The effect of three types of framework's design on their load bearing capacity of posterior FRC IFPDs: Invitro Study

Using fiber reinforced composites in recent years is expanding and different methods in preparation and framework design have been developed. The aim of this literature is to study a special method for using prefabricated fiber reinforced posts, in designing posterior FRC-IFPDs’ frameworks. Also invitro fracture resistance of this framework is compared with two different traditional intercoronal inlay bridge designs, all of them have been directly fabricated. This study was done experimentally. 60 freshly extracted, intact human mandibular teeth were used to make three groups (ten each)of three-unit posterior inlay bridges, for mandibular second premolar replacement. Group A was prepared using FRC fibers and box-shaped preparation, group B with FRC fibers and tub-shaped preparation, and group C, which is newly designed, with prefabricated FRC posts and groove-preparation. After covering with artificial PDL, the abutment teeth were embedded in PMMA resin 7 mm apart, using a surveyor instrument, and the FRC bridges which replaced second premolars were directly fabricated. Then samples were loaded into initial failure at a crosshead speed of 1 mm/min in a Universal Testing Machine (Instron 1195),and forcing graphs and fracture sites were recorded. Mean fracture resistance in groups A,B and C, were reported as 512 ±101 (N), 548.2±155 (N) and 584±136 (N) respectively. Using Kruskal-Wallis and Bonferroni-Dunn’s multiple comparisons post hoc statistical tests, no significant difference among 3 groups were observed.(p>0.05)The failures were detected as cracks and fractures in veneer composite. Frameworks remained intact and undamaged in all the specimens. Fracture resistance were higher than occlusal forces in premolar region in all three groups. Although no significant difference in fracture resistance was observed among three groups, due to significant decrease in preparation curettage of abutment teeth in new framework design (group C), this method can be accepted as a satisfactory way for replacement of a small posterior tooth with minimal curettage of the adjacent teeth.