SUMMARY Crown/implant (C/I) ratio has been proven to not affect the survival of the implants; however, it is also a fact that no evidence exists with regard to the use of single short implants in the mandibular molar. The aim of this study was to determine whether the crown/implant ratios of single implant-supported fixed restorations on implants of 6–8 mm in the mandibular molar have an impact on the implant survival and marginal bone maintenance. Twelve short dental implants (6–8 mm) were installed and restored with single crowns, loaded after 3 months of healing. The restorations were divided according to crown-toimplant ratio into two groups: Group 1: C/I < 20 and Group 2: C/I ≧ 20. Alveolar bone loss was measured using CBCT scan, taken at the implant placement and after 12 months follow-up from loading. Reduced implant/crown ratio shown no statistic significant differences on implant survival and the alveolar bone level compared with recommended implant/crown ratio. Within the limitation of this study, it can be concluded that reduced C/I ratio could be used as a substitute for recommended C/I ratio in severely mandibular atrophic residual alveolar ridges. KEYWORDS: dental implants, single tooth, mandible, prostheses and implants, bone resorption, treatment outcome