Optical Properties of Restorative Glass-ionomer Cements

The first commercial  glass ionomer cement (GIC) restorative Aspa had poor mechanical properties. These have been improved and this has been widely reported. Aspa also had poor match to tooth due to opacity. Improvements in this property have been less widely evaluated.

Objective: This study evaluates the translucency of 10 modern commercial materials.

Materials and Method: Nine restoratives [Chemfil Rock (CR) Chemfil Superior (CS) Ionofil Molar (IM), Ketac Molar (KM), Ketac Fil (KF), Zero Glass (ZG),Amalgomer (AM), Riva Selfcure, Fuji IX (FIX)] , one luting cement [Ketac Cem (KC)] and Aspa were used. Materials were mixed and formed into discs measuring 1mm thick and 10mm diameter. These were stored for 1 hour in water at 37^oC. Thereafter, the discs were placed on the division between a black and white surface and digitally photographed. The discs were then stored again for 23 hours in water at 37^oC and photographed again. Grayscale values were measured from the photographs.

The discs were also photographed under ultraviolet light to determine whether attempts had been made to match the fluorescence of tooth enamel.

Results: “Opacity” was ratio of greyscale value on black surface divided by that on white surface (where 1.00 is totally opaque).

All the modern GICs were less opaque than Aspa. All materials including Aspa became less opaque after 24 hours. Aspa reduced its opacity value by 5.6% whereas the other GICs had a mean reduction of 14.1%. Only Aspa and Ketac Fil showed any appreciable fluorescence.

Conclusions: It is concluded that modern GIC restorative have lower opacity than Aspa; this difference increases with time.