The Effect of Bonding Surface Design on Shear Bond Strength of 3D-Printed Orthodontic Attachments.

Abstract

<h4>Introduction</h4>This study compared the shear bond strength (SBS) of four innovative designs of the bonding surface of 3D-printed orthodontic attachments with conventional mesh design.<h4>Methods</h4>In this in vitro study, the bonding surface design in different groups was as follows: Group 1, flat surface without any feature as a negative control; Group 2, concentric circles with no cuts; Group 3, concentric circles with 16 radial cuts; Group 4, concentric circles with 32 radial cuts; Group 5, small cones with a flat end and rounded edges; Group 6, mesh-based commercially available metal brackets of the maxillary central incisor (standard edgewise, Dentaurum®) as a positive control (<i>n</i> = 20). In Groups 1-5, attachments were designed with SolidWorks® Software and printed with a 2K DLP-LCD printer with hard tough resin (eSun®). All the samples were bonded to the restorative composite resin (Solafil®) surfaces with orthodontic composite resin (CuRAY-ECLIPSE®). The samples were examined for SBS with a universal testing machine after thermocycling (1,000 cycles of 5‒55°C). Data were analyzed with Shapiro-Wilk, one-way ANOVA, and Bonferroni tests. The statistical significance level was set at 0.05.<h4>Results</h4>The mean SBS was significantly different between all the groups (<i>P</i> < 0.001) except for Groups 2 and 5 (<i>P</i> = 1.00) and Groups 2 and 6 (<i>P</i> = 1.00). Group 4 had the highest mean of SBS.<h4>Conclusion</h4>The bonding surface design significantly influenced the SBS of orthodontic attachments. The concentric circles with 32 cuts had higher bond strength than other designs and can be suggested as a new bonding surface design for orthodontic attachments.