Effect of Light Irradiation Time on the Mechanical Properties of Two Flowable Composites with Different Initiation Systems in Bonded and Unbonded Cavities

Abstract

The aim of this study was to evaluate the regional mechanical properties of flowable composites with different initiation systems under free and constrained conditions. Forty cavities fabricated in resin blocks with or without bonding treatment were bulk-filled with Estelite Flow Quick (EFQ) or Palfique Estelite LV (ELV), followed by light irradiation for 10 or 30 seconds. Each specimen was sliced to three slabs parallel to the long axis. The middle slab was serially sliced from top to bottom to harvest three sticks for ultimate tensile strength (UTS) measurement. The remaining slabs were polished for microhardness (KHN) measurement. The results indicated that the UTS and KHN of both flowable composites decreased toward the bottom of the cavity and increased with prolonged light irradiation time. At the upper cavity region, UТS values of the bonded groups were significantly lower than those of the unbonded groups, except for the 10-second light irradiation group of EFQ. As for KHN, the values did not change significantly for both flowable composites between the unbonded and bonded groups.

Bond strength and ultimate tensile strength of resin composite filled into dentine cavity; effect of bulk and incremental filling technique

“…Recent studies have demonstrated that the mechanical properties of resin composites were significantly reduced under constrained conditions. [11][12][13] However, there is limited information on the relationship between bonding to cavity walls and the mechanical properties of resin composites. Many questions still remain on how stresses compromise the interface and/or the internal cohesion of the resin restoration.…”

Can extended photoactivation time of resin-based fissure sealer materials improve ultimate tensile strength and decrease water sorption/solubility?

“…Ultimate tensile strength (UTS) is a physical property which shows the maximum cohesive resistance to tensile force of a material. 10 Thus, examination of cohesive strength of fissure sealer materials may predict their resistance to fracture in a clinical environment. It was demonstrated that increasing light exposition time improves the UTS of flowable composites.…”

Effect of Speed of Loading on Compressive Strength and Flexural Strength of Dental Resin-Composites

“…This requires adequate irradiance of the curing unit, enough curing time, proper determination of the thickness of resin-composite material to be cured, and the contact between the curing tip and the specimen. It was said that incomplete polymerization may produce a heterogeneous specimen that has an uneven stress distribution during loading which, in turn, adversely affects the results of the mechanical properties measured [15,29] .…”

“…Strength values of resin-based restorative materials are usually related to their composition [13] , irradiation time and packing procedures [5,14] . Strength properties have been utilized to characterize and compare resin-composite materials [15] .…”