An experimental comparison of vertical tooth movement of 33 degrees and 0 degree teeth after denture processing procedures.

Movement of teeth during denture processing is an unsolved problem. This study investigates the amount of vertical tooth movement during controlled processing of acrylic, using 33 degrees and 0 degree teeth invested in specific mixes of plaster of Paris or dental stone. Forty sample set-ups each containing four posterior teeth were processed under strictly controlled laboratory conditions. Twenty of these samples carried 33 degrees teeth and the other twenty carried 0 degree teeth. Each group of twenty samples was randomly divided on a factorial design into batches of ten for investment in plaster of Paris or stone. The vertical movements were measured with a greater degree of accuracy than is required for clinical application. All results were analysed statistically. Significantly greater movement occurred with teeth invested in stone than those invested in plaster of Paris. Whereas, for teeth invested in stone, significantly greater movement occurred with 33 degrees than with 0 degree teeth, no such effect was found with teeth invested in plaster of Paris.