In vitro evaluation of aligner attachment bond strength on enamel, composite, and lithium disilicate surfaces using different resin composites

Abstract

The aim of this study was to evaluate the shear bond strength (SBS) of aligner attachments bonded to enamel, composite-restored, and lithium disilicate glass-ceramic surfaces using flowable and high-viscosity resin composites. Ninety extracted premolars were divided into three groups (n = 30) according to surface type: enamel (Group 1), composite resin restoration (Group 2), and lithium disilicate glass-ceramic (Group 3). Groups 1 and 2 were etched with 37% phosphoric acid, while Group 3 was etched with 9.6% hydrofluoric acid. A universal adhesive was applied to all specimens. Each group was divided into two subgroups based on composite type (flowable or high-viscosity universal; n = 15). SBS and adhesive remnant index (ARI) were evaluated. One-way ANOVA, Student’s t-test, and Fisher Freeman Halton test were used for statistical analyses (p < 0.05). The highest SBS were obtained in Group 1 bonded with high-viscosity universal composite attachments (mean (± SD), 19.6 (± 6.7 MPa)), and the lowest were obtained in Group 2 bonded with flowable composite attachments (mean (± SD), 7.3 (± 1.8 MPa)). Comparison of three groups within themselves according to the composite resin factor, the mean SBS of Group 2 for high-viscosity universal resin was higher than for flowable resin (p < 0.001). ARI scores did not show a significant correlation with either tooth surface or composite resin type. High-viscosity resin composite provides more reliable bond strength than flowable composite when bonding aligner attachments to composite-restored surfaces. Both composite types demonstrated clinically acceptable bond strength on enamel and lithium disilicate surfaces.