Peri-Implant Strain in an In Vitro Model
An in vitro experimental model was designed and tested to determine the influence that peri-implant strain may have on the overall crestal bone. Strain gages were attached to polymethylmethacrylate (PMMA) models containing a screw-type root form implant at sites 1 mm from the resin-implant interface. Three different types of crown superstructures (cemented, 1-screw [UCLA] and 2-screw abutment types) were tested. Loading (1 Hz, 200 N load) was performed using a MTS Mechanical Test System. The strain gage data were stored and organized in a computer for statistical treatment. Strains for all abutment types did not exceed the physiological range for modeling and remodeling of cancellous bone, 200–2500 μɛ (microstrain). For approximately one-quarter of the trials, the strain values were less than 200 μɛ the zone for bone atrophy. The mean microstrain obtained was 517.7 μɛ. In conclusion, the peri-implant strain in this in vitro model did not exceed the physiologic range of bone remodeling under axial occlusal loading.
Schematic of the resin box used to stabilize the implant and attach the strain gages. (a) The resin tube into which the implant is inserted. The strain gages were attached to the outer walls of the tube. Following this, the box was filled with resin.
Figure 2. An experimental sample prior to placing the strain gages. The walls of the resin cylinder containing the implant are being reduced to a thickness of 1 mm. Figure 3. A completed specimen with the strain gages attached. The implant is in the center of the sample. The leads from the strain gages attached to the acrylic extend outward from the sample. Figure 4. The MTS system with loaded sample.
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