How can discolored front teeth be restored?

Discolouration can be external or internal. External discolouration can be improved by scaling and polishing, home or in surgery whitening, veneers or crowns while internal discolouration is due to endodontic treatment which can usually be dealt with internal whitening.

Whitening , veneers , lumineers

There are three options: Inside tooth whitening, composite veneer and porcelain veneer.
I recomend the last one only in very specific situations...

if discolored because of endo problem then you have to do endo treatment first and then whitening or veneers or crowns