Also, regarding the bad breath, I highly recommend a tongue scraper that you can get at any drug store in the section where they sell oral hygene stuff like dental floss, etc. Then, after scraping your tongue, you can brush your tongue after brushing your teeth with the same toothpaste. Then use Orajel antibacterial mouthwash for bleeding gums. Do this tongue scraping twice a day indefinitely, and yoI've see a marked improvement.
Here's some info on a very good online article from the Journal of Cntemporary Dental Practice. It presents presents three studies carried out from 1992 through 1997 on the source of volatile sulphur compound (VSC) production and tongue coating. It highly supports the practice of tongue scraping for the longer lasting reductions in VSC levels. It identified several malodourous bacteria, such as Bacteroides, Fusobacteria spp., Peptococcus., and Peptostreptococcus, amongst the prominent cultivable microbiata.
Recent studies implicate the dorsum of the tongue as the primary source of VSC production both in periodontally healthy and diseased populations. These studies demonstrate (1) that removal of the tongue coating reduces VSC production and (2) when comparisons are performed in samples of mouth air following tongue scraping, tooth brushing, and rinsing with water in subjects with malodour, the longer lasting reductions in VSC levels are followed after tongue scraping.(1)
In the previous page, there is an article entitled, Fundamentals of Breath Malodour, The Role of Substrates, it explains the composition of saliva and the effects of an increased pH. TMA has an alkaline pH of 9.8, whereas the average pH range of both urine and saliva is approximately at 6.4.
Various authors have tried to reproduce the halitosis process in the laboratory by incubating saliva under different conditions. Saliva consists of a complex mixture of secretions from the salivary glands together with multiple species of bacteria, desquamated epithelial cells, leukocytes, and food remnants. Under healthy conditions, saliva does not have an odour. When its pH is increased, however, it turns into an increasingly putrefied odour.(2)
I think that since lemon juice has a pH range of 1.8 to 2.3, it would stand to reason that putting a few drops of sugar-free lemon juice various times a day on the dorsum of the tongue after tongue scraping in an effort to decrease the pH, thus creating an unfavorable environment for bacterial overgrowth. On the other hand, it's also imptorant to not let the lemon juice stay on your teeth for an extended period of time, as it may be harmful to the tooth enamel.