I do not react well to foreign materials and my immune system is weak. shall i have a dental post placed in a root canal treated bicuspid?

Yes: A post that is placed after a root canal is inside the root and not exposed to your body and the immune system. Do you know what kind of materials you react to? Talk to your dentist about the different materials that can be used for the crown that should be made for this tooth.

Post in tooth: Immune systems tolerate dental materials well. There are much better ways to manage teeth which require posts. Posts actually weaken a tooth and fracture occurs when stress is placed on the tooth during chewing. The tooth it may actually be fractured during its placement . Discuss an implant, which despite immune concerns are almost universally well tolerated.

Posts: Not all teeth require posts. You can have a titanium post placed which is used in all kinds of prosthetic devices in the body and reactions are relatively rare if at all. Titanium posts are inside the tooth and not exposed to your bodies ability to detect it. I can't determine what is best treatment for you but i certainly wouldn't be concerned about any reactions to a titanium post.