The retrospective analysis evaluates patients who underwent implant therapy with or without accompanying augmentation procedures between August 1991 and December 2011 in three private practices. Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines were followed. To investigate the effect of the different techniques applied on implant survival without overlapping impact of contraindications, the following exclusion criteria were applied: patients with uncontrolled diabetes mellitus, severe cardiovascular diseases (e.g. severe heart insufficiency), organ transplants, intake of bisphosphates and smoking of ≥20 cigarettes/day. Only patients with complete data regarding implantation procedure and implant survival were included. During this time period, a total of 10,165 implants were inserted either with or without augmentation. Seven implants were excluded from the evaluation because the date of implantation was not documented. Thus, 10,158 implants in 3095 consecutively treated patients were included in the retrospective analysis. Of these patients, 1693 (54.7%, 5626 implants) were female, 1401 (45.3%, 4539 implants) were male. For one patient, the sex was not documented. Mean age at the time of the implantation was 52.4 years (14.8 to 89.5). There was no difference regarding age or distribution of sex between patients with or without augmentation. On average, female patients received 3.32 and male patients 3.24 implants per patient.
Surgeries as well as pre- and postsurgical care were performed according to the standard procedures used in the three centres. Implants were inserted according to the manufacturers’ instructions. Patients were scheduled 3 months post-implantation followed by yearly control visits after the completion of the implant-supported restorative therapy.
The following graft materials were used: autogenous bone blocks, autogenous bone particles, Geistlich Bio-Oss (granules or collagen block, Geistlich Pharma AG, Wolhusen, Switzerland), Cerasorb (Curasan, Kleinostheim, Germany), Bioresorb (Implant Direct, Zurich, Switzerland), Bonitmatrix (DOT, Rostock, Germany), Biovin Bovine Bone (OT Medical, Bremen, Germany), Nanobone (Artoss, Rostock, Germany), Osteograf (Dentsply Tulsa Dental Specialities, Oklahoma, USA), Biogran (Biomet 3i, Munich, Germany), Easygraft (Degradable Solutions, Zurich, Switzerland), Endobone (Biomet 3i Deutschland GmbH, Munich, Germany), Pepgen P15 (Dentsply Tulsa Dental Specialities, Oklahoma, USA), Bioseed Oral Bone (Biotissue AG, Freiburg, Germany), Ostim (Heraeus Kulzer, Hanau, Germany), Perioglass (Novabone, Jacksonville, FL, USA) and Rebone (Schütz Dental GmbH, Rosbach, Germany). Autogenous bone was harvested during drilling and from the chin, tibial plateau, iliac crest, maxillary tuberosity and retromolar space.
The membranes applied included the native collagen membrane Geistlich Bio-Gide (Geistlich Pharma AG, Wolhusen, Switzerland) either alone or combined with one of the following membranes: Vicryl (Johnson & Johnson Medical GmbH, Norderstedt, Germany), Biovin Membran (OT Medical, Bremen, Germany), Parasorb Vlies (Resorba, Nuremberg, Germany), Gore-Tex Resolut (W.L. Gore & Associates, Flagstaff, USA), Kollagenresorb (RESORBA Medical GmbH, Nuremberg, Germany), Epi-Guide (DSM, Exton, USA), Gore Resolut Adapt Regenerative Membrane (W.L. Gore & Associates, Flagstaff, USA), Osseoguard (Biomet 3i, Munich, Germany), Ossix (Tel Aviv, Israel), Parasorb Resodont (RESORBA Medical GmbH, Nuremberg, Germany), Tefgen (Lifecore Biomedical, Chaska, USA), Tutodent (Tutogen, Neunkirchen, Germany), non-resorbable Gore-Tex membrane (GT, W.L. Gore & Associates, Flagstaff, USA), Osseoquest (W.L. Gore & Associates, Flagstaff, USA) and Inion GTR (Curasan, Kleinostheim, Germany). If a titanium mesh was used (Tiomesh, Dentaurum, Germany), the membranes were placed over the mesh.
Patient data files were analysed regarding personal patient information, implantation process and implantation outcome in terms of implant loss. Patient data included information about the sex, date of birth, the number and position of implants placed as well as the date of implantation and explantation or last control visit. Regarding the implantation procedure, the use of graft materials and membranes were documented.
Collected data were retrospectively analysed in terms of explantation rates to evaluate the survival between implants undergoing augmentation or not. Additional subgroup analysis included comparisons of different augmentation procedures, graft materials and membranes. In order to compare augmentation procedures, they were categorised into lateral augmentation, three-dimensional augmentation using a titanium mesh, bone splitting/bone spreading, use of autogenous bone blocks, internal sinus floor augmentation using the Osteotome technique and external sinus floor augmentation using a lateral window approach (one- and two-step procedure), bone condensing or combinations of these procedures. Bone splitting/spreading and bone condensing describe accompanying augmentation procedures to equalise the bone level with neighbouring sites.
The statistical analysis was performed using SPSS 11.0.0 (IBM, Armonk, NY, USA) as well as SAS Version 9.2 (SAS Institute Inc., Cary, NC, USA). Metric parameters were descriptively analysed for arithmetic mean and standard deviation. To test the hypothesis of “no differences between augmented sites and non-augmented sites in regard to survived implants”, survival of implants was compared based on Kaplan-Meier survival curves using log-rank test and included patient data up to a 20.2-year observation period . Subgroups were exploratory analysed for statistical differences using log rank. A p value of 0.05 was regarded to be significant.