Low Temperature Polymerization of Acrylic Resins

DENTISTRY finally has been presented with resins which will polymerize at room and body temperatures to a hard and esthetic mass. The so-called self-curing resins are being received with open arms and not in all quarters with the reservations that some past experience might dictate. Although we do not feel that we are reactionary, we are of the opinion that some of the properties and characteristics of the resin should be considered and evaluated in terms of established requirements. The self-curing resins, if they are to find dental application for all restorations, should fulfill the requirements which have been accepted as minimum standards for material polymerized in the normal manner. In some aspects, there appears to be reasonable doubts as to whether or not these products will prove to be satisfactory for general use. Some attention in the discussion should be focused upon (a) color stability; (b) mechanical properties; (c) degree of polymerization, and (d) properties generally referred to as accuracy of reproduction and dimensional stability. Some phases of these properties will be discussed with the hope that the results may be supplemented, complemented, or refuted, and that we all may have a better appreciation of self-curing resins. In considering the polymerization reaction of self-curing resins, the three stages of the polymerization reaction have an increased importance because in this instance each stage, initiation, propagation, and termination, must be considered almost as a separate entity in order to understand and appreciate the manner in which the phenomena take place and to attempt to explain some of the observations. The initiation stage of the polymerization reaction is actually a combination of two phases. The first phase of the initiation stage is the decomposition of the peroxide to form free radicals