患儿，10岁。两侧下颌乳磨牙早失。X线片示下颂第1前磨牙根形成2/3,下颌第2前磨牙根形成1/3。设计适合的间隙保持器是

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SQL Error: select id,body,options from ***_enewstiku where sourceid='29938' and id < 2427740 and id<>'2427740' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='29938' and id > 2427740 and id<>'2427740' order by id asc limit 5