Any part that goes into the mouth for more than 30 minutes requires FDA "approval". They are connected into or onto an implant, touch bone or tissue, and are either temporary or permanent solutions. The part that you casted with such as an all plastic abutment or a UCLA gold adapt abutment or chrome cobalt abutment all where supposed to go through the FDA approval process as well as the screw that connects this. The instructions for use document is also supposed to be submitted to the FDA and MSDS to ensure that the materials that the product is made of as well as the the materials that are to be used by the lab/dentist are approved to be used with part. The issue with any part is biocompatibility, cleanliness of the product that is being made (if you are making a custom part what steps do you go through to ensure that the product is properly cleaned, and is the part that is being made going to last in the mouth permanently without failure. This is why you see that companies are producing 15 degree angled locators and that is as extreme of an angle they are allowed to make them per FDA and also knowing that past that it risks failure or other issues.