Personal Hygiene! The ADA (American Dental Association) recommends replacing your brush (manual or electric) every three to four months, more often if the bristles are obviously in bad shape. You can tell if the brush is past its shelf life by looking physically at the bristles, you’ll notice that the tips of the bristles are starting to fray. Or the strands of the bristles may even start to unweave. Flossing regularly helps promote gum health.. Personal Hygiene. Oral Hygiene. Dental Care.