Despite minimal invasive orientation in restorative dentistry, in Romania the necessary for extensive restorative treatment in posterior teeth is still high. The silver amalgam still remains a social treatment option for such situation. The purpose of this study was to analyze the efficiency of a new method for analytical determination of the volume of restoration in posterior teeth, knowing that the risk for coronal fracture depends on the size of restoration. The study correlated the results obtained through this method with the real values (mathematically determined) of restorations and the anatomical crowns volumes in order to assess the risk fracture. Amalgam restorations of different types and sizes were placed in 24 extracted premolars and molars. A good global correlation was observed between the true and calculated value (98.321%). The best correlation was observed for MOD restorations (93.042%) while the worst coefficient was obtained for MO restorations (83.378%). The medium restorations presented o correlation of 99.288% and the extensive restorations had an index around 96.957%. This method is based on physics principles and objective measurement resulting in a good correlation with the real dimensions of cavities. Therefore it could be used to assess the risk of crown fracture in teeth with amalgam restorations.