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': 'Overdentures are indicated over retained roots instead of extracting them and making complete dentures because: \nSelect and explain. \nA. To preserve the alveolar bone, B. To allow proprioception from the periodontal ligament of remaining teeth, C. Carrier for patient to adjust, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Advantages of overdentures:\n\nRidge preservation\nProprioception\nSuperior patients acceptance\nOpen palate possible\nDefinitive vertical stop for denture base\nSupport, stability and retention are improved\nLess trauma to supporting tissues\nFewer post insertion problems than a conventional complete denture\nConversion to complete denture\nIncreased biting force (pacer FJ, Bowman DC. Occlusal force discrimination by denture patients. J Prosthet Dent 1975; 33: 602-9)\nPhysiological advantage.', 'role': 'assistant'}]