Is it okay to use bonding agent and then cement veneer back on teeth? (photo)

My first thought is "What EXACT ceramic was used to make the veneers?"  as that normally dictates a successful bonding/cemention and ceramic priming protocol.  There are many types and brands of bonding agents, cements and primers as well as ceramics.  Some work well together, some do not and some ceramics bond weaker than others.  Also as Dr. Estep mention, function or para-function needs to be evaluated as mechanical forces are necessary to "pop" veneers off.  I would prefer them pop off verses them break off!  I am sure your dentist will get it figured out as some custom adjustments are necessary for extensive dental work.

Most of us use the terms "cement" and "bond" synonymously.  Your dentist probably used the same procedure both times to "glue" the porcelain to your tooth.  If your veneers are popping off like you describe, then I would be looking for root cause - not a stronger bonding agent.  There is likely an underlying bite issue that is putting too much force on the porcelain causing the bond to fail.  Your tooth underneath the veneer does look small -- if there was old bonding/fillings or decay on that tooth, all of that needed to be removed in order to prepare the tooth for veneers.There are minimally invasive ways to do these procedures as long as the tooth is healthy with no old fillings.

Hi:
In order to give accurate advice on the cementation, I need to know the type of cement that was used.  One of the main reasons for the veneers coming off is either bite or clenching or grinding pressure.  Wearing a nightguard at night might also solve the problem