According to the eighth European Workshop of Periodontology (EFP), evaluation of the effectiveness of different peri-implantitis therapies should be based on a composite outcome of disease resolution, including resolutions of mucosal inflammation, reductions in probing pocket depths, and no further bone loss [3].

The current retrospective clinical investigation evaluated treatment outcomes following combined surgical therapy for peri-implantitis at formerly grafted and non-grafted implant sites. A composite outcome of disease resolution as the absence of BOP and PD ≥ 6 mm was considered. Accordingly, peri-implantitis resolution was achieved in 33% of the treated implants, corresponding to 28% of the patients. Although no significant difference regarding grafting of the implant site was detected at the patient level (grafted sites 4/10 (40%), non-grafted sites 7/29 (24.1%), p = 0.579), implant-level analysis pointed to a higher disease resolution at the grafted implant sites (9/16 (56%) at grafted sites, 10/41 (25%) at non-grafted sites, p = 0.048).

The disease resolution noted in the present analysis is in line with the data reported in previous clinical studies. In particular, the treatment success (defined as absence of BOP) following combined surgical therapy was obtained in 60% (9/15) of the patients in the 7 years of clinical investigation [16]. Additionally, according to the results of the studies reporting on the composite treatment outcomes following surgical regenerative peri-implantitis therapy, treatment success was achieved in 35% (9/26) (treatment success defined as PD < 5 mm, absence of BOP/suppuration, no further bone loss) [17] to 51.1% (23/45) of the implants (treatment success defined as evidence of ≥ 25% bone fill, PD < 5 mm, BOP score ≤ 1) at 5 and 7 years of follow-up, respectively [18]. However, in this context, it should be realized that these studies used different criteria to define treatment success; hence, clinical outcomes cannot be compared directly.

In the present study, mean BOP reduction ranged from 60.64 to 77.45% at the patient level and from 54.88 to 74.96% at the implant level, with no significant difference between the grafted and non-grafted implants sites. Slightly higher mean BOP reduction values, ranging from 75.5 to 90%, were indicated in the long-term (7 years) clinical investigations following regenerative surgical therapy of peri-implantitis [16, 17]. It is interesting to note that BOP reduction was found to be significantly influenced by the implant-surface characteristics [17]. This observation is in agreement with the data presented in a 3-year randomized controlled clinical trial, where superior treatment outcomes were noted for implants with non-modified surface implants compared to modified surfaces [11].