The selection of an adhesive should consider the substrate materials being bonded, the fabrication process, and should contemplate the total use scenario to ensure that the adhesive is appropriate. The process for selecting an adhesive should involve more than consulting the manufacturer’s product datasheets, which typically provide guidance with general performance data for the material. Although the process typically begins there, the datasheets cannot be expected to be specific for the conditions and adhesive use situation relevant for the current device.
Even past performance or experience may not provide all the relevant details for the current use scenario. For dentist equipment, bonding dissimilar materials often with low surface energies, specific manufacturing assembly requirements, and product sterilization all present challenges for creating durable adhesive bonds.
The effects of sterilization of dental autoclave sterilizer are often overlooked or considered simply in regard to material compatibility instead of the broader system impact. Sterilization—whether steam autoclave, ethylene oxide, radiation, or chemical treatments—is an aggressive exposure condition for a medical device and its constituent materials that is typically harsher than the general use and exposure conditions of the device. Sterilization can be extremely demanding of the adhesives and their function, especially if the device is reusable and will experience the cumulative effect of multiple sterilization cycles over the course of its life.
Sterilization not only tests the integrity of the adhesive material, which can degrade chemically and in performance on an individual basis, it also challenges each of the material interfaces and all the process steps leading to the finished device. Imperfections and deficiencies of the material, interfaces, or processes can lead to these latent issues becoming exacerbated by sterilization and then realized as failures under the stresses of use.
For medical devices, adhesive materials need to perform reliably even after being subjected to relatively extreme conditions, including sterilization. However, the adhesive performance is dependent on the numerous decisions and steps taken to create the bond, each of which have the potential to be the weak link in the chain.