For the most part, authorities will agree that noncount (or uncountable or uncount or mass) nouns are generally treated as singular when it comes to agreement. The Voice of America guidance, for example, states
Grammatically, a noncount noun is always singular, even if it refers to multiple items like furniture, luggage, or equipment.
This is somewhat overstating things, as some collective nouns may represent an uncountable concept (e.g. police, clergy) but be customarily paired with a plural verb.
The police are investigating his disappearance.
× The police is investigating his disappearance.
× The polices are investigating his disappearance.
Additionally, a great many nouns primarily used in an uncountable meaning can also be used with a countable meaning, especially when referring to varieties or portions of something. Toothpaste is just such a noun; for example, one can refer to brands or types of toothpaste as different toothpastes.
There is toothpaste that is not safe.
There are toothpastes that are not safe.
These kinds of toothpaste are pleasant to the taste.
These toothpastes are pleasant to the taste.