New Innovations in Fiber Posts: A Case Report

Dentists take comfort in providing services that are scientifically valid. With such rapid changes occurring in the field of clinical dentistry, we are guilty occasionally of utilizing a material or technique which has scant scientific support as we try to provide the latest and best for our patients. Dentists should take comfort then in knowing that placing certain fiber posts, to stabilize a core and reinforce an endodontically-treated tooth, is one of the most well-documented, scientifically-supported techniques available to us. Two decades of research have reinforced time and again the merits of fiber posts over other traditional prefabricated or custom fabricated post systems.1-10
Other post systems include cast metal post/cores, custom made to conform to the canal morphology, and prefabricated metal and ceramic posts of varying construction, configuration, and design. Clinicians have historically preferred to utilize systems that enhance their practice efficiency, and the 2 appointment limitation of the cast-post systems has proven to be a deterrent for some practitioners. While prefabricated metal and ceramic posts offer the advantage of one-visit treatment, they, like the aforementioned cast posts, have proven frequently to be irretrievable. Furthermore, some post designs require the removal of excessive tooth structure (especially when approaching the apical one-half of the root) in order to accommodate their cylindrical shape.

A BRIEF HISTORY OF FIBER POSTS

Fiber posts were introduced 2 decades ago as an alternative to these systems. Drs. M. Reynaud and Bernard Duret were responsible for the development work that led to the 1988 introduction of the original carbon fiber post11 (Composipost, Recherches Techniques Dentaires [RTD]). This unique fiber post was made up of long, equally pretensed carbon fibers. These doctors were determined to find the right material, manufacturing process, and clinical technique that would hopefully save teeth that had been endodontically treated from their historical 8% to 12% failure rate.
The early versions were constructed of carbon fiber embedded in a resin matrix, and these posts, when compared to metal posts, possessed different physical properties from their inception. Unfortunately, their use met with some resistance as they were black in color, leading to poor aesthetics under all-ceramic restorations. They were also radiolucent and unfortunately this sometimes led to well-intentioned dentists cutting into a core in order to place a post, only to find a black Composipost was already in position.

ALL FIBER POSTS ARE NOT THE SAME

One of the structural differences is that some manufacturers incorporate reduced numbers of fibers in their post design, effectively reducing their flexural strength12,13 and their fatigue resistance, which is an in vitro predictor of clinical longevity. The RTD D.T. (Double Taper) LIGHT-POST has demonstrated more fatigue resistance in vitro than some other fiber posts.14,15 Literally millions of these posts have been used. Clinical studies confirm the performance of these particular Quartz fiber posts and, presumably of profound interest to the clinician and patient, they seem to be incapable of fracturing roots in vivo.16-21

ADVANTAGES OF FIBER POSTS

The RTD fiber post, as it is currently manufactured, demonstrates very desirable characteristics: it is aesthetic, anatomically tapered, and radio-paque22; bondable to the remaining radicular tooth structure23 and composite core24, allows for more conservative preparations due to its tapered design.25-27
The removal of an RTD fiber post requires only a few minutes28-32, and is accomplished most ideally by using a reaccess kit containing a pilot-hole bur and a carbide bur, followed by the use of the corresponding sized drills used in the post placement. Furthermore, composite cores will bond directly to these fiber posts.
The fibers themselves are embedded in a resin matrix that is then linked chemically to a composite core. This linkage is facilitated by applying a bonding agent to the post surface immediately prior to the placement of the post into the canal. This is usually followed immediately by the placement of a core. This clinical post/core-placement technique can be completed very simply and with great efficiency.

RECENT FIBER POST INNOVATIONS

One of the leaders in composite technology, BISCO recognized the clinical advantages of these fiber post systems, and arranged to distribute these posts in North America beginning in 1995, in conjunction with their bonding systems. These were marketed as the C-Post system in the United States and as Composipost in Canada.
RTD continued to innovate, and has recently introduced quartz-fiber posts that not only possess essentially the same physical properties and attributes of their predecessors, but are also aesthetic and more radiopaque than previous editions. In 2008, RTD and BISCO introduced D.T. LIGHT-POST ILLUSION, incorporating another patented innovation in fiber-post technology.
The post itself incorporates color-change technology to allow the clinician to readily visualize this inherently pigmented translucent post at room temperature, yet it virtually disappears at mouth (body) temperature. One can readily appreciate the advantages of such a system. During instrumentation, the air/water spray cools the post/core complex, allowing the clinician to determine exactly where the post is located. This feature greatly increases the precision attainable during placement or, if ever needed, a removal procedure.

