14 Clinical evidence and Science Fig. 9_Rotational freedom of regular polygonal patterns, polygon profiles, and other patterns. Measuring points and measuring results of (A) the hexagonal positional index (SteriOss), (B) of the dodecagrammal positional index (Astra Tech), (C) of the octagonal positional index (Straumann), (D) of the polygonal profile positional index (Replace Select), (E) of the cam-groove connection (Camlog). 3D simulation: rotational freedom (F) of the Steri-Oss system (hexagon), (G) of the Astra Tech system (dodecagram), (H) of the Straumann system (octagon), (I) of the Replace Select system, (J) of the CAMLOG® system. Abbreviations: V = width across corners, F = width across flats demonstrated at the implant positional index, K = radius of the bulge, R = radius of the outer arc at the notch of the implant, D = distance from the center of the outer arc of the implant to the rotational axis, d = distance from the center of the inner arc to the rotational axis, S = diameter demonstrated at the implant positional index. (Semper et al. 2009, reproduced with kind permission of Thomson Reuters Corp., USA) B C D E A Fi = 2.683 mm Fa = 2.726 mm Va = 3.147 mm Fi = 2.527 mm Fa = 2.481 mm Vi = 2.872 mm Fi = 3.119 mm Fa = 3.072 mm Vi = 3.402 mm Si = 3.683 mm Sa = 3.628 mm Si = 3.050 mm Sa = 3.020 mm Simulation of rotational freedom of angulated abutments on CAMLOG® Implants With the help of a three-dimensional computer simulation, the same group evaluated clinical relevance of the rotational freedom of angulated abutments on the marginal fit of the prosthetic superstructures (Semper et al., 2010) (15). The horizontal displacement of virtually constructed idealized abutments with different angulations (range from 0 to 20°) was simulated with various degrees of rotational freedom (range from 0.7 to 1.85°) as previously described (14). After quantification of the resulting displacement, a subsequent simulation was performed where the superstructure with different defined internal gaps (5 µm, 60 µm and 100 µm) was positioned pressure- less on the displaced abutments. Finally, the resulting marginal gap between the abutment and the superstructure was measured with the software (Tab. 1). This gap depended on the degree of abutment angulation and the rotational freedom. Based on this investigation the authors concluded that the rotation of the abutment is of clinical relevance because of its impact on the marginal fit of the prosthetic superstructure. Again, the precisely manufactured cam-groove index design of the implant-abutment connection seem to support precision-fit prosthetic restorations with little to no post-processing during placement. SCIENCE BEHIND THE IMPLANT-ABUTMENT CONNECTIONS
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