How to give a special thank you?

Last Saturday I had a fall and broke three of my front teeth which left me in a lot of pain, embarrment and looking like a tramp! Someone I barely know who is a dentist fixed my teeth to perfection and did not charge me. How can I say thank you and not break the bank? I already bought a nice bottle of champagne and can't afford much else, but I am truly grateful and want him to know.