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': 'Who gave the concept of well adapted crown? \nSelect and explain. \nA. Winkler, B. Spedding, C. Webber, D. Wilkinson', 'role': 'user'}, {'content': 'Answer: B \nExplanation: - The smallest crown that completely covers the preparation should be chosen.\n- Spedding has advocated adhering to two important principles that will help consistently to produce well-adapted stainless steel crowns.\na. The operator must establish the correct occluso-gingival crown length; and\nb. The crown margins should be shaped circumferentially to follow the natural contours of the tooth’s marginal gingivae.', 'role': 'assistant'}]