This would depend on whether the boy has one sister or multiple sisters.
If he has one sister it would be: "his sister's teeth are very healthy"
If he has multiple sisters it would be: "his sisters' teeth are very healthy"
The possessive form for "the teeth of the horse" (singular) is "the horse's teeth".The possessive form for "the teeth of the horses" (plural) is "the horses' teeth".
If you are talking about the tooth of Fang or fangs that are teeth,then it would be Fang Teeth.
The singular possessive is tooth's.
No, "teeth" is the plural form of "tooth."
tooth. Teeth is plural, tooth is singular.
Yes, the possessive form for the plural noun teeth is teeth's.Example: The teeth's luster shows well in the photograph.
Yes, 'oxen's teeth' is correct for the plural possessive. Example: Both oxen's teeth were examined by the vet.
The possessive form for the plural noun teeth is teeth's.Example: The teeth's luster shows well in the photograph.Example: Her teeth's whiteness is the result of a special treatment.
Singular. Teeth is the plural
Use of teeth in a sentence.These are your teeth. pluralThis is your tooth. Singular
The noun teeth is plural.The plural form is tooth.
The possessive form for the noun monster is monster's.Example: The monster's teeth were fearsome.