| The conversion degree of composite resins after curing directly affects their biological, chemical, physical and mechanical performances. At present in application and development of composite materials, it is an imperative matter to get rid of all unfavourable factors which hinder the curing of composites, thus promoting their conversion degree to the best extent. In this investigation, the polymerization paterns of chemically-cured and visible-light-cured composites and the influences of various factors on their polymerization degree were comprehensively examined. Also, the relationships between conversion degree of composites and many indirect parameters were inspected. The main results read as follows.1. Different brand of commercially available dental composite resin showed different polymerization degree, owing to their differences in formulation and catalyzing mode. Their conversion degree of donble bonds ranged from 45% to 75%. The conversion degree of visible—light-cured resins was higher than that of chemically cured ones.2. In the initial stage of polymerization reaction of composites, conversion degree of donble bonds increased slowly. Then it increased high—speedly, followed by another slowly increasing phase. After 24 hours, the conversion degree became stable, not changing significantly with the prolonging of time.3. After activating light source being removed, polymerization reaction of visible—light-cured composites continued in progress. Within 1 hour after irradiation, conversion degree on the top of specimens increased significantly, whereas the increasing of conversion degree at the bottom of specimens lasted until 24 hours after irradiation. Conversion degree at the bottom increased to a greater extent than on the top.4. With increasing content of diluent in monomer mixtures, conversion degree of double bonds of resins rose, a significantly positive correlation appearing between both of them. Whthin a certain extent of concentration, diluent content positively...
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