Kinetics of polymerization and contraction stress development in self-adhesive resin cements.

OBJECTIVES: The aim of the study was to evaluate the contraction stress, microhardness and polymerization kinetics of three self-adhesive cements vs. conventional dual-cure resin cement. METHODS: Cements tested were: RelyX Unicem (3M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Clearfil SA Cement (Kuraray, Tokyo, Japan) and Duolink (Bisco Inc., Schaumburg, IL, USA). Cements were irradiated with a LED-curing unit (bluephase, IvoclarVivadent) for 20 or 40 s and the contraction forces (N) generated during polymerization were continuously recorded for 6 h with a universal testing machine. Polymerization kinetics were monitored using micro-Raman spectroscopy and degree of conversion was calculated. Vickers microhardness was also recorded. All measurements were performed at 10 min and 6h. Data were statistically analyzed by three-way ANOVA with repeated measures and Tukey's post hoc test (?=0.05). RESULTS: Irrespective of exposure time, stress analysis ranked in the following order: Clearfil SA Cement