Effect of surface topography on pull-out strength of cortical screw after ultrasonic bone drilling: an in vitro study

Drilling of bone is required to repair and align the bone when faced with a major fracture. The screw and implant are used for fixing the fractured part of the bone. The failure of osteosynthesis is due to strength between the bone and screw, which majorly depends upon the pull-out strength of the cortical screw. Pull-out strength is the force required to pull a screw out of its foundation from the bone. After the fixation of cortical screws, the major forces acting on the fixation of the screw and the implanted device in the bone. Therefore, it needs to make sure that the screw must fit into the place and grasp the bone within the drilled hole. The intended focus of this research is to see the effect of surface roughness induced during the bone drilling operation on pull-out strength with rotary ultrasonic bone drilling (RUBD) and standard conventional bone drilling (CBD). This is observed that a drilled hole in a bone exhibits greater pull-out strength with more surface roughness because more anchoring is provided by the roughened surface. Also, the apatite formation of the bone shows the biocompatible nature of porcine bone in the simulated body fluid (SBF) solution. RUBD using different grit size in a hollow drilling burr resulted that coarse abrasive have maximum effort for higher surface roughness. Furthermore, the higher surface texture provides a better bone growth rate as it provides peaks for branching and nucleation when preserved in SBF. RUBD provides precise cutting to the bone as compared to CBD. On the 28th day of the bone-screw samples to be immersed in SBF results 42.82% higher pull-out strength of screw in case of RUBD as compared to CBD.