Your dentist told you to avoid sweets, but you may actually be able to fight tooth decay by sucking on candy—if it’s laced with the right dead bacteria. In a new study, volunteers who consumed such candies lowered the levels of cavity-causing bacteria in their saliva, presumably because the dead bacteria tie up the living ones, which are then swallowed.
The surfaces of our teeth teem with millions of bacteria. They churn out acid after meals, etching away at each tooth’s enamel. If unchecked by regular cleaning, these microbes eventually carve a hole, or cavity, in the enamel that a dentist must drill and fill. One group of bacteria, known as mutans streptococci, is the prime perpetrator. Researchers already knew about a strain of “good” bacteria called Lactobacillus paracasei found in fermented milk called kefir that can bind with mutans streptococci in saliva. Previous research demonstrated that this bacterial latching can reduce the number of cavities in rats.
Now, Christine Lang, a microbiologist at ORGANOBALANCE, a biotech firm based in Berlin, and colleagues have shown that L. paracasei reduces the amount of mutans streptococci in the saliva of people. The researchers tested the saliva of 60 volunteers for mutans streptococci. Then, some participants ate mint candies infused with L. paracasei that the scientists had killed with heat. In the double-blind study, other volunteers sucked on bacteria-free mints that tasted exactly the same. The team took another saliva sample after the first round of candies. Each volunteer had another three candies that day and one more the next morning before giving a final sample of spit.
About three-quarters of the volunteers given bacteria-laced candies had fewer mutans streptococci in their saliva than they had just the day before, the team reports this month in Probiotics and Antimicrobial Proteins. About 60% of the volunteers who ate unaltered mints lowered their bacterial loads, an insignificant change that could be explained by their mere participation in the study, the researchers suggest.
The candies target mutans streptococci when chewing or brushing dislodges the bacteria from the surface of a tooth. A sugar structure on the surface of the L. paracasei, which isn’t damaged when scientists kill the bacteria, hooks onto free-floating mutans streptococci and prevents those cells from returning to teeth, the researchers hypothesize. The volunteer then swallows or spits out the new bacterial buddies, Lang explains. Although some bad bacteria remain in the mouth, L. paracasei can get rid of enough mutans streptococci to lower the risk of developing cavities, the researchers maintain. “This is a completely different way to think about bacteria,” Lang says. “We don’t want to kill them. We just want to move them.”
Cavity-busting candies are plausible, but David Beighton, an oral microbiologist at King’s College London and editor of the journal Caries Research, says he’s not convinced. A complex stew of bacteria creates cavities, Beighton notes. It’s possible that a probiotic bacteria, combined with a fluoride-containing toothpaste, could reduce cavities, he notes. But researchers would need to test thousands of people over at least 2 years to demonstrate effectiveness across a population, Beighton says.
A version of that test may be going on now in Croatia. Residents of the former Yugoslav republic can purchase fluoride toothpaste supplemented with L. paracasei. Manufacturer Plidenta—a company affiliated with BASF, the world’s largest chemical company—has followed 50 toothpaste users for just 4 weeks to date. Results show that the toothpaste cut mutans streptococci concentrations in the majority of users, according to preliminary research from the University of Zagreb. Lang says ORGANOBALANCE, which is not working with Plidenta, is conducting additional research to potentially expand the market for bacteria-bearing products.