Any major changes, in this case material composition changes, needs to be reported to the FDA. In the event that it is a novel material or a novel use of the material, in vivo studies will have to be done to verify and validate its performance because the material plays a huge role in the performance, safety, and function of a device. By changing the material, the device is no longer the same device and may have to go through 510(k) that requires clinical trials because of the unknown risks associated with the new material or even need to go through a PMA. In either case an IDE will most likely be required along with animal models to prove the similarity of performance or that the new material does not pose a greater risk than the original material used.
While I don’t know the ins and outs of the FDA, should the risk associated with Plastic B be statistically significantly greater than Plastic A, the chances of the product being approved will be much slimmer unless the factor of pricing is that significant of a factor when considering patients, where in the case of a syringe it is not.
The compatibility of Plastic B with all the chemicals, drugs, and fluids conventionally used with that type of syringe will also need to be tested. From a company standpoint, the initial investment to get the new product will out weigh the gains for quite some time. If it takes 10 years to make back your initial investment, then even if your saving your losing. Further research should be done into the applications the material is being used for to see if they can make a product that they claim only works for specific tasks like drawing blood when laced with an anticoagulant and over the years slowly expand the claims through various projects. This will reduce the initial investment required and make it possible to avoid clinical trials since the plastic is not coming into contact with the body, and only validations on the materials compatibility with contents placed in it need to be done. Since testing has been done for certain applications already, the company can avoid the unnecessary cost of proving something that is already proven or need as strong evidence since they are corroborating what is already found.