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ePaper created 2017-11-09, 09:28:26 | version 1.38.0
designed. Designing a zirconia implant should be based on material properties and should simplify surgical and pros- thetic steps for the doctor. Size limitations should be con- sidered, in order to produce an implant that is not prone to fractures. A clinical study by Gahlert et al. (2012) showed a marked tendency of one-piece implants with a narrow diameter (3.25 mm) to fracture, with a percentage that reached 92 per cent of the fractured implants.21 Threads and shape of implants should be designed according to the needs, always with respect to material. Size and shape precautions should also be applied to the implant head in order to avoid the risk of creating mi- crocracks during implantation. The implant head if posi- tioned at the gingival level or even higher, could eliminate the need for a second surgery, as well as to bypass the bacterial growth in the gap between implant and abut- ment. The decision of choosing between a one- and a two-piece implant could be influenced by the design of the implant, the available space to be installed, and the prosthetic rehabilitation that follows. Implant-abutment connection Connection of the abutment with the implant is per- formed by three ways: either by screwing, cementing, or even as a combination of both. When screwing, the mate- rial of the abutment and the connecting screw is of crucial importance for the implant to be intact. As a consequence from titanium knowledge, screwing an abutment made from the same material as the implant was a “natural” step. Screwing though zirconia inside a zirconia, unlike titanium, cannot result in a tight connection, because of the stiff- ness of the material. This loosening could possibly result in fracture and if this happens to the implant, it could jeop- ardise everything. In case of abutment failure, one should estimate the convenience of removing the abutment screw. A recent in vitro study by Preis et al. (2016) comes to strengthen the aforementioned performance of different implant-abutment connections, was investigated in six groups of different two-piece zirconia implant systems.22 In group 1, the abutments were cemented to an alumi- na-toughened zirconia implant. In group 2, the abutments were screwed with a carbon fibre reinforced polymer screw on an alumina-toughened zirconia implant. In the remain- ing four groups, the abutments were screwed with titanium screws on tetragonal zirconia polycrystalline implants. A standard screw-retained titanium implant served as the control. The bonded zirconia system and the titanium refer- ence survived without any failures. Screw-retained zirconia systems showed fractures of abutments and/or implants, research | AD LOW COST & HIGH SPEED IMPLANT / ABUTMENT TESTS FOR DIN/EN/ISO 14801 NORM UP TO 8 UNITS ON 1 CONTROLLER DEVELOPED FOR DIN/EN/ISO 14801 TESTS NO CONNECTION TO AIR OR HYDRAULIC REQUIRED DYNAMIC FORCES TO 800N, 1500N TO STATIC MEASUREMENT CYCLES OF 1-15 HZ SAVES SPACE AND LOW NOISE PRODUCTION Fig. 3: Unlike titanium, screwing zirconia inside zirconia cannot result in a tight connection; again, knowledge about material properties is the key to success. COST EFFICIENT © bookzaa/Shutterstock.com 09 www.14801.de implants 1 2017