Interfacial Characterization of a Conventional Glass-Ionomer Cement after Functioning for 1-year In Vivo.

Purpose: To morphologically evaluate the interface between a conventional glass-ionomer cement (GIC) and dentin one day after placement, as well as the changes at the interface after one year of aging/functioning in monkey teeth.

Materials and methods: On the buccal surfaces of seven intact teeth in each of two monkeys, shallow class V cavities were prepared, which were then filled with Fuji IX GP (GC) to provide 1-year in vivo data. A year later, two more teeth in each monkey were similarly prepared and restored for the 1-day in vivo group. The following day, the restored teeth were extracted and the restoration interfaces observed using transmission electron microscopy (TEM). In addition, restorations were similarly placed in two extracted human teeth (control, 1-day in vitro group) and observed a day after placement using TEM.

Results: The 1-day in vivo and in vitro results showed that the GIC appeared to bond to dentin through a demineralized zone similar to the hybrid layer produced by resinous adhesives. However, the interface between GIC and dentin after 1 year in vivo appeared to change over time: many needle-like crystals were detected within the remineralized layer and along the collagen fibrils. Slow diffusion of ions resulted in pores, which filled with mineral crystals and made the pores smaller.

Conclusion: The interface between GIC and dentin morphologically changes over time, and recrystallization or remineralization at the interface may occur (1 year in vivo).