Bone implant contact and its relationship with strain in the surrounding bone

Abstract

Objective: The objective of this study is to measure the strain developed in the simulated bone around implants with different percentages of bone implant contact (BIC), namely 50%, 75% and 100%, with loads of 200, 400, 600, and 800 N. Materials and Methods: Thirty implant replicas of dimension 3.75 mm × 11.5 mm were mounted in simulated bone blocks of auto-polymerizing acrylic resin. The difference in the BICs was created by selectively covering the threaded portion with modeling wax. The wax used for covering the implant surface was eliminated by injecting hot water through sprues created in the resin blocks. Radiographs of the prepared acrylic blocks were taken to ensure different BICs. Metal-ceramic crowns were cemented over abutments. Strain gauges were bonded and static loads of 200, 400, 600, 800 N were applied using a universal testing machine. Data were statistically analyzed with factorial ANOVA. Results: An increase in strain was observed when the percentage of bone to implant contact increased. For specimens with 50% BIC, at 200 N load peri-implant strain of 42.8 μe was recorded, and which progressively increased with increase to 94.02 μe with increase in load to 800 N. For the specimens with 75% BIC, at 200 N load peri-implant strain of 208.9 μe was recorded, which increased to 254.5 μe when the load increased to 800 N. Similarly, for the specimens with 100% BIC, at 200 N load peri-implant strain of 347.02 μe was recorded and this increased to 427.7 μe when the load was increased to 800 N. Conclusions: An increase in BIC by 1.5 times, from 50% to 75%, resulted in an increase in peri-implant strain by 3.5 times. On the other hand, when BIC increased 1.3 times from 75% to 100%, an increase in peri-implant strain was 1.6 times. Insignificant effect of load on the peri-implant strain was observed when the load increased by 200 N. Rise in occlusal load by 400 N showed significant increase in the peri-implant strain.