Dental Emergency - Knocked Out Permanent Tooth. For a knocked-out permanent tooth, keep it moist at all times. If you can, try placing the tooth back in the socket without touching the root. If that’s not possible, place it in between your cheek and gums, in milk, or use a tooth preservation product. Then, get to our office right away! You only have about 30 minutes for the best possible outcome and there's still hope within an hour.