The survival rate of fiber-reinforced composite inlay bridges after two million load cycles: An in vitro study

Fiber reinforced composite (FRC) inlay bridges have become popular for being conservative, simple and relatively inexpensive. The aim of this in vitro study was to determine the survival rate of FRC inlay bridges replacing missing maxillary lateral incisors, after being subjected to a cyclic mechanical load of 2 million cycles with a force of 30 N at a frequency of 2 Hz. In this experimental study, 30 anterior bovine teeth were used as abutments to make 15 anterior FRC inlay bridges. Fifteen acrylic resin blocks were fabricated utilizing a dentoform. The teeth were mounted in the resin blocks while trying to simulate normal tooth angulations, PDL and biologic width. Pontics were made indirectly and bridges were directly fabricated in 222 mm prepared cavities using Nulite F fiber- reinforced composite resin and polyethylene fiber based braids (NSI, Australia). The specimens were thermocycled for 2000 cycles between 5°C and 55°C and were then exposed to two million load cycles (30 N, 2 Hz) at 130°C to the long axis of the pontics (3mm under the incisal edge) in a cyclic loading machine. Three specimens were excluded due to experimental mishandling. All 12 remaining bridges (%100) survived the applied loads. Based on the results of this study, it may be concluded that FRC bridges can tolerate more than 2 million normal masticatory forces which is equivalent to 7-9 years of clinical service.