What's the point of brushing teeth in the morning?

Question

Why should I brush my teeth in the morning? My teeth are just going to get dirty again when I eat breakfast 5 minutes later. Plus, I've already done an extensive cleaning (floss, brush, mouthwash) the night before. My teeth should not be getting dirtier as I sleep.

I've heard people say their breakfast tastes better after brushing their teeth. I've never experienced bad taste from not brushing. I only care about the hygiene reasons for brushing in the morning.

Answer 1

Brushing at night is the most important. Saliva naturally fights the growth of bacteria on your teeth. Your mouth dries out at night and reduces your mouth's ability to do this. Ideally, you would keep your teeth clean at all times but that's of course not realistic. A while back I read many websites and opinions about this very question. The main consensus seemed to be that people brush in the morning because it makes them feel good to start their day with a clean mouth (not because it's the best time to do it).

Here is a discussion about it on Ask MetaFilter:

During the day, you're flapping your jaw, drinking water, chewing gum, and moving your tongue, all of which help to clean things off of your teeth. At night, your mouth is much less active, which allows bacteria more time to grow without being mechanically sloughed off.

Many years ago my orthodontist told me that it was most important to brush your teeth before going to sleep (I guess either for the night, or for a nap). Saliva production is down, and if you happen to sleep with your mouth gaping open, your teeth dry out and don't have that protective layer of saliva. Just the lack of movement of your lips and tongue while sleeping gives decay more of an opportunity to do its dirty work.

Here is an article by Dr. H.S. Chawla:

Brushing before meals: Most people normally brush their teeth in the morning before breakfast. That is beneficial, as you have reduced the number of bacteria before exposing them to food. The amount of acid production is expected to be less, and so would be the damage to the teeth. You get an additional benefit if you use fluoride tooth paste, as the fluoride gets incorporated into the enamel and makes it strong and resistant to the effect of acid. (Fluoride converts the hydroxyl-apatite of enamel to calcium fluor-apatite).

If you are going to brush in the morning, it may actually be better to brush before you eat rather than after.

brushing right after eating is not at all advised, as the acid produced [by bacteria] has already begun the process of eroding enamel. If you brush promptly after a meal, you rub off part of the dissolved minerals of the enamel.

Answer 2

Expanding on Logicbird's answer, here is what the British Dental Health Foundation says:

Acidic foods and drinks, such as oranges, grapefruit and fruit juices that are often eaten at breakfast time, soften the enamel on your teeth.

Brushing immediately afterward wears the enamel away, and can cause dental erosion, which may lead to pain and extreme sensitivity in the teeth, and also lead to cosmetic problems.

The saliva in your mouth neutralises the acidity and restores its natural balance. However research has shown that this can take up to an hour.

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Their tips for avoiding dental erosion are:

• brush teeth before breakfast if you have fruit or fruit juice, or

• wait one hour after eating or drinking anything acidic before
  brushing

• use a straw when drinking acidic drinks to reduce contact with teeth

• drink water and milk between meals in preference to juice and fizzy drinks

• chew sugar-free gum - this will produce more saliva to help cancel
  out acid in your mouth

• finish a meal with cheese or milk to help neutralise any acids

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The NHS says the same:

Brush your teeth in the morning before breakfast and last thing at night before you go to bed (and ideally at least an hour after your evening meal).

Brushing your teeth straight after a meal can damage your teeth, especially if you've had fruit, fizzy drinks, wine or any other food that contains acid. This is because tooth enamel is softened by the acid and can be worn away by brushing. Waiting an hour gives your saliva chance to neutralise the acid.