The application of magnetic resonance microimaging to the visible light curing of dental resins. Part 2. Dynamic imaging by the FLASH-MOVIE pulse sequence.
OBJECTIVE
To investigate the application of a rapid NMR imaging pulse sequence, FLASH-MOVIE, to the visible light curing of dental restorative materials.


METHODS
The light guide was applied at one end of a cylindrical specimen of visible light curing unfilled resin and the light directed along the cylinder. During polymerisation an NMR imaging pulse sequence, FLASH-MOVIE, was run at 15s intervals with a 50 ms repetition time. The image of a 1mm thick vertical slice was recorded with a (125 microm)2 pixel size.


RESULTS
Images with good contrast were obtained from all resin monomers. The image intensity from the polymer was indistinguishable from the background intensity. Thus, the progress of light activated polymerisation in the material could be followed in real time through a series of up to 16 images. Initially the image intensity increased in the material closest to the light guide, then decreased over time to zero. Concomitant with this fall, a "cure-front" moved through the specimen.


CONCLUSIONS
The FLASH-MOVIE NMR pulse sequence applied to microimaging of dental diacrylate resins can be used to obtain a dynamic record of visible light curing. A more refined experimental protocol will be required to apply this unique data to models proposed for this polymerisation mechanism.
Lloyd
C H
CH
Dental School, University of Dundee, DD1 4HN, Dundee, UK. c.h.lloyd@dundee.ac.uk
Scrimgeour
S N
SN
Chudek
J A
JA
Hunter
G
G
MacKay
R L
RL
D000465:Algorithms; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008027:Light; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D011092:Polyethylene Glycols / Q000737:chemistry / Q000528:radiation effects; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D011109:Polymethacrylic Acids / Q000737:chemistry / Q000528:radiation effects; D019163:Reducing Agents / Q000737:chemistry / Q000528:radiation effects; D013499:Surface Properties; D013729:Terpenes / Q000737:chemistry / Q000528:radiation effects; D013997:Time Factors
D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D011108:Polymers; D011109:Polymethacrylic Acids; D019163:Reducing Agents; D013729:Terpenes; C080508:poly(triethylene glycol dimethacrylate-1,6-bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane) copolymer; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C048339:camphoroquinone; C049840:2-(dimethylamino)ethyl methacrylate