Effect of composite fiber insertion along with low shrinkage composites on cuspal deflection and fracture strength of root filled maxillary premolars

Abstract

Introduction of composite resins with low polymerization shrinkage might decrease the polymerization stress at tooth-restoration interface compared to that with the currently used methacrylate composite resins. The aim of the present in vitro study was to evaluate the effect of three methods of composite fiber placement along with silorane-based composite resins on cuspal deflection of root-filled maxillary premolars. Methods and Materials. MOD cavities were prepared in 60 sound extracted human premolars subsequent to root canal therapy. The remaining buccal and lingual cusp thicknesses at height of contour were 2.50.2 mm and the gingival cavosurface margin was 1.5 mm coronal to CEJ. The teeth were randomly divided into 4 equal groups. In the no-fiber group, the cavities were only filled with Filtek Silorane. In the other three groups, composite impregnated glass fibers were placed at gingival, middle and occlusal thirds, respectively, and the cavities were restored similar to the no-fiber group. Inter-cuspal distances were measured and recorded before and 180 seconds after restoration using a stereomicroscope and the differences were calculated as cuspal deflection. In addition, fracture resistance of the samples was measured in Newton at a strain rate of 0.5 mm/min subsequent to thermocycling. Results. The highest cuspal deflection was recorded in the no-fiber group and the difference from other groups was statistically significant (P<0.001). The mean differences in cuspal deflection between the fiber groups were not statistically significant (P>0.05). The highest fracture resistance was recorded in the occlusal fiber group (P<0.001). Conclusion. In restoring root-filled premolars with silorane-based composite resins, cuspal deflection was not eliminated; however, cuspal deflection decreased with the use of glass fibers.