Dynamic monitoring of refractive index change through photoactive resins.
OBJECTIVE
The change in optical characteristics through the bulk of curing photopolymers is not fully understood. Photopolymerization processes are accompanied by photoinitiator absorption, density changes and volumetric shrinkage, which alter optical properties and affects curing efficiency through depth.


METHODS
This investigation demonstrates the use of a novel low coherence interferometry technique for simultaneous measurement of optical (refractive index) and physical (shrinkage) properties throughout curing of photoactive monomers containing various concentrations of bisphenol-A-diglycidyl ether dimethacrylate and triethylene glycol dimethacrylate.


RESULTS
Reliability of the interferometry technique was compared with an Abbé refractometer and showed a significant linear regression relationship (p<0.001; adjusted R(2)>0.99) for both uncured and cured resins. The extent and rate of refractive index change and magnitude of shrinkage strain was dependent upon monomer formulation.


CONCLUSIONS
The development of this interferometry technique provides a powerful non-invasive tool that will be useful for improving light transmission through photoactive resins and filled resin composites by precise control of optical properties through material bulk.
Hadis
M A
MA
University of Birmingham, United Kingdom.
Tomlins
P H
PH
Shortall
A C
AC
Palin
W M
WM
D000042:Absorption; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects; D055598:Chemical Phenomena; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D006801:Humans; D007368:Interferometry / Q000295:instrumentation / Q000379:methods; D008027:Light; D008422:Materials Testing; D055668:Photochemical Processes; D058567:Photoinitiators, Dental / Q000737:chemistry / Q000528:radiation effects; D011092:Polyethylene Glycols / Q000737:chemistry / Q000528:radiation effects; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry / Q000528:radiation effects; D012031:Refractometry; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013499:Surface Properties
D003188:Composite Resins; D058567:Photoinitiators, Dental; D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate