We used the link:
http://www.facebook.com/sharer.php?u=[shared URL]
...to share a particular page. However, Facebook Sharer uses the cache
Append a ?v=random_string to the url. If you are using this idea with Facebook share, make sure that the og:url param in the response matches the url you are sharing. This will work with google plus too.
For Facebook, you can also force recrawl by making a post request to https://graph.facebook.com
{id: url,
scrape: true}