Abstract: Objective To explore the range of the distance between the dental implant tip and mandibular canal.Methods 15 dental implants （including soft tissue level and bone level implants） from 12 patients whose distance between the tip of dental implant and the superior border of mandibular canal was less than 2 mm were selected and the real distance was measured and after surgery the inferior alveolar nerve symptoms were recorded.Results The average distance between the tip of dental implant and the superior border of mandibular canal in 15 implants was (0.94±0.50)mm（0.24~1.52 mm） and one patient experienced numbness of the chin in one week.Conclusions Considering the possible problems such as mandible infection,inferior alveolar nerve damage,periimplantitis、Retrograde PeriImplantitis，the safe range of distance may be less than 2 mm.

Key words: implant, mandibular canal, periimplantitis, safety distance