“…Second, due to the retrospective design of some studies the classification of the patients with respect to their experience of periodontal disease could be based only on preoperative radiographic data describing the amount of bone support at remaining teeth, since clinical data regarding the periodontal conditions at time for implant therapy or at subsequent follow-ups are not retrievable. [44][45][46] Third, there are no RCTs in the analysis, and potential biases are likely to be greater for non-randomized studies compared with RCTs.…”