The influence of bracket type and etching time on shear bond strength to enamel: An in vitro study

Abstract

Introduction/Aim. The length of tooth enamel conditioning time and the size of bracket bases are some the factors influencing the bond strength between the two adherents. The aim of this study was to compare the shear bond strength (SBS) between two different types of bonded metal brackets and acid-etched enamel surface in two different times. Material and methods. Forty extracted human premolars were randomly divided into four groups. In groups 1 and 2, metal brackets Topic (Dentaurum, Germany) were bonded after etching with 37% phosphoric acid (Gel, Reliance, USA) for 15 s and 30 s, while in groups 3 and 4, metal brackets Equilibrium mini (Dentaurum, Germany) were bonded after etching for 15 s and 30 s. Brackets were bonded using flowable composite Heliosit Orthodontic (Ivoclar Vivadent, Liechtenstein) and light-cured using a LED lamp. The SBS was measured by an electronic dynamometer at a cross-head speed of 5 mm/min. Results. Statistical analysis revealed that SBS is affected by both bracket type (t = 10.62; p < 0.01) and etching time (t = 2.81; p = 0.008). The Equilibrium mini brackets with previous enamel etching for 30 s showed the highest SBS values of 10.8 ± 0.75 MPa, while the Topic brackets with previous enamel etching for 15 s showed the lowest values of 4.85 ± 0.53 MPa. Conclusion. Increasing the etching time of tooth enamel leads to higher values in bond strength, especially when using a bracket with a smaller base.