest among the 3 functional monomers investigated.…”

In vitro Bond Strengths and SEM Evaluation of Dentin Bonding Systems to Different Dentin Substrates

“…The relatively large standard deviations are a reflection of the differences in dentin substrate which have been described by several authors (Pashley et al, 1978(Pashley et al, ,1984(Pashley et al, ,1987Pashley, 1989;McGuckin et al, 1991;Fowler et al, 1992). The low bond strengths to demineralized dentin suggest that a micromechanical infiltration into etched dentin is a more important factor in adhesion than chemical bonding to collagen (Erickson, 1989;Misra, 1989).…”

Clinical effectiveness of contemporary dentin bonding agents

“…This hydrophilic monomer improves the wetting on the moist surface[61] and in addition the hydroxyl groups chelate with calcium forming chemical bonds. [65] This leads to stabilization on the interfacial bond. These systems (Clearfil SE Bond/Bond Protect/S3 Bond, G Bond, All Bond SE, Fluorobond Shake One, One up Bond F+ and Xeno III) also contain silica nanoparticles which result in a thicker adhesive layer acts a flexible interface that relieves interfacial stress between shrinking composite and rigid dentin.…”