hello the reason for a bad breath could be either oral related or systemic (gastric problems) try doing these 4 things regularly twice daily morning and at night 1 proper brushing 2 use interdental aids (proxa brush & dental floss) to clean in between teeth areas 3. tongue cleaning is very important (use tongue cleaner) 4. start using mouth wash ( for 3 weeks use chlorohexidine and then you can use the milder one like listrein regularly) follow this strict regime of oral hygiene along with this u need professional cleaning every 6 months do visit dentist regularly and if it still persist than u might be having some gastric related problem hope this help regards dr rakesh mishra