The Influence of Pressing Methods on the Change of Vertical Dimension of Occlusion in Full Dentures.

The objective of this study was to evaluate the alteration of the vertical dimension of occlusion (VDO) of full dentures when different pressing methods are used during the laboratory procedure.Sixty specimens were divided into four groups ( = 15). In all cases, as an antagonist model, a standard assembly with cast alloy teeth was used, all the top pressed models were mounted in semiadjustable articulator through a metal reassembly plate. The vertical distance evaluation was performed by vertical measurement, using a digital caliper. The groups were divided as follows: group 1 (the muffle was not opened, and the space propitiator was not used), group 2 (the muffle was opened and the space propitiator was not used), group 3 (the muffle was not opened and the space propitiator was used), and group 4 (the muffle was opened and the space propitiator was used). In the four groups inclusions were carried out with zero expansion gypsum, 1000 kgf press, Vipi STG muffle and Vipi thermopolymerizable resin. The four groups were polymerized by the microwave power system with 800 watts of power.Statistical analysis was performed using one-way analysis of variance and Tukey's test (  = 0.05).Groups 3 and 4 presented the smallest change in the vertical occlusion dimension.Given the methodology applied in this study, the space propitiator was able to act significantly in reducing the change in VDO. There are many factors related to dimensional changes in the bases of full dentures. The dimensional changes and its relationship with the movements of artificial teeth have been observed. Some studies have shown that fixing or not fixing the artificial teeth before pressing does not prevent tooth displacement during subsequent polymerization and flasking stages.The use of the space provider was effective in decreasing the vertical occlusion dimension, while the opening of the muffle for removal of the excess acrylic resin proved to be dispensable.