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Reinforcing a Traumatized Maxillary Incisor Using an Esthetic Post
Traumatized or fractured teeth in pediatric or adolescent patients present a restorative challenge. Using a fiber-reinforced post bonded within the root canal can be the key to long-term success.
Traumatic injury to the anterior teeth is a frequent occurrence with children and adolescents. Frequently, when young teeth are traumatized or fractured and require endodontic treatment, the size of the root canal is enlarged, which leaves a thinner wall of dentin at the dentin-enamel junction (DEJ) after endodontic therapy. If the fracture leaves little of the crown remaining, restoration with a cast-metal post and core is contraindicated because this closely adapting rigid post can lead to undesirable wedging effects that, in turn, can lead to vertical root fracture.1 Research has shown that thin-walled, endodontically treated teeth can be restored and reinforced using dental adhesives with composite resin in the root canal.2-4
There is a need for fiber posts when restoring endodontically treated teeth. Fiber-reinforced posts are not as rigid as metal or ceramic posts. When restored with a post and bonded composite resin versus an integral cast metal post and core, functional stresses to the tooth crown can result in failure at the interface between the restorative material and the tooth;5,6 the thinner the root, the greater the flexion, and the greater the failure. Less tooth structure will contribute to flexion of the crown and potential post fracture.7 As a guideline when using a fiber post, there should be at least one quarter of the crown remaining to allow for the development of at least 1.5 mm to 2 mm of ferrule.5,6,8 A ferrule refers to the development of a preparation margin that has a width apical from the tooth with the margin extending 360° circumferentially around the tooth. The influence of the remaining coronal tooth structure increases the fracture resistance of the restored/endodontically treated tooth, especially in the anterior region. This amount of ferrule when preparing teeth will ensure clinical success.9-12
Fiber posts offer benefits when restoring the endodontically treated tooth of a younger patient. When a fiber-reinforced post is bonded within the root canal, it dissipates functional and parafunctional forces and reduces the stress on the root.13 When catastrophic force is placed on the crown of the tooth, the post or crown will fracture instead of transmitting the energy of force down the root to create a vertical root fracture.14-18 Adhesion of the fiber post within the root canal has been shown to be clinically acceptable and root reinforcing.2-4,7,15,19-21
For the case described, it was decided to use the Rebilda® Post, fiber-reinforced composite post system (VOCO America, Inc, www.vocoamerica.com). The Rebilda Post allows for an even distribution of loading during masticatory function and any parafunction to minimize the stresses that can cause root fracture. Also, the distribution of glass fibers within the fiber posts provides for a high transverse strength to the post to ensure resistance to fatigue failure and fracture of the post in function. The post has the recommended true root taper shape at its apical end combined with a parallel cylindrical wall at the cemento-enamel junction (CEJ) of the tooth to maximize retention once bonded into place. The post is available in three diameters (1.2 mm, 1.5 mm, and 2 mm) with matching canal reamers. What makes the system unique is VOCO’s development of a dual-cure, self-etch adhesive resin (Futurabond® DC) that can be used with a dual-cure composite resin when cementing the post into the root canal.
A 20-year-old male patient with a past history of trauma to the maxillary central incisors 10 years previously and endodontic treatment of the left central incisor presented to the dental school clinic with a fracture to the left central incisor close the gingival line (Figure 1 and Figure 2). A thorough evaluation revealed minimal crown length to achieve a ferrule design for a crown to the fractured incisor. Because the original root canal treatment was done when the incisor was younger, an enlarged root canal and a compromised biologic width was evident (Figure 3). Other anterior teeth demonstrated some chipping consistent with trauma in the anterior region. The treatment plan included restoration of both maxillary central incisors. The left central incisor would receive a fiber post with a tooth-shaded composite resin core and an all-ceramic crown; the right central incisor would receive a direct composite resin incisal edge repair with a resin veneer. To achieve an adequate ferrule in the crown preparation of the left incisor, a periodontal crown-lengthening procedure was also planned.
Canal Preparation and Post Try-In
The maxillary left central incisor was anesthetized. An attempt was made to place a dental dam with a gingival retraction clamp, but the fracture did not allow for a stable dam to be placed. Post space was prepared using heat (Touch n’ Heat, SybronEndo, www.sybronendo.com) and a #4 Gates-Glidden drill in a slow-speed handpiece. The gutta-percha was removed to half the length of the root (Figure 4). Failure to remove the gutta-percha and/or cement sealer from the canal walls can interfere with the bonding of the fiber post and resin cement within the root canal.
