Document Detail

Shrinkage strain-rates of dental resin-monomer and composite systems.
MedLine Citation:
PMID:  15769537     Owner:  NLM     Status:  MEDLINE    
The purpose of this study was to investigate the shrinkage strain rate of different monomers, which are commonly used in dental composites and the effect of monomer functionality and molecular mass on the rate. Bis-GMA, TEGDMA, UDMA, MMA, HEMA, HPMA and different ratios of Bis-GMA/TEGDMA were mixed with Camphorquinone and Dimethyl aminoethyle methacrylate as initiator system. The shrinkage strain of the samples photopolymerised at Ca. 550 mW/cm2 and 23 degrees C was measured using the bonded-disk technique of Watts and Cash (Meas. Sci. Technol. 2 (1991) 788-794), and initial shrinkage-strain rates were obtained by numerical differentiation. Shrinkage-strain rates rose rapidly to a maximum, and then fell rapidly upon vitrification. Strain and initial strain rate were dependent upon monomer functionality, molecular mass and viscosity. Strain rates were correlated with Bis-GMA in Bis-GMA/TEGDMA mixtures up to 75-80 w/w%, due to the higher molecular mass of Bis-GMA affecting termination reactions, and then decreased due to its higher viscosity affecting propagation reactions. Monofunctional monomers exhibited lower rates. UDMA, a difunctional monomer of medium viscosity, showed the highest shrinkage strain rate (P < 0.05). Shrinkage strain rate, related to polymerization rate, is an important factor affecting the biomechanics and marginal integrity of composites cured in dental cavities. This study shows how this is related to monomer molecular structure and viscosity. The results are significant for the production, optimization and clinical application of dental composite restoratives.
Mohammad Atai; David C Watts; Zahra Atai
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Publication Detail:
Type:  Comparative Study; Evaluation Studies; Journal Article    
Journal Detail:
Title:  Biomaterials     Volume:  26     ISSN:  0142-9612     ISO Abbreviation:  Biomaterials     Publication Date:  2005 Aug 
Date Detail:
Created Date:  2005-03-16     Completed Date:  2005-07-27     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8100316     Medline TA:  Biomaterials     Country:  England    
Other Details:
Languages:  eng     Pagination:  5015-20     Citation Subset:  IM    
Department of Polymer Science, Iran Polymer and Petrochemical Institute (IPPI), Tehran-Karaj Highway, Exit 17, Pa... Tehran, P.O. Box 14965/115, Tehran 1497713115, Iran.
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MeSH Terms
Acrylic Resins / analysis,  chemistry*
Composite Resins / analysis,  chemistry*
Materials Testing
Molecular Conformation
Molecular Weight
Stress, Mechanical
Reg. No./Substance:
0/Acrylic Resins; 0/Composite Resins

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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