Polymerization Kinetics of Pre-heated Composite

Abstract

Temperature affects the polymerization behavior of dimethacrylate-based materials. This study describes the influence of pre-polymerization temperature and exposure duration on polymerization kinetics of a commercial dental photo-activated composite at the top and at 2-mm depth. We used the temperature-controlled stage of a diamond-attenuated-total-reflectance unit to pre-set composite temperature between 3 degrees and 60 degrees C. Composite was light-exposed by a conventional quartz-tungsten-halogen curing unit for 5, 10, 20, or 40 sec. Real-time conversion, maximum conversion rate (R(p)(max)), time to achieve R(p)(max), and conversion at R(p)(max) were calculated from infrared spectra. Composite pre-warming enhanced maximal polymerization rate and overall monomer conversion (top significantly greater than 2 mm). Time when R(p)(max) occurred did not change with temperature, but occurred sooner at the top than at 2-mm depth. Conversion at R(p)(max) increased with temperature, allowing more of the reaction to occur prior to vitrification than at room temperature.

Pre-heated dual-cured resin cements: analysis of the degree of conversion and ultimate tensile strength

“…Such a finding corroborates previously reported results 10,11 and might be attributed to the increased radical mobility and collision frequency of the unreacted active groups and radicals resulting from the decrease in RC viscosity promoted by increased RC temperatures.…”

“…A temperature of 50º C was chosen based on other studies 10,11,23 and was maintained for 5 min during specimen polymerization. This methodology may differ from a clinical situation where a drastic drop in temperature of the heated resin composites is observed when they are placed in tooth cavities.…”

“…3,[6][7][8][9] Some studies have shown that pre-heating the resin composite to 50º C or 60º C increases its degree of conversion (DC). 10,11 As a result, increased hardness and fracture strength, increased flexural strength and modulus, and increased resistance to wear are expected. 12,13 Therefore, it is reasonable to assume that dual-cured RCs polymerized at increased temperature might show higher DC and improved mechanical properties than RCs polymerized at room temperature.…”

Dielectric analysis of depth dependent curing behavior of dental resin composites

“…An important issue in visible light-curing (VLC) composites development and research as well as in photo-chemistry in general is the question: How fast do composites cure, and how deep are they properly cured [1][2][3][4][5][6]? Since the development of VLC dental restoratives numerous studies have investigated the curing kinetics [7][8][9][10][11], the degree of cure (DC) [11][12][13][14] and the depth of cure (DC) [14][15][16][17][18][19][20][21].…”

“…In order to get a better understanding of the curing process and its dependency on curing parameters such as curing time, light intensity, resin formulation, initiator system etc., various test methods have been applied in real time curing investigations. The most common techniques determine the curing-enthalpy via Differential Scanning Calorimetry (DSC) [7,[22][23][24], the DC via Fourier Transformed Infrared Spectroscopy (FTIR) [3,4,[12][13][14], the shrinkage strain via dilatometric devices (e.g. bonded-disk method) [9][10][11][12]25], the shrinkage stress via stress-analyzer [13,26,27] and light transmission via radiometer [6,8,28].…”