In a previously answered question, I talked about why your new dentures may not look like your old ones.
A lot of it depends on the age of your old dentures and how much more support had to be added to your new ones to properly support your lips and cheeks.  Sometimes, this added support such as  thicker borders and higher teeth may be to much and would have to be gradually reduced.
The actual teeth may have been placed either to far forward or to far inward which alters your appearance. In this case the teeth will have to be remade to fix this situation.
It is a good idea to see and try on your new dentures while they are still been made to check and see if you are pleased with the appearance before they are finished, it’s an easy thing to do.
Either way, discuss this with your practitioner and ask him or her to adjust your new dentures so you are please with your new appearance. Please see my earlier answered question on appearance with new dentures.
Thank you,