Restoration of Endodontically- Treated Teeth Using Fiber Posts
An effective protocol for success
Manfred Friedman, BDS, BChD
Since the introduction of fiber-reinforced posts to restorative dentistry, there have been numerous advances to both their technology and physical design. There is also a growing body of evidence to support the use of quartz fiber-reinforced posts in endodontically-treated teeth as a means to increase their resistance to fracture. Subsequently, the notion that all posts weaken teeth seems to be dispelled.1,2
There are, of course, several other factors that contribute to the success of this endo-restorative procedure. Mechanical design of the post, its physical properties, and the fiber content all relate to the post itself, however, a critical factor that is often overlooked (or treated too casually), is the technique and compatibility of the materials used in their placement. It is essential to use a predictable and repeatable protocol in order to ensure maximum bond strength. After all, this post-and-core substructure will be supporting your carefully prepared permanent restoration. While endo-restorative materials and techniques do evolve over time, the ultimate goal is the same—“to restore teeth to function and comfort, and in some cases, aesthetics.”3 This technique should also address any anatomical anomalies and be tailored to canal shape.4
All procedures performed within the root canal system should focus on the bottom up approach. The canal(s) should be prepared with matching sized posts and post drills and all remnants of gutta percha removed from the walls of the post space to ensure an optimal bonding surface. The fiber post is generally shortened to the height of the core with a diamond (a diamond disc is best but a diamond bur may also be used) before the bonding procedure is started, but may also be reduced after the core is fully cured. A strong, dual-cured cement/core material, such as Zircules™ (Clinician’s Choice, www.clinicianschoice.com) may be used both to bond the post to the root structure as well as used immediately to continue with the build-up of the core. If a self-cure core material is being used, the post should always be cut to length first as the vibrations may disrupt the setting of the cement. A color-changing post, such as the Macro-Lock Illusion X-RO (Clinician’s Choice), should be buried within the core material and, therefore, requires shortening prior to the bonding procedure.
Case Presentation
After discussing options with the patient, it was decided that root canal therapy would be performed through a full coverage porcelain/metal crown on an upper first molar (Figure 1). The amount of tooth structure remaining after both the initial crown preparation and the accessing of the canals was assessed. It was determined that a post-and-core restoration was required to enhance structural integrity as the patient elected to keep the existing crown.
In this case, the combination of Zircules Zirconia Nano-filled Core Material and a Macro-Lock Illusion X-RO post were used. The adhesive is critical here, as sixth and seventh generation adhesives are not compatible with dual-cured materials generally, and result in significantly reduced bond strengths. MPa Max (Clinician’s Choice) was chosen for this procedure. These three materials are compatible and, when used together, produce high bond strengths, virtually eliminating post debonding.
Post-and-Core Treatment Protocol
1. Phosphoric acid etch the canal, starting at the deepest part of the prepared canal, using an Endo-Eze® 20 or 22 gauge tip (Ultradent, www.ultradent.com) (Figure 2).
2. The etchant should be agitated in the canal with a Microbrush® X (Microbrush, https://microbrush.com/).
3. Rinse and lightly dry (using gentle air flow) the canal from the bottom up using a 20 or 22 gauge Endo-Eze Tip attached to a Stropko Irrigator (Henry Schein Dental, www.henryschein.com).
4. Place an adhesive, such as MPa MAX, per manufacturer’s instructions, into the canal. This adhesive must be compatible with dual-cure cement. Agitate the adhesive with a Microbrush X (or similar product) (Figure 3); air thin and evaporate the solvent from the bottom up using a 20 or 22 gauge Endo-Eze Tip adapted to a TriAway Adapter (Ultradent) or Stropko Irrigator.
5. Before proceeding, confirm there is no pooling of excess bonding agent with a paper point. Then light-cure the bonding agent for 30 seconds.
6. After preparing the post space with the corresponding sized drill, inject Zircules Zirconia Nano-filled Core Material into the canal from the bottom up using an integrated needle mixing tip and fill the canal.
7. Insert the pre-bonded and pre-shortened Macro-Lock Illusion X-RO post into the Zircules core material immediately (Figure 4). If the canal is very ovoid or flared, place additional accessory FiberCone™ posts (Clinician’s Choice) beside the Macro-Lock Illusion X-RO post. FiberCone posts can also increase retention and provide anti-rotational security in auxiliary canals. This has shown, clinically and scientifically, to increase fracture resistance in teeth with flared or ovoid canals.5 Light-cure for 30 seconds. (Note: light-curing times will vary based on the power of the light source and distance from the post.)
8. Add more core material to form the core of the restoration and light-cure for at least 40 seconds (Figure 5). In this case, opaque white was used for contrast. Blue could also be used. A tooth shade, such as A2, is recommended in the esthetic zone. Wait several minutes before preparation of the core if using a bulk-fill method for a large core build-up, where light may not fully penetrate to the base of the core to ensure that the vibrations from the bur do not interfere with the core material set times.
This patient chose to retain this crown after root canal therapy rather than replace it. The technique and materials used yielded a successful outcome (Figure 6).
Disclosure
The author has no relevant financial relationships to disclose.
References
1. Ferrari M, Vichi A, Fadda GM, et al. A randomized controlled trial of endodontically treated and restored premolars. J Dent Res. 2012;91(7 Suppl):S72-S78.
2. Adanir N, Ureyen Kaya B, Kececi AD. Fracture resistance of roots restored with four different fiber-reinforced composite posts. Med Princ Pract. 2015;24(6):538-543.
3. Ree M, Schwartz RS. The endo-restorative interface: current concepts. Dent Clin N Am. 2010;54(2): 345-374.
4. Boksman L, Hepburn AB, Kogan E, et al. Fiber post techniques for anatomical root variations. Dent Today. 2011;30(5):104, 106-111.
5. Alkumru H, Akkayan B, Gaucher H, Atalay S. Fracture strength of teeth in oval-shaped root canals restored with post systems and accessory post systems. Canadian Journal of Restorative Dentistry & Prosthodontics. 2013;6 (1).
About the Author
Manfred Friedman, BDS, BChD
Adjunct Professor
Endodontics Lab Director
Schulich School of Medicine and Dentistry at Western University
London, Ontario, Canada
Private Practice
London, Ontario, Canada
