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While everyone is telling us that we should brush our teeth twice a day, the human species has evolved for several million years without any teeth brushing. Apes don't brush their teeth, and they don't have a mechanism to change their teeth like sharks and crocodiles.

So why do human need to brush their teeth?

If we do, do we only need to brush them to clean and remove food stuck in them, or is the use of Fluoride based toothpaste is needed as well?

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Human lifespan for the last million years has also averaged about 40 years old. ;-) Our teeth haven't needed to last longer than that. Also, our diets have changed to include a lot more carboyhydrates in the last few thousand years, which is great bacteria-chow. Not a full answer, but stuff to consider. –  MCM Nov 7 '12 at 14:39
    
yeah apes don't eat candy though –  isJustMe Nov 7 '12 at 16:56
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Good points in these comments. Not only did we eat less carbs, the share of fibre in our food might have been higher. The more you have to chew on low-carb/fibrous food the cleaner your teeth get. As mild evidence, chewing sticks for dogs are supposed to be good for the dog because they clean their teeth when chewing, like Wrigley "Pro" gum...Besides that, in one of the earliest Simpsons episodes Homer and Bart have to survive in the woods and Homer tells Bart to clean his teeth with his fingers and some sand. Actually, apes clean each others teeth by picking food which is stuck between teeth. –  Konsta Nov 7 '12 at 19:04
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So, where is the claims? Sounds like a question for Biology.SE –  default locale Nov 9 '12 at 9:57
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There are currently news reports of lots of cavities in Australian children, so, unless they're debunked, it's not just because we're living longer. –  Mark Hurd Nov 10 '12 at 1:44

2 Answers 2

up vote 20 down vote accepted

Do we need to brush our teeth?

Yes, there are health benefits from brushing your teeth. Done correctly, it reduces the incidence of caries and periodontitis.

When you brush your teeth, you help remove plaque — a sticky film that forms on your teeth because of bacteria in your mouth. The bacteria in plaque causes the two major tooth-related diseases, cavities (dental caries) and gum disease (periodontitis).

Mayo clinic


In normal use it must be concluded that the benefits of tooth brushing far out-way the potential harm.

Can tooth brushing damage your health? Effects on oral and dental tissues.


The Cochrane Collaboration performed a meta-analyses of several studies:

The review of trials found that children aged 5 to 16 years who used a fluoridated toothpaste had fewer decayed, missing and filled permanent teeth after three years (regardless of whether their drinking water was fluoridated). Twice a day use increases the benefit.

In another meta-analysis, they looked at young children, and found that may be side-effects of fluoride toothpastes - a risk of fluorosis/mottling of teeth - especially in children younger than 12 months or under 5-6 years with high fluoride levels, but that for children at high-risk of tooth decay, this risk may be outweighed.


the human species has evolved for several million years without any teeth brushing. ... So why do human need to brush their teeth?

Graph of carious teeth per 100 vs last 500 years From EPIDEMIOLOGY OF DENTAL DISEASE

As others have pointed out

  • We don't eat what people ate 5000 years ago (let alone 150000 years ago)
  • We need our teeth to last longer as we mostly don't expect to die before age 40.

Studies of the dentitions of ancient English populations show that a change in the prevalence and distribution of caries took place between the seventeenth and nineteenth centuries and was closely associated in time with an increase in the consumption of refined carbohydrates, especially sugar.

From The role of sugar in the etiology of dental caries via Wikipedia

Bacteria in a person's mouth convert glucose, fructose, and most commonly sucrose (table sugar) into acids such as lactic acid through a glycolytic process called fermentation.


Apes don't brush their teeth

That doesn't mean they wouldn't benefit from so doing.

Caries is moderately common among the great apes, particularly the chimpanzees. Of the great apes, chimpanzees have a diet most similar to our own;

EPIDEMIOLOGY OF DENTAL DISEASE

Caries in great apes is usually observed later in life when occlusal enamel is lost through wear and approximal enamel that maintains a tight contact between teeth breaks down and allows food and plaque stagnation between teeth.

