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Thermal Shrinkage Reveals the Feasibility of Pulse-delay Photocuring Technique



Sri Vikram Palagummi, Taeseung Hong, Li Jiang, Martin Chiang


Objectives: To resolve applicability of the pulse-delay photocuring technique to restorative dental composites as a clinical strategy for the reduction in the detrimental polymerization stress. Methods: Model dental composites with high and low-filler contents were photocured with several different combinations of pulse-delay photocuring variables (irradiance, exposure time, and delay time). A cantilever-beam based instrument (NIST Standards Reference Instrument 6005) was used to implement the photocuring technique for the measurement of the polymerization properties (the degree of monomer conversion, polymerization stress induced due to shrinkage, and temperature change due to the reaction exotherm and absorbance) simultaneously in real-time. These properties were compared to that obtained using the conventional photocuring technique (i.e., using a constant irradiance for a fixed exposure time, a uniform exposure). Results: There exists a minimum radiant exposure through which a certain reduction in polymerization stress can be achieved by using the pulse-delay photocuring technique when compared with the conventional photocuring technique, without sacrificing the degree of monomer conversion. Lower thermal shrinkage, during the post-curing process, rather than the stress relaxation or lower degree of monomer conversion as claimed in the literature is the cause of the reduction in the polymerization stress. Significance: The study clarifies a long-standing confusion and controversy on the applicability of the pulse-delay photocuring technique for reducing the polymerization stress and promotes its potential clinical success for dental restorative composites.
Dental Materials


polymerization stress, thermal shrinkage, radiant exposure, exposure reciprocity law, additive manufacturing


Palagummi, S. , Hong, T. , Jiang, L. and Chiang, M. (2021), Thermal Shrinkage Reveals the Feasibility of Pulse-delay Photocuring Technique, Dental Materials, [online],, (Accessed May 21, 2024)


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Created December 1, 2021, Updated November 29, 2022