ABSTRACT
PURPOSE: This in vitro study assessed the accuracy of multiple implant-level impression techniques (open tray and closed tray) for the fabrication of 3-unit implant prostheses with strain gauge (SG) analysis. MATERIALS AND METHODS: A polyurethane master model was designed to simulate a clinical situation. Two rigid custom trays were fabricated for the model. The impression material used was polysulfide. Transfer implant impressions were made using 2 techniques; ten tapered copings not splinted (custom closed tray) and ten square copings splinted with acrylic-resin (custom open tray). The improved stone models were allowed to set for 1 hour before being separated from the impression. The superstructures were sprued, invested, and cast with a cobalt-chromium alloy. Four SGs were bonded on the surface of each polyurethane block. RESULTS: A statistically significant difference was found between the 2 impression techniques tested (P = 0.000). This study found a significant average difference of 144.68 ± 5.53 µÎµ for open custom tray and 253.3 ± 16.7 µÎµ for closed custom tray. CONCLUSION: The custom open tray technique was the most accurate impression for multiple implants compared with closed custom tray.
ABSTRACT
PURPOSE: The present study was designed to analyze strain distributions caused by varying the fixture-abutment design and fixture alignment. MATERIALS AND METHODS: Three implants of external, internal hexagon, and Morse taper were embedded in the center of each polyurethane block in straight placement and offset placement. Four strain gauges (SGs) were bonded on the surface of polyurethane block, which was designated SG1 placed mesially adjacent to implant A, SG2 and SG3 were placed mesially and distally adjacent to the implant B and SG4 was placed distally adjacent to the implant C. The 30 superstructures' occlusal screws were tightened onto the Microunit abutments with a torque of 10 N cm using the manufacturers' manual torque-controlling device. RESULTS: There were statistically significant differences in prosthetic connection (P value = 0.0074 < 0.5). There were no statistically significant differences in placement configuration/alignment (P value = 0.7812 > 0.5). CONCLUSION: The results showed fundamental differences in both conditions. There was no evidence that there was any advantage to offset implant placement in reducing the strain around implants. The results also revealed that the internal hexagon and Morse taper joints did not reduce the microstrain around implants.
