Cure Mode on Biaxial Properties of Resin Cements  

Objective: To determine the effect of curing mode on 1-hour biaxial modulus and strength values of commercial and experimental dual-cured resin cements.  Method: Paste components of four commercial, dual-cured resin cements (RELY X UNICEM2, RELY X ARC, and RELY X ULTIMATE (3M/ESPE); Panavia F2.0 (Kuraray)) were dispensed and mixed according to manufacturers instructions and placed into Teflon molds (6.5 X 0.5 mm). The material was immediately light-cured (S10, 3M ESPE) or allowed to self-cure. Specimens were isothermally conditioned at 35°C for 1 hour immediately after placement into mold: the in-vivo temperature of freshly prepared tooth structure. Cured specimens were retrieved, trimmed of flash, and tested. Ten disc-shaped specimens from each test group were placed into a biaxial-flexure jig and a vertical load was applied (1.27 mm/min) on a universal testing machine (model 5844, Instron Corp., Norwood, MA) until specimen fracture. Software calculated biaxial flexural strength and modulus from the recorded data. Statistical analysis consisted of a 2-way ANOVA and Tukey's post-hoc test at 0.05 pre-set alpha among products and cure modes within each test parameter.  Result: ANOVA for modulus indicated significant effects of product and cure mode (p<0.001), but not their interaction (p=0.212). ANOVA for strength revealed significant effect of product and cure more with significant interaction ((p<0.001). Table provides mean (sd) values.  Within parameter column (cure mode) values with similar letters are not significantly different.

All material properties significantly increased when light-cured, except strength of Panavia F2.0 (p=0.961).  Flexural modulus of Panavia F2.0 was significantly greater than all others, regardless of cure mode. RELY X ARC strength was greatest in either cure mode.

Conclusion: Providing direct light curing of resin cements significantly improved flexural modulus and strength for most products, while strength of one product remained unchanged.