Advanced Surface - NDI Dental Implants

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Grade 4 titanium alloy is a biocompatible and bioinert material. Implants of the German NDI system are manufactured in strict accordance with DIN EN ISO 13485:2012 of Grade 4 titanium alloy and undergo surface treatment using the Advanced process.

In recent years, this surface treatment process has been intensively tested both in vitro and in vivo. Cell culture tests, bone histologies, and removal torque tests in animals demonstrate the Advanced surface to be a superior choice for the implant contact surfaces. This trend for a better and faster bone integration of Advanced implants in the initial healing period is based on higher production of local cytokines and growth factors. The in vivo studies demonstrated predominantly superior results for the Advanced surface concerning implant integration and implant anchorage compared with other surfaces (titanium plasma-sprayed, machined, hydroxyapatite-coated, etc.), in particular during the initial healing period after implant placement.

The surface was developed to produce both high percentages of bone-to-implant contact in descriptive histomorphometric studies as well as high removal torque values in functional studies.

The Advanced surface is produced by a large grit sandblasting process with corundum particles that leads to a macro-roughness of the titanium surface. This is followed by a strong acid-etching bath with a mixture of HCl and H2SO4 at elevated temperature. This produces the fine 2-4 micrometer micropits superimposed on the rough-blasted surface. The surface is not microporous and therefore provides no site for tissue inclusions, thereby decreasing vulnerability to bacterial colonisation.

Fig. 1. Scanning electron microscope pictures of the Advanced surface with identifiable macro- and micro-roughness. The chemical composition of the Advanced structure was found to be titanium oxide (TiO2) using X-ray photoelectron spectroscopy. This method analyses the first few atomic layers of the surface, and thus the chemical composition of the material which is in direct contact and interacts with tissue fluids and cells.

 

In vitro Data

The first reaction that occurs between the patient and the implant is conditioned by tissue fluids. This produces a layer of organic macromolecules and water, which influences the behaviour of cells when they encounter the surface. Following these events, a series of cell/surface interactions takes place leading to the release of chemotactic and growth factors, which modulates cellular activity in the surrounding tissue. Because the surface-chemical composition of all titanium surfaces studied is almost identical, any differences in cell modulation are most likely to be due to variations in the surface topography.

Surface roughness was shown to have an effect on the proliferation, differentiation, and protein synthesis (including growth regulatory substances) of human osteoblast-like cells. The Prostaglandin enzyme E2 [PGE2] production of MG63 human-like cells, which are similar to human cells, formation of the enzyme prostaglandin E2 [PGE2], which serves as a marker for early differentiation, is enhanced at increasing substrate roughness and is significantly higher on the Advanced surface than on other surfaces     . PGE2 is a local factor produced by osteoblasts and is important in promoting wound healing and bone formation, and a high production enhances implant integration. Cytokines and growth factors, which could influence the quality, extent, and rate of bone formation at the bone/implant interface were also studied. This surface roughness dependence may be a result of the roughness itself or the result of the reactions which occur as the material surface is conditioned by the media and serum. This initial interaction produces a layer of macromolecules that modify the behaviour of the cells.

These in vitro studies have shown that osteoblasts grown on the Advanced surface exhibit properties of highly differentiated bone cells, suggesting that this surface is osteoinductive. Results from these experimental studies reinforce the concept of enhanced bone formation around the sand-blasted and acid-etched surface and the possibility of reduced clinical healing times prior to restoration.

In vivo Data

The anchorage of implants in grown bone was analysed in in vivo studies. The rigid bone/implant interface was originally observed in a histological investigation. The bone-to-implant contact is found to be higher on rougher surfaces like the Advanced than on smooth surfaces.  With five different titanium surfaces, it was demonstrated that a positive correlation exists between the percentge of bone-to-implant contact and the roughness value of implants made for comparison after short-term healing periods of 3 and 6 weeks.

Many dental clinical implant studies have focused on studying the clinical results of implants with a variety of surface characteristics. Most of the surface alterations have been aimed at achieving greater bone-to-implant contact. Thanks to biomechanical studies of the Advanced surface in jaw bone, the interface shear strength of Advanced implants in the maxilla of miniature pigs was evaluated. This animal was chosen as the pig bone structure is comparable to the bone structure of humans. The two best-documented titanium surfaces in implant dentistry, the machined and the TPS (titanium plasma-sprayed) surface, served as controls.

Furthermore, the bone/implant interface was analysed histologically after the removal process. The histological samples of the machined implants always demonstrated a separation along the implant surface at the bone/implant interface. The Advanced surface, on the other hand, often showed fractures of bone trabeculae close to the implant surface, but an intact bone/implant interface, indicating a strong physical interlock between the rough titanium surface and bone.

These findings indicate that Advanced implants feature a greater bone-to-implant contact and higher removal torque values than implants created for comparison that have different surfaces.

In a prospective clinical study, it was found that implants after installation can be predictably and safely restored as early as six to eight weeks after implant placement for bone classes I to III, and 12 to 14 weeks for bone class IV. Clinical results demonstrate that the restoration of an Advanced implant from six weeks after implant placement is an excellent treatment option in healthy patients with good bone.

In summary, the performance of the rough Advanced surface is superior to smooth surfaces with respect to bone contact levels and removal torques and thus early loading. Cell culture studies found that the surfaces modify the phenotypic expression of osteoblasts, suggesting that surface-modulated cellular processes may explain the histological and biomechanical performance. The most important property of this surface, which is relevant to implant design and use, is its high load bearing capability, as demonstrated in the removal torque experiments. With all kinds of testing Advanced surface was more effective than others the tested titanium surfaces and is the newest level of technology in the field of dental implants.