If you are like most people I know, you don’t feel you floss enough. Each time you go to the dentist you get scolded for not flossing at least once a day. You promise to be a good patient but after a week or two go back to flossing every few days, if that. The last time I went to the dentist however I had two cavities and am supposedly at risk of more. The unpleasantness and cost of the experience got me thinking seriously about flossing every day, and for the last six months I have stuck to it.
But maybe I was right when I couldn’t be bothered flossing. What evidence do I actually have that flossing regularly is worth it, given the frequent if small inconvenience it involves?
Whether or not you floss on any particular occasion is a minor decision, but whether you do so over your whole life is a significant one. The cost of dealing with fillings, root canal surgery and decaying teeth can easily run into hundreds or thousands of dollars a year – tens of thousands over a lifetime. On the other hand, if you floss every day for the next sixty years, taking two minutes each time, that would come to around 730 hours, or some 90 eight-hour work days spent flossing! It’s tempting to follow instinct, dentist advice or habit but I don’t see why any of those would be reliable guides in this case. Given the substantial costs and benefits at stake it’s worth looking at the evidence and making a considered decision.
For some reason though it looks like I’m one of the first people to want a cost benefit analysis of flossing. Google and Google Scholar turned up nothing. Economist Bryan Caplan wanted to produce one but didn’t get very far. Tim Harford laughed at the idea. An hour’s search couldn’t even provide me any figures on how much flossing could be expected to reduce the appearance of cavities! There must be research out there but it isn’t easy to find.
But uncertainty is no reason not to run some numbers. Guesses about the individual parts of the overall equation will be better than guesses about the final result. If we put in some reasonable numbers and end up with a strong conclusion (that is floss a lot, or don’t floss at all) we will some guidance as to what we should do.
Here are some spreadsheet results
- Annual discount rate (0%)
- Age (25)
- Life expectancy (85)
- Financial and non-financial cost of getting a filling ($300)
- Average lifetime of a filling (8 years) [1]
- Unpleasantness of having a filling ($50 per filling per year)
- Value of time ($20 per hour)
- Attention-adjusted time taken to floss (1 minute)
- Unpleasantness of flossing ($0.20 each time)
- Cost of 50m of floss ($4)along with guesses about
- frequency of new cavities, depending on the frequency of flossing
to produce a dollar ‘loss’ from the costs you incur both due to flossing and dental work. You can try various combinations, and see which minimises your loss.
Based on past experience, I have guessed that with occasional flossing I will get a new cavity roughly each four years. This will probably vary a lot between people; some teeth stay good no matter how much people abuse them. If I floss daily though, I expect to get a new cavity only each 8 years. With these numbers I come out about $15,000 ahead over my lifetime from flossing daily relative to flossing once a week. Sounds like a good idea!
Unfortunately the result is not very robust. If flossing takes two minutes of my undivided attention, and a high wage makes you value each hour at $40 rather than $20, then flossing looks like a bad idea. Of course, with a higher income you might also be willing to pay more to have nicer teeth and not endure fillings. The other key determinant of the outcome is age. The older someone gets the less valuable continued flossing is as they will not have to deal with any additional damage to their teeth for as long.
Overall however it looks like someone who is young and has teeth that are vulnerable to decay should probably floss regularly.
by Robert Wiblin
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