How Much Length Can a Veneer Add to Canine Teeth?

From the picture that you provided it seems that you could add some length back to your canine, but I am not sure about 3mm.  You are limited on the length of your canine based on how your lower jaw moves when you move it side to side.  I would consult with a cosmetic dentist and let them assess just how much length can be added without risking fracturing the veneer.  Good luck.

It does appear that your canines are too short. Sadly you cant get your enamel back but you can do bonding or veneers on those canines. When you slide your teeth from side to side your upper and lower canines should slide up one another. Canine guided bite is what is optimum.

Porcelain veneers can help you re-establish the length that you desire but it will be limited depending on your bite.  The aesthetics of a new length can be tested out by placing a resin bond or a temporary which can be fabricated by the lab.  From your photos 3mm seem to be too long.  But the most important thing  before you commit to any veneer treatment  would be  to determine why one of your canines chipped and what can be done to prevent this from happening again?  Otherwise this could reoccur with the veneer as well.

The length of your two cental incisors is a good guide for cusped length.  3 mm would be way too much I think from seeing your photos.  I would suggest adding some bonding material to the cuspids as a test to see what looks good to you.  If you proceed with veneers the length of the temporaries can be adjusted as you wear them to establish what length you want for the final restoratins.

You're thinking is absolutely correct.  A porcelain veneer can add length to a tooth.  If you are considering a veneer, you would probably want to reproduce your original length of the canine.  The maximum length would be determined by your bite.  Also it is important to consider why the tooth fractured originally.  If you grind your teeth, you may want to consider a protective night guard. 

The length of veneers will be limited to your bite and lateral (side-side) movements of your jaw. For best results consult with your dentist to make a study model with wax ups on both canine to determine the most esthetic and functional length to your teeth. You may also consider going with invisalign or ortho tx first to align your teeth for ideal esthetic position.

 

But there are limits to how long.  SOME people can add 3 mm, but most people have bites that limit how long the teeth can be.  

From your photo, you display some flaring of teeth, which may indicate that the lower jaw pushes extra hard against the upper teeth.  This MAY mean that you exert forces that a long veneer can't survive (you report that the canine did chip previously).

You would benefit from an office that can thoroughly evaluate your bite before you start any treatment.  Often, this requires sophisticated computer equipment for complete accuracy (K7 from Myotronics, JVA from Bioresearch or a Tek scan).