PVC-Matrix Impression Product and Thickness Effects on Underlying Composite Cure

Objectives: Polyvinylsiloxane (PVS) impression materials are used to create intraoral replications of wax-up forms whereby underlying composite is directly photocured through the matrix. This research examined effects of PVS products and thicknesses on monomer conversion (MC) of an underlying flowable composite throughout a simulated clinical scenario.
Methods: Thicknesses (1, 2, 3, 4, 5mm) of 10mm-diameter PVS matrix products (Memosil 2 (Kulzer), Registrado (VOCO), EXACLEAR (GC)) were made between glass slides. Clear impression tray was simulated using 2-mm thick thermoplastic suck-down material. A 5-mm diameter, 2-mm cylinder of composite (A2, G-ænial, GC) was centered over the diamond of an attenuated total reflectance accessory and covered with a Mylar strip. The glass-contained PVS sandwich was placed overtop, followed by the tray material. A multiwave LED curing light (VALO GRAND, Ultradent) photocured through the assemblies. Mid-infrared spectra (Invenio-R, Bruker) were continuously collected every 0.4s for 5min. Sequences of 10-s exposures were given: through the entire assembly, through only the PVS, through only 2 clear glass slides: 20s between exposures. Bottom resin surface MC was determined after 5 min. MC values were normalized to that of 20-s direct exposure values through glass slides after 5min. Effects of materials and thickness were analyzed using a 2-factor ANOVA and Tukey post-hoc tests. N=5, pre-set alpha=0.05.
Results: PVC Material, thickness, and their interaction significantly affected the results (p<0.001) The table presents mean percentages of direct resin cure for each. MC tended to decrease with thickness. After 5min, there was very little difference in MC relative to the direct resin cure.
Conclusions: Although significant differences were found among materials and thicknesses, the differences were thought not to be clinically relevant. Clinicians need not be concerned about the effect of PVS material type or its thickness to adequately polymerize a 2-mm thick composite increment using the matrix-replication technique.