The root canal was sized for selection of the fiber-reinforced composite post (Rebilda Post) using the corresponding post reamers provided in the kit. A stopper was placed on the reamer to verify the length to be coincident to the length of the canal preparation (Figure 5). The fiber post was cut so that it would extend 3 mm to 5 mm out of the root canal (Figure 6). Be sure to cut fiber posts with a diamond and air-water spray, not with a fluted bur; the bur will break apart the fibers from the resin matrix of the post.18
Intra-Radicular Dentin Bonding and Root Reinforcement
The canal was irrigated and flushed of all debris created during the canal preparation. At this point the root canal was ready for the bonding procedure. In the past, it was recommended that an etch-and-rinse adhesive be used because of the reported negative effects of fifth-generation and self-etching adhesives on the bonding to self- and dual-cure composite resin cements.22-25 Some recent studies evaluating self-etch systems and compatibility with dual-cure and self-cure composite resins have demonstrated changes in chemistry that have resulted in composite resin-adhesive compatibility.26,27 Recently, a new dual-cure, self-etch adhesive (Futurabond DC) was introduced that is chemically compatible with self-cure and dual-cure composite resins. The adhesive was applied and agitated for 20 seconds to the entire length of the root canal surface and coronal tooth structure using the thin Endo Brush microapplicator provided in the Rebilda Post kit (Figure 7). After agitation, a gentle air stream was blown over the tooth for 5 seconds to thin the adhesive and evaporate organic solvent from the adhesive. Because this is a dual-cure adhesive, there will be dark and complete polymerization within the root canal without concern for the depth of penetration of the curing light.
Fiber Post Cementation
The fiber post was surface treated with a silane (Ceramic Bond, VOCO America) to enhance the bond between the composite resin and glass-fiber post.28,29 The post was then painted with the dual-cure adhesive resin (FuturaBond DC, VOCO America) (Figure 8). An automix dual-cure composite resin core (Rebilda DC, VOCO America) was used to cement the fiber post. The choice was made of using a restorative composite core with higher physical properties than a resin cement to adhere to the dentin walls of the root canal and for the composite resin to simulate the physical properties of dentin and create a dentin substitute with the composite adhesively bonded to the thinned dentin walls of the root canal preparation at the CEJ.18 Using a specialized thin canula tip provided with the dual-cure composite resin core material, the composite resin was syringed into the root canal so that the composite could be placed to ensure complete filling of the canal with cement (Figure 9). The fiber post was gently seated into the composite-filled canal with excess composite cleared away before curing. A light-curing probe was placed touching the fiber post and the entire complex was light-cured for 2 minutes (Figure 10).
After light-curing, a matrix was placed and the crown was rebuilt using the tooth-colored composite resin core material (Rebilda DC). The restoration was finishing and polished (Figure 11) and the patient was appointed for the periodontal crown-lengthening surgery to allow for the all-ceramic crown preparation with a 2-mm ferrule. Ten weeks after crown-lengthening surgery, the all-ceramic crown preparation was completed. A mock-up of the final composite resin restoration for the adjacent central incisor was placed to provide the laboratory with guidance during the crown fabrication (Figure 12). The impression was made and sent to the dental laboratory. The all-ceramic crown (NobelProcera™, Nobel Biocare, www.nobelbiocare.com) was tried-in. Using an etch-and-rinse adhesive (Solobond M, VOCO America), a nano-hybrid composite resin (Grandio, VOCO America) veneer was sculpted, light-cured, and finished and polished for the right central incisor to best match the shade and shape of the adjacent all-ceramic crown. The crown was then cemented with a resin-modified, glass-ionomer cement (Meron Plus, VOCO America) (Figure 13).
For this case, the use of a fiber post was a good choice with the patient’s past history of trauma to the anterior teeth. To avoid disastrous consequences of root fracture and tooth loss, the fiber-reinforced resin post offers an excellent alternative to metal or ceramic posts that can cause root fracture. Using the Rebilda Fiber post bonded within the enlarged root canal provided the tooth with root reinforcement. Because of the post’s high degree of light translucency, the esthetics were similar to enamel, allowing it to blend in with both the composite resin core and the ceramic crown. Also, the true root taper design of the post ensured the conservation of sound radicular and coronal tooth structure. Using a simplified bonding and cementation technique with a unique dual-cure, self-etch adhesive with a dual-cure, composite-core restorative, the fiber post was placed. When considering restoring endodontically treated teeth, fiber posts should be part of a clinician’s armamentarium.
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About the Authors
Howard E. Strassler, DMD
Professor and Director of Operative Dentistry
Department of Endodontics, Prosthodontics, and Operative Dentistry
University of Maryland
Babak Ganjavian, DDS
Advanced Education General Dentistry
University of Maryland
Jason Zitofsky, DDS