TY - JOUR
T1 - Polymerization development of "low-shrink" resin composites
T2 - Reaction kinetics, polymerization stress and quality of network
AU - Yamasaki, Lilyan C.
AU - De Vito Moraes, André G.
AU - Barros, Mathew
AU - Lewis, Steven
AU - Francci, Carlos
AU - Stansbury, Jeffrey W.
AU - Pfeifer, Carmem S.
N1 - Funding Information:
This study was funded by Capes (Coordination of Improvement of Higher Education) , grant no. BEX 1079-11-5 . The authors would like to express their gratitude to Antônio Gentil (Technological Research Institute - Laboratory of Electrical and Optical Engineering - University of São Paulo) for his assistance with the irradiance measures. The composites tested in this study were kindly provided by the respective manufacturers.
PY - 2013/9
Y1 - 2013/9
N2 - Objectives. To evaluate "low-shrink" composites in terms of polymerization kinetics, stress development and mechanical properties. Methods. "Low-shrink" materials (Kalore/KAL, N'Durance/NDUR, and Filtek P90/P90) and one control (Esthet X HD/EHD) were tested. Polymerization stress (PS) was measured using the Instron 5565 tensometer. Volumetric shrinkage (VS) was determined by the ACTA linometer. Elastic modulus (E) and flexural strength (FS) were obtained by a three-point bending test. Degree of conversion (DC) and polymerization rate (Rp) were determined by NIR spectroscopy (6165 cm -1 for dimethacrylates; 4156 and 4071 cm-1 for P90). Photopolymerization was performed at 740 mW/cm2 × 27 s. Glass transition temperature (Tg), degree of heterogeneity and crosslink density were obtained in a DMA for the fully cured specimens. Analysis of extracts was done by 1H NMR. Data were analyzed with one-way ANOVA/Tukey's test (α = 0.05). Results. The control presented the highest shrinkage and Tg. P90 showed the highest modulus, and NDUR demonstrated the highest conversion. The polymerization rates were comparable for all materials. NDUR and KAL had the highest and the lowest network homogeneity, respectively. The multifunctional P90 had the highest crosslink density, with no difference between other composites. The control had the greatest stress development, similar to NDUR. Crosslinking density and polymer network homogeneity were influenced by degree of conversion and monomer structure. Significance. Not all "low-shrink" composites reduced polymerization stress. P90 and NDUR had no leachable monomers, which was also a function of high crosslinking (P90) and high conversion (NDUR).
AB - Objectives. To evaluate "low-shrink" composites in terms of polymerization kinetics, stress development and mechanical properties. Methods. "Low-shrink" materials (Kalore/KAL, N'Durance/NDUR, and Filtek P90/P90) and one control (Esthet X HD/EHD) were tested. Polymerization stress (PS) was measured using the Instron 5565 tensometer. Volumetric shrinkage (VS) was determined by the ACTA linometer. Elastic modulus (E) and flexural strength (FS) were obtained by a three-point bending test. Degree of conversion (DC) and polymerization rate (Rp) were determined by NIR spectroscopy (6165 cm -1 for dimethacrylates; 4156 and 4071 cm-1 for P90). Photopolymerization was performed at 740 mW/cm2 × 27 s. Glass transition temperature (Tg), degree of heterogeneity and crosslink density were obtained in a DMA for the fully cured specimens. Analysis of extracts was done by 1H NMR. Data were analyzed with one-way ANOVA/Tukey's test (α = 0.05). Results. The control presented the highest shrinkage and Tg. P90 showed the highest modulus, and NDUR demonstrated the highest conversion. The polymerization rates were comparable for all materials. NDUR and KAL had the highest and the lowest network homogeneity, respectively. The multifunctional P90 had the highest crosslink density, with no difference between other composites. The control had the greatest stress development, similar to NDUR. Crosslinking density and polymer network homogeneity were influenced by degree of conversion and monomer structure. Significance. Not all "low-shrink" composites reduced polymerization stress. P90 and NDUR had no leachable monomers, which was also a function of high crosslinking (P90) and high conversion (NDUR).
KW - Composite
KW - Degree of conversion
KW - Dynamic mechanical analysis
KW - Extraction study
KW - Polymerization kinetics
KW - Polymerization stress
KW - Silorane
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U2 - 10.1016/j.dental.2013.04.021
DO - 10.1016/j.dental.2013.04.021
M3 - Article
C2 - 23849746
AN - SCOPUS:84882456540
SN - 0109-5641
VL - 29
SP - e169-e179
JO - Dental Materials
JF - Dental Materials
IS - 9
ER -