An Advancement in Fiber Reinforcement for Restorative Dentistry
EverStick is a predictable tool to improve the applications of composite resins
Fiber reinforcement in resin-based restorative materials has been in clinical use for many years. Fibrous materials act to reinforce a matrix material such as acrylic, bis-acrylic, or composite by transferring the stress under applied load from the weaker resin material to the much stronger fiber.
A popular clinical application for the use of fiber reinforcement in the general dental practice is for provisional crown and bridge restorations, particularly ones with long spans and multiple pontic designs. In many cases, these restorations are subjected to increased occlusal loading, which can fracture these high-modulus, brittle materials, necessitating additional chair time to repair or replace the restoration. Currently, fiber products available on the market are made of polyethylene, which limits handling properties and makes them more challenging to use for direct applications. The mechanical properties of polyethylene fibers are also widely varied, and their use often does not yield consistent clinical results.
There is a unique product on the market, everStick® (GC America Inc., www.gcamerica.com), which raises the bar in fiber reinforcement of dental restorations. The unique composition of everStick also expands the clinical application for the uses of fiber reinforcement in the general dental practice. The product itself has different designs (eg, diameter, number of fibers) for different dental applications. Each consists of fiber reinforcement imbedded in a matrix of polymethyl methacrylate (PMMA) and bis-GMA (interpenetrating polymer network), making the fibers bondable not only to direct but also to indirect dental materials. EverStick® C & B is commonly used for direct resin bridges and provisional dental restorations. EverStick® Post is used for endodontic posts in combination with direct resin crown build-ups. Finally, everStick®Perio is typically used for periodontal splints and orthodontic retention. This article describes and demonstrates some of the clinical uses of this very useful and unique dental material.
Fiber-Reinforced DirectComposite Bridges
For many clinicians, a missing tooth means replacement by a laboratory-fabricated fixed bridge or an implant-retained restoration. Both of these options can be a very expensive solution for some patients. In cases where economics is the sole decision maker, the only “economical” alternative has traditionally been a removable prosthodontic appliance, which for the replacement of a single tooth is usually not something a patient will be happy with long term. Using current composite technology and fiber reinforcement, such as everStick products, a good long-term solution is now available for a single missing tooth that can be much more economical than the laboratory alternatives and still provide an excellent service to the patient.
For the 72-year-old patient in Figure 1, who had lost a mandibular lateral incisor, an implant or conventional fixed bridge would not be a good solution because of the advanced alveolar bone loss and long clinical crowns of the abutment teeth. A fiber-reinforced fixed bridge was the perfect solution. Because treatment was needed in the anterior, it was decided to prepare slots into the lingual surfaces of the abutment teeth to place the fiber intracoronally. For posterior applications, the fiber can be bonded directly to the enamel on facial or lingual surfaces and covered with composite, which is then blended into the adjacent tooth structure. This, in addition to the intracoronal fiber on the occlusal surface, will help to protect against lateral forces on the pontic. Once the fiber is in place splinting the two abutment teeth together, a composite pontic can be “freehanded” to place, contoured, and polished. Figure 2 shows a facial view of the completed restoration. The pontic overlaps the adjacent canine in a similar fashion to the patient’s natural condition on the mandibular right side.
Another indication for a fiber-reinforced direct bridge is when a tooth is lost due to periodontal compromise and requires immediate replacement. The patient in Figure 3 had a periodontally hopeless tooth (No. 8) with an existing porcelain fused-to-metal crown that needed extraction. The plan was to extract the tooth and make the crown a pontic that would be attached via fiber reinforcement to the adjacent teeth. This procedure can also be performed on an unrestored tooth using the patient’s own tooth as the pontic. After extraction, the root was cut off and the bottom of the crown was covered with composite and polished in the form of an ovate pontic that resembled the large side of an egg. A slot was cut in the back of the crown and adjacent teeth in which to embed the everStick C & B fiber. Once the pontic was in place, the slot preparations on the abutment teeth were first covered with a bonding agent (G-aenial™ Bond, GC America), then filled with flowable composite (G-aenial™ Universal Flo, GC America) and finished (Figure 4). Since the fiber was coated with active resin, there was no need to apply a coupling agent such as silane.
