Effects of reducing light-curing time of ahigh-power LED device on shear bond strength of brackets.

Abstract

To assess the effects of reducing the curing time of ahigh-power light-emitting diode (LED) unit (Valo, Ultradent, South Jordan, UT, USA) on shear bond strength (SBS) of metal brackets and on the amount of adhesive remnant of two orthodontic composites. Eighty human premolars were divided into four groups (G1-4) according to curing time and composite: G1 (Transbond XT, 6 s), G2 (Opal Bond MV, 6 s), G3 (Transbond XT, 3 s), and G4 (Opal Bond MV, 3 s). Twenty-four hours after bonding, brackets were subject to aSBS test performed with auniversal testing machine. Enamel surface was analyzed by SEM and the amount of adhesive remnant was assessed by the ImageJ software area calculation tool. Two-way analysis of variance was used for statistical analysis of SBS data, while Friedman and Mann-Whitney post hoc tests were used to analyze data on the amount of adhesive remnant. Time and composite significantly affected SBS (p < 0.001). The 6 s curing showed ahigher SBS value (21.56 MPa) in comparison to 3 s curing (15.79 MPa). Transbond XT composite showed asignificantly higher SBS value (21.06 MPa) compared to Opal Bond MV (16.29 MPa). After the SBS test, Opal Bond MV showed asignificantly greater amount of composite adhered to enamel (p < 0.001). Reducing exposure time from 6 to 3 s significantly decreased mean values of SBS, even with the use of ahigh-power LED unit. Reduction in time did not affect the amount of adhesive remnant.