The aim of the study was to evaluate the spatial variations in the biomechanical properties of the bone around the implants retrieved from human subjects due to fixture head fracture after almost 20 years of loading. The implant-in-bone specimens were prepared for the histomorphometry and nanoindentation test to measure the bone-to-implant contact ratio (BIC ratio) and elastic modulus (E) of peri-implant bone. The indentations were performed in the up, center, down, and away regions of the bone tissues within all the thread spaces. The BIC ratios were 91.0% for Patient #1 and 95.8% for Patient #2. The E values assessed from the up region within the thread spaces were significantly higher than those measured from the center region. The elastic properties assessed from center and down regions within the thread spaces were similar to those assessed from the away region. The representative E values showed no significant thread-dependent linear trend. Within the limitation of this study, the peri-implant bone tissue showed spatial variation of its elastic modulus after long-term functioning.
Keywords: Biomechanical properties; Dental implant; Nanoindentation; Retrieval study.
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