This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'A 40 year old male patient complains of decayed tooth. Patient gives history of cavity preparation and restoration with low copper amalgam done with 26. Intra-oral examination reveals proximal caries with 26. During electrochemical corrosion of this restoration, which of the following helps in sealing the space against microleakage?\u200b \nSelect and explain. \nA. Sn-O, B. Sn-O-Cl, C. Sn-Hg, D. Ag-Sn', 'role': 'user'}, {'content': 'Answer: A \nExplanation: During electrochemical corrosion of low-copper amalgams, the Sn-Hg phase is oxidized into Sn-O and/or\u200b Sn-O-Cl. The oxychloride species is soluble. The oxide precipitates as crystals and tends to fill up the spaces\u200b occupied by the original Sn-Hg phase. Along the margins of the amalgam, Sn-O helps seal the space against\u200b microleakage.\u200b\nReference: Sturdevant’s Art and Science of Operative Dentistry, Mosby, 4th Edition, Page No: 155\u200b', 'role': 'assistant'}]