Germs that cause gum disease, gingivitis, and tooth decay live in groups. These bacteria are much less destructive when their groups, called colonies, are mechanically broken up with a toothbrush. Another problem caused by bacterial colonization is the production of foul odors.
The surface of the tongue is covered with many little tissue projections, called papillae, which serve various functions such as detecting taste. Papillae also provide protection for bacterial colonies. Since foul odors originate from bacteria, an unclean tongue is a major source of bad breath, or halitosis.
Brushing the tongue is an effective way to manage halitosis. It also reduces overall amount of germs in the mouth to help prevent gum disease and tooth decay. Some dentists also advocate scraping the tongue routinely with special tools as treatment for halitosis. Probably the most effective time for brushing and/or scraping the tongue for the management of halitosis is when brushing the teeth in the morning.
Some general tips:
Tilt the brush at a 45 degree angle against the gumline and sweep or roll the brush away from gumline.
Gently brush the outside, inside and chewing surface of each tooth using short back-and-forth strokes.
Gently brush your tongue to remove bacteria and freshen breath.