Effect of Yd:YAG laser irradiation on the shear bond strength of orthodontic metal brackets

Abstract

Objective: The purpose of this study was to evaluate the effect of the Yd:YAG laser irradiation on orthodontic bracket base surface. Shear bond strength (SBS) values and sites of the bonding failure interfaces were quantified. Methods: Brackets were divided into two groups: OP (One Piece - integral sandblast base) and OPL (One Piece - laser irradiation). The brackets were randomly bonded on an intact enamel surface of 40 bovine incisors. The SBS tests were carry out using a universal test machine. A stereomicroscopy was used to evaluate the adhesive remnant index (ARI), and surface characterization was performed by scanning electron microscopy (SEM). Student’s t-test was used to compare the SBS between the two groups (p< 0.05). Frequencies and chi-square analysis were applied to evaluate the ARI scores. Results: OPL group showed higher value (p< 0.001) of SBS than OP group (43.95 MPa and 34.81 MPa, respectively). ARI showed significant difference (p< 0.001) between OPL group (ARI 0 = 100%) and OP group (ARI 0 = 15%). SEM showed a higher affinity between the adhesive and the irradiated laser base surface. Conclusions: Yd:YAG laser irradiation on bracket base increased SBS values, showing that bonding failure occurs at the enamel/adhesive interface. Laser-etched bracket base may be used instead of conventional bases in cases where higher adhesion is required, reducing bracket-bonding failure.

Bonding Surface Designs in Fixed Orthodontic Attachments

“…The attachments with larger apertures show better air displacement from the surface and better resin penetration into the spaces, resulting in higher bond strengths [ 14 , 20 ]. Although several studies have reported that fine mesh gauges due to larger apertures demonstrate higher bond strength, some studies have indicated no significant differences between various mesh gauges [ 8 , 13 , 16 , 24 , 26 – 29 ].…”

“…Furthermore it seems that laser etching of the bonding surface can improve the bond strength of other ABS designs [ 13 ].…”

“…Sandblasting, microetching, and laser etching of ABSs can improve bond strength due to increased microscopic contact area [ 20 ] although the effect of laser etching is more [ 13 , 49 ].…”

“…Te attachments with larger apertures show better air displacement from the surface and better resin penetration into the spaces, resulting in higher bond strengths [14,20]. Although several studies have reported that fne mesh gauges due to larger apertures demonstrate higher bond strength, some studies have indicated no signifcant diferences between various mesh gauges [8,13,16,24,[26][27][28][29]. Knox et al revealed that certain combinations of bonding composite resin and mesh gauge could result in maximum bond strength, so determining an exact trend seemed difcult.…”

“…Primary attempts to improve bond strength include increasing ABS macroscopic area and better ABS adaptation on the tooth surface [1,7,9,[12][13][14]. Round or triangular ABSs have less area than quadrangular ones.…”