POLISH AND GLOSS RETENTION OF RESINS
The long-term gloss of resin restorations depends on:
- Proper cure, isolation, and placement without material compromises
- The largest particle size of the resin, which limits the achievable finish if large. Many popular paste resins have particles of 3000 to 5000 nanos, which will never polish highly.
- The finishing system creating the initial polish of the resin. Carbides, diamonds,points and pastes are compared in Clincians Report, April 2014
LARGEST PARTICLE SIZE OF THE RESIN
Largest particle size can be difficult information to obtain, because most manufacturers specify an average particle size for their resin formulations. The average is meaningless and not predictive of gloss. Terms such as “nano-hybrid” are also not helpful, because it is the largest particle size which determines the luster or lack of it, even if a resin contains a large percentage of nano-particles to in-fill around these large “boulders” of filler.
“Gloss Index” (GI) is the best indicator of polishabiity, and it is a scientific parameter indicating the % of light reflected back from the polished surface. A figure of over 90% indicates a resin that will be suitable for cosmetic applications. A survey of newer resins including GI and GI retention was published by Clincians Report, April 2019, Volume 12, Issue 4. Subscription is required for online access.
It should be noted that gloss retention is as critical a variable as particle size, because initial gloss may not persist due to formulation factors other than particle size.
For another source, see clinical studies by The Dental Advisor Their reports usually include GI and gloss retention.