Figure 1. Lingual view of upper left lateral incisor showing previously restored endodontic access opening and lingual lesion.	Figure 2. Labial view upon presentation. Shade tab used in photo to assist with lab communication.
Figure 3. Universal starter drill used to remove gutta-percha to depth of roughly 8 mm.	Figure 4. Finishing drill used to shape canal to correspond exactly to morphology of post.
Figure 5. The 37% phosphoric acid gel injected into canal and onto exposed dentin in core area for maximum of 15 seconds.	Figure 6. Paper points used to blot the canal dry after rinsing off phosphoric acid with water.
Figure 7. Bonding agent is applied to canal and exposed dentin surfaces.	Figure 8. Excess bonding agent removed from canal by blotting with paper points.
Figure 9. Dual-cure resin cement is injected into injection tip for insertion to the depth of the canal.	Figure 10. Dual-cure resin cement (DUO-LINK [BISCO]) is injected into canal starting from the apical area.

Once the crown was removed and the lingual defect was visualized in its entirety, the decision was made to attempt to restore this tooth again. The lesion was thoroughly excavated. The remaining tooth structure was inadequate to support the coronal prosthesis. Approximately 10 mm of gutta-percha was removed from the canal (Figure 3) using the pre-shaping drill (D.T. LIGHT-POST Starter Drill, BISCO Dental Products) which accompanies the posts in the post kit (D.T. LIGHT-POST ILLUSION; RTD/BISCO Dental Products). The canal shape was then refined (Figure 4) using the appropriately sized finishing drill (also provided in the post kit), and the canal was cleaned and dried.
Next, 37% phosphoric acid was injected to the depth of the canal preparation and over any of the coronal tooth structure that was to be bonded to the core. This was left in contact with the dentin for a maximum of 15 seconds (Figure 5). The dentin was then rinsed and dried, being careful not to desiccate the coronal part of the preparation. The canal was primarily dried through the judicious use of suction and the insertion of paper points, leaving a moist dentin surface (Figure 6).
ONE-STEP (BISCO Dental Products) was applied to the canal and the post to thoroughly saturate these surfaces, and then left on the dentin for a minimum of 20 seconds (Figure 7). Next, the post was air-dried, and the canal was dried by blotting it (Figure 8). A dual-cured resin cement (DUO-LINK, BISCO Dental Products) was injected via the automix tip provided, into a low-viscosity placement tip (AccuDose NeedleTube, Centrix, Figure 9). The filled tip was then inserted to the depth of the canal preparation and injection of the cement was done from the bottom up, being careful not to remove the tip from the cement until it could be seen extruding out of the access opening (Figures 10 and 11).
The post was then immediately inserted (Figure 12) and core build-up material was applied around the post and onto any exposed dentin (Figure 13). One can observe the blue post slowly becoming translucent as it warms up to mouth temperature. The ONE-STEP bonding material is extremely sensitive to light exposure, and the translucent fiber post functions as a fiber optic bundle channelling light into the depths of the post preparation space. This allows for excellent light-curing of the bonding resin, cement, and core material—all at once (Figure 14). The post is trimmed and the core is refined with rotary instrumentation. Once at mouth temperature, the post and core became virtually invisible (Figures 15 and 16). Air/water spray allows for post revisualization, as it returns to blue when cooled (Figure 17 and 18).
One week later the patient returned to have the permanent crown delivered, completing the restorative procedures (Figures 19 and 20).

Figure 11. Dual-cure resin cement fills canal, and covers exposed dentin in core build up area.	Figure 12. A fiber post (D.T. LIGHT-POST ILLUSION [BISCO]) is inserted into canal. Note the blue color as the post is at room temperature.
Figure 13. The translucent, composite core material is layered around the post and onto the dentin/cement surface. As it warms to mouth (body) temperature, the post becomes clear.	Figure 14. The post and core are cured at the same time. The post itself functions as a fiber-optic bundle, transmitting light deep into the canal.
Figure 15. Labial view of the completed post and core at mouth temperature.	Figure 16. Occlusal view of the completed post and core at mouth temperature.
Figure 17. Labial view of the completed post and core after water cooling.	Figure 18. Occlusal view of the completed post and core after water cooling.
Figure 19. Labial view of the completed restoration.	Figure 20. Occlusal view of the completed restoration.

CONCLUSION

Simply put, deciding on what type of post system to use in clinical dentistry is a fait accompli. Fiber posts, with the many proven advantages cited in this article, fulfill all of the requirements necessary for clinical success; this is documented by extensive clinical research.

References

Dr. Pensak has been in full-time private practice for almost 3 decades, with an emphasis on aesthetic rehabilitation. He lectures internationally on the subjects of aesthetic reconstruction, occlusion, and practice management. He is a published author and is a clinical evaluator for several major dental manufacturers including BISCO, 3M ESPE, and DENTSPLY. He can be reached at (403) 278-8482 or contacted via e-mail at pensakt@telus.net.

AUTHOR’S NOTE: The D.T. LIGHT-POST ILLUSION (available in the United States) is known as the Double Taper LIGHT-POST ILLUSION in Canada.

Dr. Tony Pensak has no financial interest in any of the companies mentioned in this article.