I have had several discussions with people here at the village about when to brush your teeth. I was really quite surprised to hear them say that it is better to brush your teeth in the morning than at night before you go to bed. They have insisted they heard this from dentists.
I have been told that we don't produce much saliva with which to kill bacteria while we sleep. If we don't brush our teeth before we go to bed, the bacteria multiply rapidly throughout the night, doing damage to our teeth and gums. This seems quite apparently true to me, so it seemed odd that anyone had heard something different. So now I have looked.
The American Dental Association and the American Dental Hygienists Association both say you should brush your teeth twice a day, but neither says when. In fact, I found several places on the ADA site that say brush twice a day, and every one carefully avoids saying when is best. The ADHA site also avoids saying when is best, and it even adds, in its faq section, that there is evidence that once a day is enough for some people.
So it seems that the authorities on brushing your teeth refuse to answer the question for us! However, being the argumentative type, that won't stop me from producing some evidence for my side. Kidshealth.org says you should brush after breakfast and before bedtime. Healthyteeth.org avoids the issue like the ADA, but they let us off the hook on two times a day. At least once a day is their advice. It may not be good advice, though, because their web site isn't around anymore. It's replaced by nsdental.org, which recommends two to three times per day. With this, Emergency Dentists USA agrees. Again, though, none of these say when!
Here's the kicker I want to present for my case for brushing at night (plus one other unspecified time):
Are you the type who doesn't brush before bed? You might want to consider:
Mutans streptococci, the bacteria involved in causing tooth decay, multiply 30 times overnight if you haven't brushed your teeth before going to bed! (Lion Oral Care Institute, 7/04)
I found that at dentalgentlecare.com, the web site of dentist Dr. Dan Peterson of Gering, Nebraska, whose web site indicates he cares about reading the scientific literature. I didn't find any dental web sites recommending waiting until morning or avoiding brushing at night. I did find web sites where many people were expressing their uneducated opinions on both sides of the issue, and those sites did have the occasional, but minority, opinion that one shouldn't brush at night.
So, unless something else comes out, my advice is that brushing at night is best. Why let those bacteria reproduce without defense all night?
One person writing a note on an ask everyone what they think web site wrote, If brushing once a day reduces the risk of tooth decay by 2X, then it's 2X no matter what. Changing the time of day won't reduce it to 1.8X. This is nonsense. Of course it can make a difference! If you brush at night, reducing the bacteria to a minimum, and then enter the day with a greatly reduced number of bacteria, you will be much better off than if you let the bacteria work on your teeth all night, then kill them off in the morning.
Oh, and don't forget to floss.