Self repair bumper?

do bumpers sometimes repair themselves if they only need to be bumped out?

Metal or plastic?

Tester

Bumpers on most modern cars are poly-urethane. They want to stay in the shape they were molded in. A moderate hit may not permanently deform the bumper. A strong hit that deforms the supports under the bumper and bends the crumple zones may. What did you observe?

Even though the bumper is plastic and somewhat flexible it is doubtful it will pop back out but it really depends on the size of the dent. Could you post a picture? If it does pop back out it will happen this summer when the temp is very hot for an extended period of time.