In vivo study of the pulp reaction to Fuji IX, a glass ionomer cement

Objective: Our aims were to investigate the pulp biocompatibility of Fuji IX, a glass ionomer cement (GIC) used as a restorative material in cavities prepared in ratʹs upper molars, and to assess the value of this in vivo model for testing dental biomaterials. Method: Half-moon class V-like cavities were drilled on the mesial aspect of 26 rat upper first molars. Half of the experimental rats whose molars were restored with the GIC were killed after 8 days and the second half after 30 days. They were compared with two control groups, also submitted to cavity preparation, but with cavities left unfilled. Again, half of the control rats were killed at 8 days and the second half after 30 days. Following intracardiac perfusion with the fixative solution, the specimens were processed to histologic procedures. Results: After 8 days, in both groups a few inflammatory cells were observed. The odontoblastic layer was disrupted and dilated blood vessels were seen in the pulp area related to the cut tubules. The experimental group displayed a moderate inflammatory reaction whereas only a slight reaction was detected in the control group. In few teeth, bacteria were visualized in dentine tubules beneath the GIC restoration. Such colonies were not observed in unfilled molars. After 30 days, in both groups, the pulp tissue recovered and displayed a normal appearance. Disruptions of the odontoblast layer were not visible anymore. Bacteria penetration into dentine tubules was reduced compared with the 8-day situation. A thick layer of reparative osteodentine was formed. However no difference in thickness was detected between the experimental and control groups, supporting that the formation of reparative dentine is not impaired. Irregular mineralizations including calcospherites were induced by the GIC. Conclusions: This study demonstrates that, despite small alterations in the mineralization processes, the GIC Fuji IX has a good biocompatibility and does not induce any harmful effect on pulp cells.