Class I, Class II, and Lab Products
Dental applications fall into one of three different categories:
- Class I products;
- Class II products; and
- Lab products
Class I products are used for short treatments in the mouth that could be completed in under an hour.
Class II products are suitable for long-term oral use for over 30 days.
Lab products are only used for visual purposes, assemblies, such products are only in touch with the skin for short periods of time.
The risks posed by non-conformance to medical standards
All resins, based on the chemical compositions, are carcinogenic in nature in a liquid state. Therefore, they must be cured correctly. If you were to not completely cure a Class 2 resin, a reactive residue would remain on the surface of the piece and this in turn would react with the blood stream.
Over curing a resin is even more dangerous because the excess UV light damages the surface of the resin, making it highly toxic.
Proper post curing is something the resin producer must test thoroughly and after doing so, recommend a specific UV box and curing time that yields safe and consistent results so that other parts produced under the same condition are to be considered medically safe and compliant with ISO standards.
The process of validating a resin
Resin validation requires the following steps:
- Determine a curing time;
- Testing the physical properties;
- Determining the shrinkage and optimizing accuracy;
- Determining the optimal process for cleaning the part by taking into consideration the duration and concentration of the alcohol that is used; and
- Finding and testing optimal post curing times for safe results.
This procedure must be documented and recorded in an Instructions for Use (IFU) which are to be performed by both the printer and resin manufacturer. This gives users a well-defined workflow on how to go about producing safe, high-quality medical devices.