The prospective study was to determine how the crown-implant length ratio(CA ratio affected the dental crest bone loss and the dental implant success rate after 6 years follow up in fibula bone flap combined with dental implants in cross midline of mandible ablated surgical cases. Total 14 cases with cross midline of mandible tumor accepted ablated surgery reconstructed by fibula bone flap combined with dental implants for oral functional rehabilitation from 1995 to 2010. Group A with 7 patients got the fibula bone graft reconstruction with immediate dental implants placement. Group B with 7 patients got the fibula bone graft reconstruction combine the vertical distraction treatment for 6 months then accepted dental implants placement. After the radiograph study, there is no difference of bone resorption between Group A and Group B. The CVI ratio and different treatment procedure showed that did not affect the dental implant success and crest bone loss in our study.