Flexural strength and modulus of elasticity of four dental composites polymerized with light emitting diode (LED) and halogen light

Douglas Michielin Sari,Josué Martos,Prudêncio Willy Rodo Osinaga,Rita De Cássia Duquia

doi:10.14295/bds.2006.v9i3.244

Abstract

The purpose of this investigation was to evaluate the flexural strength (FS) and modulus of elasticity (ME) of three microhybrid resins (Filtek Z250; Charisma; P60) and one submicrohybrid resin (Concept) using LED or halogen light polymerization. Twenty specimens (25x2x2 mm) per tested material were prepared and polymerized using a halogen or LED curing unit and stored in distilled water. FS and ME tests were performed on an Instron universal testing machine (0.75mm/min). ANOVA and multiple comparisons (SNK) showed that the two polymerization systems resulted in no significant differences (p>0.05) in the FS of Charisma and Filtek Z250. The two curing systems also produced similar results in the ME of Charisma, Concept and Filtek Z250. Significant differences were found in FS and ME, with the halogen curing light system showing better results than the LED system. The LED LCU systems did not exhibit a superior performance in our investigation of any of the composite resins, in terms of flexural strength and modulus of elasticity.

Highlights

The curing of dental composites with blue light, which was introduced in the 1970s, initially showed several drawbacks[2]
The mean flexural strength of Charisma and FiltekZ250 specimens polymerized with the halogen Light curing unit (LCU) was statistically similar to that polymerized with LIGHT EMITTING DIODE (LED) LCU
The average modulus of elasticity of the composite resin P-60 was higher when it was polymerized with halogen LCU than with LED LCU

Summary

Introduction

The curing of dental composites with blue light, which was introduced in the 1970s, initially showed several drawbacks[2]. The curing of composite resins depends on the intensity and spectral output of the curing unit and on the chemical characteristics of the resin composition[9]. Very slight changes in the intensity of the light unit cause significant alterations in the degree of conversion on a superficial area of the composite resin[17]. The main factors responsible for the success of restorations with photoactivated resins are sufficient light intensity, correct wavelength and appropriate time of polymerization[1,2]. Unlike polymerization of chemically activated resins, polymerization in photoactivated systems does not take place in the entire mass but only where the light reaches into the absorption spectrum of the camphorquinone photoinitiator[16]

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