Generally speaking, the bristles of the toothbrush should be long on the outer edges and short in the center. The long bristles clean the spaces between the teeth and the tartar along the gums. The short bristles clean the surface of the teeth.
一般說來，牙刷的毛宜外長內短，長毛用來刷清牙縫和牙齦邊緣的齒垢，短毛則清潔牙面。