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': 'Least rigid maxillary major connector is: \nSelect and explain. \nA. Complete palate, B. Single palatal strap, C. Double palatal bar, D. U-shaped', 'role': 'user'}, {'content': "Answer: D \nExplanation: U -Shaped Palatal Connector:\nFrom both the patient's standpoint and a mechanical standpoint, the U-shaped palatal connector is\xa0 the least desirable of maxillary major connectors. It should never be used arbitrarily. When a large\xa0 inoperable palatal torus exists and occasionally when several anterior teeth are to be replaced, the U-\xa0 shaped palatal connector may have to be used. In most instances, however, other designs will serve\xa0 more eﬀectively. The following are the principal objections to the use of the U-shaped connector:\n\nIts lack of rigidity (compared with other designs) can allow lateral ﬂexure under occlusal forces,\xa0 which may induce torque or direct lateral force to abutment teeth.\nThe design fails to provide good support characteristics and may permit impingement of\xa0 underlying tissue when subjected to occlusal loading.\nBulk to enhance rigidity results in increased thickness in areas that are a hindrance to the tongue.", 'role': 'assistant'}]