Effect of exposure time on the depth of polymerization of a visible light‐cured composite resin

Abstract

The effect of exposure time of a visible light source on the depth of polymerization and degree of hardness of a sample of Occlusin posterior composite resin was investigated. The border between cured and non-cured composite resin was identified by a change in colour and by applying pressure with a scalpel. Knoop hardness tests were performed perpendicular to the long axis of illumination. The composite resin nearer to the light source underwent more complete polymerization. Increased exposure time resulted in greater depth of cure. The rate of polymerization was greatest in the first 10 s. Maximum hardness measured up to a depth of 1 mm obtained after 80 s of exposure time. At greater depth, a decrease in Knoop hardness was observed. At exposures under 80 s, maximum hardness was not achieved even at a depth of only 1 mm.

Surface and bulk properties of dental resin- composites after solvent storage

“…Additionally, micro-hardness is considered as a strong indication to the degree of conversion of the material. Accordingly, measuring the surface microhardness could be a method of determining the longevity and the service life of the direct resin-based restorations [11,23,26,32,33]. Top surface hardness was measured as it received the maximum irradiance from the light curing unit and to avoid the attenuation of the light by passing through the bulk of the material [34].…”

Do new matrix formulations improve resin composite resistance to degradation processes?

“…Therefore, it may be hypothesized that hybrid composites with zirconia-derived fi llers could lead to a freer volume among the fi llers, considering KH is a mechanical property that may be related to the wear resistance of materials and their ability to remain stable. 25 The solubility parameter of absolute ethanol is near that of some dimethacrylate resin composites. The extent that a composite may be affected depends on the crosslink density formed in the polymerization processes.…”

Evaluation of Light Intensity Output of QTH and LED Curing Devices in Various Governmental Health Institutions

“…15 This results in a more polymerized composite material at the surface when compared with the deeper part of the same increment. 12,[16][17][18] Ideally, clinicians and dental assistants should examine the intensity of the light curing devices using a radiometer that measures the wavelength in a range of 400 to 520 nm. [19][20][21] Quartz-tungsten-halogen (QTH) curing lights were the standard for clinical use due to their dependability and satisfactory performance until the late 1990s.…”