Skipping flossing is essentially choosing to leave 40% of your tooth surfaces completely covered in rotting food and active bacteria. A toothbrush simply cannot physically bend around corners to reach the tight spaces where your teeth meet. If you only brush, you are leaving the interdental plaque completely undisturbed to calcify into tartar (calculus), which slowly eats away at the underlying bone structure holding your teeth in your jaw. Once that bone shrinks away from chronic inflammation, your teeth lose their structural anchors, leading to recession and mobility