Determination of double bond conversion in dental resins by near infrared spectroscopy.
OBJECTIVE
This study determined the validity and practicality of near infrared (NIR) spectroscopic techniques for measurement of conversion in dental resins.


METHODS
Conversion measurements by NIR and mid-IR were compared using two techniques: (1) The conversion of 3mm thick photopolymerized Bis-GMA/TEGDMA resin specimens was determined by transmission NIR. Specimens were then ground and reanalyzed in KBr pellet form by mid-IR. (2) As further verification, thin resin films were photocured and analyzed by mid-IR. Multiple thin films were then compressed into a thick pellet for examination by NIR.


RESULTS
Conversion values obtained by NIR and mid-IR techniques did not differ significantly. A correction for changing specimen thickness due to polymerization shrinkage was applied to NIR conversion measurements since an internal standard reference peak was not employed. Sensitivity of the NIR technique was superior to those based on the mid-IR.


CONCLUSIONS
The nondestructive analysis of conversion in dental resins by NIR offers advantages of convenience, practical specimen dimensions and precision compared with standard mid-IR analytical procedures. Because glass is virtually transparent in the NIR spectrum, this technique has excellent potential for use with filled dental resins as well.
Stansbury
J W
JW
Biomaterials Group, Polymers Division, 100 Bureau Drive/Stop 8545, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA. jeff.stansbury@uchsc.edu
Dickens
S H
SH
D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003432:Cross-Linking Reagents; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D013055:Spectrophotometry, Infrared / Q000379:methods*
D003188:Composite Resins; D003432:Cross-Linking Reagents; D011108:Polymers; D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate