[Axial compressive strength of amalgam fillings in correlation with cavity preparation]

Different types of cavities were prepared in 96 model teeth: simple preparations without ledges and with Amalgapins, slots or a post; proximal box preparations with an occlusal ledge, and box preparations with or without Amalgapins or slots. The amalgam fillings were subjected to axial load by means of a Zwick machine until the filling or the tooth fractured.

--Occlusal ledges and box preparations allow high load values. --Surprisingly high loads can be placed on simple preparations without ledges but with a post. --Preparations without ledges but with Amalgapins or slots rate lowest. --In box preparations and preparations with ledges, Amalgapins or slots fail to offer any significant increase in compressive strength.