Human ex vivo bone tissue strains around immediately loaded implants supporting maxillary overdentures

Purpose: To evaluate ex vivo bone tissue strains around maxillary implants supporting immediately loaded bar-retained overdentures. Material and methods: Ninety degree two-element rosette strain gauges were bonded on the labial bone of four ITI (R) dental implants placed in the maxillary anterior region of four completely edentulous maxilla of fresh human cadavers. The installation torque value (ITV) of each implant was measured by a custom-made torque wrench and resonance frequency analyses (RFAs) were undertaken. A bar-retained overdenture was fabricated for each cadaver, and two miniature load cells were integrated in the first molar region of the overdentures for controlled loading experiments. Strain measurements were performed at a sample rate of 10 kHz and under a maximum load of 100 N, simultaneously monitored from a computer connected to a data acquisition system. Finally, removal torque values (RTVs) of the implants were measured. Results: RFA values did not mirror ITVs, while RTVs of implants were slightly lower than the ITVs. Any correlation could not be obtained between RFA values and ITVs or RTVs. Maximum strains around loaded implants ranged between -100 and -550 mu epsilon under 25-100 N. The axial and lateral strain values of posterior implants of both sides were higher than those of anterior implants under all loads (P < 0.05). Conclusion: Because occlusal forces in humans tend to decrease because of age-related factors, maximum strains around immediately loaded implants supporting maxillary overdentures fall within physiologic levels.