Fluoride Release and Surface Characteristics of a Glass Ionomer

Objectives: The aim of this study was to evaluate in-vitro the fluoride release and the surface characteristics of a glass ionomer cement (Fuji VII) that is uncoated or coated with a resin. Methods: Fourteen specimens were prepared in brass rings with 8,90mm diameter and 2,15mm thick. Seven of the specimens were coated with Optibond Solo. All the specimens were stored in distilled water at 37°C. The water was refreshed daily and measurements of fluoride release were made initially at daily intervals and continued for 350 days using a combination fluoride ion-selective electrode. At that stage the surfaces of all the specimens were examined under a light microscope to qualitatively analyze their surface characteristics. Samples were also freshly prepared to investigate the surfaces. Results: Fluoride release from the uncoated specimens was significantly greater than the fluoride release from the coated specimens over the study period. Most of the fluoride released from both groups occurred in the first 10 days of the experiment. About 1,5 mg/mm² was released during the first day from the uncoated samples but only 0,5 mg/mm² from the coated samples. A markedly diminished release of fluoride occurred from both groups over the rest of the 340 days of the experiment. The surfaces of all the specimens had cracks but in the case of the resin coated specimens the cracks were covered by resin. However at 340 days the resin coating from the coated specimens was missing, damaged or had lifted away from the glass ionomer cement for up to 90% of the surface. Conclusion: The clinical implications of this study are that if glass ionomers are to be used as restorative materials they should be coated with a resin to protect the ionomer from disintegrating. In addition resin coatings must be replenished or renewed during this period.