Many of you must be thinking that the word "sweet tooth" must be related to tooth. But let me tell you this has nothing to do with tooth/teeth.
There are people who have strong urge to eat something sweet like chocolates, ice-creams, pastries, sweets, cakes, toffees or any other food item that is sweet in taste. This urge is even stronger at times after having lunch or dinner. I am sure, some of you must have experienced this! This strong appetite for sweet food is called "Sweet tooth".
The word sweet tooth is a noun. Refer to the examples given below for sample usage.
1. I always keep toffees with me as I have a sweet tooth.
2. Those who have family history of diabeties and who have sweet tooth too, should be careful.
3. Since he has a sweet tooth, he went to the cafetaria to eat pastry.
4. I have a really strong sweet tooth, and I almost have to follow every meal with some type of sweet.
5. James has a sweet tooth. He is overweight now.