It is called xerostomia and is caused by a decrease in the quality and quantity of saliva secreted, usually caused by some drugs used in cancer treatment.
It is advisable to always carry a small water bottle to be able to take small sips as needed.
To avoid irritation and discomfort, use non-irritating toothpaste and soft toothbrushes and dental floss. Rinse your mouth with mouthwash.
You can use water and baking soda, lemon, or chamomile to rinse your mouth.
It is important to brush your teeth after meals.