The Effects of Surface-Coatings on Microhardness of Different Glass-Ionomer Materials

Objectives: The glass-ionomer materials have many advantages such as the ability to form chemical bonding at the tooth-restoration interface, release and recharge of fluoride and high biocompatibility. But their low mechanical properties and susceptibility to moisture limit their usage. The surface coatings are used to protect the physical and mechanical properties of these material. Therefore, this study aims to evaluate the effects of surface coatings on microhardness values of different glass ionomer materials.
Methods: Three glass-ionomer materials; Ketac Molar Easymix-3M ESPE (conventional), EQUIA Forte Fil-GC (high-viscosity hybrid), and ChemFil Rock-Dentsply (high-viscosity zinc) were tested. Each material were subdivided into control (no surface coating), petroleum jelly (Vaseline), and coat (Equia Forte Coat-GC) groups (n=7). The microhardness was assessed using a universal testing device at baseline and after 130 days.
Results: The highest microhardness was observed in EQUIA Forte Fil/control (baseline), and the lowest was in EQUIA Forte Fil/coat (baseline) (p≤0.05). Both EQUIA Forte Fil/control and ChemFil Rock/control showed decreased microhardness over 130 days (p≤0.05). The pairwise comparison within EQUIA Forte Fil groups, at the end of 130 days, there was a decrease in the microhardness values of the control group and an increase in the coat group (p≤0.05). It was observed that microhardness reduction in the ChemFil Rock/control group was statistically significant (p≤0.05). The microhardness values of Ketac Molar Easymix materials covered with petroleum jelly and coat were increased (p≤0.05).
Conclusions: The surface coating reduces the deformation in the structure of the material and microhardness change depending on the material characteristics. These effects should be consider during the usage of glass ionomer materials.