Bone Cement
Polymerization
When the polymer powder and monomer liquid meet, the polymerization process starts. During polymerization of the monomer, the original polymer beads of the powder are bonded into a dough-like mass. The mass hardens approximately 7-15 minutes after the start of mixing, depending on temperature.
The polymerisation process can be divided into four different phases: mixing, waiting, application and setting.
Mixing phase:
In the mixing phase, the cement should be mixed homogeneously, minimising the number or pores. Vacuum mixing has been shown to reduce the cement’s porosity and increase its mechanical strength. 2,3
Waiting phase:
During this phase, the cements achieve a suitable viscosity for delivery of bone cement. The cement is still a sticky dough.
Working phase:
The working phase is the period during which the cement and the implant can be introduced with ease. The cement must not be sticky, and its viscosity should be suitable for application. If viscosity is too low, the cement may not be able to withstand the bleeding pressure and prevent blood from entering the cement.
Hardening phase:
During this phase, the cement hardens and sets completely. Hardening is influenced by the cement temperature, the OR temperature as well as the body temperature.4
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