Abstract
Although the fabrication of passively fitting superstructures of dental implants is generally considered difficult, most clinicians agree that the impressions should be highly accurate. Numerous impression techniques have been reported to date. In this study, we evaluate the impression accuracy of low-elasticity additional silicone impression material using the ITI and Brånemark implant systems.
A master cast that replicated the human edentulous region was constructed from a stainless steel block. Three implant analogues for each system were placed at intervals of 12 mm. Master frameworks that accurately fitted the analogues of each master cast were fabricated. Impressions were made in five groups using the following impression copings and techniques: (1) ITI screw-retained impression copings (Group Ⅰ); (2) ITI screw-retained impression copings splinted with acrylic resin (Group Ⅱ); (3) ITI snap-on plastic impression copings and positional cylinders (Group Ⅲ); (4) Brånemark squared impression copings (Group Ⅳ); and (5) Brånemark squared impression copings splinted with acrylic resin (Group Ⅴ). The impressions were made using Examixfine Regular Type and Examixfine Regular Hard Type in each group. Stone replicas were fabricated after impression. Misfits between the master frameworks and stone replicas were evaluated using the one-screw test.
The results show that: (1) the low-elasticity impression material improves impression accuracy for non-splinted Brånemark and ITI plastic copings, which were the most difficult cases in this study; (2) the splinting technique helps to improve impression accuracy; (3) impression accuracy is strongly influenced by the component configuration.
