By Janice Neumann
(Reuters Health) - A study of mouth microbes finds that antibacterial toothpaste and mouthwash with essential oils work much better in combination than separately to banish bacteria that cause gum disease.
Researchers looked at bacteria clinging to wires used in dental retainers that are bonded to the backs of teeth. These retainers are known to host bacterial colonies that promote bleeding and receding gums as well as cavities.
"Bonded retainers are very commonly used and are a very effective form of retention," said Marije Jongsma, who led the study. "Since the retainers usually stay in place for an extended period of time, it is very important to find a way to minimize these adverse effects."
Plaque and bacterial colonies called biofilms tend to accumulate on retainer wires, and antibacterial products help but they don't eliminate the harmful bacteria, Jongsma's team writes in the International Journal of Oral Science.
Jongsma and her colleagues at the University of Groningen and University Medical Center in the Netherlands tested three types of toothpaste and a mouth rinse, in combinations and separately, to understand their effects on the size and makeup of biofilms living on retainer wires in human volunteers.
The study included 22 adults wearing either single-strand or multi-strand wired retainers, which were bonded to the mouth side of the top front teeth. For the experiments, volunteers brushed a minimum of twice daily with a manual toothbrush.
They were separated into three groups, one assigned to a toothpaste without antibacterial properties and the others assigned to antibacterial toothpastes containing either stannous fluoride or triclosan.
After a week of using toothpaste alone, the groups took six weeks off, then used their assigned toothpaste for another week, this time with a mouth rinse containing essential oils (Cool Mint Listerine).
After each of the weeks when volunteers used their assigned products, their retainer wires were removed and researchers analyzed the living and dead bacteria on the wires.
Overall, multi-strand wires accumulated more bacteria than single-strand wires, probably because the microbes sheltered in the gaps between strands, the authors note.
When volunteers used a toothpaste without antimicrobial ingredients, however, there were more live bacteria remaining on single-strand wires than on multistrand wires, regardless of whether mouth rinse was used. The study team points out that on single-strand wires the bacteria are better exposed to nutrients, and that may be why they appeared to thrive.
Using antibacterial toothpaste alone did not much affect the total number of bacteria on the wires, but it did significantly reduce the proportion of living microbes.
Using antibacterial toothpaste together with the mouth rinse left the smallest number of bacteria and the lowest proportion of living bacteria. Importantly, that combination also produced a shift in the bacterial population. Cavity-causing Streptococcus mutans, for example, went from 30% to 5% of the biofilm's makeup.
"The results show that after the use of oral antimicrobials, a shift occurs in the composition of the oral biofilm in a more healthy direction. Several species that can cause caries such as S. Mutans and Lactobacillus, decrease in prevalence, whereas the more harmless species increase in prevalence," said Jongsma, a doctoral student in orthodontics, in an email.
The researchers think the antibacterial toothpastes may slightly alter the properties of the bacterial cell walls in a way that makes them more likely to cling to the oil-containing mouth rinse and be washed away.
Mannish Valiathan, associate professor of orthodontics at the Case Western Reserve University School of Dental Medicine in Cleveland, Ohio, said the findings were similar to those of other studies of retainer biofilms but a reminder of the importance of oral hygiene, particularly for people wearing the devices.
"While oral hygiene should be kept up by all, individuals with fixed retainers may benefit from a regimen designed for them by their care provider followed by periodic monitoring of the oral health status," said Valiathan, who was not involved in the study, in an email.
Jongsma said she doesn't think everyone wearing retainers needs to contact the dentist. "However, if your dentist notices . . . you have some difficulties cleaning your retainer, leading to gingivitis around the wire, it might be a good idea to talk to your dentist about using an antimicrobial toothpaste and mouth rinse," she said.
She notes that her group's study did not examine whether the antibacterial toothpaste and mouth rinse combination led to less gum disease or cavities over time.
"The results are very promising . . . However, before real recommendations can be made, it should be verified if the antibacterial regimes actually lead to less gingivitis and caries in the clinical situation," Jongsma said.
Int J Oral Sci 2015.