Effect Of Various Types, Placement Techniques and Aging of Composite Resin on The Fracture Resistance of Upper Premolars

Aim: to assess the influence of multiple composite resin types, application methods, and aging on the fracture resistance of premolars with Mesio-occlusal-distal (MOD) cavities.Materials and methods: Forty sound upper premolars with standardized MOD cavities, were randomly distributed into two main groups (n=20) according to the type of resin composite. Then, each group of them was distributed into two subgroups (n=10) according to the application methods. Each subgroup was further distributed into two divisions (n=5) according to the effect of aging.G-premio adhesive system was applied in accordance with the guidelines provided by the supplier. Restorations were grouped: Group 1 (Incremental G-aenial posterior), Group 2 (Bulk-fill EverX posterior), Group 3 (Incremental G-aenial Injectable), and Group 4 (Bulk-fill EverX flow).Half the number of each of the 4 groups (n=20) was randomly chosen and underwent 5000 cycles of thermocycling (between 5 and 55 °C). The specimens were affixed to a 5 kN load cell on an Instron 3345 computer-controlled material testing apparatus.Results: Group 4 gave the greatest fracture resistance value in the aged groups and Group 2 gave the greatest fracture resistance value in the non-aged groups. While Group 1 gave the least value of fracture resistance in the aged groups.Conclusions: The bulk-fill short fiber reinforced composites, used as restoration of premolars with MOD cavities, could have a significant reinforcing effect on the treated teeth more than the incremental conventional technique.