I Have Problems with Front 2 Veneers Coming off or Loose. Can I Replace Them with Crowns for a Stronger Bite and Stronger Teeth?

I can feel the frustration in your question, and want you to know that you are not alone. Not only are you frustrated with loose veneers, but so is your dentist.  As you have experienced, veneers require proper equilibration of your occlusion ( balanced bite) and adequate tooth structure to retain them. In your case, it may be a question of one or the other, or both. My suggestion would be 1) to have your occlusion looked at and adjusted if necessary to avoid hitting those veneers harder than the others,  2) have a nightguard made to prevent you from clenching and or grinding at night, then have the loose veneers rebonded. If all else fails, perhaps there was inadequate tooth structure to retain them and then, crowns for those 2 teeth would be indicated. But again, the bite would definitely require adjustments so as not to chip and wear the opposing teeth. 

As most of the other doctors have indicated,  Your problems are either fully or partially related to your bite and in some movement your teeth are hitting to hard and popping off the veneers.  You are lucky none have broken which is common with a heavy bite on porcelain.  You should have the bite checked.  It is possible that they made your veneers longer for cosmetic reasons and they may be hitting now due to that reason.  Crowns are stronger, but if it is the bite, it will still cause problems.  Go in and get an opinion from a dentist or two and see if they agree on the problem and the solution.  Good luck!

While I agree with the statements below ie. 1) most likely a problem with your bite 2) either regular night guard appliance wear or neuromuscular bite assessment needed to be done, it is possible that there just isn't enough tooth structure left, or the preparation design of the teeth do not offer enough retention to support the veneers.  This is difficult to say unless we are able to see your teeth with the veneers off.  If crowns would offer extra retention that you are missing, then it may indeed work.  However, if you are grinding your teeth at night, I would still follow this up with the night guard appliance to prevent any chipping of the porcelain during grinding.