For sparkling-clean dentures, brushing may be best, the authors of a new review of the medical literature say.

But because there were actually very few published studies of denture cleaning methods, and those that they found were likely biased, the reviewers say it's hard to draw any firm conclusions.

Just as on real teeth, plaque can build up on dentures, leading to inflammation and infection of the gums. And studies have found that many denture wearers don't clean them effectively.

Dr. Raphael Freitas de Souza of the Ribeirao Preto Dental School at the Unviersity of Sao Paulo in Brazil and his colleagues hunted through the medical literature to determine the best strategy for denture hygiene, reporting their findings in The Cochrane Library, which publishes systematic reviews of medical research.

Cleaning methods typically fall into two categories: mechanical, meaning the cleaning involves applying force to remove plaque (i.e. brushing or ultrasonic cleaning); or chemical, typically soaking the dentures in some type of solution.

Dr. de Souza's team identified six randomized controlled trials of denture cleaning methods. While all involved looking at the effectiveness of some type of chemical method, they found, the studies were so different from one another that it was impossible to draw any clear conclusions from them, aside from the probability that soaking in an enzyme cleaner is more effective than using a placebo.

In addition, the researchers note, every study showed evidence of selective reporting, meaning that unfavorable findings might have been left out.

For a shorter soak of about 15 minutes, enzymatic and effervescent solutions are likely to be equally effective, the researchers say; for longer soaks of eight hours enzymes are probably better.

And when a high-enough enzyme concentration is used, according to the reviewers, soaking can remove as much plaque as brushing.

Brushing with paste also looked to be more effective at removing plaque and destroying bacteria compared to "inactive treatments," they found.

"We cannot be...sure what the most effective methods for denture cleaning are," de Souza noted in a press release from Health Behavior News Service. "But we can infer possibly that brushing can give better results."

For those who have trouble brushing their dentures effectively, he added, soaking may be the best option.