Residual periodontal pockets are a risk indicator for peri-implantitis in patients treated for periodontitis

Objectives: The aim of this retrospective study was to compare the clinical outcomes of implant treatment in periodontally compromised and periodontally healthy patients (PHP), with a minimum follow-up period of 5 years.

Methods: Thirty treated periodontally compromised patients (PCP) and 30 PHP, with a total of 117 Straumann implants (PCP = 56, PHP = 61) were matched for age, gender, smoking and implant characteristics. The PCP group was further stratified with patients having at least one periodontal pocket ≥6 mm at follow-up examination allocated to a "residual periodontitis" (RP) group, while the remaining patients were assigned to a "no residual periodontitis" (NRP) group. These groups were compared with respect to probing pocket depth (PPD), bleeding on probing (BOP) and marginal bone loss.

Results: The mean follow-up period in the PCP and PHP groups was 7.99 years (range 5.04-14.40) and 8.20 years (range 5.00-13.46) respectively. There was no difference in mean PPD between the PCP and PHP groups, but the prevalence of implants with PPD ≥5 mm + BOP was greater in the PCP group than in the PHP group, at both implant- (27% vs. 13%) and patient- (37% vs. 17%) level analyses. Mean implant PPD was significantly greater in the RP group (3.18 mm) than in both the NRP (2.67 mm) and PHP (2.81 mm) groups. Mean bone loss was also significantly greater in the RP group (0.68 mm) than in the NRP (0.23 mm) and PHP groups (0.26 mm). The prevalence of bone loss and PPD ≥5 mm + BOP at the implant level was significantly greater for the RP group compared with both the NRP and PHP groups.

Conclusions: Implants in PCP with residual pocketing at follow-up had increased PPD and bone loss compared with implants placed in PHP and PCP without residual pocketing. Hence, it is the maintenance of periodontal health rather than a previous history of periodontitis that is the critical determinant of increased risk of peri-implantitis, highlighting the importance of effective periodontal therapy and maintenance in patients with a history of periodontitis.