Polymerization-induced shrinkage of dual cements through different thicknesses of ceramic materials

Resumen

Dual resin based cements used for indirect aesthetic restorations sustain shrinkage due to polymerization, which can increase as the ceramic restoration thickness increases. This shrinkage generates contraction efforts which induce  problems in the  inner phase located between the tooth and restoration. The objective of this study was to determine the influence exerted by the thickness of the ceramic restoration in the polymerization shrinkage of three dual luting cements. 1mm, 1.5 mm and 2 mm thick IPS Empress ®  ceramic disks were manufactured . Polymerization shrinkage of cements Variolink II (Ivoclar, Vivadent, Liechtenstein), Maxcem (  Kerr, Orange, USA) and Duolink (Bisco, Schaumburg, USA) was assessed using the Watts and Cash method. For each cement, 10 control determinations were performed  impacting the  light without  using a ceramic disk; 10 impacting the light through a 1 mm ceramic disk, 10  through a 1.5 ceramic disk and 10 through a  2 mm ceramic disk.  Results were analyzed with ANOVA. Statistically significant differences were found among the three cements in the control group when compared to experimental cements. Variolink II was the cement exhibiting lesser shrinkage percentage in all groups. Thickness of restorations  significantly influenced polymerization shrinkage. This fact must be well taken into account by the clinical operator when dealing with dental preparations.