In general, a toothbrush head should be small (1″ by 1/2″) for easy access. It should have a long, wide handle for a firm grasp. It should have soft, nylon bristles with round ends. Some brushes are too abrasive and can wear down teeth.
A soft, rounded, multi-tufted brush can clean teeth effectively. Press just firmly enough to reach the spaces between the teeth as well as the surface. Medium and hard bristles are not recommended.