I started using my little sister's Colgate strawberry flavoured toothpaste two months ago, and I'm wondering if it's okay to use long term. Any idea?

the main difference between adult and children's toothpaste is in the fluoride content. junior toothpasta has less than half(on average) it is also less abrasive/stain removing. if you are prone to decay it is not a good idea. kids have to have less fluoride, it can cause mottled(but superstrong)second teeth. fluoride is valuable for adults, cos it can remineralise(reverse) early decay and our teeth are already formed.

I am not familiar with Colgate's strawberry flavored toothpaste. I would check the active ingredient. It should contain Sodium Fluoride 0.243% (0.15% fluoride ion) which is the same amount of fluoride in adult toothpaste. I am not familiar with any kid's toothpaste that contains 1/2 the amount of fluoride. They do make some that does not contain any fluoride. If this is true of your toothpaste I would switch to a different toothpaste with fluoride to help with cavities. Another option is to use a fluoride rinse after you brush.