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

1. 冲击试验材料为下第一磨牙瓷牙和树脂牙。冲击试验采用跌落冲击装置进行。测量了坠落物体的加速度。铝制冲击器重量为0.24N，从15.0 cm的高度向下落在钢台上试样的中趾尖上。树脂牙的吸收能量明显大于瓷牙。义齿动态粘弹性性能采用粘弹性谱仪比较义齿后牙模型和义齿基托树脂模型的动态粘弹性性能。瓷牙和树脂牙分别安装在义齿基托树脂上。测量了压缩动态刚度和相位差。试件的刚度与频率无关。在相同条件下，瓷试件的刚度高于树脂试件。试样的相位滞后与频率有关。在相同条件下，瓷样的相位滞后小于树脂样。本研究表明，丙烯酸树脂牙比瓷牙具有更强的韧性和更强的减震能力，而无论是分离牙还是假牙，瓷牙都比丙烯酸树脂牙更脆。

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.