Abstract
Background: The aim is to evaluate methods to quantify the interstitial splitting force and thermal load input of self-tapping and self-drilling osteosynthesis screws. Methods: A specialized modular test bench was developed to measure the induced splitting force of self-drilling and self-tapping osteosynthesis screws using porcine mandibular bone. In addition, a fundamentally new approach to measure the temperature near the contact zone of osteosynthesis screws (fiber-optic sensor in the axis of the screw) was established. Results: The self-drilling screw type induces a splitting force of about 200 N in the surrounding tissue, so that microdamage of the bone and increased resorption can be assumed. Even pre-drilling induces a short-time force into the tissue, which is comparable to the splitting force of the self-tapping screw. The temperature increase in the screw is clearly higher compared to the temperature increase in the surrounding tissue, but no significant difference in temperature between the two screw types could be measured. Based on the measured temperatures of both screw types, the temperature increase in the contact zone is considered critical. Complications during the screwing process caused by the manual tool guidance resulted in numerous breakages of the fiber-optic sensors. Conclusions: The developed methods provide additional insight regarding the thermomechanical load input of self-drilling and self-tapping screws. However, based upon the optical fiber breakages, additional refinement of this technique may still be required.
Highlights
With the rotation of the tool, a thrust force is intuitively applied by the operator to prevent the tool from slipping and to enable a penetration into the material. These force peaks are paralleled by an increase in the measured splitting forces
When the tool is re-gripped, a drop in the splitting force signal is evident, resulting on the one hand from the drop in the thrust force and the associated lower compression of penetrating pattern of the thrust force and torque of self-drilling screws, which is typical for manual screwing processes, is clearly visible for the manual screwing process (Figure 7)
The developed methods generated an enormous gain in knowledge regarding the thermomechanical load input of self-drilling and self-tapping screws
Summary
The aim is to evaluate methods to quantify the interstitial splitting force and thermal load input of self-tapping and self-drilling osteosynthesis screws. Methods: A specialized modular test bench was developed to measure the induced splitting force of self-drilling and selftapping osteosynthesis screws using porcine mandibular bone. A fundamentally new approach to measure the temperature near the contact zone of osteosynthesis screws (fiber-optic sensor in the axis of the screw) was established. Results: The self-drilling screw type induces a splitting force of about 200 N in the surrounding tissue, so that microdamage of the bone and increased resorption can be assumed. Even pre-drilling induces a short-time force into the tissue, which is comparable to the splitting force of the self-tapping screw. Conclusions: The developed methods provide additional insight regarding the thermomechanical load input of self-drilling and self-tapping screws. Based upon the optical fiber breakages, additional refinement of this technique may still be required
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