Effect of closing torque on the implant-abutment seal
Objective: To find out and compare the effect of abutment screw torque (closing torque) on the seal of implant-abutment junction
Methodology: The test specimens were three implant analogues (4.0 by 13 mm), embedded in acrylic blocks. Using a micropipette 0.7 μL of Toluidine blue colour marker was dispensed into the implant analogue well. Standard abutments were then placed on the implant analogues. Based on the torque of the abutment screws (20N, 30N and 40N), the specimens were divided into three groups. Torque was measured using a digital torque gauge. The implant-abutment complex of each group was then placed in 15ml vials filled with 1.5 ml of distilled water. For each specimen, 0.5 ml of the test contents were retrieved from the respective vial after 24, 48, 72, 96 and 144 hours of storage time at room temperature. Spectrophotometric analyses of the samples were performed for absorbance determination of the colour marker at 560nm wavelength.
Results: Absorbance value of Toludine blue for specimens torque at 40 N, 30 N, 20N at the end of 144 hrs was 0.01, 0.05 and 0.15 respectively.
Conclusion: Leakage at the implant-abutment interface does varies with different torques. Microleakage decreased significantly as the torque increased. Thus, abutment closure at recommended closing torques reduces microleakage.