My breath is very bad but I was told I have no cavities. What could be causing it?

Even without cavities, most causes of bad breath are inside the mouth. 1) Coating on the back of the tongue - the most common cause, and it often improves if you clean well toward the back with a tongue cleaner. 2) Gum disease (periodontitis) and tartar - these improve with scaling and gum treatment. 3) Dry mouth - when saliva decreases, bacteria multiply. If the odor persists after the oral causes are treated, it may come from tonsil stones, rhinitis, or a digestive problem, so we would recommend an ENT or internal medicine examination.