Contemporary Restoration of Endodontically Treated Teeth. Nadim Z. Baba
posts have become quite popular, and a wide variety of commercial systems are available. More recently, in response to a need for tooth-colored posts, several nonmetallic posts made of zirconia, glass fiber–reinforced epoxy resin, and ultrahigh polyethylene fiber–reinforced posts are available.
Fiber posts require optimal length to avoid post loosening. In laboratory studies, they produced fewer root fractures or more favorable root fractures than metal posts, making them desirable for avoiding clinical root fractures.124–134 Most clinical studies found no root fractures,135–146 but three studies147–149 reported a relatively small number of root fractures (2 of 173, 1 of 106, and 15 of 985, respectively) while one other investigation150 reported a modest number of root fractures (14 of 99). Fiber posts are not as resistant to post fracture as metal posts, and a small number of post fractures have occurred in clinical studies (1 of 173 and 7 of 105).147, 148 Fiber posts have lower failure risk when there are three or four walls of coronal tooth structure,151 indicating that crown ferrules are important to the success of fiber posts. When parafunctional habits are present, fiber posts have been reported to have higher failure rates.25
The first author of this chapter and the editor of this textbook both have placed a number of fiber posts and observed both success and failure. The post failures involved either post loosening or actual post fracture. These clinical observations, although not being part of a rigorous scientific investigation, suggest that there are some conditions where fiber posts are more likely to fail clinically. Therefore, until more definitive clinical data are available that identify all the factors responsible for fiber post failures, the following guidelines are proposed to help minimize, if not prevent, clinical failure of fiber posts:
• Appropriate post length is required because fiber posts are more prone to loosening if their length is not optimal.
• Fiber posts can fracture when little or no circumferential ferrule (sound tooth structure) is present.
• Fiber posts can fracture, loosen, or induce root fracture when they are subjected to heavy occlusal forces, so excessive tooth contact and all occlusal interferences should be eliminated.
Some clinicians consider a fiber post to be a good choice for ETT even when the root is short, there is no tooth structure below the core material (no ideal cervical crown ferrule), and heavy occlusal forces are present. The thought process expressed by these clinicians is that failure of a fiber post, including post fracture, still leaves the root in a restorable condition. Indeed, this situation may occur clinically, but the premise that the remaining root is restorable may not always be true.
The first author of this chapter has encountered both loosening and fracture of fiber posts. Most, but not all, of those failures resulted in a root that could be restored again. However, challenges can arise with removal of the remaining post segment because the process is not as easy as some would portray. These fractures of fiber posts often occurred within the first 1 to 3 years in service. The thought of charging the patient to remove the fractured post, place another fiber post, and make a replacement crown was not appealing. Moreover, the patient might reasonably have concluded that the same type of failure could occur again before an appropriate period of clinical service had transpired.
In light of such failures, a metal post was used to replace the failed fiber post to provide more sustained clinical service for patients. Therefore, while fiber posts are an option, they are not the most cost-effective treatment when the post is shorter than ideal, when there will be little or no ferrule, or when excessive occlusal forces are present.
Summary
The information presented in this chapter is intended to permit clinicians to make data-driven decisions in their clinical treatment of ETT based on known clinical complications. Guidelines have been provided for the decision of whether or not to place a post, the selection of an appropriate type of post material (if a post is used), and the indications and contraindications to placing crowns on ETT.
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