Surely the twice-a-year teeth cleanings matter? In 2005, Evidence-Based Dentistry highlighted a systematic review on the effects of routine scaling and polishing (you call it teeth cleaning). Researchers found eight randomized controlled trials that were on point, but they were all judged as having a high risk of bias. The results were all over the map. Their conclusions were that the evidence isn’t of sufficient quality to reach any conclusions as to the benefits or harms of scaling and polishing.

Regardless, I’ve been told by all the dentists I know to have it done every six months.

When filling cavities, some dentists advocate bonded amalgams over non-bonded amalgams. There’s pretty much no evidence to support that practice, though. The one randomized controlled trial didn’t seem to support their use, especially since they cost much more. Previous, nonrandomized controlled trials in children didn’t really show a difference either.

Has anyone ever told you to use an interdental brush to get at the plaque between your teeth? In 2015, Evidence-Based Dentistry summarized a Cochrane Review of seven randomized controlled trials looking at how interdental brushing in addition to tooth brushing compared with toothbrushing alone or toothbrushing with flossing. Almost no long-term benefits have been proven.

What about preventive dental visits themselves? In 2013, Bisakha Sen, Nir Menachemi and colleagues used data from the Alabama Children’s Health Insurance Program to follow more than 36,000 children to see how preventive dental visits affected dental care and spending over time. They found that preventive visits were associated with fewer visits for restorative dental care in the future, implying that there was an improvement in oral health. But they found that, for the most part, more than one annual preventive visit in children was not cost-effective.

Further work found that it may have been the use of sealants, and not preventive visits in general, that had this protective effect. Since sealants could be applied without an actual visit to the dentist, that brings into question whether a more cost-effective means of getting sealant on children’s teeth might be possible — using a lower-cost dental hygienist, perhaps. Fluoride varnish appears to work well, too.

No review of dental health would be complete without at least acknowledging water fluoridation. Much of the evidence is old because it’s getting hard to do studies. It would be somewhat unethical to withhold fluoridation at this point from some people, because the evidence in favor of the practice is so compelling.

In fact, fluoride is so important that the U.S. Preventive Services Task Force recommends that in areas where the water supply is deficient, providers prescribe oral fluoride supplementation to children. They recommend the use of fluoride varnish as well.