Two patients have identical small cavities but different caries risk. Why might treatment differ? A low-risk patient with one small lesion gets a minimal filling. A high-risk patient (frequent sugar, dry mouth, multiple past fillings) gets the filling plus a prevention plan — diet counselling, fluoride varnish, shorter recall — because without risk control, new cavities will follow. Teaching: treat the lesion, but manage the risk; drilling alone doesn't stop the disease.