E.K. VILJANEN1, M. SKRIFVARS2, and P.K. VALLITTU1, 1 University of Turku, Finland, 2 University College of Borås, Sweden
Objectives: In this work we studied the residual
methyl methacrylate content of photo- and postpolymerized dendrimer copolymers
that might be used in dental applications.
Methods: The experimental dendrimers used were
D12 with 12 reactive methacrylate groups and D24 with 24 reactive methacrylate
groups. One of these dendrimers and methyl methacrylate (MMA) were mixed in
weight ratios of 50:50 and 80:20. 3 wt-% of camphorquinone and 3 wt-% of 2-(N,N-dimethylamino)ethyl
methacrylate were used as the light activated initiator and catalyst.
Photopolymerized specimens (n=6) were polymerized with blue light (400-520 nm)
for 40 seconds (750 mW/cm2). An additional group of specimens
(postpolym.) were postcured at 120oC for 15 minutes after light
polymerization.
The residual MMA was extracted with 1:4 mixture of tetrahydrofuran and methanol
for 72±2 hours and analyzed with HPLC.
Results: The released residual MMA quantities are
presented in the table as percentage
of mass of the polymerized specimen. Standard deviation in parenthesis.
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D12
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D24
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D:MMA
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Photopolym.
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Postpolym.
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Photopolym.
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Postpolym.
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50:50
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4.5 (1.0)
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n/a
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3.5 (1.0)
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n/a
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80:20
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1.7 (0.2)
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1.0 (0.1)
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3.1 (0.7)
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1.5 (0.7)
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Conclusions: The results support our hypothesis,
based on earlier degree of monomer conversion measurements, that the
dendrimer-monomer mixture reacted probably in two phases: the dendrimer was
polymerized with light and MMA was polymerized with increased temperature.
Funded by National Technology
Agency TEKES, Finland.
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