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The world I'm making isn't hard science fiction nor science fiction, really, but I'd like to be somewhat realistic in some aspects, like this one.

I'd like my humanoid fantasy/alien species to have teeth that aren't white or yellow-ish like those of most creatures on earth. The species are humanoid, omnivores, but have long and sharp incisors and canines. Their world is more or less earth-like though there are some minor differences (atmosphere density, pressure, gravity, etc.) which I don't think play much of a role here

I've looked at beaver teeth since those are orange/yellow and apparently that's due to the iron in the enamel. I'd rather not use orange teeth, though, and have gone down the research rabbit hole. Limpet-like teeth would be an option (giving blue-ish teeth, from google), but those are rated in tensile strength, which I don't think plays much of a role regarding teeth hardness? Could be wrong though. I thought about just taking a random organically occurring oxide (since beaver teeth contain iron oxide) and choosing one that's as high on the Moh scale of hardness as our teeth or higher, but that list is long and I'm not sure what would realistically make sense.

To summarise: What kind of material or chemical makeup could the teeth of a humanoid fantasy species have so that they aren't whitem except for iron (because I don't want them to have orange teeth)? Bonus points if that material somehow makes those teeth "stronger" which for teeth I assume would mean more durable and sharper. And dark tooth colours like black or dark blue would be the coolest

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  • $\begingroup$ A little copper for blue? I don't understand chemistry enough to explain how, but that might look cool. $\endgroup$
    – user458
    Commented Jan 8, 2023 at 16:51
  • $\begingroup$ As far as I know, healthy teeth are white-ish in all species. This rather suggests that all species use the same optimum solution, and any non-white teeth are probably due to disease. Lead poisoning, for example, can give you grey-blue teeth. Sea-shells are a different material, but they are also made by cells laying down a ceramic microstructure, and they can be coloured. Your fantasy teeth could have iridescent colours like opals. $\endgroup$ Commented Jan 8, 2023 at 17:15
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    $\begingroup$ @RichardKirk: Some species, for example beavers, have reddish teeth. $\endgroup$
    – AlexP
    Commented Jan 8, 2023 at 17:42
  • $\begingroup$ @fredsbend Coppery-blue does look pretty! I could probably handwave how it is in their teeth, somehow and it seems hard enough for teeth, though I have no idea about the chemistry either $\endgroup$ Commented Jan 8, 2023 at 18:41
  • $\begingroup$ Is the orange color the only reason, why you don't want iron? Iron is not necessarily orange but can take on almost any color if the right iron compound is used. $\endgroup$
    – Matthias
    Commented Jan 10, 2023 at 12:15

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Short answer: Iron is not necessarily orange and quite strong

Iron can take on almost any color, so you could design the teeth similar to beavers teeth in any color you want (see below). Some of these compounds (at least the black ones) are also quite stable (mechanically) unlike to typical brittle orange rust.

You could also use steel in different colors, although you might have to be creative about the way this is formed because it usually requires heating beyond the possibilites of life (at least life which wants to continue living):

enter image description here

Iron in different shades of red:

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Blue iron compound:

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Green iron compound:

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  • $\begingroup$ Would it be "realistic" to have the iron in the teeth be a compound? If I remember right the iron in beaver teeth isn't pure but mixed, which is a compound right? So any colour would do, basically, from what I gather from this and other comments. $\endgroup$ Commented Jan 11, 2023 at 15:52
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    $\begingroup$ @SaintDiabolus it is not only realistic but basically inevitable. There is basically no pure iron from natural sources on the earths surface, because it is not stable in the atmosphere. A lot of the compounds I've shown appear naturally. $\endgroup$
    – Matthias
    Commented Jan 11, 2023 at 17:54
  • $\begingroup$ I figured as much but better be save than sorry. Thank you! $\endgroup$ Commented Jan 12, 2023 at 11:56
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Copper Oxide

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Copper turns bluegreen when it rusts. Copper oxide is bluegreen.

Cobalt Blue

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From Wikipedia

"Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with aluminum(III) oxide. . . ."

Cadmium

Cadmium is a metal. Bob Ross uses Cadmium Yellow all the time.

enter image description here

See the yellow bit? That's a happy little Cadmium Yellow for our painting. So glad you could join us today.

There is also Cadmium red, orange, and green!

Chromium

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Chromium is another metal. It goes green when it oxidises. Chromium oxide is why wine and beer bottles are traditionally dark green.

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  • $\begingroup$ Your list made me google all those metals/oxides and surprisingly enough copper teeth do exist in the animal kingdom (bloodworms). Cobalt blue does not naturally occur, so I think it wouldn't be feasible for what I want, unless I handwave a lot. Cadmium I would say isn't hard enough from wikipedia and apparently isn't yellow by itself? Chromium is very interesting! Very hard, according to Moh, and a pretty colour too. $\endgroup$ Commented Jan 8, 2023 at 18:57
  • $\begingroup$ Though apparently copper is neither strong nor hard, so hm, unsure if it's feasible $\endgroup$ Commented Jan 8, 2023 at 19:15
  • $\begingroup$ @SaintDiabolus You seem to have assumed beaver teeth are strong like iron because they are full of iron. Beaver teeth do not contain iron. They contain iron oxide. Iron oxide is rust. Rusted things are weak and not strong. $\endgroup$
    – Daron
    Commented Jan 9, 2023 at 12:05
  • $\begingroup$ @SaintDiabolus I do not know what the iron oxide does or whether it makes the teeth strong. But there is more to it than iron = hard. $\endgroup$
    – Daron
    Commented Jan 9, 2023 at 12:06
  • $\begingroup$ You're absolutely right, I probably misunderstood the articles I read that though link another thread on here says that beaver teeth are harder than ours thanks to the iron in them $\endgroup$ Commented Jan 10, 2023 at 11:37
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Colloidal silver or nanosilver

