What technique of polymerization is shown in the graph?

A concept that may be used to reduce shrinkage stress is the use of “soft-start” polymerization. This approach utilizes a number of procedures to prolong the gel phase of the setting reaction of the composite resin material. The theory is that the longer the setting composite can maintain a gel or flowable condition, the better it can distribute the stresses resulting from shrinking. Procedures to do this include the use of ramped lights, pulse curing, or simply holding the curing light some distance from the material for the initial exposure.