Influence of thermal expansion on shrinkage during photopolymerization of dental resins based on bis-GMA/TEGDMA

Influence of Bis-GMA Derivative Monomer-Based Particulate Composite Resins on the Cuspal Deformation and Microleakage of Restored Teeth

“…The current study supports previous studies that indicate the properties of light-activated composites continue to change after irradiation stops (Sakaguchi, Wiltbank, and Shah 2004). It was found in the literature that the volumetric change measured during lightcuring of exothermic dymethacrylic systems is a combination of contraction due to the polymerization reaction and expansion or contraction due to the exothermic polymerization and subsequent heat loss to the environment (Mucci et al 2009). …”

“…The absolute values of the current studies were not compared to other studies because this would be possible only if the same conditions were used, and only if evaluations were performed with the same gage of cuspal deformation, materials, and light-curing system (Musanje et al 2005). In order to most objectively distinguish the cuspal deflection due to polymerization shrinkage out of the complexity of polymerization processes, many tests would be needed in a study that should include the measurement of the volumetric shrinkage, double bond conversion, elastic modulus of the composite, evaluation of cuspal deformations and marginal integrity of the restorations, and the tests used by Mucci et al (2009) to assess the thermal contribution to the overall shrinkage (temperature evolution during photopolymerization, coefficiant of thermal expansion, specific heat, and molar extinction coefficient of CQ).…”

Methacrylate and Epoxy Resins Photocured by Means of Visible Light-Emitting Diodes (LEDs)

“…29 The volume shrinkage during polymerization should be related to the number of functional groups that have reacted before the system enters the glassy state. A linear correlation, between volume contraction and mole of converted double bonds, was first proposed in 1953 by Loshaek and Fox 30 and more recent literature 31 still refers to this early work.…”

“…Figure 15.8 shows typical plots of shrinkage vs. irradiation time of a methacrylate resin photoactivated with CQ/amine. 29 Specimens were irradiated with a blue LED (11.5 mW cm À2 , peak 467 nm) for 5, 10 and 20 s. The shrinkage was monitored during and after exposure to complete 300 s. The lines show the times at which the LED was turned off. Only the first 120 s of test are shown to make the plot clearer.…”

Evaluation of polymerization shrinkage of dental composites by an optical method

“…The majority of these methods can be divided into two groups: those that evaluate the change in density and volume (dilatometer and pycnometer) and those that take linear measurements (linometer, interferometer, thermo-mechanical and optical analyses) [14]. Some of these methods involve direct contact with the sample, i.e., Linear Variable Differential Transformers (LVDT), dilatometers, pycnometers, and strain gauges.…”