Benefit No. 1: Fiber Posts Should Be Bonded Into Place
Fiber posts are (optimally) placed using a bonding agent, followed by resin cement (preferably dual cure) and a composite for the core build-up. Brief exposure of light-cure energy from the occlusal aspect will initiate the cement catalysts. While polymerization will continue below the surface for a few minutes, the clinician can go directly to the placement of the core without waiting. This saves the few minutes you don’t wait for the Civil Warera ZnPO4 cement to set. Those few minutes you save pay for the post itself. Bonding the post with a resin cement builds a monobloc of “dentin-type strength,†thus elevating fiber posts to a higher plane than metal.
Benefit No. 2: Micro-Retention Superior To Macro-Retention
Figure 3. Micro-retentive surface of the UniCore Post, very similar to that of an etched veneer.
Once viewed as heretical, etching of natural dental substrates has changed dentistry as much as anything has over the last 100 years. Creating micro-retentive surfaces is the safest, most conservative way to increase surface area and therefore increase retention. With metal posts and even some fiber posts, macro-retentive features were absolutely necessary for reliable retention. These macro-retentive features induce stress concentration in either the post or the tooth or both.14-15 Today, the best fiber posts are manufactured to provide a micro-retentive surface (Figure 3), one that doesn’t require ridges and grooves for retention. This micro-retentive surface on bonded fiber posts is hard to beat.20-22 When my veneers come back from the lab, they’re etched to present a micro-retentive surface to receive my bonding materials, and I never give it a second thought. There is no macro-stress concentrating feature, so it works.
Benefit No. 3: Fiber Post/Core Is Minimally Invasive
Fiber posts are bonded and need only be seated to a depth of approximately one half of the root length, OR the equivalent of the length of the clinical or prosthetic crown.23 In contrast, with metal posts, increased insertion depth should equate to higher retention. However, this naturally threatens the apical seal, increases the risk of perforation and dislodgement of the gutta-percha, and worst of all, transfers stress apically to the narrowest, most vulnerable part of the tooth.
Benefit No. 4: Tapered Is Now Better Than Parallel
Once upon a time, when only metal posts existed, and prior to the ability to predictably bond to both the post channel and the post surface, it was determined in vitro that parallel metal prefabricated posts provided superior retention to tapered metal posts (except screw types)24 and that tapered metal posts demonstrated a propensity toward typical wedge-type activities (like splitting things in half).25-26 Also, in too many cases this parallel shape condemned me to sacrificing more dentin just to get some surface interface/adaptation. Fiber posts can be obtained in either parallel or tapered design. If one uses predictable bonding techniques, and fiber posts are bondable, the tapered design provides the additional benefit of conserving radicular dentin and reducing functional stresses towards the apex, and all of this without compromising strength. A tapered post in a tapered root makes a lot of sense. Most everything we use in roots is tapered. For example, we use endo files and reamers that are tapered, not parallel, and GP cones, and paper points, and I have never made a rectangular RCT in a mature tooth.
Well fitting parallel posts maintain a close approximation to the sidewall of the post space from the very moment of initial penetration, throughout total movement, and to complete seating. They are like a piston. Because of this, they required a vertical channel or slot to facilitate venting of cement and/or air from the depth of the post channel. Without such, they would not fully insert or possibly “float back†once pressure for placement stopped. Tapered posts have the unique capability of being “self venting.†This occurs because significant space exists between the tapered channel preparation and the post for cement and/or air to flow from until the post finally comes to its fully seated position adjacent dentin. It’s like an inlay. The architectural design, and hence strength of the post, is not compromised simply in the name of venting.
The more we “listen to the needs of the tooth,†complete with listening to its anatomical shapes and physical properties, the more important insights we gain towards optimum rehabilitation.
Benefit No. 5: Aesthetics Is Now A Standard, Not An Option
Excepting the antique carbon fiber post you might find somewhere, fiber posts are tooth colored or translucent. Either version will eliminate the need for the opaquing or masking often required over metal posts. This saves time and materials in direct operative composite restorations and all-ceramic fixed prosthodontics.
Benefit No. 6: Corrosion Is Removed From The Equation…For Good
Fiber posts, titanium alloys, and ceramic posts cannot corrode, but base casting metals and stainless steel posts all exhibit corrosion potential, especially in the presence of bi-metalism and/or moisture, which contributes to decementation and root fracture…smells bad, too. In a study of 468 teeth with vertical or oblique root fractures, 72% were attributed to electrolytic action of dissimilar metals used for the post and core; reaction between the tin in the amalgam core and the stainless steel post.27
Benefit No. 7: Remove The Post, Not More Dentin
As many as 15% to 20% of root canal treatments may require reaccess/retreatment.28 This in and of itself is reason for us to seriously study our approach to root canal treatment. Approximately 25% of those will have a post in the way.29 Fiber posts can be removed invitro in a matter of minutes30-31 without further trauma to the tooth.
Benefit No. 8: Fiber Posts Are More Fatigue Resistant
Fatigue follows us everywhere. Put simply: “Fatigue is considered one of the principal causes of structural failure in restorative dentistry…restorations fail more often with repetitive loads that are below the mechanical resistance limit of the restoration itself than with the application of a single force, even if relatively greater.†In a 2007 study, Wiskott33 demonstrated in vitro that the fiber posts tested proved more fatigue resistant than the stainless steel and titanium posts. This may be related directly to the fact that fiber posts are designed to flex slightly, when necessary, and some fiber posts have a greater flexural strength than stainless steel or titanium.
Benefit No.9: Fiber Posts Can Be Radiopaque…
…and translucent at the same time. About half of the fiber posts on the United States market today are radiopaque, as compliant with ISO Spec No. 4049; equivalence to aluminum.
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