Intake of colloidal silver is known to cause a disease know as argyria, in which the skin turns blue. The most famous example of this I can think of is the man nicknamed “Papa Smurf” (Paul Karason) because his chronic drinking of silver turned him blue like a Smurf.

There is no evidence that drinking colloidal silver affects tooth enamel, but a quick Google search turned up another more likely candidate: nanosilver, an antibacterial agent. Treating teeth with nanosilver has led to scientifically proven tooth discoloration, to grey and even to black!

See this article for details. The article also discusses other compounds that caused discoloration, but nanosilver seemed to most similarly exhibit the effects you are looking for.

Silver nanoparticle coated with imidazolium has been suggested as an intra-canal irrigant. However, some studies showed that the silver-based materials such as silver-containing sealers (e.g. AH26 and Kerr pulp canal sealer) could make grey to black tooth discoloration.

Note that the antibacterial effect of nanosilver might also achieve the hardness you want. Keep in mind that bacteria can erode enamel and expose inner softer layers, thus softening teeth. So it makes sense that an antibacterial agent would have the opposite effect of maintaining their hardness.

The above-quoted article compared the effects of several compounds on tooth enamel and came to the conclusion that nanosilver does indeed turn teeth grey or black, and is thus not recommended as an antibacterial agent. However... if you want your aliens to have black teeth... they include silver in their diet. Maybe they think it's healthy. Maybe they like the taste. Maybe it helps with indigestion. Or maybe their planet is full of it. The reasoning doesn't matter so long as they eat it and it causes black teeth.

Which it does, interestingly enough.

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  • $\begingroup$ Thank you so much for that link and your answer! That is exactly what I was looking for. Silver it is! $\endgroup$ Commented Jan 9, 2023 at 9:43
  • $\begingroup$ I can only find information on grey-black teeth but since your comment mentioned blue too, is that based on the "blue man" and silver's known side-effect of turning skin blue or on something else too? $\endgroup$ Commented Jan 9, 2023 at 10:05
  • $\begingroup$ @SaintDiabolus You are right, I meant to write grey or black. There's no evidence that the same condition that causes blue skin would also cause blue teeth. Editing that now. $\endgroup$ Commented Jan 9, 2023 at 16:29
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    $\begingroup$ @SaintDiabolus Didn't include this in my answer, but the article notes that nanosilver has the same effects as blood. Meaning blood could also stain teeth grey or black. Maybe your extraterrestrial beings are some kind of alien vampires who drink blood. That would have the same effect (maybe because of the copper in it)? But I highly doubt that blood would make teeth hard. $\endgroup$ Commented Jan 9, 2023 at 16:32
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There are all sorts of different kinds of biomineralisation, any of which you might consider. The classic is of course stuff based on calcium phosphates (like your own teeth probably are) and carbonates (like shellfish shells) but there are others of possible interest. You've already ruled out iron, which therefore excludes the hardest teeth in the real world (with chitons and limpets using iron oxides and oxyhydroxides) but in theory other kinds of biomineral could be used for teeth.

Consider, for example, silica. Lots of plants contain silica phytoliths (possibly to discourage grazing) and various kinds of unicellular sea creatures have silica shells. Amorphous silica is interesting, because it is very hard (Mohs 5.5 to 6.5, making it harder than the geothite in limpet teeth) but also because it can look very interesting... you've probably heard of it in the form of opal.

Teeth could perhaps made from biologically deposited silica microspheres or microcrystals in a protein matrix. They have the potential to be very wear resistant... I'm honestly not sure what sort of biological pressure would encourage large complex animals to have teeth suitable for grazing on rocks, but maybe the local vegetation is also highly mineralized, and softer teeth wouldn't be up to the job? Not sure about that. Regardless of the explanation of the origins, the color and appearance of the teeth can very wildly according the structure of the silica crystals and protein matrix. Different colors and iridescent rainbow finishes are all quite possible.

If you wanted even more industrial teeth, then there are bacteria that can do biosynthesis of carborundum, which is substantially harder than silica. Carborundum, also known as silicon carbide, has a Mohs' hardness of 9, making it second only to diamond. In its pure form it is clear like silica, but various impurites can change its color. Iron can cause it to be black, for example.

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  • $\begingroup$ I only mainly ruled out iron because of the colour the oxide presents as in beavers, but as someone else has pointed out, it does not necessarily need to be orange. Both of your examples sound verrrry interesting - particularly that impurities can change the colour, which I imagine would be present in naturally occurring teeth. $\endgroup$ Commented Jan 10, 2023 at 12:29

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