The purpose of this study was to observe the aging effects of post surface treatment with nonthermal plasma using air or helium mixed with 2% oxygen as the working gas. Two groups of fiber posts were treated with one of the nonthermal plasmas. Both groups were further divided into four subgroups, each receiving an air exposure time of 0, 1, 12, or 24 hours before being bonded with composite resin cement. The microtensile bond strength of each subgroup was measured. The results showed that the improvement in bond strength disappeared when fiber posts were exposed to air for 1 hour or longer after being treated with plasma.