[Dimensional instability of zinc oxide-eugenol based temporary sealing materials used in endodontics].

The dimensional instability of temporary sealing materials based on zinc oxide-eugenol was studied in vitro by chemical reaction between an indicator solution (5% nickel sulfate) and a developing solution (1% alcohol dimethylglixime). Thermal cycling was performed (5, 37 and 60 degrees C). Zinc acetate was added to zinc oxide to test its action on dimensional instability. The materials were divided into two groups. 1) group with double sealing (gutta-percha + sealing material), and 2) group without double sealing. It was concluded that none of the temporary sealing materials tested, with or without double sealing, prevented marginal infiltration when submitted to thermal cycling. The addition of zinc acetate to zinc oxide was not effective in preventing marginal infiltration.