Effect of Roughness on Pullout Strength during Ultrasonic Bone Drilling: An in Vitro Study

Abstract

Bone drilling is one of the most common operations used in direct approach to repair fractured parts of bones and to produce hole for screw insertion to fix the fractured parts for immobilization and alignment of parts for proper healing. The failure of screw is due to strength between the bone and screw, which majorly depends upon the Pullout strength of cortical screw. Pullout Strength is the force required to pull a screw out of its foundation in the bone. As after fixation, major forces acts on the fixation screw of the implanted device in the bone. Therefore, it need to make sure that screw must fit into the place or grasp the bone with in the drilled hole. The intended focus of this research is to see the effect of roughness induced during the bone drilling operation on Pullout strength. This may be expected that a drilled hole in a bone exhibit more Pullout strength with more surface roughness. The probable reason is that more anchoring is provided by the roughened surface. Also, how the apatite formation will enhance further with this roughness during various time span is also to be explored during the research. An ultrasonic drilling process is employed for the purpose and it is expected that varying the grit size of a drilling burr result in different outcomes. Hence, a process optimization with an objective to enhance the surface roughness and effect of this enhanced roughness on Pullout strength would be the key findings of the research.