It has been recognized for a long time that the longer the implant, the better the success rate, and this idea is no longer valid since the advent of short implants, which currently represent reliable solutions that respond favourably to some situations like low bone height, thus offering a good alternative to more invasive bone augmentation surgeries and often not accepted by patients. The aim of our systematic review is to answer the following question: Why the principle of ratio crown / implant identical to that of the dental organ seems today somewhat out-dated? We meant to provide an electronic search on Pubmed using the Mesh Key words: Crown to implant ratio AND Marginal Bone Loss. We included only the Randomised controlled trials to have the best evidence level, we selected only publications in English and limited the date between 26/08/2007 and the 22/08/2017 (last 10 years) to assess the latest findings in this area. The screening and abstraction of the results were achieved by two independent reviewers. After a synthesis, we concluded that there is no cause/effect relationship between the crown / implant ratios and the increase in marginal bone loss, however caution is required in cases of available coronal height> 15mm or in the case of cantilevering.