Comparison of shear bond strength and wear resistance of different composite materials used in clear aligner therapy

The aim of this study is to comparatively evaluate the shear bond strength (SBS) and wear resistance of six different composite resins used as attachment materials in clear aligner treatments. In the study, flowable and packable composite resins that are widely used in clinical applications were examined. The research was conducted in vitro and in two main stages. In the first stage, the shear bond strength of attachment samples prepared using the determined composite groups was measured under standardized test conditions, and the obtained values were calculated in MPa. In the second stage, the same composite groups were subjected to a wear test performed under a specified load, number of cycles, and sliding distance; wear rates and friction coefficients were evaluated. In order to examine the types of detachment of the attachments from the tooth surface, Adhesive Remnant Index (ARI) scores were analyzed. All statistical analyses in the study were performed using the IBM SPSS (Version 26.0, IBM Corp., USA) software. The distribution characteristics of the variables were evaluated using the Shapiro–Wilk normality test, and since p < 0.05 was found in all groups, it was determined that the data were not normally distributed. Therefore, non-parametric methods were preferred. The Kruskal–Wallis H test was applied to examine differences between groups. As a result of the analysis, a significant difference was detected between the groups. In order to determine which groups caused the difference, a Bonferroni-corrected Dunn post-hoc test was performed. In addition, since the relationship between two independent numerical variables did not show a normal distribution, the Spearman correlation test was applied. The chi-square test was used to compare ARI scores between groups. In all analyses, the level of statistical significance was accepted as p < 0.05. According to the findings obtained, statistically significant differences were found among the composite materials in terms of shear bond strength and wear rate (p < 0.05). It was determined that high-viscosity composites generally exhibited higher SBS values and lower wear rates, whereas flowable composites showed a higher tendency for wear in some groups. The distribution of ARI scores revealed that the composite material used affected the bonding characteristics at the attachment–enamel interface. As a result, in the selection of attachment materials in clear aligner treatments, the viscosity and filler content of the composite resin are clinically important parameters in terms of bonding success and wear resistance. It is considered that the findings obtained from this study will provide clinicians with a scientific guide in the selection of attachment materials and will contribute to increasing treatment effectiveness.