You probably have a few things from your childhood that you've hung onto for sentimental reasons. These might be a few toys, your favorite books from when you were growing up, or perhaps a souvenir from a childhood vacation. There's one thing from your childhood that you wouldn't have deliberately hung onto, and this is your primary (baby) teeth. Why exactly have some of your baby teeth refused to loosen and dislodge? And do you actually need to do anything about your retained primary teeth?

Dental Agenesis

Retained primary teeth is a form of dental agenesis, which relates to the absence of permanent teeth. There can be multiple causes for this issue, which are either genetic or environmental, and which will have occurred during odontogenesis (the development and growth of your teeth). Certain infections and trauma during odontogenesis could also have resulted in your issue. But while your permanent teeth failed to develop, your baby teeth have remained in place, so it's not as though you even have gaps in your smile. So will your baby teeth be able to serve you throughout adulthood?

Retained Baby Teeth

Your baby teeth might be perfectly adequate as permanent teeth, even though this is not their intended purpose. As long as the tooth remains functional, it can act as a permanent tooth. This functionality relies on the tooth staying immobile (as in, it hasn't loosened in any way), as well as being an acceptable size (as in, a baby tooth may appear too small for an adult mouth). A baby tooth can be resized, and this involves a dental veneer, a dental crown, or dental bonding (depending on your specific needs). However, when a baby tooth lacks the necessary strength to be a suitable adult tooth, you will need to consider your options.

Replaced Baby Teeth

Dental implants are about the best option, as this results in a permanent, adult-size prosthetic tooth, with a dental crown and artificial root structure that mimics a natural tooth. The baby tooth will be carefully extracted, and this will be done with incredible delicacy. This extraction is structured in a way to avoid trauma to the surrounding bone and tissues, leaving them intact so that they can support the dental implant (which can sometimes be placed immediately after extraction). Although it might sound harsh, your dentist will often use a sharp tool known as a periotome to loosen the tooth, before gripping it with forceps and gently rotating the tooth to ease it out. This makes the process as atraumatic as possible, and you will be given pain relief beforehand. 

It really depends on the tooth in question, but some retained baby teeth can be left as-is (with or without modification), but in some instances, a dental implant is your best bet.