Evolution of Fiber Posts in Dentistry

There is a long history and continual evolution in the materials and shapes used to manufacture dental intra-radicular posts.


Early attempts at prefabricated metal posts contributed to root fractures as they were designed to replicate custom cast posts and were manufactured with a wedge shape. Upon mastication, forces were transmitted through the root, causing a known problem of root fractures.


This led to the development of parallel-shaped metal posts which have been in use for decades now. The parallel shape eliminated this wedge effect and was a statistically superior solution. However, obvious limitations persisted. To insert a parallel post into a tapered canal means one of two things (or in many cases - both): Unnecessary reduction of tooth structure in the apical portion of the canal will weaken the root at the tip of the post, and increases risks during post space preparation. If a smaller diameter post is chosen, then the coronal portion of the post must be filled with cement. The cement is the weakest link in the solution and doesn't offer much support for the crown.


Several other metal post designs were then developed to deal with these issues, however others were turning to fiber-resin solutions, which have since dominated post developments.


The 1st post design introduced by Synca, Logipost-UM, was evaluated by a well-known American independent research institute in 1998. Even with this early version, 92% of evaluators rated the product as excellent or good. It virtually eliminated the potential of root fracture, as the fiber exhibited the same modulus of elasticity as dentin. It was not parallel, but offered a .02 taper, which was a step in the direction of anatomical design. Lastly, the fiber-resin in the posts bonded to current dental bonding materials, creating the potential to reinforce remaining tooth structure following root canal therapy.


These early designs were immediately adopted by many clinicians, but still had limitations. They were radiolucent. When looking at an x-ray, one could think that the clinician had created a post room, but failed to insert the post. They were made from black carbon fiber. This potentially created a problem in esthetic anterior restorations. Lastly, the post shape, though somewhat anatomical, did not fully exploit the properties of fiber to design the most anatomical post possible.


Early commercial success of fibers posts led to a multitude of products to flood the market. All are somewhat successful to a varying degree, however, unlike stainless steel, all fiber is not created equally. There are significant differences in both the materials used and the shapes of current fiber posts.


Irrespective of posts that are used, current literature maintains that 2mm of remaining tooth structure or ferrule preparation are key factors in clinical success. In addition, the overall minimal reduction of healthy tooth structure has been noted as the most important factor in clinical success. While some literature questions the need for posts when ferrule preparation is present, other literature supports the increase in fracture resistance and an overall strengthening of the tooth when a post is placed. Studies which have compared different post diameters in the coronal area have noted an increase in fracture resistance. Studies that evaluated resistance to breakdown from fatigue could be more pertinent.


Regardless of the frequency that the clinician chooses to place posts, it is important to remember that all fiber posts are not created equally. The two most important factors are the shape of the post and the physical properties of the post material.
dual_problem1

Fracture of the
supporting root

dual_problem2

Decementation and
post fracture

dual_problem3

Casting porosities,
fatigue

dual_problem4

Non-parallel root canals
prepared with cast post

dual_problem5

Oversized posts

dual_problem6

Paralled and
cylindrical posts

dual_problem7

Delamination

dual_problem8

Poor fiber post