What is the correct way to brush teeth? What is the right size of toothbrush? And when is it changed? What are the potential harms from not brushing before going to sleep?

The correct way to brush your teeth

According to the Qatari Ministry of Public Health, the healthy way is as follows:

Place the brush at a 45-degree angle between the tooth and gums, then move it in a circular motion, then down to the upper teeth.
Bend the brush slightly to clean the inner surface of the teeth, making circular and then downward motions.
Don’t forget to brush the inner surfaces of the teeth until you reach the back teeth by applying the brush at an angle and then making circular motions.
Swipe the brush to clean the tongue from back to front.