And here's something from the Curt Jest regarding incorruptible bodies of the saints.
With the recent display of St. Padre Pio's body I think many people are under the impression that Padre Pio 's body is incorrupt. I see this statement made on some Catholic blogs from time to time where they look at the recent photos and assume this is the case. The multiple reports I have seen have stated that they used a wax mask in his case.
"When Pio's crypt was opened earlier this year, the head was described as partly skeletal, though the hands were reportedly in perfect shape, with no traces of stigmata. A wax mask was ordered from a London company that once supplied Madame Tussauds. They worked entirely from photographs."
The Church has never seen the incorruptness of a body as proof of anything and is not considered as part of the process for canonization. It certainly appears that God has done this as a miracle from time to time such as in the case of St. Bernadette and others.