Comparison of the Transfer Precision of Impression Materials for the FRIALIT®-2 System

Transfer of the precise position of implants to a master cast is a prerequisite for an accurate and passive fit of the superstructure. Implants lack the mobility of natural teeth and therefore inaccurate frameworks result in stress within the mechanical parts and the implant-bone interface. Various impression methods have been described to achieve accurate reproduction of the intra-oral relation of the implants. The aim of this experimental study was to compare three different impression materials (polyether, polyvinylsiloxane, hydrocolloid) with the FRIALIT®-2 system and the indirect technique. In addition, the use of transfer caps to improve the transfer precision was tested with all three materials. All measurements were performed using a 3D co-ordinate measuring machine that is capable of locating points in space and calculating the relative distortions as angles of tilt (rot-xy, rot-xz, rot-yz) and 3D displacement. The results suggested that addition silicone and polyether are the materials of choice for implant transfer procedures. The use of transfer caps resulted in a significantly reduced rotation in the xy-plane, but did not improve the absolute 3D displacement. Addition silicone with the use of transfer caps proved to be most precise. The comparison between polyether and polyvinyl siloxane showed significant differences in the xy-rotation and the 3D displacement in favour of the silicone.Since the mean distortion between the original model and the master casts were about 100 µm, absolutely precise fit may be unattainable due to the physical properties of the materials. Further studies will have to evaluate the amount of tolerable stress at the implant-bone interface. Keywords: dental implants, Frialit-2, transfer cap, impression material, impression technique, transfer precision, polyether, polyvinyl siloxane, hydrocolloid, 3D co-ordinate measurement