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ePaper created 2017-12-06, 12:03:50 | version 1.38.0
| research etched with hydrochloric acid and sulphuric acid. The result is a moderately rough surface (Sa ≈ 1.5 µm) characterised by rapid osseointegration and is there- fore optimal even for early implant loading.28 The sur- face is composed predominantly of TiO2 with residual Al from the sandblasting process.44, 45 Some studies have reported as high as a 97–100 % success rate with this surface at the five-year follow-up, after early loading at six weeks (Figs. 1a & b).46, 47 Biocompatibility and clinical applicability of SLA In vitro studies Aybar et al. performed an immunohistochemi- cal study of osteoblast-like cells on four different types of Ti discs: SLA1 (Grade 4, Straumann), SLA2 (Grade 5, Alpha-Bio Tec), acid-etched (Grade 5, Alpha-Bio Tec) and machined (Grade 5, Alpha-Bio Tec).48 Proliferation and DNA synthesis of pri- mary rat calvarial cells were evaluated after one and seven days of incubation. After 24 hours, the highest level of DNA synthesis was observed on SLA1, but after one week, the proliferation of os- teoblast-like cells decreased significantly on this surface, while a significant increase of DNA pro- duction was observed on the Grade 5 surfaces. In another in vitro study, the adsorption of different human plasma proteins to three different implant surfaces (SLA, machined, acid-etched, Alpha- Bio Tec) was examined. Singh compared polished and SLA surfaces in terms of osteogenetic potential, and found SLA significantly superior (Figs. 2a & b).55 The quantity and quality of adsorbed plasma proteins ( albumin, fibronectin and fibrinogen) was the highest in the SLA group, as demonstrated by enzyme-linked immunosorbent assay and confocal scanning laser microscopy.49 Implant removal torque testing also resulted in better bone anchorage and higher stiff- ness values of the SLA surface compared with the machined and acid-etched surfaces.50 Clinical studies Roccuzzo et al. examined 106 implants (53 SLA, 53 control TPS) in 27 patients and found no implant loss after five years’ follow-up (100 % success rate).46 No significant differences were seen in the basic peri- odontal indices (bleeding on probing, probing pocket depth, bone loss) between the two surfaces,46 indi- cating superior biocompatibility. Van Velzen et al. evaluated the ten-year survival of 374 SLA-modified dental implants in 177 patients with special attention to peri-implantitis. The success rate was 99.7 % at the implant level and 99.4 % at the patient level, with 7 % prevalence of symptoms specific to peri-implantitis.40 In the clinical study of Strietzel et al., the survival of 283 immediately loaded screw-type Alpha-Bio Tec SLA implants was assessed.47 It was found that, Fig. 1a Fig. 1b Figs. 1a & b: Scanning electron Biochemical methods microscopy images of Alpha-Bio Tec’s SLA surface at x 1,000 (a) and x 2,500 (b) magnification. These methods augment the physicochemical processes based on the latest knowledge in biology and biochemistry. The aim is to immobilise various proteins, enzymes and molecules to better control the specific bone–implant interface.29–31 These mole- cules can interact with or promote the adsorption of desired proteins to enhance osseointegration. Pro- teins and/or steroid growth factors have been shown to promote the proliferation of different connective tissue and inflammatory cells.32, 33 Besides promot- ing the attachment of host cells, the inhibition of bacterial colonisation is desirable and is the focus of intensive research.34 In order to prevent the initial attachment of bacte- ria and biofilm formation, anti-biofouling and bacte- ricidal surfaces have been developed. Anti-biofouling surfaces prevent the initial attachment with specific surface topography or chemistry.35 In addition, bac- tericidal surfaces cause the death of the bacterial cell typically on contact.36 Coatings that release nano- silver, photocatalytic TiO2 or nitric oxide have been shown to be bactericidal.37, 38 Sandblasting with large-grit corundum and acid etching Figs. 2a & b: Scanning electron microscopy images of smooth (a) and SLA (b) surfaces after attachment of human osteosarcoma osteoblast cells.55 SLA is one of the most widely studied and well-doc- umented Ti implant surface modifiers39–42 and was originally introduced by Buser et al.43 As the name suggests, the surface is first sandblasted with large- grit corundum (aluminium oxide) particles, then acid- Fig. 2a Fig. 2b 08 implants 4 2017