Mechanical properties of different types of composite resin used as clear aligner attachments: an in vitro study

Composite resin is often used as an orthodontic attachment due to its esthetic appearance, ease of clinical manipulation, and micromechanical bonding to etched enamel tooth structures. The aim of this study was to compare the Vickers microhardness (VMH) and shear bond strength (SBS) of six types of composite resins (Tetric PowerFlow, Filtek™ Supreme Flowable Restorative, Clearfil Majesty Flow, Tetric PowerFill, Filtek™ Supreme XTE Universal, and Estelite Sigma Quick). Twelve composite resin discs were fabricated for VMH test for each composite group. And 15 rectangular composite resin attachments were bonded on natural extracted premolars for each SBS test. VMH values were retrieved using an INOVATEST microhardness device at T1 and T2 after thermocycling and toothbrushing intervention. SBS values were retrieved using a Universal Testing Machine after thermocycling aging. The VMH values of all materials showed statistically significant differences (p = < .01) between T1 and T2, as Clearfil Majesty Flow material did not show a significant difference and Filtek™ Supreme XTE Universal material showed a significant difference at (p = < .05) but not at (p = < .01). ANOVA revealed no statistically significant difference in the SBS values between the six composite resin materials. The Clearfil Majesty Flow composite resin was not affected by thermocycling or toothbrushing compared to all other composite groups.