Implant mobility and bone formation surrounding implants under occlusal functioning were investigated using 3 different stress-absorbing mechanisms: an Intramobile Element (IME), an Intramobile connector (IMC), and a Ti Element (Ti), and 2 conditions of occlusal contact. Occlusal contact was set at either a uniform contact position, so that the implants evenly contacted the remaining teeth, or in a slightly elevated (by approximately 60 μm) position.
Two adult Japanese monkeys were used. They received 3 single-implant crowns, and, each stress absorbing element (IME, IMC, or Ti) was connected to an implant. In one, the occlusion was set at a uniform contact position, while the other had the occlusion adjusted to a slightly elevated position.
Implant mobility was judged weekly, from the second surgery until 4 weeks after connecting the implant crowns, for a total of 7 times. Four weeks after connecting the implant crowns, bone formation around the implant fixtures, and changes in microvasculature, were observed, using a plastic injection method with a scanning electron microscope.
The results were:
1. After connecting the implant crowns, mobility reduced over time as occlusal function increased. The reduction in mobility index (MI) scores showed a significant difference between the level at 1 week after connecting and that at 4 weeks, after adjusting for both the uniform and slightly elevated contact positions. However, no significant differences were found among the 3 stress-absorbing elements.
2. For both uniform and slightly elevated contact, and with each of the stress-absorbing elements, osseointegration was maintained. There were no differences in the implantal alveolar proper between the uniform and slightly elevated occlusions around the upper portion of implants, for any of the 3 stress-absorbing elements. However, around the middle portion and the bottom portion of the implants, the implantal alveolar proper, as well as the trabecula supporting it, was thicker with IMC and Ti, than with IME.