Oxygen inhibition of autopolymerization of polymethylmethacrylate-glass fibre composite.
The aim of this study was to determine the thickness of the unpolymerized surface layer of autopolymerizing polymethylmethacrylate (PMMA) and PMMA-glass fibre (GF) composite. Powder-to-liquid (P/L) ratios of 10 : 8, 10 : 9 and 10 : 10 by weight of the commercial PMMA was tested and the E-glass fibre weave was used as filler in the PMMA-GF composite. The resin was polymerized between two glass plates at 55 degrees C in air under an air pressure of 300 kPa. Five samples were polymerized for each test group. The inhibition depth was measured by a light microscopic technique with polarized light. The inhibition depth was affected by the P/L ratio of the PMMA: the mean inhibition depth of the unfilled PMMA with the P/L ratio of 10 : 10 was 248.6 microm, while it was 175.4 microm in PMMA with the P/L ratio of 10 : 8 (p=0.044). The inhibition depths were higher in the PMMA-GF composite than in the plain PMMA, which was explained by an inadequate impregnation of the GF weave with the PMMA resin. The results suggest that improper impregnation of the fibre product with autopolymerizing PMMA resin can cause oxygen inhibition of the polymerization reaction which should be taken into account when fibre products are clinically used.
Vallittu
P K
PK
NIOM Scandinavian Institute of Dental Materials, Norway and Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Finland.