Dental hygiene is one of the most important parts of our daily routines, and the most important dental product many people have is also the simplest.

Choosing the right toothbrush is about finding a brush that you will feel comfortable using twice a day, morning and night, for two minutes at a time. Whether that involves a manual or electric, round-headed or oblong-headed, tongue cleaner or interdental bend is up to you.

The key is to be comprehensive and complete with your cleaning, which is why automatic toothbrushes are often so appealing. Unfortunately, the data that exists also suggests they leave a lot to be desired.

An automatic or mouthpiece toothbrush is a U-shaped toothbrush that you place across your entire mouth like a retainer. The idea is that it has brushes on both sides of your teeth and across your entire mouth, allowing you to clean the whole of your upper and lower teeth in one go, far faster than a typical brush.

The theory is excellent, as it so often is with dental innovations, but the results could be charitably described as leaving a lot to be desired. They were often uncharitably described as shockingly terrible.

There were two pilot studies comparing an automatic toothbrush to using a manual toothbrush, an electric toothbrush, and not brushing at all.

The first study even set the automatic toothbrush to run for two minutes, even though the longest cleaning mode was just 45 seconds, but found that the automatic brush was barely better than not brushing at all.

The second study used a different type of brush but found very similar results; the automatic brush was evidently inferior to using a simple manual toothbrush.

The fundamental problem is that everyone has a differently sized and shaped jaw, and unless you happen to perfectly fit the often one-size-fits-all mouthpiece, the brush would barely work at all.

It is possible for this to change, but it would require a fundamentally different design philosophy and much greater research into the principle.