Polymerization shrinkage strain of interocclusal recording materials

Objectives. The aim of this in vitro study was to investigate the polymerization shrinkage behavior and to measure the polymerization shrinkage-strain of interocclusal recording materials. Methods. The materials investigated in this study were five polyvinylsiloxane (Imprint (TM) Bite, Silagum Automix Bite, O-Bite, Blu-Mousse (R) Classic and Exabite II), one polyether (Ramitec) and one dimethacrylatebased (Luxabite) materials. The polymerization shrinkage values of ten specimens for each material were measured by the Bonded-disk method at 1, 3, 5, 7 and 10 min after mixing at 37 C. The amount of shrinkage-strain (%) was derived and all data were statistically analyzed by one-way ANOVA and the multiple comparison Scheffe test (alpha = 0.05). Results. The representative shrinkage-strain kinetic graphs showed that all specimens shrank immediately, except Luxabite which expanded for the initial few seconds. After that, the shrinkage-strain values increased in the magnitude up to 10 min, but its rate decreased gradually with time. The shrinkage-strain values (0.18 +/- 0.03-0.16 +/- 0.03%) of O-Bite at 5, 7 and 10 min were significantly lower than the other materials, but Luxabite exhibited the highest values (3.10 +/- 0.17-3.30 + 0.16%). Significance. The interocclusal recording materials investigated presented significantly different polymerization shrinkage-strain kinetics and showed dimensional changes even after the setting time indicated by respective manufacturers. (C) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.