Study of criteria of denture tooth selection Evaluation of mechanical properties of denture teeth by a dynamic viscoelastic test and an impact test.

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1. An impact testThe materials were lower first molar porcelain and resin teeth. The impact test was performed with a drop impact apparatus. The acceleration of a falling impactor was measured. The aluminium impactor was 0.24N in weight and was dropped downwards onto the mesialbuccal cusp of the specimen on a steel table from a height of 15.0 cm.The absorbed energy of the resin teeth was significantly more than that of the porcelain teeth.2.Dynamic viscoelastic properties of denture teethThe purpose of this investigation was to compare dynamic viscoelastic properties of models composed of posterior denture teeth and denture base resin using a viscoelastic spectrometer. The specimens were porcelain and resin teeth mounted in denture base resin. Compressive dynamic stiffness and phase differences were measured. The stiffness of the specimens was independent of the frequency. The stiffness of the porcelain specimens was higher than that of the resin specimens measured under the same conditions. The phase lag of the specimens was dependent on the frequency. The phase lag of the porcelain specimens was lower than that of the resin specimens measured under the same conditions. This study showed taht the acrylic resin teeth had greater toughness and higher shock-absorbing ability than the porcelain teeth and that the porcelain teeth were more brittle than the acrylic resin teeth whether the teeth were isolated or in dentures.