Source 15

I read an article that dealt with the antibacterial properties of neem in the mouth. This was beneficial because it shows that it is a valid way of helping control bacterial growth in the mouth.
Chewing twigs of the mango or neem tree is a common way of cleaning the teeth in the rural and semi-urban population. These twigs are also believed to possess medicinal properties. The present study was conducted to evaluate the antimicrobial effects of these chewing sticks on the microorganisms Streptococcus mutans , Streptococcus salivarius , Streptococcus mitis , and Streptococcus sanguis which are involved in the development of dental caries. An additional objective was to identify an inexpensive, simple, and effective method of preventing and controlling dental caries.

They found some interesting data:
Mango extract, at 50% concentration, showed maximum zone of inhibition on Streptococcus mitis . Neem extract produced the maximum zone of inhibition on Streptococcus mutans at 50% concentration. Even at 5% concentration neem extract showed some inhibition of growth for all the four species of organisms.

Mangifera indic a (Mango) contains tannins, bitter gum, and resins. At 5% concentration, this herbal extract did not show any antimicrobial activity, but at higher concentrations antimicrobial activity was present. When compared to neem, extract of mango chewing stick showed more antimicrobial activity, i.e., at 50% concentration the maximum zone of inhibition for Streptococcus mitis was 5.0 mm. This could be due to the presence of a combination of the ingredients mentioned earlier.Tannins and resins supposedly have an astringent effect on the mucous membrane, and they form a layer over enamel, thus providing protection against dental caries.

Neem contains the alkaloid margosine, resins, gum, chloride, fluoride, silica, sulfur, tannins, oils, saponins, flavenoids, sterols, and calcium. Even at 5% concentration this extract showed some antimicrobial activity. Maximum anitimicrobial activity was observed on Streptococcus mutans at 50% concentration, with a zone of inhibition of 3.8 mm. This may be due to the presence of fluoride, which is known to exert an anticariogenic action, and silica acting as an abrasive and preventing accumulation of plaque; alkaloids, known to exert an analgesic action, also contribute towards dental well-being. The oils have carminative, antiseptic, and analgesic effects. Tannins exert an astringent effect and form a coat over the enamel, thus protecting against tooth decay. Wolinsky reported that the pretreatment of saliva-conditioned hydroxyapatite with neem-stick extract prior to exposure to bacteria, yielded significant reduction in bacterial adhesion. This result suggests that neem-stick extract can reduce the ability of some streptococci to colonize tooth surfaces. Another study conducted by Khalid in 1999 at Saudi Arabia examined the effectiveness of the antimicrobial activity of aqueous extracts of neem at various concentrations. He reported that neem was effective at 50% concentration on Streptococcus mutans.
This article is interesting because it shows the validity of an old and simple practice. I am sure that if this tree is present, it will be used for any things. It appears to be an anti-everything, which makes it a universal plant. I look forward to looking more into this tree and its properties.