Hi Bad breathe may be due many causes In relation to Dental cause Deposits(plaque and calculus) or due to Dental caries In relation to ENT cause Throat infection,sinusitis In relation to gastric cause Gastric ulcers also cause mouth ulcers which leads to bad breathe In case of deposits and dental caries you need to go for complete scaling and ental filling

There can be multiple reasons for bad odour from the mouth, the most common one being calculus deposits on the teeth.... most likely, you will require a session of teeth cleaning followed by a guidance from the dentist about the proper brushing technique.... also, make sure to use your tooth brush to clean your tongue also every time when you brush your teeth.... also check for your lifestyle and food habits.  Eat healthy greens,  vegetables and fruits.  Have plenty of water.

Please get a dental consultation done.. scaling or teeth cleaning must be done minimum once every year to remove all the stains, tartar and other deposits on ur tooth surface, following which u should be brushing twice everyday and start using Chlorhexidine mouthwash once a day to avoid halitosis or bad breath.. grossly decayed tooth if any needs root canal or extraction depending on the condition and cavities if any would need fillings too, all of these do contribute to the bad odour from ur mouth..

There are number of problems which can be associated with bad breath. Dental n respiratory disease may be diagnosed. You should take a good opinion from a dentist nearby. He may suggest fir cleaning and scaling of the calculus deposits on the tooth. Get a thorough check up done even fir cavities on tooth.