It is impossible for fully adapted porcelain veneers to cause bad breath. The cause of the bad breath is neglected oral care. Porcelain veneers rot in a poorly cared for mouth. Consumption of carbohydrate foods and lack of oral care as a result cause bad breath, which also means cavities and gum problems for patients. In other words, when the person's original tooth or the veneered tooth is not well cared for and hygiene rules are not followed, the bacterial environment in the mouth causes bad breath.