Does filing the tooth decay prevent it from further decay in future?

Yes and no. If the tooth is filled properly and all decay removed and a protective base is placed over the decayed area than no further decay should happen. Poor oral hygiene and poor diet as well as leakage could result in future decay. I have fillings that have lasted over ten or more years.

A dental restoration is a repair of a broken down tooth. Restorations, if well maintained, can last for many years. Few last forever. Recurrent decay is always a possibility, but a properly placed restoration arrests the current decay and returns to tooth to proper form and function.

Dentist will remove all damaged infected tooth material before placing restorative material. "Permanent" fillings generally last for years, and usually need replacement after time. Decay can recur for many reasons, which is just one of the many reasons 6 month dental Recare appointments are recommended.

No it does not. A filling replaces an area of decay that has been removed. You can still get new decay around the edges of the filling where it meets the tooth if you do not properly take care of your teeth. The best way to prevent recurrent decay is good oral hygiene, a diet low in cavity causing foods, and routine preventative dental visits.