My 780 had this issue when my 2nd son was a toddler. What I did was to use Johnson Baby oil, just a tad and lightly coat the squished dome. My 780 is rubber domed so with this baby oil and lightly rubbing in circular motion, the dome will get back it shape. Although the dome is back to its original shape but there will be lines visible (creases). This line will go away as and when the oil evaporates. Now my son is 2nd year MSU, means 19 years later still no issue. On the otherhand if the dome is punctured, thats different story.