Yellowness of teeth can be extrinsic or intrinsic. You may have deposits on your teeth or discolouration may be because of foods or medications. Bad smell can be because of cavities in teeth or gum disease.. Smoking, dry mouth and certain medical conditions can also be the reason.
Next Steps
You need a thorough check up by a dentist who will tell you whether you need scaling and polishing, Bleaching of teeth can be done if needed.
Health Tips
Regular brushing and flossing will help in maintaining oral hygiene.