How long it work for crown on mole tooth?

What do you mean by : "it"? If "it" is the dentist, then depending on the dentist, patient and twenty other factors then anywhere from a 1/2 hour to 2 hours. If "it" refers to the length of time a crown will last on a molar tooth, "it" varies depending on tooth structure, materials chosen, patient homecare, bruxing and many others. Most insurance companies will pay their portion for a crown replacement every 5 years.

crown: Crowns on molar teeth can last a long time if you take care of it and it is done well- see a dentist twice a year to check on it and how you are doing.

Depends: The longevity of any crown is dependent on many factors. How well it fits, material used, home care, etc. I have seen well made crowns last 30 years, but the average is 10 years.