藻酸盐印模材料的形变恢复率与材料的_______等因素相关。
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应力集中在很大程度上提高了()，降低了金属的塑性。
A. 变形抗力
B. 弹性
C. 硬度
Prolonged contact between all irreversible hydrocolloid impression material and gypsum should be avoided because()
A. the gypsum will show large cracks
B. a soft，chalky surface call form. on the gypsum
C. discoloration ofthe gypmlm will occur
D. the inclusion ofpowder in a hydrocolloid impression material
Alginate impressions should be poured()
A. Within 10 minutes
B. Within 1 hour
C. Within 24 hours
D. As soon as possible
加成型硅橡胶印模材料制造商特别指出，应取印模后1小时才能灌制高强度人造石模型。环氧树脂模型比较理想，因此灌制被推迟1小时。在分离时，模型上有小凹陷。造成这一问题的原因是什么？如何避免？
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