Laser sterilization of hydroxyapatite implants as an alternative to using radioactive facility

Modern technology, including 3D printing, provides enormous potential for shape- and size-tailored treatments, especially in orthopedic surgery and dentistry. However, for a medical device produced in the clinical setting that is not compatible with autoclaving or gas sterilization, the choices are very limited, especially because there are a lot of obstacles to using a radiation facility to sterilize a few small-size devices. The goal of this study was to verify the efficacy of laser sterilization of discs made from hydroxyapatite (HA), a material that can be 3D printed and widely used as bone substitute. For this purpose, we compared sterilization efficacy for E. coli and S. mutans when using a range of laser, γ-ray, and e-beam irradiation. Furthermore, we compared biocompatibility by culturing adult stem cells and MC3T3-E1 on HA discs before and after irradiation. Irradiation by UV-C (266 nm) at 100 mJ/cm2 showed 3 kGy of γ-ray or e-beam equivalent sterilization efficacy, without causing physical or chemical changes in the HA discs. In conclusion, in addition to offering affordable maintenance costs, laser sterilization can be used in small-size facilities and can sterilize an object within nanoseconds; this demonstrates its potential to be used on custom small-size medical devices as an alternative sterilization technique that can replace autoclaving, gas sterilization, or the use of radiation facilities.