Custom Fiber Reinforcement for Root Canal Post and Cores
Many of the prefabricated fiberglass posts for direct post and core fabrication are round in shape and do not anatomically conform to the root canal space or provide much surface area and coronal support to the composite cores that surround them in the clinical crown. This can cause stress concentrations that can lead to fracture of the post at the orifice level. Any clinician who must try to retrieve a post in that situation knows how difficult it can be.
Using everStickPost is an ideal way to custom fit a root canal post to the canal anatomy and reinforce the core material by spreading the fibers in the coronal aspect of the core portion of the preparation. This can significantly decrease the amount of stress at the level of the orifice, where the post enters the root canal space. Each everStickPost can be custom tapered and fit to the post space length prior to cementation (Figure 5). The intra-coronal portion of the fiber can be “feathered out” to increase the surface area of the fiber that integrates with the resin build-up material (Figure 6). EverStickPost is cemented with resin cement (G-CEM LinkAce™, GC America) then light cured (Figure 7). Once the core build-up material is placed and light cured, it can be prepared and a master impression of the crown made.
Periodontal Splinting andOrthodontic Retention
EverStickPerio is an ideal material to use in conjunction with traditional dentin bonding and composite technologies to splint teeth. The fact that it is composed of a series of fibers surrounded by a PMMA/bis-GMA matrix allows this material to be shaped and placed much more easily than any polyethylene fiber material. A specially designed placement instrument is used to tack the fiber to each tooth while at the same time protecting the remaining fiber from the light. Once the fiber is in place, it is covered with flowable resin (G-aenial™ Universal Flo), which is light cured, contoured, and polished to complete the procedure (Figure 8).
Conclusion
The clinical applications discussed and shown using everStick fiber reinforcement material only improve on the present clinical offerings, but they give the clinician a predictable tool to do many more procedures using composite resins that ultimately will benefit their patients.
Disclosure
Robert A. Lowe, DDS, FAGD, FICD, FADI, FACD, received an honorarium from GC America.
About the author
Robert A. Lowe, DDS, FAGD, FICD, FADI, FACD
Lecturer, Educator
Private Practice
Charlotte, North Carolina
For more information, contact:
GC America
800-323-7063
www.gcamerica.com
References
1. Göncü Başaran E, Ayna E, Üçtaşli S, et al. Load-bearing capacity of fiber reinforced fixed composite bridges. Acta Odontol Scand. 2013;71(1)65-71. doi: 10.3109/00016357.2011.654240.
2. Yokoyama D, Shinya A, Gomi H, et al. Effects of mechanical properties of adhesive resin cements on stress distribution in fiber-reinforced composite adhesive fixed partial dentures. Dent Mater J. 2012;31(2):189-196.
3. Bijelic J, Garoushi S, Vallittu PK, Lassila LV. Fracture load of tooth restored with fiber post and experimental short fiber composite. Open Dent J. 2011;29(5):58-65.
4. Le Bell-Ronnlof AM, Lassila LV, Kangasniemi I, Vallittu PK. Load-bearing capacity of human incisor restored with various fiber-reinforced composite posts. Dent Mater. 2011;27(6):e107-115. doi: 10.1016/j.dental.2011.02.009.
5. Nagas E, Cehreli ZC, Durmaz V, et al. Shear bond strength between a polyester-based root canal filling material and a methacrylate-based sealer with an intermediate layer of fiber-reinforced resin-based material. J Adhes Dent. 2009;11(4):325-330.
6. Yokoyama D, Shinya A, Lassila LV, et al. Framework design of an anterior fiber-reinforced hybrid composite fixed partial denture: a 3D finite element study. Int J Prosthodont. 2009;22(4):405-412.
7. Eronat N, Candan U, Turkun M. Effects of glass fiber layering on the flexural strength of microfill and hybrid composites. J Esthet Restor Dent. 2009;21(3):171-178; discussion 179-181.
8. Ozel E, Soyman M. Effect of fiber nets, application techniques and flowable composites on microleakage and the effect of fiber nets on polymerization shrinkage in class II MOD cavities. Oper Dent. 2009;34(2):174-180.
9. Bagis B, Ustaomer S, Lassila LV, Vallittu PK. Provisional repair of a zirconia fixed partial denture with fibre-reinforced restorative composite: a clinical report. J Can Dent Assoc. 2009;75(2):133-137.
10. Xie Q, Lassila LV, Vallittu PK. Comparison of load-bearing capacity of direct resin-bonded fiber-reinforced composite FPDs with four framework designs. J Dent. 2007;35(7):578-582.
