Rationale

ASTM 1538-24 was originally approved in 1994 (after 18 months of drafting various versions) to create some guidance for materials which were, at the time, new to medical device field. Note that the first successful commercial product introduced to the market using a glass biomaterial (454S5 Bioglass in this case, was the “ERMI” (Endosseous Ridge Maintenance Implant) which was a conical implant used to fill the void after tooth extraction. While that product was not very successful in the market, in 1994, PerioGlas, a particulate 45S5 glass material, was introduced and has had a very successful history. Since 1994, there has been steady growth in the use of glass materials in the field of orthopedics, dentistry and wound healing Regarding F-1538, the document is woefully out of date and has been kept alive by making minor updates and improvements. I believe it is time to discuss a major overhaul of this standard (I was the primary author of the first version of this standard in 1994). The first major point is that the document is approved as a ‘Standard Specification’. The ASTM Blue Book – Form and Style for ASTM Standards has definitions of the various classes of Standards. Here is the definition of ‘specification’: specification, n— an explicit set of requirements to be satisfied by a material, product, system, or service. DISCUSSION—Examples of specifications include, but are not limited to, requirements for; physical, mechanical, or chemical properties, and safety, quality, or performance criteria. A specification identifies the test methods for determining whether each of the requirements is satisfied. The definition of a ‘Guide’ from the Blue Book is as follows: guide, n— a compendium of information or series of options that does not recommend a specific course of action. DISCUSSION—A guide increases the awareness of information and approaches in a given subject area. While the current ASTM-1538 standard does call out specific requirements for trace elements and bulk composition for glass, the later is specific to soda-lime glass and may not be applicable to more recent commercial products in the field such as borate based, and phosphate-based glasses. While Section 2 also calls out other tests to be used for specific properties, it is not clear how relevant these are for biomaterials or if they are used by those manufacturing products that are glass based. In addition, much of the rationale and other components of this document still reflect only silicate-based materials and the references are woefully outdated. I think that the biggest issue with the document is the definition of bioactive glass (3.1.1) and bioactive glass-ceramic (3.1.2). The title of the document does not mention ‘bioactive glass’ but a definition appears in the body of the document. While there is a ‘definition’ for bioactive glass, there is no specific test method that exists to test for ‘bioactivity’, nor is there a definition that is quantitative in nature. The recent revisions to an ISO Standard, ISO 23317, which was used to test for a hydroxyapatite layer and therefore used, de facto to call a material ‘bioactive’ has been substantially changed to the point where it can no longer be used to define the bioactivity of a biomaterial. In fact, the word ‘bioactivity’ no longer appears in that document. Given the fact that the uses for these materials span orthopedics, dentistry, wound care, consumer oral care products, and that there are silicate, phosphate and borate based materials currently in the market, my opinion is that this document should be changed to a ‘Guide’ which points to various options (if they exist) for characterizing and defining the material in use. The standard has been revised at least 5 times in its history, and I assume that it would be possible to simply update some definitions, perhaps remove the reference to bioactivity, update test methods, include phosphate and borate compositions and update the rationale and references. However, I still don’t see that rising to the level of a Specification in the ASTM definition. A Workgroup exists for revising this standard, although it has been dormant for a couple of years now. Because the document was revised in 2024, we have about 3 years to create something more meaningful and useful for those in the field who rely on the use of these standards. I will be reaching out to you personally and will try to convene a meeting within the next 4 to 6 weeks.