Brushing your teeth properly is the first and easiest thing to maintain healthy teeth and gums. Incorrect brushing technique can lead to tooth abrasion.
Missing teeth can be replaced by dentures, bridges or implants. If they are not replaced, the consequence is increased risk of gum disease and tooth decay.
Your toothbrush bristles simply cannot reach between the teeth. Flossing the teeth is essential to reach these surfaces where tooth decay normally occurs.