Q: Some dentists say it is better to brush before breakfast, some say after – which is it?

A: Everyone knows that you should brush your teeth at least twice a day – once in the morning and once before bedtime. But when it comes to your morning routine, is it better to brush before or after breakfast?

The truth is that few studies have looked into this question and their results have been mixed and limited, so there is no definitive answer, said Associate Professor Apoena De Aguiar Ribeiro, a paediatric dentist and microbiologist at the University of North Carolina at Chapel Hill. But, she and other dentists said, there are pros and cons for each option to keep in mind.

Brushing before breakfast

For many people, breakfast includes sugary carbohydrates, said Professor Carlos Gonzalez-Cabezas, a dentist and associate dean for academic affairs at the University of Michigan School of Dentistry. Cereals, breads, muffins and pancakes all contain fermentable carbs that bacteria love to feed on.

And when you wake up in the morning, Prof Ribeiro added, bacterial levels in your mouth are at their peak – “that’s why we have bad breath when we wake up”.

A mouth rife with bacteria and a breakfast full of sugary carbs mean that conditions are perfect for the bacteria to flourish and multiply. When this happens, they release acids that can wear down the protective enamel on teeth, making them more prone to cavities, Prof Ribeiro said. Brushing before breakfast clears that bacteria away, denying them the opportunity to feed on your food.

Another reason to brush before breakfast is to jump-start the production of saliva, Prof Ribeiro added, which is one of the most protective forces for teeth. Saliva helps strengthen teeth by depositing minerals that bacteria may have eaten away overnight. It also contains bicarbonate that helps to neutralise the acidity in your mouth. An added bonus, she said, is that if your toothpaste contains fluoride, it will make your teeth more resistant to decay by strengthening your enamel and neutralising the acids from breakfast.

And finally, said Professor Rocio Quinonez of paediatric dentistry at the University of North Carolina at Chapel Hill, a reason to integrate brushing into your “getting up” routine is to prevent the possibility that you will run out of time or forget to do it later. This is especially true if you have kids, she added, because toothbrushing is most likely the last thing on your mind once you have scarfed down breakfast and are rushing out the door.

If this sounds like a familiar situation, or if you tend to eat breakfast outside or at work, the answer is clear, Prof Gonzalez-Cabezas said – “brush your teeth before leaving the house, otherwise you won’t brush at all”.

Brushing after breakfast

On the other hand, there are arguments for waiting until after breakfast to brush, he added.

“The reality is that most people don’t brush that well,” Prof Gonzalez-Cabezas said, so even if you brush right before breakfast, you probably will still have bacteria lingering in your mouth that could multiply and produce acids during breakfast and for the rest of the day, so you may as well brush after you eat to minimise that lingering food.

The fluoride from your toothpaste will work better throughout the day if it is not displaced by chewing food right after you brush, he added.

Some experts argue that brushing teeth too soon after a meal – especially one with acidic beverages like coffee or orange juice – will damage your enamel. That is true, Prof Gonzalez-Cabezas said, but the damage that could be done would be so minimal that it would not really affect the health of your teeth. So to him, the benefits of post-breakfast brushing outweigh the potential negatives.

Prof Ribeiro recommended that if you can, wait at least 30 minutes after a meal to brush. If you want to get rid of lingering breakfast bits before then, she suggested drinking water or gargling.

Finally, while it is true that the bacteria present in your mouth right after waking up will feast on your breakfast and produce damaging acids, Prof Gonzalez-Cabezas said that most people eat breakfast pretty quickly – usually completing their meal within 10 to 15 minutes. That is not enough time to do a ton of damage, he added, so again, he believes the benefits of brushing after breakfast outweigh the negative effects.

In his opinion, most people should brush after breakfast, schedule permitting.

Ultimately, the decision boils down to what works for you, Prof Ribeiro said, because the science is sparse and “there is no consensus in the literature”.

Prof Quinonez agreed. There is no proof either way, she said, so all of the arguments are largely theoretical. “It’s highly debated and it ultimately may not make a significant clinical difference,” she added.

In the end, she said, the most important question to ask is this: What brushing habit will make you most likely to brush your teeth consistently? Once you have your answer, she added, work it into your routine and stick with it. NYTIMES