Learn Hardcore French: Où est ton dentifrice? Mes dents me font mal aujourd’hui. - Where is your toothpaste? My teeth hurt today.

Because dentifrice (toothpaste) is a masculine noun in French: un dentifrice. Possessives agree with the noun’s gender and number, not with the possessor, so it’s ton (masc. sing.), not ta (fem. sing.) or tes (plural).

Could I say Où est le dentifrice ? instead of Où est ton dentifrice ??

Yes. Use:

Où est le dentifrice ? when you’re asking about the toothpaste everyone uses (e.g., in a bathroom or store).
Où est ton dentifrice ? when you mean the specific person’s toothpaste (their tube/brand).

Why is it est (singular) and not sont (plural) in Où est ton dentifrice ??

Because the subject dentifrice is singular. If you were asking about several kinds/tubes, you’d say: Où sont tes dentifrices ?

What’s the difference between où and ou?

où (with a grave accent) means “where.”
ou (no accent) means “or.” The accent changes the meaning; you need où here.

Is there a more idiomatic way to say “My teeth hurt” than Mes dents me font mal?

The most common, all-purpose way is J’ai mal aux dents (“I have a toothache / my teeth hurt”). Mes dents me font mal is perfectly correct and slightly more literal (“my teeth are causing me pain”), sometimes sounding a touch more specific or emphatic.

Why is it me font mal and not me fait mal?

Agreement with the subject: dents is plural, so the verb is font. If only one tooth hurts: Ma dent me fait mal or more commonly J’ai mal à une dent.

Why use me in Mes dents me font mal instead of moi?

Because me is the unstressed object pronoun used before the verb. The verb phrase is faire mal à quelqu’un (“to hurt someone”), so “to me” = me. Stressed moi is only for emphasis (e.g., à moi), not in the normal pronoun slot.

Could I drop the possessive and say Les dents me font mal?

Yes. It’s understandable and used, because it’s obvious we mean your own teeth. But when the body part is the subject, French often uses a possessive (mes dents) to make the possessor explicit. With the construction avoir mal à, French uses the definite article: J’ai mal aux dents.

Is blesser a good verb here, like “My teeth injure me”?

No. Blesser means “to wound/injure.” Use it only if your teeth literally cut or wound you (e.g., braces, sharp tooth). For pain/ache, use avoir mal or faire mal: Mes dents me font mal / J’ai mal aux dents.

How else can I form the question? Is Où est-ce que… okay?

Good options:

Neutral/standard: Où est ton dentifrice ?
Colloquial: Il est où, ton dentifrice ?
With est-ce que (more colloquial here): Il est où, ton dentifrice ? or Où est-ce qu’il est, ton dentifrice ? Avoid the clunky Où est-ce que ton dentifrice est ?; it’s technically possible but sounds awkward/redundant.

What about formal vs informal “your”? When would I use votre?

Use ton with someone you’re on “tu” terms with. Use votre for formal/polite singular or when addressing multiple people:

Informal: Où est ton dentifrice ?
Formal/plural: Où est votre dentifrice ?

Is toothpaste countable in French? How do I say “some toothpaste” or “a tube of toothpaste”?

Both are possible:

Mass noun: du dentifrice (some toothpaste). Example: Je n’ai plus de dentifrice (I’m out of toothpaste).
Countable product: un dentifrice / des dentifrices (a toothpaste / toothpastes).
Packaging: un tube de dentifrice (a tube of toothpaste).

Could the person actually mean “toothbrush”? What’s the word?

Toothbrush is une brosse à dents (note the plural “dents”). So:

Toothpaste: le dentifrice
Toothbrush: la brosse à dents Don’t mix them up.

Where can I put aujourd’hui? Is the end of the sentence the only place?

You can put it at the end or at the start:

End (very natural): Mes dents me font mal aujourd’hui.
Beginning (also fine): Aujourd’hui, mes dents me font mal.

Any tricky spelling or punctuation in aujourd’hui and où?

aujourd’hui has an apostrophe (no hyphen): aujourd’ + hui. The h is silent (h muet), which allows the elision.
où must have the accent grave to mean “where.”
In French typography there’s normally a (thin) space before ?; in everyday typing, people often just use a regular space as in your example.

Pronunciation tips for this sentence?

Où: “oo” (close to English “oo” in “food”).
dentifrice: don-tee-freess (final s sounds; the e is mute but softens c to /s/).
dents: “don,” final -ts is silent.
me font: “muh fon,” final -t silent: “fon.”
aujourd’hui: oh-zhoor-dwee (liaison between jour and d’ creates the /ʒ/ sound: “zhoor”).
Nasal vowels: ton and dents/font have a nasal “on” sound.

Is there any liaison I should make here?

No required liaisons in this exact sentence. For example, in Où est ton, the final -t of est stays silent because the next word starts with a consonant (t). In aujourd’hui, the liaison is already built into the word: you pronounce something like “zhoor-dwee.”

How would I say “I don’t have any toothpaste” or “I’m out of toothpaste”?

“I don’t have any toothpaste”: Je n’ai pas de dentifrice.
“I’m out of toothpaste”: Je n’ai plus de dentifrice. (plus = “no longer”)