A porcelain veneer holds because it is glued to enamel; the bond to dentine is weaker and degrades over the years, which is what decides veneer versus crown.
A veneer holds because of what it is bonded to, not because of what it is made of: a laminate veneer is a shell of ceramic well under a millimetre thick, fragile enough on its own to break between your fingers. It becomes strong only once it is bonded to the tooth and the two behave as a single structure. That bond is chemically reliable on etched enamel and measurably less reliable on dentine, which is wet, tubular and organic, and whose adhesive interface deteriorates with time rather than staying constant. The substrate matters more than the ceramic brand.
Enamel on an upper front tooth is thickest at the biting edge and becomes very thin near the gum, where it can approach a few tenths of a millimetre. A preparation of half a millimetre in the wrong place therefore does not thin the enamel, it removes it entirely and exposes dentine at exactly the margin that has to seal. This is also why teeth already worn down, previously prepared, or eroded by reflux or an acidic diet frequently have no enamel left to bond to.
Teeth carrying large old fillings, teeth that have had root canal treatment, heavy grinders who fracture thin ceramic, and dark tetracycline staining that a translucent shell cannot mask: in these cases a veneer is the wrong restoration and we say so. The alternative is a monolithic zirconium crown at 180 EUR, which does not depend on an enamel bond, or, in mild crowding, moving the teeth with orthodontics from 1,400 EUR instead of covering them.
Depth-cut grooves are placed with a calibrated bur so the reduction is measured rather than estimated, the margin is kept on enamel, and in additive cases the tooth is barely touched at all. Veneers are 200 EUR per tooth here, and the assessment that decides whether you are a candidate costs nothing: send photographs and any recent x-rays on WhatsApp at +905402555055 and we will tell you honestly whether the enamel supports it.
It is judged from clinical examination and x-rays, not from photographs alone. Heavy wear at the biting edges, yellowing that has increased steadily over years, and cold sensitivity on many teeth at once all suggest enamel loss and push the plan towards crowns.
A small, sound composite filling can be included if the margins of the veneer still sit on enamel. Once a filling occupies much of the bonding surface, the veneer is being glued mostly to resin and dentine, and that is the point at which a crown becomes the more honest recommendation.