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': 'An 8-year old child with normal tooth calcification and eruption has primary mandibular second molar extracted. The resulted space should be: \nSelect and explain. \nA. Maintained until the premolar root is 2/3 developed, B. Closed slightly to accommodate the smaller premolar, C. Ignored, because the second premolar will erupt in a short time, D. Left untreated, because the difference in size between the primary molar and the premolar will compensate for any drifting that might occur', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Need for Space Maintenance in Different Regions\nFirst primary molar area: Space maintainers should always be placed whenever a primary molar is lost prematurely as a general rule. The potential for space loss when first primary molar is lost, depends on the different stages of eruption of first permanent molar teeth.\nSecond\xa0 primary\xa0 molar\xa0 area:\xa0 The\xa0 potential\xa0 for\xa0 space\xa0 loss\xa0 is\xa0 even greater when the second primary molars are lost prematurely because they normally serve as a buttress for permanent molar eruption.\nAnterior\xa0 segment—primary\xa0 canine\xa0 area:\xa0 Early\xa0 loss\xa0 of\xa0 deciduous canine\xa0 is\xa0 more\xa0 common\xa0 due\xa0 to\xa0 erupting\xa0 lateral\xa0 incisors\xa0 rather\xa0 than caries.\xa0Occasionally,\xa0 roots\xa0 of\xa0 deciduous\xa0 canines\xa0 are\xa0 resorbed\xa0 and tooth\xa0 will\xa0 be\xa0 lost.\xa0 Early\xa0 loss\xa0 of\xa0 a\xa0 primary\xa0 cuspid\xa0 may\xa0 result\xa0 in\xa0 a closure\xa0 of\xa0 space\xa0 by\xa0 mesial\xa0 movement\xa0 of\xa0 the\xa0 posterior\xa0 teeth\xa0 or\xa0 by lingual\xa0 displacement\xa0 of\xa0 the\xa0 anterior\xa0 incisors\xa0 or\xa0 eruption\xa0 of\xa0 the permanent lateral into the space intended for the permanent cuspid.\nAn 8-year old child with normal tooth calciﬁcation and eruption has primary\xa0mandibular second molar extracted.\xa0 The resulted space should be maintained until the premolar root is 2/3 developed.\nReference: Pediatric Dentistry Principles and Practice SECOND EDITION, MS Muthu; pdf no 1001', 'role': 'assistant'}]