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Characterization of Polydimethacrylates and Their Composites by Dynamic Mechanical Analysis

Dental Research Center and Department of Operative Dentistry, University of North Carolina, Chapel Hill, North Carolina 27514

D.T. Turner

Dental Research Center and Department of Operative Dentistry, University of North Carolina, Chapel Hill, North Carolina 27514

The objective was to characterize, by dynamic mechanical analysis (DMA), the polymeric materials used to restore teeth and, in particular, to assign a glass transition temperature, T _g. Generally, in DMA work, T_g is taken as the temperature at which the internal damping, i.e., tan, has a maximum value. However, in the present work it was shown that the classical method of assigning T _g corresponds more closely to an assignment based on changes in elastic modulus. On this basis, a bis-GMA copolymer and a proprietary dental composite, both polymerized by exposure to light, were assigned Tg values of -25°C and +10°C, respectively. The composite had an even lower value, T_g =-10°C, after saturation with water. The value of T_g can be increased considerably by treatments which are known to increase the degree of polymerization, i.e., by heating or by -irradiation.

The present findings imply that composites made by photopolymerization may undergo marked changes in mechanical state (becoming glassy, leathery, and rubbery) in the oral cavity, due to changes in temperature from about 0°C to 50°C. It is not known which of these states would give best service properties, such as wear resistance, but in any case variation of properties in service would appear to be undesirable.

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Journal of Dental Research, Vol. 66, No. 5, 1032-1035 (1987)
DOI: 10.1177/00220345870660050801


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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Wilson, T.W. Articles by Turner, D.T. Search for Related Content PubMed PubMed Citation Articles by Wilson, T.W. Articles by Turner, D.T. Social Bookmarking                         What's this?