1. Placing a post increases the likelihood of root fracture. While dental posts are helpful in many ways, they can also be harmful to the tooth. Since the post itself is a solid and rigid material it tends to concentrate a lot of stress, particularly at the spot that it terminates within the tooth root. It is not uncommon to see the tooth fracture down the line at this exact spot where the dental post terminates. If this occurs then the root is fractured and the tooth needs to be removed. Your dentist can detect this when he or she takes an X-ray and notices a defect corresponding to the exact location where the post terminates within the tooth root.
2. Additional cost. Most dentists charge you an additional fee for the placement of the post. But don’t stress yourself too much over this charge because even if you convince them not to place the post they could still technically charge you for the core buildup material. Most insurances do cover the post placement so having dental insurance will come in handy.
3. If most of the tooth structure above they gumlines is removed then the post will not make much of a difference. The longevity of a root canal treated tooth comes down to how much natural tooth structure remains above the gumlines. If your tooth is very badly damaged then it will likely not last you very long either way. Placing a post, or even two posts which some dentists do when desperate, is just delaying the inevitable loss of the tooth. You are probably better off skipping straight to a dental implant and saving yourself the aggravation and unnecessary expenses of a treatment that is not very promising. Talk to your doctor about how they feel about the longevity of your tooth and its 5-year prognosis to get a better idea of whether you should save the tooth and place the post or simply remove it and place the dental implant instead.