Influence of Sandblasting Particle Size on the Shear Bond Strength of Orthodontic Brackets to Milled and 3D-Printed Provisional Crowns or Materials After Artificial Aging

Purpose: This in vitro study ascertained the impact of three distinct alumina particle sizes on the shear bond strength (SBS) between two distinct provisional crowns (milled and 3D-printed) and stainless-steel orthodontic brackets following artificial aging. Materials and methods: Eighty specimens [disc 10 mm diameter/15 mm height] were fabricated with two provisional crown materials, milled (CopraTemp) [group (GP) M] and three-dimensionally printed (Asiga DentaTooth) (GP P), and divided into eight subgroups based on alumina oxide (sandblasting) particle size surface treatments of 25 μm [P25, M25], 50 μm [P50, M50], and 100 μm [P100, M100], with no surface treatment specimens serving as control [PC, MC]. After thermocycling (2200 cycles), the SBS and Adhesive Remnant Index (ARI) were calculated. Statistical tests included one-way analysis of variance (ANOVA) (Kruskal–Wallis), followed by post hoc tests [Tukey HSD, Dunn’s], with the probability ‘p’ value being significant at 0.05 (p ≤ 0.05). Results: Without surface treatment, the 3D-printed provisional crown had the lowest SBS [median (IQR); 12.8 (2.74)]. The highest SBS was found in both milled and 3D-printed PMs with 50-micron particle sizes [Milled = 23.10 (2.3); Printed = 20.72 (2.31)], followed by 100-micron [Milled = 20 (2.36); Printed = 17.99 (3.45)] and 25-micron [Milled = 16.13 (2.71); Printed = 15.08 (1.55)]. The majority of cohesive failures were seen in the milled subgroups, while all subgroups of 3D-printed provisional material had adhesive bond failures. Conclusions: Sandblasting, irrespective of particle size, enhances SBS in both milled and 3D-printed provisional restorations; however, 50-micron alumina particles are recommended since they enhance SBS substantially.