Dental Biology and Disease


is the use of Fluoride based toothpaste ... needed as well?

Many medical professionals believe there is adequate evidence to support this.

Most toothpastes also contain fluoride, which helps to prevent and control cavities.

NHS

Multivariate analysis disclosed fissure sealants, early start of tooth brushing and topical fluoride application to be associated with the prevention of dental caries.

Evaluation of a preventive program aiming at children with increased caries risk using ICDAS II criteria.

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This shows that increased sugar consumption leads to more cavities and caries. This doesn't show that brushing your teeth decrease the chance of cavities and caries, nor does it show the part of Fluoride based toothpaste. –  Ilya Melamed Dec 23 '12 at 13:00
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@ilya: Answer updated. –  RedGrittyBrick Dec 23 '12 at 14:03
    
Aw, I just stumbled on a good study, but you beat me by 11 hours, with a more substantial answer. I'll add my study to your list. –  Oddthinking Dec 23 '12 at 23:28
    
I think it should be noted that claims about average life expectancy aren't as relevant as they seem, because the main reason for low life expectancy in early history is actually because of how frequently people died as infants or in childhood, thus dragging down the average. If you lived to be a healthy adult, you had a good chance of living to similar ages people live to today, so talking about how people "didn't expect to live past 40" may be inaccurate. I'm not sure how well this holds up for much earlier points in human history however, say tens to hundreds of thousands of years. –  Jack yesterday
    
@Jack: That's an interesting point. Can you provide some references to help me refine my answer? e.g. "if a person made it out of childhood, they could be expected to live into their middle forties, provided they maintained good health and weren’t killed in war. hyw.com/Books/History/Fertilit.htm"; - sarahwoodbury.com/life-expectancy-in-the-middle-ages. Though this website likes more academic refs –  RedGrittyBrick yesterday

Summary:

  • A. Using fluoridated toothpaste in both children and adults reduces the risk of dental caries.
  • B. Fluoridated toothpaste increases the risk of dental fluorosis only when children 8 years old or younger swallow it, because fluoride enters teeth via blood and not directly by brushing teeth
  • C. Brushing teeth immediately after eating acidic foods or drinks (fruits, cola, fruit juices) can damage tooth enamel.

http://www.ncbi.nlm.nih.gov/pubmed/14960006

The results revealed strong evidence (level 1) for the caries preventive effect of daily use of fluoride toothpaste compared to placebo in the young permanent dentition and that toothpastes with 1,500 ppm of fluoride had a superior preventive effect compared with standard dentifrices with 1,000 ppm fluoride.

Claims 1-5 http://lpi.oregonstate.edu/infocenter/minerals/fluoride/

  1. Topical use of fluoride (including fluoridated toothpaste) reduces the risk of dental caries in children and adults

  2. It is swallowed fluoride, which enters circulation and ends in teeth (until 8 years of age) and can cause dental mottling and not fluoride in the toothpaste - except when children swallow large amount of toothpaste. Small children can swallow 0.3 mg fluoride per brushing , which is about 1 mg per day.

  3. According to the U.S. Institute of Medicine (IMO), adequate intake (which reduces caries risk and does not cause tooth mottling) for fluoride for children 1-3 years old is 0.7 mg/liter and for 4-8 years olds 1 mg/liter (see reference above).

  4. In the U.S., fluoridated water contains 0.7-1.2 mg fluoride/liter.

  5. In areas with 1 mg fluoride/liter tap water, about 10% fluorosis in population was observed, and in areas with 2 mg fluoride/liter, 5% of moderate fluorosis was observed.

  6. http://www.ncbi.nlm.nih.gov/pubmed/18435369 Tooth brushing after acidic meals is more harmful than brushing before acidic meals.

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