Microleakage of porcelain veneers causing bluish tint at gum line? (photo)

This is from leakage that occurred due to the gums bleeding during the bonding process.  I would schedule an appointment with your dentist to evaluate and give possible solutions.  It is likely that the ones affected will need to be replaced.  Good luck.  

It is very important during the cementation for  your gums to be  healthy and have zero bleeding.  However, sometimes during removal of temporaries, gums bleed.  Also if you didn't have the proper hygiene during your temps, your gums can bleed and make cementation very hard.  At this point the only way to get rid of the blue and dark lines, is to change those veneers.  Good luck.  

It is likely to actually be the condition of your gums around the time of cementation. That most of the veneers were without problems means that the overall technique was fine, but where there is a lot of bleeding, the is a lot of fluid pressure trying to displace the adhesive and take its place. Wherever there is missing adhesive which is replaced by blood you will get this effect. On the positive, if the level at which the adhesive is displaced is outside the bond surface, the damaged glue can be chipped (or more commonly grinded) off. Speak to your dentist, and maybe start with a hygiene appointment so your gum health is imp[roved before the treatment is done.Good luckThomas Dey, BDS, MSc