I went in for my annual dental exam today.
Dentist: You need a deep cleaning.
Statistician: I don't believe in deep cleaning.
Dentist: I only manage to clean the exposed part of the teeth. In your X-ray, we can see tartar buildup underneath the gums. Your teeth will fall out eventually if we don't clean it up now.
Statistician: My teeth feel fine, in fact, the best in years. I don't like the cost-benefit tradeoff of deep cleaning. All my friends who did it did not think it helped.
Dentist: It didn't work for them because they didn't floss. Let me tell you about my friend ...
Dentists seem to have special friends who like to tell them horror stories about how their teeth fell out at a young age. I am not interested in the worst-case scenario, nor a sample size of one, not randomly selected.
So I went home and googled "deep cleaning" and "clinical trials", and "deep cleaning" and "number needed to treat". No informative results except for more scare stories with no data. If you know data or experience related to this, please comment.
I would like to understand:
- How many people have to do "deep cleaning" for one patient to benefit from the procedure? (This is the "number needed to treat". I would not be surprised if this number is 100. A lot of medicines have high NNT, meaning we are buying lottery tickets.)
- How is the "benefit" of this procedure defined in the literature? My teeth will never fall out? They will fall out two days later than if I didn't do it? The "pocket" between my teeth and gums will reduce by 1%? 5%? 10%?
- If the "pockets" are reduced in size by 1%, how much longer will I live?