OBJECTIVES: The aim of this study was to investigate the influence of the molecular mobility and the chemical structure of dimethacrylates most commonly used in dental composites on shrinkage stress from experimental matrices. METHODS: Three established neat monomers BisGMA (B), UEDMA (U) and TEGDMA (T), two experimental comonomers BisGMA-based (B-T(70/30) and B-T(50/50)) and two comonomers UEDMA-based (U-T(88/11) and U-T(66/33)) in weight%, were elaborated. Camphorquinone (CQ) and N,N-cyanoethylmethylaniline (CEMA), as photoinitiator and reducing agent, were added. Then the matrices were mixed by centrifugal force at room temperature. The viscosity (eta), the glass transition temperature of the monomers and comonomers systems (T(g(monomer)) and the maximum shrinkage stress (MSS) of each material (five replications) were statistically analysed by one-way ANOVA/Tuckey's test and Pearson's correlation procedure (p = 0.05). RESULTS: All formulations exhibited a newtonian rheological behavior. The viscosity of the comonomers systems can be divided in two groups: the pair B-T(70/30)/U-T(88/11) with the viscosity 3.5+/-3.10(-3)Pa.s and the pair B-T(50/50)/U-T(66/33) with the viscosity 0.28+/-3.10(-3)Pa.s. This pairs constituted samples allowing to compare the shrinkage stress of the BisGMA and UEDMA-based matrices with each other. The T(g(monomer)) of each group showed equivalent statistically values: -37.1 +/- 0.02 degrees C (U-T(88/11)) with -39.3 +/- 0.02 degrees C (B-T(70/30)) for the 3.5 Pa.s pair, and -53.1 +/- 0.03 degrees C (U-T(66/33)) with -58.5 +/- 0.01 degrees C (B-T(50/50)) for the 0.28 Pa.s one. There was a correlation between eta and T(g(monomer)) (r < 0.45 and p < 0.01). In decreasing order, the shrinkage stress was 14.11 +/- 0.3 MPa (T), 10.64 +/- 0.6 MPa (U-T(66/33)), 8.16 +/- 0.25 MPa (B-T(50/50)) without a significant difference compared to 8.04 +/- 0.5 MPa (U-T(88/11)), 6.83 +/- 0.52 MPa (U), 4.44 +/- 0.25 MPa (B-T(70/30)) and 0.33 +/- 0.3 MPa (B). There was a negative correlation between eta (r < -0.42 and p < 0.01), T(g(monomer)) (r < -0.41 and p < 0.01) and MSS. Whatever the viscosity, the UEDMA-based matrices developed higher shrinkage stresses than the BisGMA homologues. SIGNIFICANCE: The shrinkage stress development increase with the molecular mobility of the reacting medium. For the same molecular mobility, the large differences in stress values of the matrices studied are correlated to the structure and particularly the functionality of the monomers used.
OBJECTIVES: The aim of this study was to investigate the influence of the molecular mobility and the chemical structure of dimethacrylates most commonly used in dental composites on shrinkage stress from experimental matrices. METHODS: Three established neat monomers BisGMA (B), UEDMA (U) and TEGDMA (T), two experimental comonomers BisGMA-based (B-T(70/30) and B-T(50/50)) and two comonomers UEDMA-based (U-T(88/11) and U-T(66/33)) in weight%, were elaborated. Camphorquinone (CQ) and N,N-cyanoethylmethylaniline (CEMA), as photoinitiator and reducing agent, were added. Then the matrices were mixed by centrifugal force at room temperature. The viscosity (eta), the glass transition temperature of the monomers and comonomers systems (T(g(monomer)) and the maximum shrinkage stress (MSS) of each material (five replications) were statistically analysed by one-way ANOVA/Tuckey's test and Pearson's correlation procedure (p = 0.05). RESULTS: All formulations exhibited a newtonian rheological behavior. The viscosity of the comonomers systems can be divided in two groups: the pair B-T(70/30)/U-T(88/11) with the viscosity 3.5+/-3.10(-3)Pa.s and the pair B-T(50/50)/U-T(66/33) with the viscosity 0.28+/-3.10(-3)Pa.s. This pairs constituted samples allowing to compare the shrinkage stress of the BisGMA and UEDMA-based matrices with each other. The T(g(monomer)) of each group showed equivalent statistically values: -37.1 +/- 0.02 degrees C (U-T(88/11)) with -39.3 +/- 0.02 degrees C (B-T(70/30)) for the 3.5 Pa.s pair, and -53.1 +/- 0.03 degrees C (U-T(66/33)) with -58.5 +/- 0.01 degrees C (B-T(50/50)) for the 0.28 Pa.s one. There was a correlation between eta and T(g(monomer)) (r < 0.45 and p < 0.01). In decreasing order, the shrinkage stress was 14.11 +/- 0.3 MPa (T), 10.64 +/- 0.6 MPa (U-T(66/33)), 8.16 +/- 0.25 MPa (B-T(50/50)) without a significant difference compared to 8.04 +/- 0.5 MPa (U-T(88/11)), 6.83 +/- 0.52 MPa (U), 4.44 +/- 0.25 MPa (B-T(70/30)) and 0.33 +/- 0.3 MPa (B). There was a negative correlation between eta (r < -0.42 and p < 0.01), T(g(monomer)) (r < -0.41 and p < 0.01) and MSS. Whatever the viscosity, the UEDMA-based matrices developed higher shrinkage stresses than the BisGMA homologues. SIGNIFICANCE: The shrinkage stress development increase with the molecular mobility of the reacting medium. For the same molecular mobility, the large differences in stress values of the matrices studied are correlated to the structure and particularly the functionality of the monomers used.
Authors: Vincent S D Voet; Geraldine H M Schnelting; Jin Xu; Katja Loos; Rudy Folkersma; Jan Jager Journal: J Vis Exp Date: 2018-09-12 Impact factor: 1.355
Authors: Han Byul Song; Nancy Sowan; Parag K Shah; Austin Baranek; Alexander Flores; Jeffrey W Stansbury; Christopher N Bowman Journal: Dent Mater Date: 2016-08-11 Impact factor: 5.304
Authors: Maciej Podgórski; Eftalda Becka; Mauro Claudino; Alexander Flores; Parag K Shah; Jeffrey W Stansbury; Christopher N Bowman Journal: Dent Mater Date: 2015-09-07 Impact factor: 5.304