Evaluation of impression accuracy for osseointegrated implant supported superstructures

Statement of problem. An often-debated issue still exists concerning implan t impression techniques, whether to splint impression copings. Different co nfigurations are available for these copings for a variety of manufactures' implant systems. Purpose, This study evaluated and compared 4 impression techniques in terms of their dimensional accuracy to reproduce implant positions on working ca sts. Material and methods. A master model was designed to simulate ii clinical s ituation. Impressions were made using 4 techniques: (1) tapered impression copings trot splinted; (2) squared impression copings not splinted; (3) squ ared impression copings splinted with autopolymerizing acrylic resin; and ( 4) squared impression copings with a lateral extension on one side not spli nted. Reference points machined onto the master model and onto special heal ing abutments were compared after abutments were transferred to casts using the 4 techniques. Measurements were made using a Reflex microscope, capabl e of recording in the x-, y-, and z-dimensions. Results. The dimensional accuracy was high and, although statistically sign ificant (P=.022; power > 80%), a maximum distortion difference of only 0.31 % was registered. Conclusion. The dimensional accuracy of all the techniques was exceptional and the observed differences can be regarded as clinically negligible.