50% Inter-dentist Agreement on Cavities in Xray Photos

One of the things I like about my dentist is that she’ll tell me they think there’s cavity in xray, and want to wait to see if it goes away or gets worse before treating.  I always thought: weird, can cavities really heal?  Or are they just not sure that it’s a cavity?

From NPR:

Prof. ARIELY: So imagine: You came to a dentist; you got your X-ray. And then we took your X-ray, and we also gave it to another dentist.

SIEGEL: Right.

Prof. ARIELY: And we asked both dentists to find cavities. And the question is, what would be the match? How many cavities will they find, both people would find in the same teeth?

SIEGEL: And I’d really hope it would be somewhere up around 95-plus percent.

Prof. ARIELY: That’s right. It turns out what Delta Dental tells us is that the probability of this happening is about 50 percent.

SIEGEL: Fifty percent?

Prof. ARIELY: Fifty percent, right. It’s really, really low. It’s amazingly low. Now, these are not cavities that the dentist finds by poking in and kind of actually measuring one. It’s from X-rays. Now, why is it so low? It’s not that one dentist find cavities and one doesn’t. They both find cavities, just find them in different teeth.

(Soundbite of laughter)

Prof. ARIELY: And here is what happens. Imagine you’re a dentist, and you see a patient, and you really want to find a cavity because you get paid more if you find cavities and you can fix them. And the patient is already on the chair. He’s already prepped. You might give them the treatment right now, really good marginal income for you. How is this motivation to find cavities - will influence your ability?

Now, you look at an X-ray - which is a little fuzzy and unclear, and there are shadows and all kinds of things are happening. What happens is this unclarity of the X-ray helps, in some sense, the dentist to interpret noise as signals, and find cavities where there aren’t really any.

SIEGEL: And fill them?

Prof. ARIELY: And fill them, and drill them, expand them. I don’t think they ever tell their patients, hey, I thought it was a cavity but turns out it was just a mistake.

(Soundbite of laughter)

Prof. ARIELY: But they do fill them.

SIEGEL: You’re describing a very private relationship between patient and dentist.

Prof. ARIELY: Yes.

SIEGEL: You’re telling us we should, on average, expect our dentist to be getting it wrong on the X-rays, but that’s not how people feel about their dentists, right?

Prof. ARIELY: That’s right. And the dentists actually have a tremendous loyalty. People are really loyal to their dentist, much more than other - medical profession. And I think one of the reason - go back to cognitive dissonance. Cognitive dissonance is the idea that when people do something painful, they become more committed to the goal. If we have a fraternity and we haze people in a more difficult way, they become more loyal to the fraternity.

SIEGEL: You have dentistry as a hazing experience right now.

Prof. ARIELY: That’s right. And I think the same thing happen with dentists. Dentistry is basically the unpleasant experience. They poke in your mouth. It’s uncomfortable. It’s painful. It’s unpleasant. You have to keep your mouth open. And I think all of this pain actually causes cognitive dissonance - and cause higher loyalty to your dentist. Because who wants to go through this pain and say, I’m not sure if I did it for the right reason. I’m not sure this is the right guy.

(Soundbite of laughter)

Prof. ARIELY: You basically want to convince yourself that you’re doing it for the right reason.

SIEGEL: Every visit to the dentist is an episode in the Stockholm syndrome here, is what you’re describing. You studied these dental insurance records, and you looked at what happens over time as our relationship with the dentist grows over many years, and you find it affects the kinds of decisions the dentist and the patient make, about choices.

Prof. ARIELY: That’s right. So you can imagine that at some point in your dental treatment, you have a choice between things that have the same possible outcome, but one of them is more expensive to you and better financially for the dentist. Which one would you choose, and how the duration of relationship be affecting that?

And it turns out that the more time people have seen the same dentist, the more likely the decision is going to go in favor of the dentist. People are going to go for the treatment that is more expensive but has the same outcome. More out of pocket for them, more money for the doctor. So in this case, loyalty actually creates more benefit for the dentists.