Components of Fiber-reinforced Composite Resins

The clinical success of adhesive composite-resin restorations has changed the way that dentists treatment plan and treat periodontally mobile teeth. While adhesive composite resin provides for strong, durable, and esthetic single-tooth restorations, when placed to join teeth together, these materials—which are chemically brittle by nature—are susceptible to fracture and are not durable. When supporting pontics or stabilizing mobile teeth, cracks within the connector areas lead to outright fracture; therefore, splinting teeth as part of fixed prosthodontic provisionalization also creates challenges when the temporary restoration must function over longer periods of time. How can dentists minimize these clinical failures and still use conservative techniques for tooth stabilization with adhesive composites? How can they improve the durability of long-term provisional bridges, especially in cases of a missing tooth in an otherwise intact arch, where an implant is not desired or is contraindicated? Over the past 15 years, a new class of materials designed for reinforcing dental resins has been introduced. These products are fiber-reinforcing ropes, braids, ribbons, and bundled fibers. Clinicians and researchers have investigated the embedding of these fiber-reinforcement materials into dental resins and found that they provided for an increase in certain physical properties and for more durable tooth stabilization.1,2 Before these fibers were introduced, tooth stabilization in the anterior region was accomplished using wires twisted around the teeth and covered with dental resins.3,4 In the posterior arch, stabilization was accomplished with channels prepared into the occlusal surfaces of the teeth, and then restorations which had either cast bars or thick wires placed in the channels were covered with resins.5 The placement of embedded wires, pins, nylon, and stainlesssteel mesh into restorative resins improved the physical properties of the resins.6 A major problem with using these materials, however, was that they were never chemically joined to the dental resin, only embedded. Over time, composite-resin fractures and wear expose the fibers of the underlying reinforcing materials. The resin would then break away from the embedded metal or nylon because of a lack of chemical integration as well as the repeated loading stresses placed on the splint during normal and parafunction.4 In an attempt to minimize splint breakage, a greater bulk of composite resin was placed over the submerged wires and mesh, resulting in significant overcontouring of the restoration, higher rates of food and plaque retention, and increased difficulty in oral hygiene and periodontal maintenance of the splint. It was only with the introduction of chemically integrated, fiber-reinforced composite resins for tooth splinting and other clinical treatments that the problems associated with past attempts to reinforce composite resin were solved.