Thursday October 20 2016
Gum disease has a surprising range of effects
"Brushing teeth thoroughly to remove plaque could help prevent heart attacks … by reducing inflammation," The Daily Telegraph reports.
A study found that "Plaque HD" toothpaste was related to a drop in inflammation levels (but this could have been coincidental), but it did not investigate if this had any long-term effects on cardiovascular outcomes such as heart attacks or stroke.
The "HD" toothpaste is designed to turn plaque (clumps of bacteria) green so you can spot areas where you need to focus your brushing.
The study included 61 people who used either "Plaque HD" toothpaste or a standard toothpaste for 60 days. Researchers measured changes in the amount of dental plaque seen on people's teeth, and in a marker for inflammation in the body called high sensitivity C-reactive protein (hsCRP).
They showed that people who used the "Plaque HD" toothpaste had a bigger reduction in dental plaque than those using normal toothpaste. Analysis of a sub-group of 38 people found that those who used plaque identifying toothpaste had lower levels of hsCRP at the end of the study, while people who used normal toothpaste had higher levels.
The link between poor dental hygiene, high levels of hsCRP and increased heart disease was made in 2010, as we discussed at the time, although there's no direct evidence that one causes the other.
This study doesn't contribute any new findings. There is no evidence that this specific toothpaste is proven to reduce serious cardiovascular outcomes.
Where did the story come from?
The study was carried out by researchers from the University of Illinois and the Florida Atlantic University in the US (and possibly other institutions as not all author affiliations were reported). It was funded by TJA Health, which makes the toothpaste used in the study. The study was published in the peer-reviewed American Journal of Medicine.
The Telegraph reports the study accurately, although it doesn't make clear that the reduction in hsCRP levels was based on just 38 people, nor does it question whether this reduction was caused by lower levels of plaque. The Mail Online calls the toothpaste "revolutionary", although plaque-revealing technologies such as chewable tablets have been around for decades.
It also says that the "special" toothpaste removed twice as much plaque. You could argue that the toothpaste is no more effective at plaque removal, but that people removed more plaque while using it because they could see where the plaque was.
Neither the Telegraph or the Mail mention the potential conflict of interest in regards to the study's funding.
What kind of research was this?
This was a small randomised controlled trial. These types of studies are good ways to compare the effects of treatments. However, in this study, the effects were not actual events (such as heart attacks or strokes) but levels of markers of inflammation, and levels of plaque. This means we have to be careful how much we read into the results.
What did the research involve?
Researchers recruited 61 adults described as "apparently healthy" and randomly assigned them to either 60 days use of plaque identifying toothpaste or what they describe as "identical non-plaque identifying toothpaste".
Their plaque levels were assessed before and at the end of the study using a plaque-revealing mouthwash and photographs taken of the mouth. They had blood tests to measure CRP at the start and end of the study.
The study report is short and does not include much detail about methods. So we don't know, for example, how people were recruited, or how they were randomly assigned to the two groups.
We don't know what instructions they were given about using the toothpaste. The report says they were told to "follow the same brushing protocol", but this is not specified.
We also don't know what happened when people's plaque levels were assessed at the start and end of the study – was that immediately after brushing teeth, after eating, or did researchers specify a certain period of time since last brushing teeth or eating?
Researchers compared the reduction in plaque levels between all 30 people using normal toothpaste and 31 people using plaque identifying toothpaste. However, for hsCRP levels, they concentrated on results from 38 people (19 from each group) because, they say, some people had hsCRP levels of less than 0.5%, which means they would not reasonably expect to see a reduction in their levels.
They also excluded people with very high levels (over 10) which they said were due to "extraneous causes of inflammation," although they don't say what these were.
What were the basic results?
On average, people using plaque identifying toothpaste had a 49% reduction in plaque levels, while those using normal toothpaste had a 24% reduction (confidence intervals not given).
Looking more closely at these results, people who used "Plaque HD" toothpaste had higher levels of plaque at the start of the study, which might mean there was more scope for their levels to reduce. Levels of plaque were about the same when you compare the two groups at the end of the study.
Results for hsCRP were more complicated. When results for everyone in the study were included, the type of toothpaste used made no statistically-significant difference to the reduction in hsCRP levels.
When looking at the 38 people the researchers identify as the "pre-specified subgroup", levels of hsCRP reduced by 29% in people using plaque identifying toothpaste and increased by 25% in those using normal toothpaste (confidence intervals not given).
How did the researchers interpret the results?
The researchers say their toothpaste "produced a highly significant reduction in dental plaque" and "decreased inflammation as measured by hs-CRP." They say that their findings "support the hypothesis that this plaque identifying toothpaste reduces risk of cardiovascular disease."
They add that directly testing the hypothesis would require a large-scale randomised controlled trial big enough and long enough to find out whether use of the toothpaste actually reduces the incidence of heart attacks and strokes.
This study adds some weight to the theory that better oral hygiene may reduce inflammation in the body. However the size of the study and some concerns about its methods and findings mean we should be cautious about hailing plaque identifying toothpaste as a revolutionary new treatment to prevent heart disease.
The study does seem to show that people were able to remove more plaque from teeth while using a plaque identifying toothpaste, which is no doubt a good thing for dental health. However, we don't know exactly which sort of toothpaste was used as the comparison, or how people were told to use it.
If people were told to use the normal toothpaste as they would a plaque identifying toothpaste – for example to brush for a minute, look for signs of plaque then brush again to remove those signs – then they might stop brushing after one minute if they saw no signs of plaque. That could result in them brushing less well than they would normally.
The results on hsCRP are less convincing. Firstly, the statistically-significant results are based on only 19 people from each group. They are hard to interpret, because of the surprising increase in hsCRP among those who used normal toothpaste.
It's unclear why using normal toothpaste would be linked to an increase in hsCRP levels, especially as people using normal toothpaste did reduce their plaque, and had average plaque levels at the end of the study very similar to those who used plaque identifying toothpaste. These findings call into question whether hsCRP levels are linked to plaque levels in this study.
Looking at hsCRP results for everyone in the study (including those with low levels at baseline), average levels start off very similar, then double in the placebo group while staying much the same in the plaque identifying toothpaste group.
These results are not explained. We know that hsCRP levels rise and fall with inflammation anywhere in the body – for example after an injury or an infection. It is possible that these normal day-to-day fluctuations, rather than any reduction in plaque, are behind the results found in this study.
Due to the considerable uncertainty around the methodology of the study it may be sensible not to put too much weight into considering the results of this industry-funded study.
Questions over this study do not mean that it's not important to brush your teeth and reduce plaque, however. Good oral hygiene can prevent painful tooth decay and gum disease.
To keep your mouth healthy:
- brush teeth twice daily with fluoride-containing toothpaste
- floss between your teeth
- eat less sugar and avoid sugary drinks
- have regular dental check-ups
Read more advice about how to take care of your teeth.