Translation guide
The most common word for toothpaste is 歯磨き粉 (はみがきこ). In casual contexts, 歯磨き (はみがき) alone can also mean toothpaste. For tube toothpaste, 練り歯磨き (ねりはみがき) is used, and for tooth powder, 歯磨き粉 (はみがきこ) can also refer to powder, but 粉歯磨き (こなはみがき) is more specific.
歯磨き粉
toothpaste
The substance used for cleaning teeth, typically a paste or gel.
The standard word for toothpaste. Literally 'tooth-polishing powder', but used for paste as well.
歯磨き粉が切れたので買わないと。
We're out of toothpaste, so I have to buy some.
Often means 'tooth brushing', but in context can refer to toothpaste. Common in casual speech.
Can be ambiguous; clarify if needed.
歯磨き、どこの使ってる？
What toothpaste do you use?
Specifically paste-type toothpaste, as opposed to powder. Used in product descriptions.
この練り歯磨きはミント味です。
This toothpaste is mint-flavored.
Powdered dentifrice, less common today.
Specifically tooth powder. 歯磨き粉 can also mean powder, but this is clearer.
昔は粉歯磨きを使っていました。
In the past, people used tooth powder.
Can refer to tooth powder, especially historically. Context usually clarifies.
歯磨き粉を歯ブラシにつけて磨く。
Put tooth powder on the toothbrush and brush.
In everyday conversation, 歯磨き (はみがき) often means toothpaste, especially when context is clear. For example, 歯磨き買ってきて (Buy some toothpaste). However, it can also mean the act of brushing teeth, so if there's ambiguity, use 歯磨き粉.