Are silver crowns only temporary or are there permanent ones? Can I remove this one myself since it's loose?

These are typically temporary crowns and should not be left on long term.  They will cause gum inflammation and recurrent decay over a period of time.  I would see a dentist and have it removed.  Good luck.  

Hi:Normally silver crowns are temporary.  However, there are metal crowns that look like silver crowns as well that are permanent.  Its best to go to a dentist and have it removed.Best,Dr. Maddahi

Stainless steel crowns are prefabricated. The dentist will try to adapt it to the tooth as best as they can, but it isn't custom fit to your tooth like a lab made tooth. We don't usually do lab made crowns until a patient has finished growing, 18-20 years old. If you think there is decay under the crown, see a dentist as soon as you can.