Abstract
Aims: To compare the shear bond strength (SBS) of composite bonded to dentin cured by three light curing units (LCUs), which are quartz tungsten halogen (QTH) and two types of light emitting diode (LED) machines. Materials and Methods: Buccal dentin of 90 upper premolars was exposed, prior to restorative procedure. Samples divided into 3 groups, restoration of each group cured by Astralis 5 [Austria], Top Light, [Taiwan] and Ultradent [USA]. Each group further subdivided into three subgroups. After bonding application, each subgroup of every group restored by one of 3 composites: Point 4™, Tetric and Degufill mineral. Composite applied and cured for 40 seconds. Samples thermocycled and loaded at tooth–composite interface. Results: Analysis of variance (ANOVA) with significance p < 0.05 followed by Duncan Multiple Range Test, showed that SBS of subgroups that cured by Ultradent (400 mW/cm2) was significantly higher than Astralis 5 (405 mW/cm2) and Top Light (141 mW/cm2). The SBS of Astralis 5 was significantly higher than Top Light. No significant differences found among subgroups those cured by same LCU. Conclusions: Shear bond strength of resin composite bonded to dentin is directly proportional with the light intensity. However, better result obtained by a high intensity LEDs compared with an equivalent intensity QTH–LCUs.
Highlights
INTRODUCTIONVisible light curing materials includeing resin composite, resin modified glass ionomers, cavity liners, fissure sealants, dentin primers, bonding agents and luting agents are widely used in dentistry (1)
Visible light curing materials includeing resin composite, resin modified glass ionomers, cavity liners, fissure sealants, dentin primers, bonding agents and luting agents are widely used in dentistry (1).The efficiency of radiation source for photo polymerization has become increasingly important in daily clinical conditions
Duncan Multiple Range Test revealed that there are no significant differences in shear bond strength (SBS) among Point 4TM, Tetric and Degufill mineral composite types that cured by the same light curing units (LCUs)
Summary
Visible light curing materials includeing resin composite, resin modified glass ionomers, cavity liners, fissure sealants, dentin primers, bonding agents and luting agents are widely used in dentistry (1). The traditionally used unit for polymerization of composite is quartz tungsten halogen (QTH) light curing unit (LCU). They have some specific drawbacks including the reduction of light out–put with the time (1), the halogen lamp and reflector may deteriorate over time due to the light operating temperatures and significant quality of heat produced during the operating cycle, these result in reducetion of curing effectiveness of QTH–LCU over time (2), in addition to hazard of pulpal damage as 5.5 °C increase in the pulpal temperature may cause irreversible damage of teeth pulps (3). The aim of this study was to compare shear bond strength (SBS) of composite bonded to dentin cured by three light curing units (LCUs) which are quartz tungsten halogen (QTH) and two types of light emitting diode (LED) machines (two different intensities)
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