Lumineers are ultra thin veneers then how they provide strength to broken front tooth? i think they should chip with a simple bite.

Strength in Layers: You are right it seems they would be fragile & they are alone but there is strength in numbers - in this case the layers of the lumineers along with the tooth & the adhesive used to bond them works similarly to plywood in that the thin layers of wood gain strength by being bonded together.

Partially correct: Lumineers are like the lee press on nails. They are not meant to give a tooth strength, but are intended for cosmetics. The strength they can offer is minimal and should be used with caution. Also they are not intended to last forever and will need to be replaced in about 5 years.

Not true: You mentioned a chipped front tooth, may i assume that you are just talking about 1 tooth? The challenge is not so much durability, but the color match. If it is a small chip a composite restoration may work well. Lumineers are an excellent product, but your dentist may recommend treating more than 1 tooth. The lumineer is bonded to your enamel which is a strong bond. The porcelain is durable.

The strength of lumi: Strength of the lumineers comes from the coverage of the damaged area of the tooth. Veneers are made from very strong material. Its tested for strength and durability. A simple bite will not brake or chip them off.

Not thin everywhere.: Restoring a chipped tooth with lumineers (or porcelain laminates) can provide greater strength than crowning the tooth because they preserve more of the enamel. Enamel is the strength of the tooth, where the tooth chipped, the laminate replaces the missing structure and so the porcelain is thicker there. Also, the strongest part of the tooth to bond to is the enamel and more remains w/ laminates!