Troubled with caries? You are not alone. According to reports of the WHO (World Health Organisation) more than five billion people suffer from caries.

It’s not surprising that chewing gums and other products promising to inhibit caries are clotting the market. Dentifrices containing xylitol, a chemical sweetener, can already be found on the shelf. The use of Stevia rebaudiana, however, a mysterious plant from Paraguay, is still highly controversial. The Novel Food Regulation by the EU still forbids the use of this plant, whereas hardly any sweet dish in Japan can be found to be without Stevia. Rumours concerning a certain caries-impeding properties of Stevia abound all over the internet, but lack scientific proof. On this account, a cross-curricular project was launched at the HBLA Ursprung. Our team of 21 pupils tried to proof the caries-impeding properties of Stevia and to put controversies concerning its toxicological effect into perspective.
A challenge that could only be met through creativity and teamwork and the taking up of which yielded fascinating results. The metabolic excrements of Streptococcus mutans, a bacterium causing caries, lowers the pH-value in the oral cavity. Owing to this acidic environment the germs, taking the form of plaque - a type of biofilm - are able to adhere to our teeth and thus harm them.

Our experiments with Streptococcus mutans showed that stevioside prevents the pH-value from dropping below 5,5. In this environment the bacteria continue to reproduce, but fail to generate the harmful biofilm. On the other hand, plaque could always be observed when sugar was added and the pH-value dropped below 5. In order to sound out all the other bacteria in the mouth, we scanned our own saliva samples for common germs. Using methods suitable for genetic analyses (RT-PCR), we tried to find out how dentifrices affected the oral fauna.

For the sake of implementing the obtained knowledge, we are planning to design a stevia-sweetened dish that also inhibits caries. As we are representing an agricultural school, we we intended to closely examine the cultivation of Stevia rebaudiana in our own field experiments with the so-called “sweetleaf”.