DIEDRICHS, G.*, KIEL , V., SVOBODA, R. (Dept. of Prosthetic Dentistry, Heinrich- : Heine-University Düsseldorf, Germany)
Fixed long-term provisional restorations which are invaluable for periodontal prosthesis and/or full mouth rehabilitations require increased strength to resist occlusal forces thus avoiding the constant need of repairing.
During the recent years several investigators stressed the inadequate fracture resistance of provisional resin materials or suggested additional reinforcement by carbon fibres or metal frameworks. In a previous study in which we investigated three different resins a light cured urethan dimetacrylat resin (Triad VLC) showed significantly higher fracture strength than a heat-cured acrylic resin and an automixed two component material based on multifunctional methacrylic esters. In this study it was of interest whether the fracture strength of provisional posterior bridges could still be improved by using a non-precious alloy metal framework which transgressed the pontic and was integrated in the anchor crowns. 46 provisional bridges (23 with and 23 without metal framework) were made from the same batch of the Triad VLC material using the indirect laboratory technique. To relate to the clinical situation form and dimension of the bridges were kept constant, they were stored in water of 37° C for 3 months and 24 bridges underwent additional thermocycling. The fracture strength was tested using a Zwick tensile testing machine with a crosshead speed of 1mm/min. The results were proved for significant differences by using an analysis of variance. While after water storage a higher fracture resistance of 420.92 N could be stated for the reinforced bridges there was no significant difference after additional thermocycling (381.79 N with and 360.68 N without metal reinforcement).
The results indicate that Triad VLC provisional resin can be successfully used for long-term short- span temporary bridges without additional fabrication techniques.