DUAL CURE LUTING COMPOSITES .2. CLINICALLY RELATED PROPERTIES

Thirteen dual cure luting composites were compared in function of film thickness, consistency, and working time by using the American Nation al Standard/American Dental Association (ANS/ADA) specifications for z inc phosphate cement and direct filling resins. The effect of temperat ure and setting reaction on the film thickness was also evaluated for some representative products. All three clinically related properties varied widely among the products investigated. A strong linear correla tion was found between film thickness and consistency. This relation i s supported by the temperature dependence of film thickness of dual cu re luting composites. Cooling of the material increased the consistenc y, resulting in a larger film thickness, while heating reduced the fil m thickness because of the lower consistency. However, one product wit h a rather short working time at room temperature occasionally exhibit ed a dramatically enlarged film thickness after heating, probably caus ed by accelerated chemical polymerization. No correlation emerged betw een film thickness and maximum filler size or between consistency and filler weight content. Maximum filler size and filler weight content h ad been measured previously in Part I of this study. Scanning electron microscope (SEM) analysis of the cured film thickness samples reveale d that the largest filler particles had been crushed under the heavy l oad pressure during film thickness measurement. The lack of correlatio n between consistency and filler weight content can be explained by th e multifactorial determination of the consistency. It is concluded tha t the great diversity in the currently available luting composites mak es clear specifications with regard to the optimum composition of luti ng composites urgently needed. Furthermore, more adequate methods for testing the film thickness of luting composites are also required.