There are certain characteristics that you should look for in a toothbrush be it manual or powered.
Size.
Your toothbrush should allow you easy access to all surfaces of your teeth.
For most adult toothbrushes the head should be half-inch wide and one-inch.
Bristle variety.
If you go to purchase a manual toothbrush or a replacement head for your electric toothbrush, you will be able to select a toothbrush with soft, medium, or hard nylon bristles.
For most adults and children, a toothbrush with soft bristles and rounded tips is the most appropriate.
This type of toothbrush is gentle on gums but still allows you to effectively clean your teeth.
Depending on how hard you brush your teeth and the strength of your teeth, medium and hard-bristled brushes could actually damage the gums, root surface, and protective tooth enamel; this will can cause tooth sensitivity and other dental problems.
The best toothbrush then will be soft, flexible, and electric.
A toothbrush should be replaced AT LEAST every 3 months