Curing Capability of Halogen and LED Light Curing Units in Deep Class II Cavities in Extracted Human Molars

Abstract

SUMMARYClass II cavities were prepared in extracted lower molars filled and cured in three 2-mm increments using a metal matrix. Three composites (Spectrum TPH A4, Ceram X mono M7 and Tetric Ceram A4) were cured with both the SmartLite PS LED LCU and the Spectrum 800 continuous cure halogen LCU using curing cycles of 10, 20 and 40 seconds. Each increment was cured before adding the next. After a sevenday incubation period, the composite specimens were removed from the teeth, embedded in selfcuring resin and ground to half the orofacial width. Knoop microhardness was determined 100, 200, 500, 1000, 1500, 2500, 3500, 4500 and 5500 µm from the occlusal surface at a distance of 150 µm and 1000 µm from the metal matrix. The total degree of polymerization of a composite specimen for any given curing time and curing light was determined by calculating the area under the hardness curve.Hardness values 150 µm from the metal matrix never reached maximum values and were generally lower than those 1000 µm from the matrix. The hardest composite was usually encountered between 200 µm and 1000 µm from the occlusal surface. For every composite-curing time combination, there was an increase in microhardness at the top of each increment (measurements at 500, 2500 and 4500 µm) and a decrease towards the bottom of each increment (measurements at 1500, 3500 and 5500 µm). Longer curing times were usually combined with harder composite samples. Spectrum TPH composite was the only composite showing a satisfactory degree of polymerization for all three curing times and both LCUs.Multiple linear regression showed that only the curing time (p<0.001) and composite material (p<0.001) had a significant association with the Clinical RelevanceKnoop hardness testing showed that the new generation of light-emitting diodes (LED) have enough power to cure composites in the same time as light curing units (LCU). The composite material and curing time have a significant association with the degree of polymerization.

Microhardness of Composite Materials With Different Organic Phases in Deep Class II Cavities: An In Vitro Study

“…As observed by Hasler and others, 14 the microhardness values of all composites were lower close to the matrix. The setup in this study might account for this observation.…”

“…As a result, the microhardness numbers remained consistent throughout all depths. According to Hasler and others, 14 a cumulative curing effect can not be taken into consideration in this context. They concluded that it can not be assumed that curing further increments has an effect on the degree of polymerization of underlying layers.…”

“…A slightly modified setup according to Hasler and others 14 was used for this purpose. It has been shown that the determination of microhardness as a surrogate parameter of material properties is a suitable method to compare different resin composites.…”

“…Standardized class II cavities were prepared according to the study of Hasler and others, 14 as shown in Figure 1. The preparation was performed with a cylindrical diamond bur (Komet, Gebr Brasseler GmbH, Lemgo, Germany).…”

Influence of Curing Light Type and Staining Medium on the Discoloring Stability of Dental Restorative Composite

“…Moreover, LED systems are often considered similar or comparatively better than QTH system in terms of the degree of polymerization (Hasler et al, 2006), polymerization shrinkage (Uhl et al, 2005), microleakage (Attar and Korkmaz, 2007), wear rate (Ramp et al, 2006), flexural properties (Keogh et al, 2004) and hardness (de Araújo et al, 2008).…”