What Would Make Someone Not a Candidate for Porcelain Veneers?

Crooked teeth will need heavy cutting down for veneers. Yes they are made within 2 weeks, but if something goes wrong then the teeth are destined for further work.

If your teeth are healthy and just crooked/discoloured, then striaghten them with invisible Invisalign and bleach them.

At least you can eat into a baguette without having to suffer a fractured veneer.

Sometimes patients will present with teeth that are crooked,rotated and out of position. Cases like these sometimes are best treated first with a traditional orthodontic approach or with Invisalign aligners. After successful Orthodontic treatment a Cosmetic treatment plan can be developed to either use Porcelain Veneers or all Porcelain Crowns. However there are many instances when patients don't have the desire, time or immediate means for Orthodontics. In cases like these Veneers are not the right choice since a severely crowded or rotated dentition will lend itself to a poor Cosmetic result and premature failure. Often times these crowded arches go hand in hand with Occlusal or Biting problems that can cause cracking and dislodging  of the Veneers. After Study models and x-rays are evaluated along with developing Mock or ideal models all Porcelain Crowns can provide the ideal solution. In cases of extreme malpositioned teeth Extractions and Dental Implants are also options to consider.

All of these are contraindications to porcelain veeners.  Grinding habits and bad bites can cause too much stress on the veneer and it will break or come off.  Heavily restored teeth should receive a full porcelain crown instead of veneer because they are not strong enough.

It depends on just how crowded and crooked your teeth are. I would need to see you in person or view a set of digital study models, xrays and photos.

Many adults with crooked teeth skip the braces and go right to veneers.

If the teeth are severely malpositioned (crowded, etc) it will depend on the position of the tooth in the dental arch. Very often if the tooth is positioned very buccally it can be compromised due to the lack of bone support. In order to define what can be performed in order to improve the smile, precise and careful evaluation should be made by the specialists: prosthodontist and orthodontist. 

The other doctors have answered your question quite well. For someone who needs Veneers regardless due to staining, wear, etc and doesn't wish conventional orthodontics, might consider this alternative. Create large spaces between the teeth with abrasive strips and perform limited orthodontics for 3 - 6 months followed by veneers. You can get a good result this way by combining approaches. Hope this helps and good luck.

Depending on location, rotation or crowding, the dentist must be a bit more agressive in preparing teeth.  So while the desire may have been conservative veneers, full coverage crowns may be more appropriate.

Sometimes the teeth are extremely crowded and crowns or veneers simply won't work without braces of some sort.  Often braces done with the intent to veneer ("pre-prosthetic orthodontics") mean the treatment is short, perhaps only 3-4 months instead of 2 years.  This often gives the best result.

If braces are simply out of the question, then simply extracting a tooth that is severely out of position can be a choice, and then a bridge or implant can be placed.