Custom impression trays. Part III: A stress distribution model.
All resins used to make custom impression trays exhibit plastic deformation at some force value; therefore it is important to compare the physical property values of such materials with the stresses to which impression trays are subjected during dental procedures. A simple mathematical model of a custom tray was developed to predict stress distributions in this final part of a three-part investigation. Experimental stress analysis of such a tray confirmed the accuracy of the model, which was then used to predict the maximum stress experienced by the tray during removal of a completed impression from the oral cavity. The results of this analysis indicated that these stresses would be significantly lower than the yield stress for a commonly used polymethyl methacrylate resin or a light-polymerized resin. The stresses were also sufficiently low for us to conclude that thermoplastic resins would not permanently deform; however, the stresses encountered in the experimental confirmation procedure were close to the yield stress values for these materials.
Moseley
J P
JP
Department of Restorative Dentistry, School of Dentistry, University of Alabama, Birmingham.
Dixon
D L
DL
Breeding
L C
LC
D003760:Dental Impression Materials; D003761:Dental Impression Technique / Q000295:instrumentation*; D003799:Dental Stress Analysis; D006801:Humans; D016018:Least-Squares Analysis; D008422:Materials Testing; D013718:Tensile Strength
D003760:Dental Impression Materials