A calcium phosphate mineral found naturally in teeth and bones could be just as effective as fluoride when it comes to protecting against cavities (or caries), potentially giving us a new alternative ingredient for toothpaste.

We know fluoride is great at protecting teeth, but too much of it can be harmful. This is especially true for kids who tend to swallow more of their toothpaste, which is why younger children are advised to squeeze out a rice-grain-sized drop when it comes time to brush.

A new study by scientists from Poznan University of Medical Sciences and the Medical University of Bialystok in Poland suggests a compound called hydroxyapatite could present another option.

It's already known to help with gum disease and tooth hypersensitivity, and can easily be included as a part of our usual daily cleaning routines.

"Hydroxyapatite is a safe and effective alternative to fluoride in caries prevention for daily use," says dental scientist Elzbieta Paszynska from Poznan University of Medical Sciences.

In a double-blind randomized trial, 171 participants aged 18 to 45 were randomly given either hydroxyapatite toothpaste or fluoride toothpaste without knowing which was which.

The participants started from a similar point in terms of dental health, all used electric toothbrushes and the same brushing routine, and were told not to modify their regular diets.

After 18 months of brushing and regular check-ups by dentists, there was no significant difference in new cavities between the hydroxyapatite group or the fluoride group – around 90 percent of each hadn't developed any new cavities.

The effects of hydroxyapatite are two-fold: it limits the loss of minerals of teeth (demineralization), which leads to cavities, and it boosts the natural repair process of teeth (remineralization).

Application of the mineral also falls under the category of 'minimally invasive' dentistry, so no trips to the dentist and no procedures required. If it's put into toothpaste, it can be working twice a day during regular brushing routines to maintain as much tooth tissue as possible.

Hydroxyapatite has been approved as safe by regulators, and can be produced synthetically for adding to toothpaste. While there are a few more steps to be completed before it replaces fluoride, it's certainly making a strong case.

"Previously published clinical trials also show the caries-preventing effect of hydroxyapatite in risk groups such as children and patients undergoing orthodontic therapy," says Paszynska.

"With our new clinical trial, it has been shown that hydroxyapatite prevents dental caries in adults. This is important from a public health perspective."

The research has been published in Frontiers in Public Health.