Avoiding Childhood Dental Decay

Childhood caries (ECC), a serious type of tooth decay that may have long-term effects on oral and general health, can be caused by a high carbohydrate diet combined with inadequate oral hygiene. ECC  is caused by a bacterial species, Streptococcus mutans, as well as a fungus, Candida albicans, which was discovered by Penn’s School of Dental Medicine experts a few years ago. A biofilm, which is a sticky symbiosis formed between the bacteria and the tooth’s surface, protects the bacterium from being washed away. Another research from the team suggests that altering the yeast-bacterial interactions that cause ECC plaques to be so difficult to treat may help break up this biofilm. When compared to other existing therapies for ECC, this one utilizes an enzyme specific to the bonds between bacteria. These other treatments involve antimicrobial drugs, which may have unwanted side effects and damage healthy tissues.

ECCs may interfere with the synergistic interaction between bacteria and yeast, says Geelsu Hwang, a Penn Dental Medicine assistant professor and the study’s principal author. The findings were published in the journal mBio. As a result, “we now have another weapon in our arsenal to combat this dangerous biofilm.” Hwang and colleagues at Penn Dental Medicine, including Hyun (Michel) Koo, published a study in 2017 that showed molecules called mannans on the Candida cell wall were firmly linked to glycosyltransferases, an enzyme produced by S. mutans (Gftb). Gftb contributes to the tenacity of dental biofilms by producing gluelike polymers known as glucans in the presence of carbohydrates, in addition to promoting cross-kingdom binding. While medicines that kill the bacteria directly may reduce the amount of pathogens in the mouth in certain instances of ECC, this does not always successfully break down the biofilm and can have off-target effects on “good” microbes as well as the soft tissues in the oral cavity, this is not always the case.

Instead of going after the yeast itself, Hwang and coworkers decided to go after mannans on the Candida cell surface, which they believe are the site of contact between yeast and bacteria. For five minutes, they exposed a biofilm developing on a tooth-like surface in a human saliva medium to three mannan-degrading enzymes, one after another. They saw a reduction in the total biofilm volume after the treatment. They also saw significant decreases in the thickness of the biofilm and interactions between bacteria and yeast using advanced microscopy. When exposed to enzymes, the pH of the surrounding media rose, suggesting a less acidic environment that is less favorable to tooth decay. Using a device that produces stress, similar to brushing your teeth, the researchers also assessed how easily the biofilm might be broken up following treatment.

As a result of the enzyme treatment, Hwang notes that the biofilm’s structure was compromised. Biofilms were less difficult to remove, according to the study. The researchers utilized atomic-force microscopy to assess the bonds between Candida and Gftb to validate the mechanism of their approach: that mannan-degrading enzymes decrease the binding between yeast and bacterium. They discovered that the treatment significantly decreased the binding force. Another consideration was how well these enzymes would be tolerated in the oral cavity, because youngsters were the intended audience. Even despite using a concentrated version of the enzymes, scientists observed no adverse effects when applying them to human gingival cells in culture. As a result of these findings, scientists hypothesized that the therapy might work even if the bacteria or yeast acquired mutations that made them resistant to other kinds of treatments. Even though the application duration was limited to five minutes, the researchers are hoping to observe results in as little as the suggested two minutes for teeth cleaning. Hwang said they may look at developing an enzyme-enhanced non-alcohol mouthwash for youngsters to use as a preventative step against ECC.The researchers want to keep exploring this option, including testing these enzymes in an animal model, with further follow-up. They want to add another weapon to their arsenal in the battle against ECC’s public health danger if they continue to have success.

Journal Reference: H. E. Kim, A. Dhall, Y. Liu, M. Bawazir, H. Koo, G. Hwang. Intervening in Symbiotic Cross-Kingdom Biofilm Interactions: a Binding Mechanism-Based Nonmicrobicidal ApproachmBio, 2021; 12 (3) DOI: 10.1128/mBio.00651-21

Categories: Dental