3213: Dental Formulas

Dental Formulas

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Title text: I mean, half of these are undefined. And your multiplication dots are too low; they look like decimal points.

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Explanation

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A dental formula specifies the number of teeth of each type on each side of the jaw, with dots separating the numbers. There are two rows, representing the upper and lower jaw, separated by a horizontal line. The number of incisors is indicated first, canines second, premolars third, and finally molars, so the formula in the comic would represent 3 incisors, 1 canine, 3 premolars, and 1 molar on each side of the upper jaw, and equal numbers in the lower jaw except only 2 premolars.

Cueball is (wrongly) treating a dental formula as an arithmetic expression, with the line indicating division and the dots indicating multiplication. In the title text he notices that the "dots are too low", as in fact the dots in a dental formula are at the height of decimal point or period characters and aren't meant to imply multiplication.

Transcript

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[Cueball and Megan are standing in front of a whiteboard, on which is written

3.1.3.1
3.1.2.1

along with some other scribbles.]

Cueball: Do mammatologists think these are hard?

Cueball: I mean this one just evaluates to 3/2.

[Underneath the panel is the caption "Mathematicians encounter dental formulas".]

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Discussion

First!AmethystSky14 (talk) 21:43, 27 February 2026 (UTC)

The top left drawing is a tooth. Xkdvd (talk) 22:04, 27 February 2026 (UTC)

This confused me for a long time (partly due to the mammal/mammol thing) - I took them to be dentists. I'm now inferring that the counts are typical of a species rather than descriptive of an individual patient. Maybe the write up could make that more clear in case someone else as dumb as me passes by 2A00:23EE:10C8:110F:D992:D45:1C7A:DF02 guest

"in case someone as dumb as me passes by" - that would be everyone, see Explain xkcd: It's 'cause you're dumb. 64.201.132.210 22:21, 27 February 2026 (UTC)

Because I'm sure someone else will be wondering, based on a very cursory search, the formula on the board appears to be permanent teeth for felines. At the very least, Wikipedia's entry on Dentition lists this formula for cats, lions, and tigers. Perhaps an actual expert will come along and shed further light on this. 97.116.61.145 22:52, 27 February 2026 (UTC)
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