Introduction: Titanium and its alloys are extensively used in orthopaedic applications due to their excellent mechanical properties, biocompatibility, and corrosion resistance. Direct coupled electrical stimulation (DCES) has also been demonstrated to promote bone regeneration and osseointegration in clinical trials. However, titanium is not often the material of choice for electrically stimulating bioelectrodes, especially as both the cathode and anode. This is mainly due to titanium’s lower conductivity compared to other biocompatible materials, like gold and platinum, and the tendency for the passive oxide layer to transform, which although contributing to its excellent corrosion resistance can impact signal stability. Nonetheless, dual titanium bioelectrodes have made their way into several clinical applications, such as spinal fusion, but have not been extensively characterized.
Methods: This study explores the effects of anodization voltage (0, 5, and 10 V) and oxide layer configuration (single or double passivation) on electric field distribution under voltage-controlled constant DCES for commercially pure titanium electrodes. Computational modelling frameworks for estimating electric field distributions were also re-evaluated using COMSOL Multiphysics to address the ambiguous reporting standards that are hindering the widespread application of DCES in implant design.
Results: The results demonstrate that improper choice of the modelling framework can overestimate the electric field by up to an order of 4 in constant DCES systems. It was also found that the electric field only behaves uniformly near the centre of the stimulation chamber (roughly 3 mm from the centre), with much greater electric field gradients in the direction parallel to the electrodes.
Conclusion: These results suggest that the electric fields reported in previous in vitro DCES studies should be re-evaluated using appropriate computational electrochemical approaches. This reassessment will help inform the design of electrically stimulating medical devices and expedite the clinical translation of DCES for bone regenerative therapies.
