Effect of curing time on the bond strength of a bracket-bonding system cured with a light-emitting diode or plasma arc light

Abstract

The purpose of this study was to assess the influence of two light units, a light-emitting diode (LED) and a plasma arc light (PAC), on the shear bond strength (SBS) of brackets bonded to enamel. Ninety bovine teeth were divided into six groups, according to the light-curing unit and exposure times used. In the LED (Ortholux; 3M-Unitek) group, the specimens were light cured for 5, 10, and 15 seconds. In the PAC (Apollo 95E; DenMed Technologies) group, the specimens were light cured for 3, 6, and 9 seconds. The brackets were bonded with Transbond XT (3M-Unitek), stored in distilled water at 37 °C for 24 hours and then submitted to SBS testing in a universal testing machine. The adhesive remnant index (ARI) was used to evaluate the amount of adhesive remaining on the teeth. According to analysis of variance and Tukey multiple comparisons test, the highest mean SBS was obtained with the LED at 15 seconds (16.68 MPa), which did not significantly differ from the LED 10 (14.76 MPa) or 5 (13.92 MPa) second groups (P > 0.05). The LED 10 and 5 second groups were not significantly different from the PAC 9 second group (12.66 MPa) or from the PAC 6 second group (9.96 MPa). The lowest mean SBS was obtained with the PAC 3 second group (8.29 MPa), which did not differ significantly from the PAC 6 second group. The method of light curing did not influence the ARI, with score 3 predominant. The LED at 5 seconds and the PAC at 3 seconds provided sufficient mean SBS to resist either orthodontic or masticatory forces.

Effect of etching time and light source on the bond strength of metallic brackets to ceramic

“…Dall'Igna et al (8) also found no significant differences among the LCU units. However, Cekic-Nagas et al (10) showed significant difference between LED and QTH and PAC units.…”

“…Photo-activated resin agents are usually used for this purpose (6,7). Several lightcuring units (LCUs) presenting varied light sources are available for photo-activation (8)(9)(10)(11)(12)(13)(14). In addition to the traditional quartz-tungsten-halogen (QTH) LCUs and the increasingly popular light-emitting diodes (LEDs), plasma arc (PAC) and laser units have been introduced to reduce the curing time.…”

Effectiveness of high irradiance for short-time exposures on polymerization of composite under metal brackets

“…On the other hand, another study using a similar LED reported only a slight improvement (around 20%) in bond strength when the light-curing time was increased from 5 to 15 seconds. 20 An explanation for this difference might be in the positioning of the LED tip during light activation. While in the former study the LED tip was positioned parallel to the base of the bracket, in the second study the LED was positioned at 458 to the base, demonstrating that this position seems to favor composite epoxy resin.…”

Effect of Activation Mode on Shear Bond Strength of Metallic Brackets

“…Although the ideal substrate for this type of study is the human tooth, bovine teeth were used as a substitute because extracted human teeth are becoming difficult to obtain due to the progress in conservative dental treatment (21). Bovine teeth are easily obtainable and are reported to be a reliable substitute for human teeth in enamel bonding (22).…”