Comparison of fracture resistance of maxillary first premolars with class ii mesio-occluso-distal (mod) cavities restored with newer resin based composites – An ex vivo study

Introduction: The purpose of the study was to evaluate and compare the fracture resistance of everX posterior (Fibre Reinforced Composite, GC), SDR(Bulk Fill Flowable composite, DENTSPLY), Tetric® N-Ceram Bulk Fill (Ivoclar Vivadent) and Filtek™ Z350 XT (3M ESPE) on maxillary first premolars with class II Mesio- Occluso-Distal(MOD)cavities using an instron machine and to evaluate the mode of failure /fracture using stereomicroscope at 10x after staining. Method and Materials: 60 non carious human maxillary first premolars divided into 6 groups ,out of which 2 control groups of 6 teeth each and 4 experimental groups of 12 teeth each were subjected to axial compression test to evaluate the resistance to fracture using an Instron 3382(USA).Group I consisted of intact teeth (positive control), Group II consisted of prepared but un-restored teeth (negative control),Group III consisted of MOD cavities restored with Tetric® N-Ceram Bulk Fill,Group IV consisted of MOD cavities restored with Filtek™ Z350 XT,Group V consisted of MOD cavities restored with everX posterior and Group VI consisted of MOD cavity restored with SDR. After restoration the teeth were stored at 370 C for 24 hours and then thermo cycled for 500 cycles at temperatures of 50C and 550 C Results: Statistical analysis revealed that Group V showed the maximum mean load to fracture however there was no significant difference between Group I, Group III and Group VI. Group IV showed the least mean load to fracture. Mode of failure analysis showed more of Cohesive type of failure on tooth structure for Group V, whereas group III, IV and VI showed more of Mixed type of failure. Conclusion: everX posterior along with occlusal lining using a universal composite can be a material of choice for restoration of large class II cavities and exhibited more cohesive failure. Tetric® N-Ceram Bulk fill and SDR also showed good results of fracture resistance however showed more of Mixed type of failure. Filtek z350xt showed least fracture resistance and more Mixed failure