[Working time of bone cements].

The period of applicability during polymerisation of four well introduced bone cements (Sulfix-6, CMW, Simplex, Palacos) was measured by a subjective method in function of room respectively conditioning temperature. Simultaneously temperature in the cement and mechanical admittance (transfer of oscillation of 750 Hz) were registered. The duration of working-up period and plymerisation period depends considerably from the room temperature. An increase of 10 degree C accelerates polymerisation by a factor of 1.5 to 2.0. The working time of the products differs widely. Increased room temperature means also increasing maximum polymerisation temperature. Mechanical admittance is an interesting measure for the objectivation of the working period. Discussing new ISO standards a proposal is made for more accurate determination of the end of the working-up period (set time).