Effect of Cyclic Loading on the Fixture-Abutment Microgap in Short Implants Versus Standard Implants: An In Vitro Study

Objectives: This study aimed to assess the effect of cyclic loading on the amount of fixture-abutment microgap in short implants compared to standard implants. Materials and Methods: This in vitro experimental study was conducted on two groups of short and standard implants (n = 10). The microgap at the fixture-abutment interface was measured under a light microscope at ×75 magnification. The implants were mounted in an acrylic resin to simulate the jawbone. They were then subjected to cyclic loading by applying 75 N load with 1 Hz frequency along the longitudinal axis of each implant (perpendicular to the abutment surface). After 500,000 cycles, corresponding to 20 months of mastication in the oral environment, the implants were removed from the acrylic resin, and the microgap at the fixture-abutment interface was measured again under a stereomicroscope by a blinded examiner. Data were then analyzed by t-test using SPSS version 22 (α = 0.05). Results: The mean microgap was 13.59 ± 3.80 µm in the standard and 20.41 ± 11.30 µm in the short implants before cyclic loading (p=0.087). These values changed to 15.22 ± 5.44 and 24.53 ± 21.85 µm, respectively, after cyclic loading. No significant difference was noted in the amount of microgap between the standard and short implants after cyclic loading (p=0.222). Conclusion: Cyclic loading increased the amount of fixture-abutment microgap in both the standard and short implants. However, the difference in this respect was not significant between the two implant lengths. Thus, short implants could be reliably used in patients with limitations for surgery to restore function and esthetics.