Hi. Welcome to Healthcaremagic. I read your query. Bad breath can be due to local oral causes like plaque, gum disease, bleeding or due to some systemic cause. Dry mouth can cause bad breath. Taking odoriferous food such as onion, garlic, etc., Low carb diet also leads to smelly breath. systemic causes include GERD, diabetes, kidney or liver disease, lung disease, etc. Do you experience some regurgitation or flatulence? This can happen even without H pylori infection. You may feel acid in mouth. This cause bad breath as well as can harm your teeth. Drink plenty of water and chew sugarless gums for increasing saliva production. Get blood test (KFT, LFT), urine test and test xray done and consult physician to rule out systemic diseases. As you already said you have regular prophylaxis. but you can go to dentist every 3 months instead of 6. Get all cavities filled(if any). Brush twice a day. Use mouthwash twice a day. Do warm saline gargles. Take lots of fluid and healthy diet. At times after getting rid of bad breath, patient continues to feel it. This is psychogenic. Get a thorough check up and confirm if bad breath is still there or its just psychological. Hope the answer helps. Thank you!