問題詳情

42.關於石膏結合包埋材（gypsum-bonded investment）的吸水膨脹（hygroscopic expansion），下列何者錯誤？
(A)氧化矽（silica）的顆粒愈細，吸水膨脹越大
(B)β-hemihydrate的吸水膨脹較α-hemihydrate小
(C)當調拌時間（mixing time）變短，吸水膨脹則變大
(D)老化的（存放久的）包埋材，吸水膨脹會變小

參考答案

答案：C
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用户評論

【imcy】評論

(C) 調拌時間長、調.....看完整詳...

【robertwang】評論

課本Phillips_ Science of Dental Materials 12e P203-204VARIABLES THAT AFFECT HYGROSCOPIC EXPANSION    The magnitude of the hygroscopic setting expansionof a dental investment is generally proportional to the silica content of theinvestment, other factors being equal. The finer the particle size of the silica, the greater isthe hygroscopic expansion. In general, α-hemihydrate is apt to produce a greater hygroscopicexpansion in the presence of silica than is the β-hemihydrate, particularlywhen the expansion is unrestricted.    A dental investmentshould have enough...