11 – Orthodontic retainers

Fiber reinforced composites (FRCs) have been introduced to dental practice with several prosthodontic, endodontic, and orthodontic applications. In orthodontics FRCs have been used for anchorage units and post treatment splints. Even if for tooth retention multistranded flexible spiral wire retainers are considered the gold standard treatment option, in modern orthodontics the use of FRCs has increased over time. In fact, fibers provide high-standard mechanical properties for the resin system, while particulate resin composite offers good cosmetic/esthetic properties. Therefore, during recent years FRCs splints and retainers use is growing, with the increasing approval of both orthodontists and patients. In vitro and in vivo studies about failure rates of FRCs splints have shown encouraging results. Moreover, the manufacturers research is improving the mechanical properties and final quality of these materials, introducing new technologies such as nanofillers or different adhesive systems. The application technique is quite simple for the clinicians, and the long-term stability of the retainers has been tested and recorded in the literature. On the other hand, some clinical concerns still remain about the difficulty in repairing FRC retainers. Future research about FRCs for splinting purposes will be mostly focused in improving mechanical properties in order to avoid excessive rigidity. Also, adhesion characteristics will need more studies due to the increasing number of materials that are available on the market. Finally, biological research is necessary to test efficacy of different resin coverages and biocompatibility effects if fiber is exposed out of composite bulk.