A filling is a method used to restore a damaged tooth back to its normal function and shape. If the tooth requires restoration due to decay, we first remove the decayed tooth material thus cleaning the entire area, finally filling the cleaned out cavity with a filling material. Â This procedure prevents further decay of the tooth, and in turn saves the tooth. Â If a decayed tooth is left untreated there is a good chance the decay will get worse and you will loose the tooth, so best to act quickly.