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Determination of resin cure using infrared analysis without an internal standard
1Medical College of Georgia School of Dentistry, Augusta 30912-1260, USA.
Objectives:
The purpose of this study was to develop a methodology whereby the monomer conversion of dental restorative resins which contain no functional group acting as an internal standard can be easily determined using infrared spectroscopy.
Methods:
Calibration solutions of MMA were made from which the quantification of weight percent methacrylate groups (CH2 = C(CH3)C = O) (termed WPMG) could be determined using infrared spectroscopy. The extent of resin cure using the WPMG method consisted of calculating the changes in WPMG pre- and post-cure. The extent of cure of a commercial unfilled bonding resin was calculated using infrared methods utilizing the internal aromatic standard, and also by means of WPMG.
Results:
WPMG had an identical optical constant for a wide range of monomers: MMA, TEGDMA, EGDMA, HEMA: The extent of monomer conversion using both methods of analysis indicated statistically equivalent results: 75.2 +/- 1.0% using an internal standard, and 76.0 +/- 1.1% using WPMG.
Significance:
The methods developed in this study using infrared spectroscopic methods facilitate the determination of cure of dental resins which do not have functional groups to serve as internal standards.