To Post, or Not to Post
Several new post-and-core systems are available to help clinicians decide how to restore endodontically treated teeth.
By John C. Comisi, DDS
One of the greatest challenges facing the restorative dentist today is the rebuilding of endodontically treated dentition that has been destroyed by caries, trauma, or both. Determining the best methodology to restore these teeth can be extraordinarily complicated. Do we place a metal or fiber post? If metal, should it be cast or prefabricated? What method should be used to “bond” the post into the tooth? How long should the post be? Can the tooth withstand the forces that will be exerted upon it during the patient’s normal function and during their parafunctional habits?
It is of course fundamental to use appropriate ferrule,1 in which the final crown should envelop at least a continuous 2-mm circumferential height of tooth structure to properly protect the tooth from fracture after being prepared for a crown. Additionally, the selection of post systems and materials available today could have a significant impact on the long-term results and play a critical role in providing a long-term successful result.
The author has not used a cast post in his practice for more then 20 years. It was much easier and faster to directly place a prefabricated metal post, which were either cemented or screwed into place. There have been many designs and redesigns of these metal posts, so as to reduce radicular fracture. But as time has passed, the development of fiber-reinforced posts has been gaining more and more interest in the profession.2 These “fiber posts” claim properties that mimic the flexing of the radicular structure more closely then metal posts, thus reducing the potential fracture of the root. And with the advent of resin-bonding cement, improvements to retention of these fiber posts have resulted.3
There has always been a question as to the need for “length” in post room creation and placement. How long is too long? How short is too short? The current thinking is that post length should be as long as possible and still maintain the apical seal, and optimally the post length should extend into the tooth equal to the length of the crown.4
Post-and-Core Systems and Materials
With this in mind, there are several post-and-core systems and materials currently available. One of the newer entries to the market is Essential Dental Systems (www.edsdental.com), with the Flexi-Post® Fiber and Flexi-Flange® Fiber. These epoxy-reinforced, high-strength S-glass fiber posts claim to have superior retention and stability while producing minimal root stress. These posts are available in four sizes.
The Ti-Core® Reinforced Core Materials, also by EDS, is the only patented, titanium- and lanthanide-reinforced composite material that the company claims matches the strength of dentin. It resists ditching and grooving during preparation and provides a solid, long-lasting restoration that has been documented to have a 10-year-plus sustained fluoride release. Ti-Core is radiopaque and available in a paste formula, in a gray shade or a natural shade, and also is available in an automix syringe called Ti-Core Auto E for esthetic restorations and Tri-Core Auto White for easy contrast.
The Rebilda® Post glass fiber post system by VOCO (www.vocoamerica.com), claims dentin-like elasticity, is highly translucent and highly radiopaque, has high retention characteristics, and is available in three sizes. Rebilda DC is VOCO’s dual-cured core build-up material available in an automix delivery system. It too claims to have toothlike hardness, which cuts like dentin to eliminate ditching. It has fluoride release, is highly radiopaque, is flowable, has low heat development while curing, and comes in three shades: blue, white, and dentin.
Brasseler USA’s (www.brasselerusa.com) EndoSequence® Fiber Post System claims to be the first fully synchronized prefabricated post system that matches the rotary instrumentation used to shape the root canal. These zirconia-enriched glass fiber posts are said to be strong and flexible, are extremely radiopaque, and are factory silanated to facilitate optimal bonding. These posts are available in four sizes.
EndoSequence™ Core Build Up material, also by Brasseler USA, is a fiber-reinforced, high filler-content core material that is syringeable yet stackable, that the company also claims cuts like dentin. Available in shade A2 and Opaceous White in either a 4-ml syringe or automix cartridge. The material is highly radiopaque and contains fluoride.
C-I™ Post System by Parkell (www.parkell.com) has an endodontic post and system that has a full range of calibrated instruments and post styles for a variety of endodontic applications. The white glass fiber posts come in two sizes, Fine and Medium. The posts are prepared using the same calibrated C-I™ drills for the fiber, plastic, or steel posts that Parkell manufactures.
Absolute Dentin™ is Parkell’s core build-up material. The company has long touted this product as being one that “stacks great and preps like dentin.” It too, as the others, comes in an automix cartridge for quick dispensing. Shades for this product are white, tooth shade, and blue. This radiopaque dual-cured material is strong and densely filled with fluoride/barium glass.
DentinPost® by KOMET USA (www.kometusa.com) are prefabricated tapered posts made of uni-directional special glass fiber-reinforced composite, which the company claims gives the product dentin-like elasticity, and is available with or without the retentive head design. Interestingly the company notes in its brochure that the post is easily removable, if necessary. These posts also are available in four sizes.
BISCO’s (www.bisco.com) Core-Flo™ DC is a dual-cured, fluoride-containing core material that comes in an automix dual-syringe dispenser and is, according to the company, ideal for core build-ups, as are the others listed, but this material appears to have something more. The company states that it can, in a simplified technique, be used to cement the post and be used as a core build-up in a single application. This could be of great time savings to the clinician. The material is radiopaque and available in two esthetic shades, Natural/A1 and Opaque White, with a contrasting Blue shade as well.
Yet with all these flexible post systems and core build-up materials, questions still do come to mind. Are we creating microfractures in the roots of these endodontic teeth that ultimately will contribute to the failure of these teeth? When we create post room, are we removing too much structure that will precipitate future problems? Is one better than another? There appears to be no evidence available to answer these questions.5 It would seem that the effective studies that have been done are too few or perhaps too biased according to evidence-based analysis.
To add more fuel to the fire, a recent study6 has indicated that restorations with composite resin cores, without posts, show an increased resistance to fracture when compared to post-and-core systems as long as a minimum ferrule was established. This study concludes that preserving tooth structure was the most important factor in tooth resistance. This is still one more consideration to take into account when faced with restoring the endodontically treated tooth.
The problem here, of course, is what if there is insufficient tooth structure to create a ferrule? There are rather inventive ways of dealing with this difficulty. Ersu wonderfully presents one such way in a case study,7 where an alternative was devised to help restore an area of the mouth that had limited intra-arch space and was treatment planned for a fixed partial denture. They used cast posts and core and a milled Ceka anchor and screw system to create the substructure and final restoration. Yet, even with our ingenious problem-solving abilities, the clinician must always determine these basic things: (1) Is the tooth periodontally sound? (2) Is it restorable? (3) Can crown lengthening be accomplished and provide adequate room for ferrule, and not compromise the longevity of the tooth and the adjacent teeth? (4) Can the patient tolerate this procedure? Patients often dislike this need for surgical intervention simply because they would rather not have the surgery. Yet it is the author’s opinion that the success or failure of a procedure rests solely on the clinician using their best clinical judgment. Ultimately, it is the long-term success that should determine the direction of treatment and this must trump patient convenience. Once we have created sufficient length to have a proper ferrule, then we should be able use the system and core material of our choice to create the appropriate final restoration.
References
1. Pereira JR, Valle AL, Shiratori FK, et al. Influence of intraradicular post and crown ferrule on the fracture strength of endodontically treated teeth. Braz Dent J. 2009;20(4):297-302.
2. Narang P, Sreenivasa Murthy BV, Mathew S. Evaluation of two post and core systems using fracture strength test and finite element analysis. J Conserv Dent. 2006;9(3):99-103.
3. Schmitter M, Rammelsberg P, Lenz J, et al. Teeth restored using fiber-reinforced posts: in vitro fracture tests and finite element analysis. Acta Biomater. 2010;6(9):3747-3754.
4. McLean A. Criteria for the predictably restorable endodontically treated tooth. J Can Dent Assoc. 1998;64(9):652-656.
5. Al-Ansari A. Which type of post and core system should you use? Evid Based Dent. 2007;8(2):42.
6. Massa F, Dias C, Blos CE. Resistance to fracture of mandibular premolars restored using post-and-core systems. Quintessence Int. 2010;41(1):49-57.
7. Ersu B, Canay S. An alternative post-and-core method for patients with limited interarch space. J Am Dent Assoc. 2007;138(11):1464-1467.
About the Author
John C. Comisi, DDS
Private Practice
Ithaca, New York
