there is a limit to what we can remove with toothbrushing and flossing. What happens is that the soft bacterial plaque that forms every day, starts to calcify and turn into tartar which is not removable at home. It must be done by the hygienist under the auspices of the dentist, usually 2-4 times a year, depending on the patient's condition.
It is possible to keep your teeth for your entire life if you combine good professional care on a regular basis with good home care (frequent brushing and daily, effective flossing). Without professional care, even good home care isn't enough to ward off problems over the long haul.