An evaluation of the fracture resistance of class 2 amalgam restorations with different cavity designs on maxillary premolars

Aims and Objectives: The aim of this work was to compare the fracture resistance values of "Mesio-occlusal" preparation, "slot" preparation with "conventional grooves," "box-only," and "MOD" preparation. Materials and Methods: A total of 60, noncarious extracted maxillary premolars were selected and divided into four groups, consisting of 15 teeth each -- group A: "Mesio-occlusal" preparation, group B: "slot" preparation (conventional grooves), group C: "box-only" preparation (long grooves), group D: "MOD" cavity preparation. All the specimens were subjected to compressive axial load in triaxial testing machine at a cross head speed of 1.2 mm/min at an inclination of 13.5°. Results: Group A ("Mesio-occlusal") preparation had the least fracture resistance value and group D ("MOD") cavity preparation had the highest fracture resistance. There was a significant difference in fracture load found between groups B and C. Conclusion: Amalgam restorations with "Mesio-occlusal" preparations had the least fracture resistance. Amalgam restorations with "slot" preparations had better fracture resistance than "box-only" preparation. Amalgam restorations with "MOD" preparations had the highest fracture resistance.