Wenyuan Shi stated that the United States spent $120 billion on oral disease treatment in 2014, half of which was related to cavities. Streptococcus mutans is the primary cause of cavities. The rate of cavities has increased significantly over the past century, mainly because the sugar content in the human diet is much higher than before, providing sufficient nutrients for Streptococcus mutans to grow and reproduce, while the acidic substances they produce subsequently cause cavities.
However, Wenyuan Shi noted that, similar to current antibiotic treatments for bacterial infections, broad-spectrum antibiotics are not selective and kill all bacteria, whether good or bad. Furthermore, due to a lack of competition, bad bacteria regenerate faster than good ones. "It is like weeds in a garden; if a herbicide kills everything without distinction, the weeds will end up overgrowing the garden," which leads to side effects.
