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Influence of 3D Printer Type, Resin Material, Thickness, and Geometry on the Mechanical Properties of Directly
Fırat Oğuz1, Sabahattin Bor1, Buse Çebi Gül2
1Department of Orthodontics, Faculty of Dentistry, İnönü University, Malatya 44280, Türkiye.
Abstract:
To evaluate the effects of three different 3D printers, two clear aligner resins, two specimen thicknesses, two lengths, and two geometric designs on the tensile strength and elastic modulus of directly printed clear aligners. Specimens were produced from two orthodontic aligner resins, Clear A (Senertek, Izmir, Turkey) and Tera Harz TA 28 (Graphy Inc., Seoul, Republic of Korea), using three different 3D printers: Ackuretta SOL (LCD), Asiga MAX (DLP), and UNIZ NBEE (LCD). Specimens were designed in two forms (dumbbell, in accordance with ISO 527 3, and flat strip), in two thicknesses (0.5 mm and 1 mm), and in two lengths (short and long), yielding 24 groups with 5 specimens each (n = 120). All specimens were post processed using the Tera Harz Spinner and cured for 25 min under nitrogen atmosphere in the THC 2 MC unit, followed by a 1 min boiling water treatment. Tensile tests were performed on a universal testing machine (Shimadzu Corp., Kyoto, Japan) up to fracture. Maximum force (N) and elastic modulus (N/mm2) were recorded. Data were analyzed using Kruskal-Wallis, Mann-Whitney U, and Aligned Rank Transform ANOVA tests with Dunn post hoc and Bonferroni correction (p < 0.05). Printer type had no significant effect on maximum force (p = 0.357) or elastic modulus (p = 0.052). Resin type (p < 0.001), thickness (p < 0.001), and specimen geometry (p < 0.001) showed significant effects on both parameters. TA 28 specimens exhibited higher mechanical performance than Clear A. Increased thickness produced higher maximum force and elastic modulus values. Flat geometries showed the highest maximum force, while the short dumbbell exhibited the lowest. The long thin dumbbell geometry yielded the highest elastic modulus values. Resin composition, thickness, and specimen geometry are the primary determinants of mechanical performance in directly printed clear aligners, whereas printer type appears to play a limited role.
