Study design and participants
For this retrospective analysis, standardized clinical record forms of a total of 39 partially/fully edentulous patients (25 female and 12 male) exhibiting 57 implants were screened. All patients had attended the Department of Oral Surgery, Heinrich Heine University, Düsseldorf, Germany for the treatment of peri-implantitis between 2007 and 2010, and were under regular implant maintenance care. The mean follow-up time was 41.9 ± 34.75 months (range 6 to 126 months). Some patients were also participating in a randomized prospective clinical study, which aimed at investigating the effects of two surface decontamination methods on the clinical outcomes following combined therapy [14].
A data extraction template was generated and used for the anonymous acquisition of demographic study variables/implant site characteristics and baseline as well as follow-up clinical measurements after surgical therapy. The study was in accordance with the Helsinki Declaration, as revised in 2013 and approved by the local ethics committee.
Patient selection
For patient selection, the following inclusion criteria were defined:
-
(1)
Partially or fully edentulous patients rehabilitated with fixed or removable implant-supported prostheses;
-
(2)
Presence of at least one screw-type (one or two part) titanium implant diagnosed with peri-implantitis;
-
(3)
Respective implants had received a combined surgical peri-implantitis treatment;
-
(4)
No implant mobility;
-
(5)
Presence of at least 2 mm of keratinized mucosa;
-
(6)
Treated chronic periodontitis and proper periodontal maintenance care;
-
(7)
A good level of oral hygiene as evidenced by a plaque index (PI) at the implant level < 1;
-
(8)
No systemic diseases which could influence the outcome of the therapy (i.e., diabetes (HbA1c < 7), osteoporosis, antiresorptive therapy);
-
(9)
No history of malignancy, radiotherapy, chemotherapy, or immunodeficiency within the last 4 years and;
-
(10)
Non-smoker or light smoking habits (< 10 cigarettes per day);
-
(11)
Complied with at least 6 months of follow-up;
-
(12)
Information on the initial bone grafting procedure and protocol at the respective implant site was available.
Patients whose data files lacked information on the bone grafting procedures at the implant site or lacked information on augmentation protocols (i.e., lateral ridge augmentation or sinus floor elevation; one- or two-stage approach), and patients who did not comply with at least 6 months of follow-up were not included in the analysis.
Case definition
Peri-implantitis was defined as bleeding on probing (BOP) with or without suppuration (Supp) in addition to changes in the radiographic bone level. Interproximal bone level changes were estimated on intraoral radiographs. In the absence of available baseline radiographs taken at prosthesis installation, “a threshold vertical distance of 2 mm from the expected marginal bone level” was used to assess bone loss [3].
Initial grafting procedures
The identified patients with a history of grafting had received the following treatment protocols:
Lateral ridge augmentation
-
Simultaneous grafting (one stage) of dehiscence-type defects, employing a particulated bone substitute, and collagen membrane (2 patients; 3 implants)
-
Grafting and staged implant placement at 6 months (two stage) employing a particulated bone substitute and collagen membrane (3 patients; 3 implants)
Sinus floor elevation
-
External grafting (lateral window) employing a particulated bone substitute and collagen membrane and implant placement (2 patients; 3 implants)
-
External grafting (lateral window) employing a particulated bone substitute and collagen membrane and staged implant placement at 6 months (4 patients; 7 implants)
To be included, the radiographic bone loss at baseline (i.e., prior to treatment) in respective patients had to extend to the formerly grafted area.
Treatment procedures
After an initial course of non-surgical therapy, each subject had received a combined (i.e., implantoplasty + augmentative therapy) surgical treatment procedure [14] at respective implant sites (Fig. 1). This procedure included open flap debridement and a meticulous granulation tissue removal using conventional plastic curets (Straumann Dental Implant System; Institut Straumann AG, Basel, Switzerland) and an implantoplasty at both buccally (i.e., Classes Ib and Ic) and supracrestally (i.e., class II) (Fig. 1) exposed implant surfaces. This was accomplished using diamond burs (ZR Diamonds; Gebr. Brasseler GmbH & Co. KG, Lemgo, Germany) and Arkansas stones under copious irrigation with sterile saline. The remaining unmodified implant surfaces at the respective intrabony defect areas (i.e., classes Ib, Ic, and Ie) were decontaminated using either an Er:YAG laser device (energy density of 11.4 J/cm2, 10 Hz) (elexxion delos; elexxion AG, Radolfzell, Germany) or debrided using plastic curetes and cotton pellets soaked in sterile saline (Straumann Dental Implant System). Respective intrabony defect compartments were homogeneously filled using NBM (BioOss spongiosa granules, particle size 0.25–1 mm; Geistlich, Wolhusen, Switzerland) and were covered with CM (BioGide; Geistlich). Transmucosal healing was supported by a peri- and postoperative antibiotic medication for 5 days.
Clinical examination
For all patients, the following clinical parameters were available: BOP (as measured within 60 s after probing) and PD (as measured in millimeters from the mucosal margin to the bottom of the probeable pocket). BOP and PD were assessed at six aspects around the implant: mesio-buccal, mid-buccal, disto-buccal, mesio-oral, mid-oral, and disto-oral. Maximum PD values (max PD) and mean BOP scores were evaluated before the surgical intervention and at the final follow-up.
The primary outcome variable was disease resolution (i.e., the composite outcome of the absence of BOP and probing pocket depths (PD ≥ 6 mm). Reduction of mean BOP and maximum PD values were defined as secondary outcome variables.
Data analysis
Commercially available and open source software programs (SPSS Statistics 23.0: IBM Corp., Ehningen, Germany and R Development Core Team) were used. Mean values, standard deviations (SD), medians, minimums, and maximums were calculated for mean BOP and maximum PD scores.
The analyses were performed at both patient and implant levels. Prior to this analysis, clinical parameters were pooled according to the grafting procedure (grafted or non-grafted), considering the patient as statistical unit. The differences in the baseline maximum PD values between the grafted and non-grafted implant sites were assessed using Wilcoxon rank-sum test. To evaluate disease resolution, changes in mean BOP and maximum PD between the groups (i.e., non-grafted vs. grafted) chi-square test (χ2) were applied. For the evaluation of disease resolution, if patients exhibited multiple implants with different treatment outcomes, they were assigned to a group according to the worst one. Based on the sample size calculation, for a large effect size (w = 0.5, df = 1, alpha = 0.05, power = 0.8), a minimum of 32 patients were needed [15].
The results were considered statistically significant at p < 0.05.