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': 'In case of cast restoration, if the contact is open what should be done to prevent the complications? \nSelect and explain. \nA. A new casting should be done, B. A new contact area must be soldered to the casting, C. The cavity preparation should be refined further, D. Leave it as it is, no complications occur', 'role': 'user'}, {'content': 'Answer: B \nExplanation: If the contact is open (short of touching the adjacent tooth), a new contact area must be soldered to the casting. An open\xa0contact is best detected by visual inspection with the aid of the mouth mirror. The region must be isolated with cotton rolls and dried with the air syringe. Selection of the proper horizontal viewing angle usually discloses the spaces between teeth. Such an open contact permits the passage of food, which affects and irritates the interproximal gingiva.\nSturdevant operative dentistry\xa0 7th E D I T I O N, Page No:e147', 'role': 'assistant'}]