The researchers found low-quality evidence that fluoride toothpaste containing the natural sweetener xylitol prevents tooth decay.
This was the conclusion of a new Cochrane review by researchers at the University of Manchester in the UK.
Lead author Philip Riley, of the Cochrane Oral Health Group at Manchester's School of Dentistry, says:
"The evidence we identified did not allow us to make any robust conclusions about the effects of xylitol, and we were unable to prove any benefit in the natural sweetener for preventing tooth decay."
Xylitol is a widely promoted and popular sugar substitute that is already known to cause less damage to teeth than sugar.
But there have also been suggestions that adding xylitol to products kills tooth-attacking bacteria and can prevent dental cavities - a condition that affects up to 90% of children and most adults worldwide.
Low-quality evidence of decay prevention from use of xylitol in toothpaste
For their review, the researchers searched for randomized controlled trials that assessed the effect of xylitol products on dental cavities in children and adults. Their search yielded 10 studies involving a total of nearly 6,000 participants.
Their intention was to pool the data from all 10 studies and analyze it as if it came from one large study. This type of analysis - called meta-analysis - is how researchers commonly look for summary effects that may not show up in smaller data samples.
However, you can only do a pooled analysis if the study designs are compatible. In this case, the designs were so dissimilar the researchers could only do a pooled analysis on two studies that looked at the effect of toothpaste containing xylitol on the teeth of just over 4,200 children in Costa Rica. Both studies had been carried out by the same team of researchers.
From the pooled analysis of the two studies, the authors found low-quality evidence that tooth decay was 13% lower in the children who used a fluoride toothpaste containing xylitol for 3 years, compared with counterparts who used a fluoride-only toothpaste.
When they analyzed the rest of the data, which covered other xylitol-containing products like xylitol syrup, lozenges and tablets, the authors found little or no evidence of preventing tooth decay, as Riley notes:
"For other products containing xylitol we were unable to determine whether they were beneficial. We were particularly surprised to see such a lack of evidence on xylitol-containing chewing gums."
He also says that the "limited research on xylitol-containing toothpastes in children may only be relevant to the population studied."
Studies failed to give information on side effects of xylitol
The authors also highlighted the fact several of the studies they reviewed did not give sufficient information about xylitol's side effects, such as bloating, diarrhea and laxative effects.
Riley says they expected all the studies would report adverse effects but did not find this always to be the case. He says that:
"Sugar-free gums, sweets, mints and other products are well-known for their gastrointestinal effects and these should be clearly reported in future studies."
One of the things that can cause dental cavities is loss of the enamel layer that covers our teeth, which also leads to sensitive teeth, pulp inflammation and other dental diseases.
Now, in a study that Medical News Today reported in January 2015, scientists are working on a new biocompatible material that rebuilds worn enamel, reduces tooth sensitivity and lasts much longer than current treatments.