Subject: grades of titanium
Can you tell me what the best grade of Titanium is in body jewelry? Is medical grade the highest grade and is this different than 23 grade? Is the medical grade much more expensive? Do you know what % of people are allergic to medical grade if any?
My articles at http://jewelry.piercing.org/ και http://brnskll.com/shares/titanium-standards-why-not-g23/ explain that the two most effective Titanium standards are alloyed ASTM F136 and pure ASTM F67, the most common being the former as it is stronger, harder and easier to polish. Both are used for permanent surgical implants.
Grades are not relevant, but specifications for surgical implant are important for body jewelry, and must be certified by the vendor from their material source. This certification process, and the particular refinements that must be made for the material to meet these specifications require more from the manufacturer, and therefore are sold at a higher value than other materials that do not conform.
The main purpose of requiring such specifications is biocompatibility, making a consistent material compatible with the human body to prevent allergic reactions and problems with healing and undesirable scar tissue.
These surgical implant specifications state:
X2.1 The alloy composition covered by this specification has been employed successfully in human implant applications in contact with soft tissue and bone for over a decade. Due to the well-characterized level of biological response exhibited by this alloy, it has been used as a control material in Practice F981.
X2.2 No known surgical implant material has ever been shown to be completely free from adverse reactions in the human body. Long-term clinical experience of the use of the material referred to in this specification, ωστόσο, has shown that an acceptable level of biological response can be expected, if the material is used in appropriate applications.”