Two lower middle front teeth had been worn off because of deep bite. All enamel on front surfaces were gone. Teeth had been fixed a few times with composite resin (whiting fillings) and kept coming off. Teeth became very yellowish due to lack of enamel covering dentine.
Zirconia crowns are perfect solution for this case. They are much stronger material than composite resin and last longer. These crowns not only protect teeth from being worn off, but also give an excellent result aesthetically.